The Impact of Marcellus Gas Drilling on Rural Drinking Water SuppliesMarcellus Drilling News
A multi-year study by the bipartisan Center for Rural Pennsylvania on the effects of Marcellus Shale gas drilling on rural water supplies. The study concludes that fracking does not lead to chemical contamination of water supplies, and likely does not affect methane migration into water supplies (although the authors recommend more study of the methane migration issue).
Study: Elevated Levels of Arsenic in Water Wells Near Barnett Shale DrillingMarcellus Drilling News
A study of 100 private water wells in the Barnett Shale in Texas by University of Texas at Arlington researchers claims to have found that about 1/3 of the wells close to drilling activity have dangerously high levels of arsenic. Critics of the research point out the sample size is small and relies on "before" tests of 300 wells in the same general area, but not necessarily these 100 specific wells where arsenic has been found. The report is titled, "An evaluation of water quality in private drinking water wells near natural gas extraction sites in the Barnett Shale Formation" and is published in the journal Environmental Science & Technology.
This study analyzed 550 groundwater samples from private and public water wells overlying the Barnett Shale formation in Texas where unconventional oil and gas extraction is occurring. The study detected multiple volatile organic compounds, including BTEX compounds, alcohols, chlorinated compounds, and others that have been associated with oil and gas activities. While the data do not prove that unconventional extraction caused the contamination, they indicate groundwater monitoring is needed as many compounds detected are known to be used in extraction techniques like hydraulic fracturing. The large sample size provides important data on groundwater quality in this shale region with extensive unconventional drilling.
Duke Study: Methane contamination of drinking water accompanying gas-well dri...Marcellus Drilling News
Study of 68 water wells in Pennsylvania and New York showing a link between shale gas drilling and higher levels of methane in nearby well water supplies.
This poster summarizes a study analyzing changes in water quality in the Allegheny River and its tributaries in Pennsylvania. Water samples were collected from 14 sites between 2013-2015 and analyzed for parameters like dissolved metals, bromide, chloride, and sulfate. Ratios of these parameters indicate impacts from abandoned mine drainage and hydraulic fracturing wastewater. In particular, Blacklick Creek, impacted by both issues, shows high bromide and strontium resembling fracking wastewater. Downstream sites on the Allegheny also reflect these elevated levels, demonstrating impacts on water quality in the region.
Duke University Study: Connection Between Marcellus Shale Drilling and Stray ...Marcellus Drilling News
A Duke University study published in the Proceedings of the National Academy of Sciences titled, "Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction". The study supposedly shows a connection between natural gas drilling and stray gas (mostly methane) in nearby water wells. This is the second time Duke has published such a study. The study from 2011 was criticized for funding by the anti-drilling Park Foundation and for its weak research methodology. This second study has also come under fire for some of the same weaknesses.
Drexel University Study on Air Quality Near Marcellus Shale Drilling SitesMarcellus Drilling News
A new study of the effects of Marcellus Shale extraction on air quality. The study was published in the peer reviewed journal Environmental Science & Technology and titled "Atmosphere Emission Characterization of Marcellus Shale Natural Gas Development Sites". It finds far less impact on air quality near drilling sites than previously thought, but also a measurable impact on air quality near compressor stations.
Duke University & USGS Study: Shale Drilling in Arkansas Does Not Contaminate...Marcellus Drilling News
This document summarizes a study that analyzed the geochemistry of 127 domestic groundwater wells in areas with Fayetteville Shale gas development in north-central Arkansas. The study characterized four types of shallow groundwater based on major ion chemistry and found variations in strontium, carbon, and boron isotopes reflecting water-rock interactions. While some wells contained elevated methane, isotopic signatures showed the methane was biogenic rather than thermogenic in origin. Overall, the geochemical and isotopic compositions of shallow groundwater were distinct from Fayetteville Shale produced waters, and no direct evidence was found of contamination from natural gas extraction.
The Impact of Marcellus Gas Drilling on Rural Drinking Water SuppliesMarcellus Drilling News
A multi-year study by the bipartisan Center for Rural Pennsylvania on the effects of Marcellus Shale gas drilling on rural water supplies. The study concludes that fracking does not lead to chemical contamination of water supplies, and likely does not affect methane migration into water supplies (although the authors recommend more study of the methane migration issue).
Study: Elevated Levels of Arsenic in Water Wells Near Barnett Shale DrillingMarcellus Drilling News
A study of 100 private water wells in the Barnett Shale in Texas by University of Texas at Arlington researchers claims to have found that about 1/3 of the wells close to drilling activity have dangerously high levels of arsenic. Critics of the research point out the sample size is small and relies on "before" tests of 300 wells in the same general area, but not necessarily these 100 specific wells where arsenic has been found. The report is titled, "An evaluation of water quality in private drinking water wells near natural gas extraction sites in the Barnett Shale Formation" and is published in the journal Environmental Science & Technology.
This study analyzed 550 groundwater samples from private and public water wells overlying the Barnett Shale formation in Texas where unconventional oil and gas extraction is occurring. The study detected multiple volatile organic compounds, including BTEX compounds, alcohols, chlorinated compounds, and others that have been associated with oil and gas activities. While the data do not prove that unconventional extraction caused the contamination, they indicate groundwater monitoring is needed as many compounds detected are known to be used in extraction techniques like hydraulic fracturing. The large sample size provides important data on groundwater quality in this shale region with extensive unconventional drilling.
Duke Study: Methane contamination of drinking water accompanying gas-well dri...Marcellus Drilling News
Study of 68 water wells in Pennsylvania and New York showing a link between shale gas drilling and higher levels of methane in nearby well water supplies.
This poster summarizes a study analyzing changes in water quality in the Allegheny River and its tributaries in Pennsylvania. Water samples were collected from 14 sites between 2013-2015 and analyzed for parameters like dissolved metals, bromide, chloride, and sulfate. Ratios of these parameters indicate impacts from abandoned mine drainage and hydraulic fracturing wastewater. In particular, Blacklick Creek, impacted by both issues, shows high bromide and strontium resembling fracking wastewater. Downstream sites on the Allegheny also reflect these elevated levels, demonstrating impacts on water quality in the region.
Duke University Study: Connection Between Marcellus Shale Drilling and Stray ...Marcellus Drilling News
A Duke University study published in the Proceedings of the National Academy of Sciences titled, "Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction". The study supposedly shows a connection between natural gas drilling and stray gas (mostly methane) in nearby water wells. This is the second time Duke has published such a study. The study from 2011 was criticized for funding by the anti-drilling Park Foundation and for its weak research methodology. This second study has also come under fire for some of the same weaknesses.
Drexel University Study on Air Quality Near Marcellus Shale Drilling SitesMarcellus Drilling News
A new study of the effects of Marcellus Shale extraction on air quality. The study was published in the peer reviewed journal Environmental Science & Technology and titled "Atmosphere Emission Characterization of Marcellus Shale Natural Gas Development Sites". It finds far less impact on air quality near drilling sites than previously thought, but also a measurable impact on air quality near compressor stations.
Duke University & USGS Study: Shale Drilling in Arkansas Does Not Contaminate...Marcellus Drilling News
This document summarizes a study that analyzed the geochemistry of 127 domestic groundwater wells in areas with Fayetteville Shale gas development in north-central Arkansas. The study characterized four types of shallow groundwater based on major ion chemistry and found variations in strontium, carbon, and boron isotopes reflecting water-rock interactions. While some wells contained elevated methane, isotopic signatures showed the methane was biogenic rather than thermogenic in origin. Overall, the geochemical and isotopic compositions of shallow groundwater were distinct from Fayetteville Shale produced waters, and no direct evidence was found of contamination from natural gas extraction.
Impact of contaminants on groundwater quality in patcham, south east england.Alexander Decker
This study investigated the impact of contaminants on groundwater quality in Patcham, South-East England. Data from weather stations and loggers in boreholes was used to analyze potential contaminant pathways through the chalk aquifer. Laboratory tests found that parameters like pH, conductivity and ions were within WHO guidelines, indicating water quality was suitable for use. The chalk aquifer is an important water source but is vulnerable to surface contaminants due to its karst nature with features like swallow holes.
Hydrogeochemistry and Microbiology of Wadi Al Bih Limestone Aquifer in Northe...QUESTJOURNAL
ABSTRACT: This study investigated the hydrogeochemical characteristics and microbiological pollution of groundwater in Wadi Al Bih limestone aquifer, Ras Al Khaimah area, northern United Arab Emirates (UAE). Results indicate that the decrease of groundwater exploitation in Wadi Al Bih basin from 58 million cubic meter (MCM) during the period 1991-1995 to 22 MCM during the period 2011-2015, has increased groundwater storage, raised hydraulic heads by 1 m in Al Burayrat area and 16 m near Wadi Al Bih main dam, and decreased the average groundwater salinity by 30% in Wadi Al Bih well field and 45% in Al Burayrat well field. Results of chemical analyses showed noticeable fluctuations in groundwater temperature, EC, and TDS contents, rather than concentrations of all ions. The November 2014 and June 2015 isosalinity contour maps indicate that the groundwater salinity increases from east to west, in the direction of groundwater flow. The groundwater in the eastern part of Wadi Al Bih is good for domestic purposes and irrigation. However, the water hardness is high because the aquifer is predominantly composed of limestone. Wadi Al Bih limestone aquifer is highly sensitive to urban and agricultural activities, and several well were recorded to have Coliform bacteria in Wadi Al Bih and Al Burayrat areas
Classification either on quality or type based for groundwater can offer great advantages especially in regional groundwater management. It provides a short, quick processing, interpretation for a lot of complete hydro-chemical data sets and concise presentation of the results. There is a demonstrable need for a quality assurance, with the advanced usage of world's largest fresh water storage i.e Ground water. Its getting depleted over the years and the quality of the same degrading with a rapid pace. Ground water Quality is assessed mainly by the chemical analysis of samples. The data obtained from the chemical analysis is key for the further classification, analysis, correlation etc. Graphical and Numerical interpretation of the data is the main source for Hydro-chemical studies. In this paper we test the performance of the many available graphical and statistical methodologies used to classify water samples including: Collins bar diagram, Stiff pattern diagram, Schoeller plot, Piper diagram, Durov's Double Triangular Diagram, Gibbs's Diagram, Stuyfzand Classification. This paper explains various models which classify, correlate etc., summarizing the water quality data. The basic graphs and diagrams in each category are explained by sample diagrams. In addition to the diagrams an overall characterization of hydro-chemical facies of the water can be carried out by using plots which represents a water type and hardness domain. The combination of graphical and statistical techniques provides a consistent and objective means to classify large numbers of samples while retaining the ease of classic graphical presentation.
A baseline water study conducted by Cornell University graduate students of the chemcial composition of the water in 113 water wells in Chenango County, NY. This study, published in the Journal of Hydrology: Regional Studies (titled "Assessing dissolved methane patterns in central New York groundwater") will serve as a baseline with which to compare future samples should shale drilling ever begin in New York State.
A preliminary (small) study of samples at 11 producing Marcellus gas wells in Pennsylvania to determine the actual amount of radon present. The study shows that theoretical claims by anti-drillers that Marcellus Shale gas contains high, life-threatening levels of radon are simply not true.
Gas Drilling Water Quality and Private Drinking SuppliesBruce Dickson
1) Gas well drilling produces large volumes of wastewater that can potentially contaminate nearby private water supplies if not properly managed. The wastewater contains high levels of salts like sodium and chloride as well as metals and organic compounds.
2) Contamination of private water supplies from gas drilling has occurred but is relatively uncommon, with over 95% of complaints found to be unrelated to drilling activities. A study in Pennsylvania found around 3-5% of private wells near gas drilling operations exceeded standards for certain contaminants.
3) Regulations require gas well operators to obtain permits addressing drilling, construction, and abandonment practices to protect water resources. Strict adherence to regulations has likely reduced contamination risks compared to older drilling methods
A new study by a pair of researchers from Rice University (Houston, TX). The study looks in detail at the chemical compounds found in frack wastewater from shale plays in PA, TX and NM and finds, according to the researchers, that frack water "was not quite as bad as we thought."
Feed Ratio Study Groundwater in Aquifer System Constrained Up for Urban Areaspaperpublications3
Abstract: Determining the origin of groundwater are closely related to conservation and renewable groundwater resources. Research on the source of groundwater recharge would be based on a theoretical approach, the statistical methods Principle Component Analysis and mass-balanced mixing models. Both of these methods will be tested using secondary data naturally occurring isotope of water, deuterium and oxygen-18, and ions major cations and anions in the aquifer distressed over (depth of the well between 40 dan140 meters). Source recharge ground water to be tested consists of three sources that recharge rainwater, river water and ground water.
This study aims to determine the ratio of the source of groundwater recharge using statistical methods and mass balance-mixing models. Where tracer affix source water using natural isotope parameters. In this study, physical and chemical parameters of water contained in the data of ground water, river water and rainwater are used to determine the origin or source of ground water recharge.
The results of mass balance calculation-mixing models using parameters 1H or δD and pH, to a rate of groundwater recharge source for the location of T3, T4, T6 and T13 are as follows: 43% of riverwater, 33% rainwater and 23% groundwater. Research on the ratio of recharge sources provide some information about water sources that contribute to groundwater recharge in Jakarta and surrounding areas. There are two sources that recharge rainwater and river water Bogor area near the location of groundwater. Physical development is carried out in the Bogor area will result in reduced water that seeps into the groundwater, it will bring a reduced impact to the aquifer water supply in Jakarta.
Identification of possible migration of contaminants in groundwater at a land...Alexander Decker
This document summarizes a study on identifying possible groundwater contamination at a landfill site in Barka, Oman. Borehole drilling, soil sampling, and groundwater sampling and analysis were conducted. Results showed elevated levels of contaminants like TDS, sodium, calcium, magnesium, chloride, and coliform bacteria in groundwater below the landfill compared to background levels, indicating contamination from leachate and liquid waste disposal. A pump test also found decreasing contaminant concentrations with pumping time, suggesting contaminant migration from the landfill area.
This document is a senior thesis analyzing the health status of disturbed and undisturbed non-saline estuaries in California using the California Rapid Assessment Method (CRAM). The thesis introduces CRAM as a tool to rapidly assess wetland ecological features related to water purification and wildlife habitat. It then outlines the objective to compare two restored California freshwater estuaries, Rush Ranch Estuary and Arroyo Burro Estuary, to analyze differences in their health status as indicated by CRAM assessments and quantitative data. Factors like sea level rise, saltwater intrusion, and climate change that could impact the estuaries are also discussed.
Joint Indonesia-UK Conference on Computational Chemistry 2015Dasapta Erwin Irawan
The following there slides were made for Joint Indonesia-UK Conference on Computational Chemistry 2015, consists of three abstracts:
1. Generalised mixed model of water quality in Cikapundung Riverbank using R
Author: Dasapta Erwin Irawan1*, Cut Novianti Rachmi2, Prana Ugi3, Dwi Suhandoko1, Ahmad Darul1, Nurjana Joko Trilaksono1
2. PCA computation to detect water interactions in Cikapundung Riverbank using R
Author: Dasapta Erwin Irawan1*, Cut Novianti Rachmi2, Prana Ugi3, Dwi Suhandoko1, Ahmad Darul1, Nurjana Joko Trilaksono1
3. Landfill Plume Identification : a Review
Author: Ramadhan, F.R1., Nafisah, L.A1., Yosandian, Hazmanu1., and Irawan, D.E 2.
The document summarizes concerns about threats to water quality in the Texas Hill Country from domestic wastewater discharges. It notes that Hill Country streams are more vulnerable to contamination than other parts of Texas due to steep slopes, little vegetation, and extensive caves. It finds that TCEQ wastewater permit rules are too lax, as the limits for constituents like nitrogen and phosphorus exceed EPA guidelines for protecting water quality. The document recommends that TCEQ lower wastewater limits, establish limits for additional pollutants, require more frequent sampling, improve oversight of wastewater facilities, consider local conditions better when issuing permits, and limit phosphates in detergents. It contends that without reforms, TCEQ
This document summarizes a workshop on improving freshwater monitoring frameworks in northwest India. It discusses current groundwater quality monitoring efforts and gaps. Key issues include increased pollution levels, falling water levels, and a lack of comprehensive and high-resolution spatial monitoring of parameters like heavy metals. The document outlines the need to better understand recharge processes, water quality impacts, and the properties of groundwater systems through improved monitoring protocols. Case studies from the region are proposed to help address questions around these issues and make recommendations to improve water resource management.
Bacteria & viral indicator contamination of stormwater - a multi-watershed studyTom Mahin
This document summarizes a study that analyzed stormwater samples from 18 locations across 4 watersheds in Massachusetts. A total of 131 samples were collected during 4 storm events and analyzed for various bacterial and viral indicators as well as water chemistry parameters. The results showed that enterococci levels were much higher than E. coli levels. Bacterial indicators correlated with each other but not with viral indicators. Viral indicators also did not correlate with water chemistry or land use. The study aimed to help prioritize stormwater enforcement and remediation efforts.
A so-called "fact sheet" prepared for the FreshWater Accountability Project Ohio by Dr. Marvin Resnikoff that purports to show dangers from Utica Shale drilling waste (rock, soil, etc.) that may contain low levels of radioactivity. Resnikoff is a well-known anti-driller who uses the radioactivity issue to push his agenda to curtail drilling.
CONTAMINATED LAND MANAGEMENT AND SITE REMEDYSyed Khaleem
This document is a seminar report submitted by Syed Khaleem Ahmed to Visvesvaraya Technological University for the partial fulfillment of a Bachelor of Engineering degree in Civil Engineering. The report discusses contaminated land management and site remediation. It provides an introduction to contaminated sites, describes methods for site characterization and assessment, reviews literature on various remediation techniques, and discusses the selection and planning of remediation methods as well as risk assessment of contaminated sites.
Water Quality Assessment of El-Salam Canal (Egypt) Based on Physico-Chemical ...Premier Publishers
Water quality of El-Salam Canal was assessed using physico-chemical and certain biological characteristics. Downstream increase of total soluble inorganic nitrogen (TSIN) and dissolved reactive phosphorus (DRP) indicated increasing downstream eutrophication. The significant (P ≤ 0.01) downstream increase of chloride indicated elevated pollution. Water quality index (WQI) down (53) and up-stream (48) stations indicated bad to moderate condition, respectively. The increase of N, P, heavy metals and WQI may be attributed to excessive input of wastewater from El-Serw and Hadous drains. The highest concentrations of Fe (0.138 mg/l), Mn (0.116), Zn (0.057), Cu (0.019), Pb (0.278) and Cd (0.016) were recorded at downstream stations. Accumulation of these metals by hydrophytes followed the order: Fe ˃ Mn ˃ Zn ˃ Cu ˃ Pb ˃ Cd. Fifteen different hydrophytes were recorded with marked decline in species richness during winter and at downstream stations. The epiphytic microalgae were represented by 50 different taxa, belonging to six phylla including Cyanobacteria, Chlorophyta, Charophyta, Bacillariophyta, Euglenophyta and Rhodophyta. Thespecies composition and richness of the epiphytic microalgae was largely influenced by the plant species, as the highest number of species (42 taxa) was recorded for Ceratophyllum demersum and the lowest one (31 taxa) for Phragmites australis.
CONTAMINATED LAND MANAGEMENT AND SITE REMEDYSyed Khaleem
This document discusses contaminated land management and site remediation. It defines pollution, contamination, and land contamination. Key elements for any risk of land contamination are a contaminant, receptor, and pathway. Methods for selecting and planning remediation include collecting site history, geology/hydrology, geotechnical, and waste data. Remediation methods for soil and groundwater include physico-chemical methods like removal/treatment of contaminated soil, vacuum extraction, and chemical decontamination. The conclusion states that remediation is expensive but necessary, and further research and application is needed along with training and information sharing.
The U.S. natural gas industry is undergoing radical changes due to increased shale gas production from several regions. A report from Bentek Energy found that gas production from the Northeast has increased over 500% since 2005 largely from the Marcellus Shale and Utica Shale. Major shale gas formations driving this change include the Marcellus Shale, Utica Shale, Barnett Shale, Eagle Ford Shale, and Bakken Shale, which are producing large amounts of natural gas and oil across different regions of the United States.
The document discusses U.S. shale gas resources and the challenges of developing them. It notes that shale gas reserves are conservatively estimated at 500-1000 trillion cubic feet and that hydraulic fracturing and horizontal drilling first made shale gas production economically viable. However, each shale play has unique characteristics that require tailored solutions. The document summarizes characteristics of major shale plays like the Barnett, Woodford, Haynesville, Bakken and Fayetteville and notes that best practices must evolve locally to address specific challenges in each play. Unconventional resources like shale gas require unconventional solutions to optimize production and costs.
An update on Magnum Hunter's shale drilling programs in both the Marcellus/Utica region, and in the Bakken Shale region. Total Magnum leased acreage is now 350,000 acres. The company continues to push aggressively in both shale plays, but recent activity is particularly focused on the Utica Shale.
Impact of contaminants on groundwater quality in patcham, south east england.Alexander Decker
This study investigated the impact of contaminants on groundwater quality in Patcham, South-East England. Data from weather stations and loggers in boreholes was used to analyze potential contaminant pathways through the chalk aquifer. Laboratory tests found that parameters like pH, conductivity and ions were within WHO guidelines, indicating water quality was suitable for use. The chalk aquifer is an important water source but is vulnerable to surface contaminants due to its karst nature with features like swallow holes.
Hydrogeochemistry and Microbiology of Wadi Al Bih Limestone Aquifer in Northe...QUESTJOURNAL
ABSTRACT: This study investigated the hydrogeochemical characteristics and microbiological pollution of groundwater in Wadi Al Bih limestone aquifer, Ras Al Khaimah area, northern United Arab Emirates (UAE). Results indicate that the decrease of groundwater exploitation in Wadi Al Bih basin from 58 million cubic meter (MCM) during the period 1991-1995 to 22 MCM during the period 2011-2015, has increased groundwater storage, raised hydraulic heads by 1 m in Al Burayrat area and 16 m near Wadi Al Bih main dam, and decreased the average groundwater salinity by 30% in Wadi Al Bih well field and 45% in Al Burayrat well field. Results of chemical analyses showed noticeable fluctuations in groundwater temperature, EC, and TDS contents, rather than concentrations of all ions. The November 2014 and June 2015 isosalinity contour maps indicate that the groundwater salinity increases from east to west, in the direction of groundwater flow. The groundwater in the eastern part of Wadi Al Bih is good for domestic purposes and irrigation. However, the water hardness is high because the aquifer is predominantly composed of limestone. Wadi Al Bih limestone aquifer is highly sensitive to urban and agricultural activities, and several well were recorded to have Coliform bacteria in Wadi Al Bih and Al Burayrat areas
Classification either on quality or type based for groundwater can offer great advantages especially in regional groundwater management. It provides a short, quick processing, interpretation for a lot of complete hydro-chemical data sets and concise presentation of the results. There is a demonstrable need for a quality assurance, with the advanced usage of world's largest fresh water storage i.e Ground water. Its getting depleted over the years and the quality of the same degrading with a rapid pace. Ground water Quality is assessed mainly by the chemical analysis of samples. The data obtained from the chemical analysis is key for the further classification, analysis, correlation etc. Graphical and Numerical interpretation of the data is the main source for Hydro-chemical studies. In this paper we test the performance of the many available graphical and statistical methodologies used to classify water samples including: Collins bar diagram, Stiff pattern diagram, Schoeller plot, Piper diagram, Durov's Double Triangular Diagram, Gibbs's Diagram, Stuyfzand Classification. This paper explains various models which classify, correlate etc., summarizing the water quality data. The basic graphs and diagrams in each category are explained by sample diagrams. In addition to the diagrams an overall characterization of hydro-chemical facies of the water can be carried out by using plots which represents a water type and hardness domain. The combination of graphical and statistical techniques provides a consistent and objective means to classify large numbers of samples while retaining the ease of classic graphical presentation.
A baseline water study conducted by Cornell University graduate students of the chemcial composition of the water in 113 water wells in Chenango County, NY. This study, published in the Journal of Hydrology: Regional Studies (titled "Assessing dissolved methane patterns in central New York groundwater") will serve as a baseline with which to compare future samples should shale drilling ever begin in New York State.
A preliminary (small) study of samples at 11 producing Marcellus gas wells in Pennsylvania to determine the actual amount of radon present. The study shows that theoretical claims by anti-drillers that Marcellus Shale gas contains high, life-threatening levels of radon are simply not true.
Gas Drilling Water Quality and Private Drinking SuppliesBruce Dickson
1) Gas well drilling produces large volumes of wastewater that can potentially contaminate nearby private water supplies if not properly managed. The wastewater contains high levels of salts like sodium and chloride as well as metals and organic compounds.
2) Contamination of private water supplies from gas drilling has occurred but is relatively uncommon, with over 95% of complaints found to be unrelated to drilling activities. A study in Pennsylvania found around 3-5% of private wells near gas drilling operations exceeded standards for certain contaminants.
3) Regulations require gas well operators to obtain permits addressing drilling, construction, and abandonment practices to protect water resources. Strict adherence to regulations has likely reduced contamination risks compared to older drilling methods
A new study by a pair of researchers from Rice University (Houston, TX). The study looks in detail at the chemical compounds found in frack wastewater from shale plays in PA, TX and NM and finds, according to the researchers, that frack water "was not quite as bad as we thought."
Feed Ratio Study Groundwater in Aquifer System Constrained Up for Urban Areaspaperpublications3
Abstract: Determining the origin of groundwater are closely related to conservation and renewable groundwater resources. Research on the source of groundwater recharge would be based on a theoretical approach, the statistical methods Principle Component Analysis and mass-balanced mixing models. Both of these methods will be tested using secondary data naturally occurring isotope of water, deuterium and oxygen-18, and ions major cations and anions in the aquifer distressed over (depth of the well between 40 dan140 meters). Source recharge ground water to be tested consists of three sources that recharge rainwater, river water and ground water.
This study aims to determine the ratio of the source of groundwater recharge using statistical methods and mass balance-mixing models. Where tracer affix source water using natural isotope parameters. In this study, physical and chemical parameters of water contained in the data of ground water, river water and rainwater are used to determine the origin or source of ground water recharge.
The results of mass balance calculation-mixing models using parameters 1H or δD and pH, to a rate of groundwater recharge source for the location of T3, T4, T6 and T13 are as follows: 43% of riverwater, 33% rainwater and 23% groundwater. Research on the ratio of recharge sources provide some information about water sources that contribute to groundwater recharge in Jakarta and surrounding areas. There are two sources that recharge rainwater and river water Bogor area near the location of groundwater. Physical development is carried out in the Bogor area will result in reduced water that seeps into the groundwater, it will bring a reduced impact to the aquifer water supply in Jakarta.
Identification of possible migration of contaminants in groundwater at a land...Alexander Decker
This document summarizes a study on identifying possible groundwater contamination at a landfill site in Barka, Oman. Borehole drilling, soil sampling, and groundwater sampling and analysis were conducted. Results showed elevated levels of contaminants like TDS, sodium, calcium, magnesium, chloride, and coliform bacteria in groundwater below the landfill compared to background levels, indicating contamination from leachate and liquid waste disposal. A pump test also found decreasing contaminant concentrations with pumping time, suggesting contaminant migration from the landfill area.
This document is a senior thesis analyzing the health status of disturbed and undisturbed non-saline estuaries in California using the California Rapid Assessment Method (CRAM). The thesis introduces CRAM as a tool to rapidly assess wetland ecological features related to water purification and wildlife habitat. It then outlines the objective to compare two restored California freshwater estuaries, Rush Ranch Estuary and Arroyo Burro Estuary, to analyze differences in their health status as indicated by CRAM assessments and quantitative data. Factors like sea level rise, saltwater intrusion, and climate change that could impact the estuaries are also discussed.
Joint Indonesia-UK Conference on Computational Chemistry 2015Dasapta Erwin Irawan
The following there slides were made for Joint Indonesia-UK Conference on Computational Chemistry 2015, consists of three abstracts:
1. Generalised mixed model of water quality in Cikapundung Riverbank using R
Author: Dasapta Erwin Irawan1*, Cut Novianti Rachmi2, Prana Ugi3, Dwi Suhandoko1, Ahmad Darul1, Nurjana Joko Trilaksono1
2. PCA computation to detect water interactions in Cikapundung Riverbank using R
Author: Dasapta Erwin Irawan1*, Cut Novianti Rachmi2, Prana Ugi3, Dwi Suhandoko1, Ahmad Darul1, Nurjana Joko Trilaksono1
3. Landfill Plume Identification : a Review
Author: Ramadhan, F.R1., Nafisah, L.A1., Yosandian, Hazmanu1., and Irawan, D.E 2.
The document summarizes concerns about threats to water quality in the Texas Hill Country from domestic wastewater discharges. It notes that Hill Country streams are more vulnerable to contamination than other parts of Texas due to steep slopes, little vegetation, and extensive caves. It finds that TCEQ wastewater permit rules are too lax, as the limits for constituents like nitrogen and phosphorus exceed EPA guidelines for protecting water quality. The document recommends that TCEQ lower wastewater limits, establish limits for additional pollutants, require more frequent sampling, improve oversight of wastewater facilities, consider local conditions better when issuing permits, and limit phosphates in detergents. It contends that without reforms, TCEQ
This document summarizes a workshop on improving freshwater monitoring frameworks in northwest India. It discusses current groundwater quality monitoring efforts and gaps. Key issues include increased pollution levels, falling water levels, and a lack of comprehensive and high-resolution spatial monitoring of parameters like heavy metals. The document outlines the need to better understand recharge processes, water quality impacts, and the properties of groundwater systems through improved monitoring protocols. Case studies from the region are proposed to help address questions around these issues and make recommendations to improve water resource management.
Bacteria & viral indicator contamination of stormwater - a multi-watershed studyTom Mahin
This document summarizes a study that analyzed stormwater samples from 18 locations across 4 watersheds in Massachusetts. A total of 131 samples were collected during 4 storm events and analyzed for various bacterial and viral indicators as well as water chemistry parameters. The results showed that enterococci levels were much higher than E. coli levels. Bacterial indicators correlated with each other but not with viral indicators. Viral indicators also did not correlate with water chemistry or land use. The study aimed to help prioritize stormwater enforcement and remediation efforts.
A so-called "fact sheet" prepared for the FreshWater Accountability Project Ohio by Dr. Marvin Resnikoff that purports to show dangers from Utica Shale drilling waste (rock, soil, etc.) that may contain low levels of radioactivity. Resnikoff is a well-known anti-driller who uses the radioactivity issue to push his agenda to curtail drilling.
CONTAMINATED LAND MANAGEMENT AND SITE REMEDYSyed Khaleem
This document is a seminar report submitted by Syed Khaleem Ahmed to Visvesvaraya Technological University for the partial fulfillment of a Bachelor of Engineering degree in Civil Engineering. The report discusses contaminated land management and site remediation. It provides an introduction to contaminated sites, describes methods for site characterization and assessment, reviews literature on various remediation techniques, and discusses the selection and planning of remediation methods as well as risk assessment of contaminated sites.
Water Quality Assessment of El-Salam Canal (Egypt) Based on Physico-Chemical ...Premier Publishers
Water quality of El-Salam Canal was assessed using physico-chemical and certain biological characteristics. Downstream increase of total soluble inorganic nitrogen (TSIN) and dissolved reactive phosphorus (DRP) indicated increasing downstream eutrophication. The significant (P ≤ 0.01) downstream increase of chloride indicated elevated pollution. Water quality index (WQI) down (53) and up-stream (48) stations indicated bad to moderate condition, respectively. The increase of N, P, heavy metals and WQI may be attributed to excessive input of wastewater from El-Serw and Hadous drains. The highest concentrations of Fe (0.138 mg/l), Mn (0.116), Zn (0.057), Cu (0.019), Pb (0.278) and Cd (0.016) were recorded at downstream stations. Accumulation of these metals by hydrophytes followed the order: Fe ˃ Mn ˃ Zn ˃ Cu ˃ Pb ˃ Cd. Fifteen different hydrophytes were recorded with marked decline in species richness during winter and at downstream stations. The epiphytic microalgae were represented by 50 different taxa, belonging to six phylla including Cyanobacteria, Chlorophyta, Charophyta, Bacillariophyta, Euglenophyta and Rhodophyta. Thespecies composition and richness of the epiphytic microalgae was largely influenced by the plant species, as the highest number of species (42 taxa) was recorded for Ceratophyllum demersum and the lowest one (31 taxa) for Phragmites australis.
CONTAMINATED LAND MANAGEMENT AND SITE REMEDYSyed Khaleem
This document discusses contaminated land management and site remediation. It defines pollution, contamination, and land contamination. Key elements for any risk of land contamination are a contaminant, receptor, and pathway. Methods for selecting and planning remediation include collecting site history, geology/hydrology, geotechnical, and waste data. Remediation methods for soil and groundwater include physico-chemical methods like removal/treatment of contaminated soil, vacuum extraction, and chemical decontamination. The conclusion states that remediation is expensive but necessary, and further research and application is needed along with training and information sharing.
The U.S. natural gas industry is undergoing radical changes due to increased shale gas production from several regions. A report from Bentek Energy found that gas production from the Northeast has increased over 500% since 2005 largely from the Marcellus Shale and Utica Shale. Major shale gas formations driving this change include the Marcellus Shale, Utica Shale, Barnett Shale, Eagle Ford Shale, and Bakken Shale, which are producing large amounts of natural gas and oil across different regions of the United States.
The document discusses U.S. shale gas resources and the challenges of developing them. It notes that shale gas reserves are conservatively estimated at 500-1000 trillion cubic feet and that hydraulic fracturing and horizontal drilling first made shale gas production economically viable. However, each shale play has unique characteristics that require tailored solutions. The document summarizes characteristics of major shale plays like the Barnett, Woodford, Haynesville, Bakken and Fayetteville and notes that best practices must evolve locally to address specific challenges in each play. Unconventional resources like shale gas require unconventional solutions to optimize production and costs.
An update on Magnum Hunter's shale drilling programs in both the Marcellus/Utica region, and in the Bakken Shale region. Total Magnum leased acreage is now 350,000 acres. The company continues to push aggressively in both shale plays, but recent activity is particularly focused on the Utica Shale.
Canaan Resource Partners' History and Strategy 2016Freddie Barela
Canaan Resource Partners is an Oklahoma City-based energy investment management firm that has managed private investment funds totaling $500 million since 1990. The firm was originally founded in 1987 and has evolved from managing the first eight funds until 2000 to now focusing on development drilling opportunities in major US shale plays through its current Fund 11. The founding partners Johnnie Penton and Dean Sergent have decades of experience evaluating and developing oil and gas assets and are leading Fund 11's strategy of providing capital for development drilling projects.
Challenger August Investor Presentation 290811princeslea79
Challenger Energy’s strategy is to identify, acquire and appraise material upstream oil and gas
exploration opportunities
Mercury Stetson Prospect in North Texas, US
Two proven shale formations – Barnett and Woodford
Massive potential gas in place with OGIP estimated at 360 BCF/sq mile
Large prospect area – potentially up to 55,000 acres (86 sq miles)
Prospect is close to existing infrastructure
Contiguous land position of ~ 26,000 acres with a short term target of 35,000 acres.
Triple Crown Prospect in Texas, US
Significant acreage – 45,000 acres with options over a further 6,500 acres.
Large gas charged zones, Ellenburger (dolomite) and an unconventional Hybrid play which is geologically analogous to
Montney Hybrid Play in Western Canada with an estimated OGIP of 9 TCF.
Testing to commence shortly on both the Ellenburger and Hyprid Play
Karoo Basin in South Africa
Shale gas in Karoo Basin now a major focus for international E&P companies (eg Shell, Cheasapeake, Statoil and Sasol)
Challenger Energy’s permit of approx. 800,000 acres centred on only well within basin to flow significant gas to surface to
date, awaiting approval.
Independent US Energy Information Agency report suggests Risked Recoverable Resource of more than 7 TCF in
application area.
Attractive assets have exciting potential to grow significant shareholder value
Atlas Energy Barnett Shale Acquisition PresentationCompany Spotlight
The document discusses Atlas Resource Partners' acquisition of Barnett Shale assets from Carrizo Oil and Gas for $190 million. The acquisition is expected to be 6-12% accretive to distributions in 2012 and 7-15% accretive in 2013. ARP acquired 277 billion cubic feet equivalent of proved reserves located in the core of the Barnett Shale. If ARP makes similar future acquisitions totaling $1 billion, distributions could grow 191% over multiple years. The acquisition strengthens ARP's asset base and is expected to enhance distribution growth going forward.
- Shale gas exploration and development is a lengthy and uncertain process that can take decades and involves exploring, appraising, and developing resources through a step-wise approach.
- Not all shale gas plays are economically viable, and it can be challenging to determine where a particular play falls on the spectrum from expensive to economic.
- Shale gas operations require significant upfront investment and have long payout periods, but can provide stable long-term cashflow through manufacturing-style development once established.
- Operators aim to minimize surface footprint and engage local communities to address environmental and social concerns.
Texas proppant and frac sand trends. Does more sand really equal better wells? Energent Group takes a look at the frac sand data in Permian, Eagle Ford, and Granite Wash to identify key operators and trends.
Constellation Energy Partners LLC reported financial and operational results for the fourth quarter and full year of 2013. Key highlights included:
- Oil accounted for 51% of sales revenue in 2013, with average daily oil production up 84% year-over-year.
- Operating costs were $24.69 per BOE for 2013, down 4% from 2012.
- Capital spending of $15.7 million in 2013 resulted in 79 net wells and recompletions.
- The company forecast $20-22 million in capital spending and 1,346-1,552 MBOE of production for 2014, with adjusted EBITDA of $26.7-29.9 million.
Hydraulic fracturing is necessary to produce economic quantities of gas from shale reservoirs with very low permeability. Complex fracture geometry is important to maximize contact between the fracture and reservoir. The fracturing process involves pumping fluid to create fractures, then a slurry of proppant to prop open the fractures. Proppant and fluid selection depends on factors like embedment and closure stress. While aspects like rate, volume, and proppant quantity can be controlled, the natural variations in shale make the exact fracture geometry and productivity impacts difficult to predict. Monitoring tools provide some insight into the fracture treatment results.
Unconventional Wells not yet completed.pptJerry Beets
The document contains details of over 40 wells including their API number, operator, lease name, well number, location, and target formation. The majority of wells listed are located in sections 25-33S and ranges 32-34E targeting the Avalon, Bone Spring, and Wolfcamp formations with operators including BTA and Texaco.
Permian Delaware and Midland basins play.pptJerry Beets
The document discusses the geology and production of the Permian Basin across the Midland and Delaware Basins. It covers the stratigraphy, depositional systems, structure, productive areas, key formations like the Wolfcamp and Bone Spring, resource play polygons, and production type curves. Maps show attributes like thickness, porosity, gas-oil ratios, and acreage ownership across the Permian Basin provinces in Texas.
This document discusses the occurrence of a post-oil solid bitumen network in organic-rich Woodford Shale samples from the USA. The network forms as a solid residue left behind after primary oil migration and expulsion from the shale. Three forms of the network are visible under reflected white light microscopy at 500x magnification - speckled (~1-2 μm), wispy (~2-5 μm), and connected (N5 μm). Scanning electron microscopy images confirm the network and show it provides porosity for hydrocarbon storage and pathways for migration within the shale. The network demonstrates that the shale generated and migrated oil prior to solidification of the residual carbon.
This study examined water quality in two streams - Apathy Creek and Erosion Creek - located in an urban forest preserve. Apathy Creek drains stormwater runoff from a parking lot, while Erosion Creek drains runoff from a housing development and receives discharge from a combined sewer overflow. Water quality parameters including dissolved oxygen, pH, conductivity, temperature, chlorophyll-a, turbidity, nitrates and phosphates were measured at three locations along each stream. Preliminary results found that conductivity and dissolved solids were similarly high in both streams compared to natural streams, suggesting human impact. Erosion Creek also had higher concentrations of dissolved solids, possibly from de-icing salts, sewer overflow and
This document evaluates methane sources in groundwater in northeastern Pennsylvania by analyzing data from 1701 water wells. The key points are:
1) Testing shows methane is ubiquitous in groundwater, with higher concentrations in valleys vs. uplands and in association with certain water chemistries, indicating regional distribution is correlated with topography and hydrogeology rather than shale gas extraction.
2) Isotopic and molecular analysis of gases in Dimock Township water wells show the gases are most consistent with gases from Middle and Upper Devonian formations accessed by local gas wells, not Marcellus shale gas.
3) The findings suggest methane in Susquehanna County water wells can be explained without migration of Marcellus
Study: Evaluation of Methane Sources in Groundwater in Northeastern PennsylvaniaMarcellus Drilling News
A study published in the May-June 2013 issue of Groundwater, a peer-reviewed scientific journal. The study highlights the results of data from 1,701 water wells in Susquehanna County, PA to determine whether or not nearby shale drilling causes an increase in the presence of methane in water wells. The study proves conclusively that water wells near shale drilling had no higher presence of methane than those not near any kind of drilling and that drilling in the Dimock area had nothing to do with methane in nearby water wells. It further proves that Susquehanna County, PA has a tremdendous amount of naturally ocurring methane near the surface.
1. Three wastewater samples from unconventional drilling operations in West Texas were analyzed using various analytical techniques including GC-MS, ICP-OES, HPLC-HRMS, IC, and tests for TOC/TN, conductivity, and pH.
2. Several compounds known to be components of hydraulic fracturing fluid were detected in two of the wastewater samples, including 2-butoxyethanol, alkyl amines, and cocamide diethanolamines, toluene, and o-xylene.
3. Proper management of the large volumes of wastewater generated from unconventional drilling operations will be important due to both the quantity and variable quality of the wastew
Think Earth: Water Pollution, by Saugata DattaNathan Cone
This is the PowerPoint prepared by Dr. Saugata Datta (UTSA) for Texas Public Radio's Think Earth event held on October 7, 2022. The slide presentation focuses on water pollution, and matches with the audio on this page: https://www.tpr.org/tpr-events-initiatives/2022-09-28/think-earth-pollution
This document discusses a study that measured baseline concentrations of methane in shallow aquifers in the St. Lawrence Lowlands region of Quebec, Canada prior to potential future shale gas exploitation. Methane and its isotopic signature were measured in 130 wells between 2012-2013. Methane was detected in 80% of wells at an average concentration of 3.8 mg/L, ranging from below detection to 45.9 mg/L. Isotopic signatures indicated potential thermogenic methane sources in some areas. Methane concentrations were linked to groundwater chemistry and distance to major faults, which could act as migration pathways. The study provides background data on natural methane levels and sources before potential future shale gas development through hydraulic fracturing.
This slide show presentation was utilized at the Nov. 16, 2023 event "Think Science: Geoscience & Groundwater" and features contributions from:
Dr. Ben Surpless, Trinity University
Dr. Saugata Datta, UTSA
Dr. Brady Ziegler, Trinity University
This document analyzes the impacts of Beach Drive on water quality and vegetation abundance in Rock Creek Park in Washington D.C. Water and plant samples were taken from Rock Creek adjacent to Beach Drive and from two tributaries further in the park. Analysis found that the average pH, nitrate, and phosphate levels in Rock Creek adjacent to Beach Drive were higher than in the tributaries, likely due to urban stormwater runoff from the road. Vegetation abundance was also lower along Beach Drive where it was closer to the creek, due to higher disturbance, but species richness did not vary significantly between areas. The presence of Beach Drive was found to negatively impact the water quality and plant life of nearby Rock Creek.
This document summarizes a study on analyzing ammonia levels in groundwater samples from Chittagong, Bangladesh. Nine groundwater samples were collected from shallow and deep aquifers in different parts of the city. Laboratory analysis found high levels of ammonia associated with elevated arsenic and manganese, suggesting reducing conditions may control the release of arsenic and manganese in groundwater. Standard addition calibration produced a linear calibration curve with an R2 value of 0.9977. Ammonia results from the laboratory analysis mostly matched field measurements, though some samples may need to be reanalyzed. Further study of the hydrogeochemistry is planned to better understand factors controlling arsenic mobilization.
Hydraulic Fracturing and Marcellus Shale Gas 11 22 2011Michael Klein
The drilling technique of Hydraulic Fracturing has allowed natural gas producers to extract natural gas economically from deep shale formations. This innovative drilling technique has made enormous quantities of natural gas available in wide areas of the United States from Texas, Louisiana, Pennsylvania, New York, Wyoming, North Carolina, and Colorado. The drilling technique of hydraulic fracturing accounts for roughly a quarter of total natural gas production in the United States as cited by the Energy Information Administration. With the increased emphasis on the use of natural gas in our federal energy policy, there will be new regulations, processes, and resources that will be required to mitigate the risks to human health and the environment from this new drilling technique. The presentation discusses the process of hydraulic fracturing; the threats that are posed to human health and the environment, areas in the USA where the process is used with an emphasis on the Marcellus Shale formation, current and new regulations being put into place, and plaintiff challenges to the process.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This study analyzed 20 public drinking water wells on Cape Cod, Massachusetts for 92 organic wastewater compounds (OWCs) including pharmaceuticals, hormones, and consumer product chemicals. The goals were to evaluate the presence of OWCs in the wells and determine if surrogates of wastewater impact like nitrate, boron, and residential development could identify wells most impacted by OWCs. Fifteen of the 20 wells contained at least one OWC, with the two most frequently detected being the antibiotic sulfamethoxazole and the perfluorosurfactant perfluorooctane sulfonate. Maximum concentrations of two pharmaceuticals matched or exceeded levels reported in other U.S. public water sources, indicating
The USGS Powell Center is conducting a study analyzing water quality data from areas experiencing unconventional oil and gas development involving hydraulic fracturing. Over 750,000 water quality samples from 110,000 surface and groundwater sites are being analyzed to describe baseline water quality, identify changes over time where sufficient data exists, and determine gaps in spatial and temporal data coverage. The goals are to better understand the impacts of energy production on water resources and inform future monitoring and research needs.
The USGS Powell Center is conducting a study analyzing water quality data from areas experiencing unconventional oil and gas development involving hydraulic fracturing. Over 750,000 water quality samples from 110,000 surface and groundwater sites are being analyzed to describe baseline water quality, identify changes over time where sufficient data exists, and determine gaps in spatial and temporal data coverage. The goals are to better understand the impacts of energy production on water resources and inform future monitoring and research needs.
This document analyzes sediment quality in Hussainsagar Lake in Hyderabad, India using multivariate statistical techniques. Samples were collected from four inlet channels and analyzed for 12 chemical and heavy metal parameters. Factor analysis identified five factors that explained 71.05% of the total variance, grouping parameters according to common anthropogenic sources. Cluster analysis grouped the sampling stations into clusters based on their sediment quality characteristics, with one station showing higher pollution levels than the others. Principal component analysis was used to recognize patterns among the 14 parameters measured.
The Bear Creek Watershed Group proposed a stream monitoring project in 2011 to collect water quality data along Bear Creek to guide revegetation efforts and encourage the salmonid population decline. Water quality monitoring has been ongoing since 2011 and focuses on temperature, dissolved oxygen, and pH. Sample data has been collected monthly from 2011 to 2014 at nine sites along Bear Creek, and the results for temperature, dissolved oxygen, and pH are presented on maps that relate these water quality parameters to elevation, soil/fire history, and vegetation respectively.
This project investigated using native Rio Grande cottonwood trees and zeolite to improve water quality in nearby urban streams and drains. Six test plots were established, with cottonwood trees planted in soil with or without added zeolite. Data on soil properties, plant health, weather, and water quality was collected. Initial results found the cottonwoods survived well and established baseline data on soil and plant conditions prior to irrigation testing.
1) A geospatial model of the Barnett Shale region was created using GIS software to analyze groundwater quality data and determine if variations are associated with hydraulically fractured gas wells.
2) The study found that elevated concentrations of certain groundwater constituents, including beryllium, are likely related to natural gas production and beryllium could be used as an indicator of fracturing impacts.
3) Results also indicated that gas well density and formation pressures correlate to changes in regional water quality, whereas proximity to gas wells alone does not, providing indirect evidence that micro annular fissures may transport fluids from fractured wells to groundwater.
Groundwater methane in relation to oil and gas development and shallow coal s...Marcellus Drilling News
A research paper published in the Proceedings of the National Academy of Sciences. The paper evaluated the level of methane in groundwater in Colorado going back 25 years. It finds the rate of groundwater methane did not change after the introduction of horizontal drilling combined with high-volume hydraulic fracturing in 2010. That is, fracking does not increase methane migration.
The State of Broadband: Broadband catalyzing sustainable development. Septemb...Andrés Rodríguez Seijo
This report examines the state of broadband and its role in catalyzing sustainable development. It finds that while individual internet usage and household connectivity continue growing strongly in many regions, barriers remain for some groups. Mobile broadband subscriptions are rising globally, driven by increased data consumption on smartphones. National broadband policies have expanded to cover next generation networks and satellite broadband. Regulators face challenges balancing investment, competition and consumer interests. The report argues that harnessing broadband can help achieve sustainable development goals in areas like health, education and the environment, but greater leadership and cooperation is still needed to connect the unconnected.
Este documento resume la trayectoria académica y profesional de un estudiante de doctorado. A pesar de no tener las mejores calificaciones, el estudiante aprovechó oportunidades en sus estudios de posgrado para investigar la contaminación de suelos, lo que le permitió iniciar un doctorado. El doctorando está aprendiendo sobre caracterización de suelos contaminados y toxicidad de metales pesados a través de su investigación de campo y pruebas ecotoxicológicas. Su objetivo final es publicar resultados para progresar en su carrera
Papel de las fitohormonas en el crecimiento y desarrollo de plantasAndrés Rodríguez Seijo
Las fitohormonas como la auxina, citoquininas, giberelinas y etileno juegan un papel clave en el crecimiento y desarrollo de las plantas al regular procesos como la división celular, elongación, floración y maduración de frutos. Las plantas utilizan mecanismos de homeostasis hormonal para regular los niveles de fitohormonas y responder a cambios ambientales mediante la síntesis, degradación y transporte de estas sustancias.
El documento describe experimentos de fertilización oceánica con hierro para aumentar el fitoplancton y así mejorar la capacidad de los océanos para absorber CO2 atmosférico. Sin embargo, los experimentos no tuvieron el éxito esperado debido a que no consideraron factores como la necesidad de ácido silícico y el efecto sobre otros organismos, lo que llevó a un rápido descenso de la producción de fitoplancton. El documento concluye que se necesitan más estudios antes de intentar la fertilización oceánica a gran
Rodríguez-Seijo, A. (2011) Agricultura tradicional y agricultura de conservaciónAndrés Rodríguez Seijo
Este documento compara la agricultura tradicional y la agricultura de conservación. Explica que la agricultura tradicional ha evolucionado desde la agricultura antigua hasta convertirse en una agricultura intensiva que utiliza maquinaria, fertilizantes químicos y monocultivos. Si bien esto aumentó la producción, también degradó los suelos. La agricultura de conservación reduce esta degradación mediante el uso de cubiertas vegetales, laboreo mínimo y rotación de cultivos para proteger los suelos y mejorar su calidad a largo
Rodríguez-Seijo, A. (2012) Grandes desastres ambientales con consecuencias en...Andrés Rodríguez Seijo
Este documento describe el desastre ambiental ocurrido en Kingston, Tennessee en 2008 cuando se rompió un dique de una represa que contenía residuos de carbón de una planta eléctrica, liberando millones de metros cúbicos de lodos contaminados. Esto tuvo graves efectos como la muerte de peces y otros organismos, y la contaminación de suelos y aguas con metales pesados. Se tomaron medidas de limpieza y rehabilitación a largo plazo, pero los impactos ambientales y costos serán significativos durante décadas.
Este documento describe a los denisovanos, una posible especie humana extinta descubierta a partir de restos óseos encontrados en la cueva de Denisova en Siberia. Los análisis de ADN sugieren que los denisovanos se separaron de los neandertales y humanos modernos hace unos 300.000 años y que tuvieron contacto genético con los primeros pobladores de Oceanía, lo que explicaría algunas de sus características genéticas. Los denisovanos habrían habitado amplias regiones del sureste asiático y su mez
UiPath Test Automation using UiPath Test Suite series, part 5DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 5. In this session, we will cover CI/CD with devops.
Topics covered:
CI/CD with in UiPath
End-to-end overview of CI/CD pipeline with Azure devops
Speaker:
Lyndsey Byblow, Test Suite Sales Engineer @ UiPath, Inc.
Enchancing adoption of Open Source Libraries. A case study on Albumentations.AIVladimir Iglovikov, Ph.D.
Presented by Vladimir Iglovikov:
- https://www.linkedin.com/in/iglovikov/
- https://x.com/viglovikov
- https://www.instagram.com/ternaus/
This presentation delves into the journey of Albumentations.ai, a highly successful open-source library for data augmentation.
Created out of a necessity for superior performance in Kaggle competitions, Albumentations has grown to become a widely used tool among data scientists and machine learning practitioners.
This case study covers various aspects, including:
People: The contributors and community that have supported Albumentations.
Metrics: The success indicators such as downloads, daily active users, GitHub stars, and financial contributions.
Challenges: The hurdles in monetizing open-source projects and measuring user engagement.
Development Practices: Best practices for creating, maintaining, and scaling open-source libraries, including code hygiene, CI/CD, and fast iteration.
Community Building: Strategies for making adoption easy, iterating quickly, and fostering a vibrant, engaged community.
Marketing: Both online and offline marketing tactics, focusing on real, impactful interactions and collaborations.
Mental Health: Maintaining balance and not feeling pressured by user demands.
Key insights include the importance of automation, making the adoption process seamless, and leveraging offline interactions for marketing. The presentation also emphasizes the need for continuous small improvements and building a friendly, inclusive community that contributes to the project's growth.
Vladimir Iglovikov brings his extensive experience as a Kaggle Grandmaster, ex-Staff ML Engineer at Lyft, sharing valuable lessons and practical advice for anyone looking to enhance the adoption of their open-source projects.
Explore more about Albumentations and join the community at:
GitHub: https://github.com/albumentations-team/albumentations
Website: https://albumentations.ai/
LinkedIn: https://www.linkedin.com/company/100504475
Twitter: https://x.com/albumentations
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
GridMate - End to end testing is a critical piece to ensure quality and avoid...ThomasParaiso2
End to end testing is a critical piece to ensure quality and avoid regressions. In this session, we share our journey building an E2E testing pipeline for GridMate components (LWC and Aura) using Cypress, JSForce, FakerJS…
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024Neo4j
Neha Bajwa, Vice President of Product Marketing, Neo4j
Join us as we explore breakthrough innovations enabled by interconnected data and AI. Discover firsthand how organizations use relationships in data to uncover contextual insights and solve our most pressing challenges – from optimizing supply chains, detecting fraud, and improving customer experiences to accelerating drug discoveries.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
Communications Mining Series - Zero to Hero - Session 1DianaGray10
This session provides introduction to UiPath Communication Mining, importance and platform overview. You will acquire a good understand of the phases in Communication Mining as we go over the platform with you. Topics covered:
• Communication Mining Overview
• Why is it important?
• How can it help today’s business and the benefits
• Phases in Communication Mining
• Demo on Platform overview
• Q/A
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
How to Get CNIC Information System with Paksim Ga.pptxdanishmna97
Pakdata Cf is a groundbreaking system designed to streamline and facilitate access to CNIC information. This innovative platform leverages advanced technology to provide users with efficient and secure access to their CNIC details.
zkStudyClub - Reef: Fast Succinct Non-Interactive Zero-Knowledge Regex ProofsAlex Pruden
This paper presents Reef, a system for generating publicly verifiable succinct non-interactive zero-knowledge proofs that a committed document matches or does not match a regular expression. We describe applications such as proving the strength of passwords, the provenance of email despite redactions, the validity of oblivious DNS queries, and the existence of mutations in DNA. Reef supports the Perl Compatible Regular Expression syntax, including wildcards, alternation, ranges, capture groups, Kleene star, negations, and lookarounds. Reef introduces a new type of automata, Skipping Alternating Finite Automata (SAFA), that skips irrelevant parts of a document when producing proofs without undermining soundness, and instantiates SAFA with a lookup argument. Our experimental evaluation confirms that Reef can generate proofs for documents with 32M characters; the proofs are small and cheap to verify (under a second).
Paper: https://eprint.iacr.org/2023/1886
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
Maruthi Prithivirajan, Head of ASEAN & IN Solution Architecture, Neo4j
Get an inside look at the latest Neo4j innovations that enable relationship-driven intelligence at scale. Learn more about the newest cloud integrations and product enhancements that make Neo4j an essential choice for developers building apps with interconnected data and generative AI.
2. levels of total dissolved solids (TDS) in these aquifers could be
attributed to evaporite and gypsum beds and potentially to
legacy oil and gas activities.
Here, we evaluate water quality in 100 private drinking water
wells from the Trinity and Woodbine aquifers overlying the
Barnett Shale formation and the Nacatoch aquifer east of the
Barnett Shale formation (Figure 1). Samples were collected
from areas within the Barnett Shale region both with and
without active natural gas extraction, and from areas outside the
Barnett Shale region unaffected by natural gas extraction.
Analytical tests were conducted to detect volatile and
semivolatile compounds identified as contaminants of concern
in a congressional report on hydraulic fracturing fluid
components,13
and to detect arsenic, barium, selenium, and
strontium. These constituents are often included on lists of
natural gas extraction waste components.7,13,14
These data were
compared to a historical data set from the same aquifers prior
to the expansion of natural gas extraction activities.11
This study
provides information about the potential impact of natural gas
extraction activities on groundwater quality in aquifers
overlying the Barnett Shale formation by (1) determining if
constituents thought to be associated with natural gas
extraction techniques are present in private well water samples;
(2) evaluating the relationship between water quality and
geographic proximity to natural gas extraction activities; and
(3) discussing scenarios to explain elevated constituent
concentrations.
2. MATERIALS AND METHODS
2.1. Sampling. A total of 95 water samples were collected
from private drinking water wells that draw from the Trinity
and Woodbine aquifers. Five reference wells were sampled
from the Nacatoch aquifer (Figure 1). We sampled from areas
of active natural gas extraction within the Barnett Shale (private
wells with one or more gas wells located within a 5 km radius; n
= 91), nonactive natural gas extraction areas within the Barnett
Shale (private wells with no gas wells located within a 14 km
radius; n = 4), and reference sites outside of the Barnett Shale
(private wells with no gas wells located within a 60 km radius; n
= 5).
Private well samples were obtained from a pool of volunteers
who responded to a press release calling for study volunteers
from 13 counties located in or near the Barnett Shale region
(Bosque, Denton, Hamilton, Hood, Hunt, Jack, Johnson,
Kaufman, Palo Pinto, Parker, Somervell, Tarrant, and Wise
counties; Figure 1). Reference samples from the Nacatoch
aquifer were obtained by traveling door-to-door to find
volunteers willing to participate, since well owners from this
region are not impacted by natural gas extraction and did not
respond to our call for volunteers. Sampled water wells drew
from the Trinity aquifer (n = 76), the Woodbine aquifer (n =
15), the Nacatoch aquifer (n = 5), and the Palo Pinto and
Mineral Wells formations (n = 4) at depths ranging from 9 to
427 m with an average of 105 m. Water wells were
overwhelmingly used for drinking water in rural areas without
public drinking water systems (n = 82). The remaining wells
were used to irrigate private lawns or provide drinking water for
livestock (n = 18). To avoid contamination from pesticides, we
did not sample water wells that were used for irrigating large
agricultural crops.
Water wells were purged for a minimum of 20 min, until
measurements of pH, dissolved oxygen (DO), and temperature
stabilized, indicating fresh well water was flowing. All samples
were collected as close to the outdoor wellhead as possible,
bypassing filters or treatment systems. To ensure samples were
representative of shallow groundwater quality, wells that could
not be purged, could only be accessed through taps, or that
could not be sampled before treatment or filtration were
excluded. Water quality data collected on site included DO, pH,
specific conductance, conductivity, temperature, salinity, TDS,
Figure 1. Location of private water well samples and natural gas wells in the Barnett Shale Formation of Texas. Private water wells are classified as
coming from areas of active natural gas extraction if there are one or more natural gas wells located within a 5 km radius from the water well.
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3. turbidity, and oxidation−reduction potential (ORP). Four
duplicate water samples were collected in 40 mL glass vials
without headspace and held at 4 °C during transport to The
University of Texas at Arlington for chemical analyses. Because
the objective of this study was to assess potential exposure risks
of drinking water from wells in this region, we chose not to use
filtration and acidification techniques. This allowed us to obtain
samples representing the quality of water our participants
would consume, as well as increased versatility in the number of
constituents that could be probed by analytical techniques. We
acknowledge that foregoing filtration and acidification can
introduce a negative bias into metals analysis; however, this
would result in a conservative underestimation of concen-
trations.15
Furthermore, the MCL values for drinking water are
based on unfiltered samples that have not been acidified.15
2.2. Analysis. Chemical analyses were conducted using gas
chromatography−mass spectrometry (GC-MS), headspace-gas
chromatography (HS-GC), and inductively coupled plasma-
mass spectrometry (ICP-MS). See the Supporting Information
(SI) Table S1 for a list of compounds screened. Arsenic,
selenium, strontium, barium, methanol, ethanol, TDS, and
volatile organic compounds (VOCs) such as benzene, toluene,
ethylbenzene, and xylenes (collectively referred to as BTEX)
were the primary targets of chemical analyses. Historical data
for the concentrations of target compounds (except alcohols)
in private water well samples from this region were obtained to
evaluate their occurrence before the expansion of natural gas
extraction activities.11
This historical data set is comprised of
330 private drinking water wells from the Trinity, Woodbine,
and Nacatoch aquifers sampled over a ten year period (1989−
1999) before natural gas activities began. Wells were located in
the same counties that we sampled in this study (SI Figure S1).
All wells were used for water withdrawal and ranged in depth
from 14 to 1090 m with an average depth of 207 m. For more
detailed description of methods and analyses, see the SI
Methods.
3. RESULTS AND DISCUSSION
3.1. Water Quality. The data set detailing well depth,
distance to the nearest natural gas well, concentration of
constituents, and the suite of general water quality parameters
of each private well sample is provided in the Supporting
Information (SI). We found no evidence of BTEX compounds
using both LC-UV-MS and GCMS. Levels of TDS in active
extraction areas averaged 585 mg/L and ranged 200−1900 mg/
L, while TDS in nonactive/reference areas averaged 500 mg/L
and ranged 400−600 mg/L. Exceedances for the Environ-
mental Protection Agency’s (EPA) TDS Drinking Water
Maximum Contaminant Limit (MCL) of 500 mg/L were
detected in 50 of 91 samples from active extraction areas and 7
of 9 samples from the nonactive/reference areas (Table 1). The
maximum TDS values detected in the active extraction area
were over three times higher than the maximum value from the
nonactive/reference areas. These aquifers naturally show
somewhat elevated levels of TDS, so these concentrations are
not unusual for the area,12
and the mean TDS concentration in
active extraction areas is similar to levels seen in historical data
for this region (585 mg/L versus 670 mg/L).
3.2. Levels of Heavy Metals in Private Well Water.
Arsenic, selenium, strontium, and barium are known to occur
naturally at low levels in aquifers overlying the Barnett Shale
formation.12,16
Chemical analysis using ICP-MS (see the SI
Methods) detected arsenic in 90 of 91 samples from active
Table1.ConcentrationsofConstituentsinBarnettShalePrivateWaterWellSamplesa
historicaldata(1989−99)activeextractionareawells(N=91)nonactiveandreferenceareawells(N=9)
Nrangemean±stderror%≥MCLNrangemean±stderror%≥MCLNrangemean±stderror%≥MCL
TDS344129−3302670.3±21.56191200−1900585.1±35.1*54.99400−600500±31.677.8
arsenic2411−102.8±0.10902.2−161.212.6±2.2*32.294.7−9.06.9±0.7*0
selenium3290.1−503.9±0.20.31010−108.733.3±10.5*20
strontium9920−167001028.9±213.7N/Ab
9066.2−181952319.8±330.1*N/A952.4−7646.21610±787.1N/A
barium3570.1−38257.2±2.90901.8−173.732.3±3.3*092.9−6022.4±11.3*0
methanolN/A241.3−32933.6±13.3N/A51.2−62.927.4±13.7N/A
ethanolN/A81−10.64.5±1.2N/A42.3−11.36.8±2.4N/A
a
Allvaluesaremeasuredinμg/Lexcepttotaldissolvedsolids(TDS),methanol,andethanolinmg/L.Valuesdenotedbyasterisksrepresentstatisticallysignificantdifferencesfromhistoricaldatavalues
(Mann-WhitneyUpairwiseanalysis;p<0.05).Historicaldataforthecountiessampledinthisstudywereobtainedonlineatwww.TWDB.state.TX.us/groundwater/.MaximumContaminantLimits
(MCL)obtainedfromtheEnvironmentalProtectionAgency’s(EPA)NationalPrimaryDrinkingWaterRegulations,2009.TDSMCL=500mg/L,arsenicMCL=10μg/L,seleniumMCL=50μg/L,
bariumMCL=2000μg/L,N/AindicatesnoMCLhasbeenestablished.b
EPArecommendsstablestrontiumvaluesindrinkingwaterdonotexceed4000μg/L.
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4. extraction areas and 9 of 9 samples from nonactive/reference
areas. Concentrations were significantly higher in active
extraction areas compared to reference samples and historical
samples (Table 1). Arsenic concentrations in active extraction
areas ranged from 2.2 to 161.2 μg/L, with an average of 12.6
μg/L. The maximum concentration of arsenic detected in a
sample from an active extraction area was almost 18 times
higher than both the maximum concentration among the
nonactive/reference area samples and historical levels from this
region. Notably, 29 of 90 water wells in active extraction areas
exceeded EPA’s arsenic MCL for drinking water of 10 μg/L.17
Arsenic in this region is derived from Oligocene−Miocene
volcanic ash and is adsorbed onto metal oxides and clays.18
Common forms of arsenic in groundwater are As(V) and
As(III), also known as arsenate and arsenite, respectively.19
Arsenite, a reduced form of arsenate, is more mobile and toxic
than arsenate.18,20,21
Sorption of arsenate is strongest at near-
neutral pH, with adsorption rapidly weakening above pH
∼8.5;22
the pH values in our groundwater samples averaged 7.9,
with values as high as 9.3. Although we cannot identify the
biogeochemical processes that lead to higher pH values and
subsequent arsenite mobilization, small perturbations such as
lowering of the water table either through groundwater
withdrawals or drought conditions could explain these results.18
Elevated arsenic concentrations can also occur in agricultural
areas where pesticide application leads to arsenic introduc-
tion,12
or in areas with cultivated cotton as arsenic was used as a
defoliant.23
Reedy et al.24
showed that applied arsenic is limited
to shallow surface soils due to strong interactions between
arsenic and iron oxides and clays in soil. Given the low mobility
of applied arsenic and the fact that none of our samples were
collected from private wells in or adjacent to crop fields, we find
agricultural arsenic introduction is unlikely to be the source of
elevated arsenic concentrations. Moreover, if agriculture were
the cause of elevated arsenic levels, then concentrations in the
historical data would likely have been high as well, and we
found no evidence of this.
Selenium was less prevalent in the water samples, detected in
10 samples exclusively from active extraction areas. Selenium
concentrations averaged 33 μg/L and ranged 10−109 μg/L, a
stark contrast to the historical levels, which averaged 4 μg/L
and ranged 0−50 μg/L. Two samples exceeded the selenium
MCL of 50 μg/L,17
and concentrations in active extraction
areas were significantly higher than historical levels although
our sample size is too small to make definitive conclusions
(Table 1).
Strontium was detected in 90 of 91 samples from active
extraction areas as well as 9 of 9 samples from the nonactive/
reference areas. Strontium concentrations in active extraction
areas ranged 66−18 195 μg/L and were significantly higher
than historical levels (Table 1). There is no established MCL
for the stable strontium species analyzed in this study; however,
Figure 2. (A) Total dissolved solids, (B) arsenic concentration, (C) selenium concentration, and (D) strontium concentration versus distance to the
nearest natural gas well in Barnett Shale private water well samples. The dashed lines in A−C represent the Environmental Protection Agency’s
Drinking Water Maximum Contaminant Limit (MCL) for each constituent. Note that the horizontal axis for C is a different scale.
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5. an Agency for Toxic Substances and Disease Registry
toxicological profile reports that the EPA currently recom-
mends no more than 4000 μg/L in drinking water.28
Seventeen
samples from the active extraction area and one sample from
the nonactive/reference areas exceeded this recommended
limit.
Barium was also found in 90 of 91 samples from active
extraction areas and 9 of 9 samples from nonactive/reference
areas. None of the barium samples exceeded the MCL value of
2000 μg/L;17
however, the maximum value was much higher in
the active extraction area compared to the nonactive/reference
areas (174 μg/L and 60 μg/L, respectively). Additionally, the
concentrations of arsenic and selenium as well as the
concentrations of strontium and barium were positively
correlated with one another (SI Table S2).
These constituent concentrations could be due to mecha-
nisms other than contamination of aquifers with fluids used in
natural gas extraction. For example, lowering of the water table
can lead to changes in pH that cause desorption of arsenic and
selenium from iron oxide complexes or mobilization of arsenic
through pyrite oxidation.22
The regional water table has slowly
risen in recent years as the population has shifted from
groundwater to surface water for drinking water (see SI Table
S3).29
Recent drought conditions have also not had a severe
impact on the water table, as levels in the Trinity and
Woodbine aquifers are influenced more by the amount of
groundwater withdrawal than the lack of recharge from
decreased rainfall.30
While the regional water table has not
decreased dramatically in the last 10 years, rural areas with high
water withdrawal rates and/or withdrawal of large amounts of
groundwater for use in hydraulic fracturing could lead to
localized lowering of the water table. Bene et al.30
project that
industrial use of groundwater for hydraulic fracturing will rise
from 3% of total groundwater use in 2005 to 7% in 2025, which
suggests that current and future industrial water use could cause
localized water table reductions. Additionally, pyrite is not
found at high levels in these aquifers,31
so it is an unlikely
source of arsenic.
Another potential mechanism is detailed in a report7
suggesting that mechanical disturbances, such as pressure
waves from drilling activity, could loosen iron oxide particles
from the casings of private water wells, leading to increased
turbidity of well water. Arsenic and selenium could be
mobilized into groundwater if iron oxide complexes are
agitated. Strontium and barium form sulfate or carbonate
scales on the interior casings of poorly maintained water wells
Figure 3. Barnett Shale private water well depth versus (A) arsenic concentration (Spearman correlation coefficient = −0.28; p < 0.05; r2
= 0.023),
(B) barium concentration (Spearman correlation coefficient = −0.359; p < 0.05; r2
= 0.075), (C) selenium concentration (Spearman correlation
coefficient =0.142; p = 0.715; r2
= 0.057), and (D) strontium concentration (Spearman correlation coefficient = −0.35; p < 0.05; r2
= 0.05). Note
that trend line is not shown for C due to small sample size.
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6. and mechanical disturbance could also lead to mobilization of
these constituents. While arsenic, selenium, strontium, and
barium are present at low levels in many private water
wells,9,24,25
the levels seen in this study warrant further
investigation, as arsenic in groundwater is a health concern.26,27
3.3. Constituents and Distance to Nearest Gas Well.
Arsenic, selenium, strontium, barium, and TDS reached their
highest concentrations in areas of active extraction in close
proximity to natural gas wells (Figure 2 and SI Figure S2).
Samples that exceeded the MCL for TDS, arsenic, and
selenium were located an average of 1.1 km from the nearest
natural gas well. Similarly, the highest values for both strontium
and barium were over twice as high in areas less than 2 km from
the nearest natural gas well compared to more distant gas wells.
The geographic patterns in our data suggest that lowering of
the water table during a drought period cannot fully explain
these elevated constituent levels. Concentrations that exceed
the MCL occur only in close proximity to natural gas wells
(Figure 2) suggesting that mechanical disturbances or localized
groundwater withdrawals near natural gas wells could play a
role in elevated constituent concentrations. If regional drought
or widespread public water withdrawals were the cause of
elevated constituent levels, then the geographic localities of
MCL exceedances would be more evenly distributed
throughout the study area, rather than in close proximity to
natural gas wells. Additionally, regional lowering of the water
table should have resulted in similar constituent concentrations
in these aquifers during historical periods when groundwater
withdrawal rates were even higher than present levels.
3.4. Constituents and Private Water Well Depth.
Arsenic, strontium, and barium all showed significant negative
correlations with the depth of private water wells (SI Table S2).
This could be due to contact with surface sources as the highest
concentrations of arsenic and other compounds occur at the
shallowest depths of private water wells (Figure 3). Previous
studies also found negative correlations with depth in studies of
arsenic and other compounds in the Gulf Coast aquifer of
Texas32
and the Paluxy aquifer,33
which is part of the larger
Trinity aquifer. Glenn and Lester32
attributed their elevated
constituent concentrations to a geologic origin, and we cannot
rule out that scenario with these data. It is also possible that
improper handling of waste materials and faulty gas well casings
could result in the introduction of these compounds into
shallow groundwater.34
Healy et al.35
demonstrated that fluid−
matrix interactions in unlined wastewater tanks cause
mobilization of naturally occurring salts and other constituents
into groundwater, and Vidic et al.8
indicate that faulty casing
seals in natural gas wells can cause groundwater contamination,
although these casing failures occur infrequently (1−3%
incidence rate in Marcellus Shale operations).
3.5. Heavy Metals and Total Dissolved Solids. Selenium
was not correlated with TDS (likely due to small sample size),
while strontium and barium showed significant negative
correlations with TDS (SI Table S2). Arsenic showed a
significant positive correlation with TDS (SI Figure S3 and SI
Table S2), suggesting that it may be concurrently mobilized
into groundwater with TDS during the natural gas extraction
process. Again, mechanical disturbances (high pressure fluid
injection, mechanical vibration, etc.) associated with natural gas
extraction activities could be the cause of elevated levels of TDS
and arsenic. Scanlon et al.23
also found a positive correlation
between arsenic and TDS levels from the High Plains aquifer in
a semiarid region of western Texas. They attributed this
correlation to a counterion effect from an influx of saline water
from the underlying Dockum aquifer that triggered a shift from
calcium-rich to sodium-rich water, mobilizing arsenic from
chemical complexes. Because arsenic levels in this region have
historically been low (<10 μg/L) and TDS levels have not
changed appreciably compared to historical levels, it seems
unlikely that this scenario could explain the correlation between
arsenic and TDS seen in this study.12
Additionally, the clay and
nonkarstic carbonate layers separating the Woodbine and
Trinity aquifers would not seem to allow a large influx of deep
saline water to trigger a similar change in hydrogeochemistry.
3.6. Comparison to Historical Data. Concentrations of
arsenic, strontium, and selenium were significantly higher in
samples from active extraction areas compared to historical data
(Table 1). Nonactive/reference area samples also showed a
significant increase in arsenic compared to historical data
(Table 1). Both active extraction and nonactive/reference areas
showed a significant decrease in barium concentrations from
historical levels (Table 1). Historical TDS concentrations were
not significantly different from nonactive/reference area
concentrations but were significantly higher than active
extraction area samples (Table 1). On average, wells from the
historical data set were 102 m deeper than our wells, and this
could explain the difference in some constituents. While we
cannot draw definitive conclusions due to the fact that the
historical data was collected under different sampling
conditions, these data do provide a baseline for comparison
to preindustrial conditions, which is generally lacking in studies
of this nature.8
3.7. Methanol and Ethanol in Private Well Water. SI
Table S1 lists 29 compounds selected for GCMS analysis based
on their inclusion in hydraulic fracturing fluid mixtures.13
Only
methanol and ethanol, often included as anticorrosive agents in
natural gas extraction, were detected in this study. Methanol
and ethanol concentrations were quantified using HS-GC with
flame ionization detection (see the SI Methods). Twenty-nine
private water wells contained detectable amounts of methanol
ranging 1−329 mg/L, with the highest concentrations from
active extraction areas (Table 1). All six samples from Wise
County contained methanol concentrations ranging 7−54 mg/
L, with an average concentration of 28 mg/L. These water wells
are located between 215 and 610 m from the nearest natural
gas wells and could represent concurrent contamination of
multiple private wells, although we cannot identify the
contamination source using these data. Ethanol was detected
in 12 samples, ranging in concentration from 1 to 11 mg/L.
Four out of nine samples from nonactive/reference areas
contained both methanol and ethanol, suggesting that these
chemicals are already present in groundwater in these areas and
could have been introduced through something other than
natural gas extraction. Methanol is known to occur naturally in
groundwater as a byproduct of microbial metabolism,5,36
but it
could also be introduced through contact with industrial
wastewater. Similarly, ethanol can occur naturally or be
introduced to groundwater through contact with industrial
fuels.37
Naturally occurring ethanol is ephemeral and restricted
to deep, anoxic environments different from shallow ground-
water.38
Methanol and ethanol concentrations were not
correlated with distance to the nearest gas well.
The historical data did not include methanol and ethanol, so
we cannot examine the historical occurrence of these
constituents. The samples containing alcohol were collected
and analyzed during multiple sampling and analysis events over
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7. the entire study, ruling out laboratory contamination as the
source. The occurrence of alcohols in our samples is relatively
low, but it does warrant further research, as these compounds
should have a very short lifespan in the environment and likely
require an active source to sustain high concentrations.
Our results show elevated concentrations of constituents in
the Barnett Shale region; however, we are unable to determine
the ultimate source of these elevated concentrations directly.
Previous studies in the Marcellus Shale used geochemical and
isotopic tracers to provide a direct link to the source of
industrial or geological contamination (e.g., nonthermogenic
methane and deep brine mixing with shallow groundwater5,6
).
Analyses to identify the origin of elevated constituent
concentrations are beyond the scope of this study, which was
intended simply to examine water quality in areas of natural gas
extraction. In lieu of these analyses, we chose to evaluate the
geographic occurrence and absolute concentration changes for
these constituents over time by comparing this study’s data
against previous characterizations of groundwater in this region
from the scientific literature and a large historical data set from
the same region. This comparison shows a significant increase
in the mean concentration, maximum detected concentration,
and MCL exceedances for As, Se, and Sr in our study area when
compared to historical data and previous characterizations of
these aquifers (Table 1).12,31
While our data indicate elevated levels of potentially harmful
compounds in private water wells located near natural gas wells,
it is important to recognize that there were also a number of
private water wells in close proximity to natural gas wells that
showed no elevated constituents. This indicates that natural gas
extraction activities do not result in systematic contamination
of groundwater. We suggest that episodic contamination of
private water wells could be due to a variety of natural and
anthropogenic factors such as the mobilization of naturally
occurring constituents into private wells through mechanical
disturbances caused by intense drilling activity, reduction of the
water table from drought or groundwater withdrawals, and
faulty drilling equipment and well casings. The geographic
locations of elevated constituent levels in our study are
consistent with the notion that mechanical disturbance of
private water wells and industrial accidents (e.g., equipment
failure, faulty well casings, fluid spills, etc.) are more frequent in
areas where natural gas extraction is active.
To draw definitive conclusions about the origin of elevated
constituent levels in these water wells would require a focused
study of groundwater before, during, and after natural gas
extraction activities. This was logistically impossible as
industrial activities have been ongoing for more than 10 years
in this area. Given this limitation, our discussion of the source
of elevated constituents is speculative, but we have provided
plausible scenarios to explain our data in an effort to increase
scientific understanding of this topic and spur future research.
At a minimum, these data suggest that private wells located
near natural gas wells may be at higher risk for elevated levels of
constituents than those located further from natural gas wells.
We advocate regular water monitoring utilizing targeted
analytical chemistry along with toxicity assays to understand
the complex interactions among groundwater constituents and
biological organisms.39
Future research will focus on monitor-
ing private wells in the Cline Shale in the Permian Basin region
of Texas before, during, and after natural gas extraction
activities, understanding the role of mechanical disturbances, in
mobilizing naturally occurring constituents into groundwater,
and evaluating the effects of industrial accidents and waste
disposal practices. Water quality in the Barnett Shale region is
likely to become an even more contentious issue as public
concerns and prolonged drought conditions place pressure on
water reserves in the region.
■ ASSOCIATED CONTENT
*S Supporting Information
Additional materials and methods, figures, tables, and the
complete water quality data set referenced in the text. This
information is available free of charge via the Internet at http://
pubs.acs.org.
■ AUTHOR INFORMATION
Corresponding Author
*Phone: 817-272-3541. E-mail: kschug@uta.edu.
Present Address
∥
Water Quality Protection Division, United States Environ-
mental Protection Agency, Dallas, Texas 75202
Author Contributions
⊥
These authors contributed equally to this work. Additionally,
B.E.F., L.R.H., Z.L.H., D.D.C., B.B., and K.A.S. designed the
research; B.E.F., L.R.H., Z.L.H., D.D.C., H.O., J.L.W., D.H., and
A.O. performed the research; B.B., D.H., A.O., and K.A.S.
contributed reagents, analytical machines, and field sampling
equipment; B.E.F., Z.L.H., D.D.C., A.O., and J.L.W. analyzed
data; and B.E.F., Z.L.H., D.D.C., L.R.H., and Q.H.H. wrote the
paper.
Notes
Disclaimer. This work is not a product of the United States
Government or the United States Environmental Protection
Agency, and the authors did not do this work in any
governmental capacity. The views expressed are those of the
authors only and do not necessarily represent those of the
United States or the United States Environmental Protection
Agency.
The authors declare no competing financial interest.
■ ACKNOWLEDGMENTS
We thank M. Overbay and P. Crocker for providing valuable
comments on an earlier version of this manuscript. Funds used
to support this study were from an unrestricted and unrelated
award to the corresponding author from Eli Lilly and
Company. We wish to thank Guido Verbeck IV at The
University of North Texas for assistance with ICP-MS metals
analysis and The Shimadzu Center for Advanced Analytical
Chemistry at The University of Texas at Arlington for use of
GC instrumentation. Most importantly, we would like to thank
the participating well owners for their invaluable contribution
to this research. Q.H.H. is currently supported by the
Department of Energy’s Research Partnership to Secure Energy
for America to study the fracture-matrix interaction in gas
recovery from the Barnett Shale.
■ REFERENCES
(1) Nicot, J. P.; Scanlon, B. R. Water use for Shale-gas production in
Texas, U.S. Environ. Sci. Technol. 2007, 46 (6), 3580−3586.
(2) Kerr, R. A. Natural gas from shale bursts onto the scene. Science
2010, 328 (5986), 1624−1626.
(3) Simon, J. A.; Fleming, M. E. Editor′s perspectiveShale gas
development: Environmental issues and opportunities. Remediation
2011, 21 (4), 1−10.
Environmental Science & Technology Article
dx.doi.org/10.1021/es4011724 | Environ. Sci. Technol. XXXX, XXX, XXX−XXXG
8. (4) Otton, J. K. Environmental Aspects of Produced-water Salt Releases
in Onshore and Coastal Petroleum-producing Areas of the Conterminous
U.S.A Bibliography; Open-File Report 2006-1154; United States
Geological Survey, United States Department of the Interior: Reston,
VA, 2006; http://pubs.usgs.gov/of/2006/1154/pdf/of06-1154_508.
pdf.
(5) Osborn, S. G.; Vengosh, A.; Warner, N. R.; Jackson, R. B.
Methane contamination of drinking water accompanying gas-well
drilling and hydraulic fracturing. Proc. Natl. Acad. Sci. 2011, 108 (20),
8172−8176.
(6) Warner, N. R.; Jackson, R. B.; Darrah, T. H.; Osborn, S. G.;
Down, A.; Zhao, K.; White, A.; Vengosh, A. Geochemical evidence for
possible natural migration of Marcellus Formation brine to shallow
aquifers in Pennsylvania. Proc. Natl. Acad. Sci. 2012, 109 (30), 11961−
11966.
(7) Groat, C. G.; Grimshaw, T. W. Fact-Based Regulation for
Environmental Protection in Shale Gas Development; Energy Institute at
The University of Texas at Austin: Austin, TX, 2006; http://cewc.
colostate.edu/wp-content/uploads/2012/02/ei_shale_gas_
regulation120215.pdf.
(8) Vidic, R. D.; Brantley, S. L.; Vandenbossche, J. M.; Yoxtheimer,
D.; Abad, J. D. Impact of shale gas development on regional water
quality. Science 2013, 340 (6134), DOI: 10.1126/science.1235009.
(9) Welch, A. H.; Westjohn, D. B.; Helsel, D. R.; Wanty, R. B.
Arsenic in ground water of the United States: Occurrence and
geochemistry. Ground Water 2000, 38 (4), 589−604.
(10) Squillace, P. J.; Scott, J. C.; Moran, M. J.; Nolan, B. T.; Kolpin,
D. W. VOCs, pesticides, nitrate, and their mixtures in groundwater
used for drinking water in the United States. Environ. Sci. Technol.
2002, 36 (9), 1923−1930.
(11) Texas Water Development Board Groundwater Database
Website; http://www.twdb.state.tx.us/groundwater/data/gwdbrpt.asp
(accessed January 15, 2012).
(12) Reedy, R. C.; Scanlon, B. R.; Walden, S.; Strassberg, G.
Naturally Occurring Groundwater Contamination in Texas; Final Report
1004831125; Texas Water Development Board: Austin, TX, 2011;
http://www.twdb.state.tx.us/publications/reports/contracted_
reports/doc/1004831125.pdf
(13) Chemicals Used in Hydraulic Fracturing; United States House of
Representatives Committee on Energy and Commerce: Washington
DC, 2011; http://democrats.energycommerce.house.gov/sites/
default/files/documents/Hydraulic-Fracturing-Chemicals-2011-4-18.
pdf.
(14) Guerra, K.; Dahm, K.; Dundorf, S. Oil and Gas Produced Water
Management and Beneficial Use in the Western United States; Science
and Technology Program Report No. 157; Bureau of Reclamation,
Department of the Interior: Washington DC, 2011; http://www.usbr.
gov/research/AWT/reportpdfs/report157.pdf.
(15) Nielson, D. M.; Nielson, G. L. Groundwater Sampling. In
Practical Handbook of Environmental Site Characterization and Ground-
Water Monitoring, 2nd ed.; Nielson, D. M., Ed.; CRC Press: Boca
Raton, FL, 2006.
(16) Bush, P. W.; Ardis, A. F.; Fahlquist, L.; Ging, P. B.; Hornig, C.
E.; Lanning-Rush, J. Water Quality in South-Central Texas, 1996−98;
US Geological Survey Circular 1212; United States Geological Survey:
Washington DC, 2000; http://pubs.water.usgs.gov/circ1212/.
(17) National Primary Drinking Water Regulations; Environmental
Protection Agency: Washington DC, 2009; http://water.epa.gov/
drink/contaminants/upload/mcl-2.pdf.
(18) Gates, J. B.; Nicot, J. P.; Scanlon, B. R.; Reedy, R. C. Arsenic
enrichment in unconfined sections of the southern Gulf Coast aquifer
system, Texas. Appl. Geochem. 2011, 26, 421−431.
(19) Cullen, W. R.; Reimer, K. J. Arsenic speciation in the
environment. Chem. Rev. 1989, 89, 713−764.
(20) Goldberg, S. Competitive adsorption of arsenate and arsenite on
oxide and clay minerals. Soil Sci. Soc. Am. J. 2002, 66, 413−421.
(21) Hu, Q. H.; Sun, G. X.; Gao, X. B.; Zhu, Y. G. Conversion,
sorption, and transport of arsenic species in geological media. Appl.
Geochem. 2012, 27, 2197−2203.
(22) Goldberg, S.; Johnson, C. T. Mechanisms of arsenic adsorption
on amorphous oxides evaluated using macroscopic measurements,
vibrational spectroscopy, and surface complexation modeling. J. Colloid
Interface Sci. 2001, 234 (1), 204−216.
(23) Scanlon, B. R.; Nicot, J. P.; Reedy, R. C.; Kurtzman, D.;
Mukherjee, A.; Nordstrom, D. K. Elevated naturally occurring arsenic
in a semiarid oxidizing system, Southern High Plains aquifer, Texas,
U.S.A. Appl. Geochem. 2009, 24, 2061−2071.
(24) Reedy, R. C.; Scanlon, B. R.; Nicot, J. P.; Tachovsky, J. A.
Unsaturated zone arsenic distribution and implications for ground-
water contamination. Environ. Sci. Technol. 2007, 41 (20), 6914−9.
(25) Scanlon, B.; Nicot, J. P.; Reedy, R. C.; Tachovsky, J. A.; Nance,
S. H.; Smyth, R. C.; Keese, K.; Ashburn, R. E.; Christian, L. Evaluation
of Arsenic Contamination in Texas; Report Prepared for Texas
Commission on Environmental Quality; Texas Commission on
Environmental Quality: Austin, TX, 2005; http://www.beg.utexas.
edu/staffinfo/pdf/Scanlon_As_r2005.pdf.
(26) Sengupta, M. K.; Mukherjee, A.; Hossain, M. A.; Ahamed, S.;
Rahman, M. M.; Lodh, D.; Chowdhury, U. K.; Biswas, B. K.; Nayak,
B.; Das, B.; Saha, K. C.; Chakraborti, D.; Mukherjee, S. C.; Chatterjee,
G.; Pati, S.; Dutta, R. N.; Quamruzzaman, Q. Groundwater arsenic
contamination in the Ganga-Padma-Meghna-Brahmaputra plain of
India and Bangladesh. Arch. Environ. Health 2003, 58 (11), 701−2.
(27) Ahamed, S.; Sengupta, M. K.; Mukherjee, S. C.; Pati, S.;
Mukherjeel, A.; Rahman, M. M.; Hossain, M. A.; Das, B.; Nayakl, B.;
Pal, A.; Zafar, A.; Kabir, S.; Banu, S. A.; Morshed, S.; Islam, T.;
Quamruzzaman, Q.; Chakraborti, D. An eight-year study report on
arsenic contamination in groundwater and health effects in Eruani
village, Bangladesh and an approach for its mitigation. J. Health Popul.
Nutr. 2006, 24 (2), 129−41.
(28) Toxicological Profile for Strontium; Agency for Toxic Substances
and Disease Registry; U.S. Department of Health and Human Services,
Public Health Service: Atlanta, GA, 2004; http://www.atsdr.cdc.gov/
toxprofiles/tp159.pdf.
(29) Bene, J.; Harden, R. W.; Henkel, B.; Kaiser, R.; Spencer, K.;
Zimmerman, J.; Burton, S.; Donnelly, A.; O’Rourke, D.; Shaw, K.;
Griffin, S.; Schuster, S. Northern Trinity/Woodbine Aquifer Groundwater
Availability Model; Texas Water Development Board: Austin, TX,
2004; http://www.twdb.state.tx.us/groundwater/models/gam/trnt_
n/TRNT_N_Model_Report.pdf.
(30) Bene, J.; Harden, R. W.; Griffin, S.;Nicot, J. P. Northern Trinity/
Woodbine GAM Assessment of Groundwater Use in the Northern Trinity
Aquifer Due to Urban Growth and Barnett Shale Development; Texas
Water Development Board: Austin, TX, 2007; http://www.twdb.state.
tx.us/groundwater/models/gam/trnt_n/TRNT_N_Barnett_Shale_
Report.pdf .
(31) George, P. G.; Mace, R. E.; Petrossian, R. Aquifers of Texas;
Texas Water Development Board: 2011; http://www.twdb.state.tx.us/
publications/reports/numbered_reports/doc/R380_AquifersofTexas.
pdf
(32) Glenn, S.; Lester, J. L. An analysis of the relationship between
land use and arsenic, vanadium, nitrate, and boron contamination the
Gulf Coast aquifer of Texas. J. Hydrol. 2010, 389 (1−2), 214−226.
(33) Fritch, T. G.; McKnight, C. L.; Yelderman, J. C., Jr.; Arnold, J.
G. Environmental Auditing: An aquifer vulnerability assessment of the
Paluxy Aquifer, central Texas, U.S.A., Using GIS and a modified
DRASTIC approach. Environ. Manage. 2000, 25 (3), 337−345.
(34) Howarth, R. W.; Ingraffea, A.; Engelder, T. Natural gas: Should
fracking stop? Nature 2011, 477 (7364), 271−5.
(35) Healy, R. W.; Bartos, T. T.; Rice, C. A.; Mckinley, M. P.; Smith,
B. D. Groundwater chemistry near an impoundment for produced
water, Powder River Basin, Wyoming, U.S.A. J. Hydrol. 2011, 403 (1−
2), 37−48.
(36) Grossman, E.; Coffman, B.; Fritz, S.; Wada, H. Bacterial
production of methane and its influence on ground-water chemistry in
east-central Texas aquifers. Geology 1989, 17, 495−499.
(37) Oremland, R.; Whiticar, M.; Strohmaier, F.; Kiene, R. Bacterial
ethane formation from reduced, ethylated sulfur compounds in anoxic
sediments. Geochim. Cosmochim. Acta 1988, 52, 1895−1904.
Environmental Science & Technology Article
dx.doi.org/10.1021/es4011724 | Environ. Sci. Technol. XXXX, XXX, XXX−XXXH
9. (38) Ulrich, G. The Fate and Transport of Ethanol-Blended Gasoline in
the Environment: A Literature Review and Transport Modeling;
Governor’s Ethanol Coalition: Lincoln, NE, 1999; http://nlcs1.nlc.
state.ne.us/epubs/E5700/B055-1999.pdf
(39) Lapota, D.; Osorio, A. R.; Liao, C.; Bjorndal, B. The use of
bioluminescent dinoflagellates as an environmental risk assessment
tool. Mar. Pollut. Bull. 2007, 54 (12), 1857−67.
Environmental Science & Technology Article
dx.doi.org/10.1021/es4011724 | Environ. Sci. Technol. XXXX, XXX, XXX−XXXI