This document summarizes a study that measured the flux of methylmercury (MMHg) across the sediment-water interface at four stations in Boston Harbor. The stations varied in infaunal population densities and bioirrigation intensities. Total MMHg fluxes, measured using sediment core incubations, ranged from -4 to 191 pmol/m2/day and were strongly correlated with burrow densities. Estimated diffusive fluxes, based on porewater MMHg gradients, were lower than total fluxes at three stations, indicating bioirrigation enhances MMHg exchange over molecular diffusion. Porewater exchange of both MMHg and radon, a porewater tracer, increased with burrow density, suggesting burrows enhance both MMHg production
Experimental Study on the Settling Velocity of
Coastal Mud in Quiescent Water: The Case of
Huangmaohai Estuary, South China Sea by Dong XU in Examines in Marine Biology and Oceanography: Open Access
9. vasiliniuc i. hydrophysical indicators of the soils in horoiata basinVasiliniuc Ionut
The document analyzes hydrophysical indicators of soils in the Horoiata basin in Romania. It finds that Chernisols and Luvisols dominate the soil cover, making up over 70% of the area. It computes hydrophysical indices like hygroscopicity coefficient, wilting point, field capacity, available water capacity, and draining capacity for soils using pedotransfer functions. It finds the highest values for indicators like hygroscopicity coefficient and wilting point in soils with high clay content, and the lowest values in sandy soils. Field capacity and available water capacity values are generally high across the basin.
This document describes a study comparing the partitioning of 137Cs between solid and liquid phases in three prealpine lakes: Lake Constance in Germany, Lake Lugano in Switzerland, and Lake Vorsee in Germany. The researchers applied a methodology using the exchangeable distribution coefficient and exchangeable radiocaesium interception potential (RIPex) to estimate 137Cs distribution between sediments and water in the lakes. Good agreement was found between estimated and measured 137Cs concentrations in Lake Constance and Lake Lugano, but a discrepancy was found for Lake Vorsee, likely due to its bottom sediments consisting mainly of organic material.
151111 Abstract - DB Sediments - 6th Arab-German Energy ForumDietrich Bartelt
This document discusses sustainable water storage and sediment management in reservoirs. It notes that sedimentation reduces global water storage capacity by around 1% each year, costing billions to address. The ConSedTrans process aims to restore natural sediment transport continuity while maintaining reservoir capacity. It involves continuously transferring sediments from areas of deposition within reservoirs to areas where flows allow natural downstream transfer, using automated vessels. This avoids problems from blocking sediment transport while meeting EU directives on achieving good water status. It is a cost-effective, scalable, and sustainable approach to managing sediments in reservoirs and rivers.
This document summarizes a study that evaluated the relationship between natural methane occurrence in groundwater and three principal environmental factors - groundwater redox state, water type, and topography - using pre-drill water well sample data from Pennsylvania, Ohio, and West Virginia. The study found that higher natural methane concentrations were strongly associated with reducing groundwater conditions characterized by low nitrate and sulfate. Methane concentrations were also significantly higher in sodium-rich waters compared to calcium-rich waters. Samples exhibiting reducing conditions, sodium-rich water, and being located in valleys had a median methane concentration of 10,000 μg/L and offered strong predictive power regarding natural high methane occurrence. These relationships can help distinguish natural from anthropogenic methane sources
This summarizes the key findings from direct sampling of Subglacial Lake Whillans (SLW) beneath the West Antarctic Ice Sheet:
1. SLW supports a diverse and metabolically active microbial ecosystem, as evidenced by heterotrophic and autotrophic production rates and microbial community analysis.
2. The lake water is derived primarily from glacial ice melt with solutes from lithogenic weathering and a minor seawater component. Microbes play a role in biogeochemical transformations.
3. SLW has distinct physical and chemical properties compared to the borehole water used for access, including higher temperature, pH, conductivity, and dissolved organic carbon levels. This indicates little mixing between the bore
This paper discusses an integrated approach to characterizing water saturation in a low-resistivity carbonate reservoir in Abu Dhabi. Traditional resistivity-based analyses overestimated water saturation in this reservoir. The integrated approach combined resistivity logs, core analysis including NMR and capillary pressure tests, and production test data. It identified microporosity from thin sections and NMR as contributing to the low resistivity pay. The combination of multiple data sources reduced uncertainty and improved understanding of reservoir properties, saturation estimates, and reserves calculations compared to resistivity-based analyses alone.
This document presents a sensitivity study of low salinity water injection in the Zichebashskoe Oilfield in Russia using 24 years of production data, including 7 years where low salinity water was injected. 3D reservoir simulations showed low incremental oil recovery from low salinity water injection likely due to significant mixing between formation and injected waters which decreased the effect of low salinity, and an already high sweep efficiency from previous water injection into the water zone. The sensitivity study found that incremental recovery increased with greater relative permeability reduction from the formation water to the injected low salinity water, though recovery was still negligible even with a 20-fold decrease in water relative permeability.
Experimental Study on the Settling Velocity of
Coastal Mud in Quiescent Water: The Case of
Huangmaohai Estuary, South China Sea by Dong XU in Examines in Marine Biology and Oceanography: Open Access
9. vasiliniuc i. hydrophysical indicators of the soils in horoiata basinVasiliniuc Ionut
The document analyzes hydrophysical indicators of soils in the Horoiata basin in Romania. It finds that Chernisols and Luvisols dominate the soil cover, making up over 70% of the area. It computes hydrophysical indices like hygroscopicity coefficient, wilting point, field capacity, available water capacity, and draining capacity for soils using pedotransfer functions. It finds the highest values for indicators like hygroscopicity coefficient and wilting point in soils with high clay content, and the lowest values in sandy soils. Field capacity and available water capacity values are generally high across the basin.
This document describes a study comparing the partitioning of 137Cs between solid and liquid phases in three prealpine lakes: Lake Constance in Germany, Lake Lugano in Switzerland, and Lake Vorsee in Germany. The researchers applied a methodology using the exchangeable distribution coefficient and exchangeable radiocaesium interception potential (RIPex) to estimate 137Cs distribution between sediments and water in the lakes. Good agreement was found between estimated and measured 137Cs concentrations in Lake Constance and Lake Lugano, but a discrepancy was found for Lake Vorsee, likely due to its bottom sediments consisting mainly of organic material.
151111 Abstract - DB Sediments - 6th Arab-German Energy ForumDietrich Bartelt
This document discusses sustainable water storage and sediment management in reservoirs. It notes that sedimentation reduces global water storage capacity by around 1% each year, costing billions to address. The ConSedTrans process aims to restore natural sediment transport continuity while maintaining reservoir capacity. It involves continuously transferring sediments from areas of deposition within reservoirs to areas where flows allow natural downstream transfer, using automated vessels. This avoids problems from blocking sediment transport while meeting EU directives on achieving good water status. It is a cost-effective, scalable, and sustainable approach to managing sediments in reservoirs and rivers.
This document summarizes a study that evaluated the relationship between natural methane occurrence in groundwater and three principal environmental factors - groundwater redox state, water type, and topography - using pre-drill water well sample data from Pennsylvania, Ohio, and West Virginia. The study found that higher natural methane concentrations were strongly associated with reducing groundwater conditions characterized by low nitrate and sulfate. Methane concentrations were also significantly higher in sodium-rich waters compared to calcium-rich waters. Samples exhibiting reducing conditions, sodium-rich water, and being located in valleys had a median methane concentration of 10,000 μg/L and offered strong predictive power regarding natural high methane occurrence. These relationships can help distinguish natural from anthropogenic methane sources
This summarizes the key findings from direct sampling of Subglacial Lake Whillans (SLW) beneath the West Antarctic Ice Sheet:
1. SLW supports a diverse and metabolically active microbial ecosystem, as evidenced by heterotrophic and autotrophic production rates and microbial community analysis.
2. The lake water is derived primarily from glacial ice melt with solutes from lithogenic weathering and a minor seawater component. Microbes play a role in biogeochemical transformations.
3. SLW has distinct physical and chemical properties compared to the borehole water used for access, including higher temperature, pH, conductivity, and dissolved organic carbon levels. This indicates little mixing between the bore
This paper discusses an integrated approach to characterizing water saturation in a low-resistivity carbonate reservoir in Abu Dhabi. Traditional resistivity-based analyses overestimated water saturation in this reservoir. The integrated approach combined resistivity logs, core analysis including NMR and capillary pressure tests, and production test data. It identified microporosity from thin sections and NMR as contributing to the low resistivity pay. The combination of multiple data sources reduced uncertainty and improved understanding of reservoir properties, saturation estimates, and reserves calculations compared to resistivity-based analyses alone.
This document presents a sensitivity study of low salinity water injection in the Zichebashskoe Oilfield in Russia using 24 years of production data, including 7 years where low salinity water was injected. 3D reservoir simulations showed low incremental oil recovery from low salinity water injection likely due to significant mixing between formation and injected waters which decreased the effect of low salinity, and an already high sweep efficiency from previous water injection into the water zone. The sensitivity study found that incremental recovery increased with greater relative permeability reduction from the formation water to the injected low salinity water, though recovery was still negligible even with a 20-fold decrease in water relative permeability.
The document discusses using borehole-to-surface electromagnetic (BSEM) monitoring to track carbon dioxide sequestration in deep saline reservoirs. BSEM involves a borehole transmitter and surface receivers. It can accurately resolve fluid movement at depth compared to surface-only methods. The authors modeled BSEM over a 3D resistivity model of the Kevin Dome sequestration site. Inversion of simulated BSEM data accurately recovered the expanding CO2 plume at different radii, showing potential for EM monitoring of CO2 sequestration.
This document provides background information for a student project on saltwater intrusion detection methods. It includes:
1) An introduction that lists the student's name, number, and date of submission.
2) Overviews of various geophysical methods for detecting saltwater intrusion, including the theoretical principles and what to expect when applying each method to map the intrusion of saline water. The methods discussed are DC resistivity, ground penetrating radar, time domain electromagnetics, and audio magnetotellurics.
3) Context about the aquifers in the Perth Basin study area and details on the superficial aquifer, which is the target of the student's field work.
This document provides a basic overview of the fundamental rock properties. It delivers a detailed analysis of the basic reservoir rock properties like porosity, permeability, Fluid saturation , wettability, etc.
79307422 2-wettability-literature-survey-part-1Jonatan Sierra
This document summarizes literature on how the wettability of rock/oil/brine systems can be altered by core handling and experimental conditions. It discusses how wettability affects core analysis results and the need to restore cores to their native wetting state. The document also reviews methods for classifying wettability based on contact angle measurements and findings that many reservoirs exhibit intermediate or oil-wet properties rather than being strictly water-wet.
This study analyzed changes in thermokarst lakes near Chersky, Russia between 1965 and 2011 using historical photographs and satellite imagery. The total lake area increased by 2,801,400 square meters over this period. Specifically, the number of small lakes increased while the number of large lakes decreased. Additionally, small lakes made up a greater percentage of the total lake area in 2011 compared to 1965. This suggests climate change is contributing to the drainage of larger lakes and expansion of smaller, more numerous water bodies in the region.
This document summarizes a study of water quality and chemistry in a pond and wetland system on Railroad Branch in Vermont. Samples were taken from 7 sites, including the inlet and outlet of the pond, under various hydrologic conditions. Laboratory analysis found fluctuations in temperature, pH, dissolved oxygen, conductivity, and cation concentrations between sites. Results showed the wetland was able to regulate cation flow between the inlet and outlet. Organic constituents in the pond/wetland also appeared to influence acidity. The data provides insight into the biochemistry of the area and establishes a baseline for further study.
1) Reverse osmosis membrane technology has advanced significantly since the 1950s. Early membranes allowed separation of salt from water but had low water fluxes, making the process impractical.
2) In the 1960s, Loeb and Sourirajan developed asymmetric cellulose acetate membranes with higher water fluxes and separations, making reverse osmosis separation possible on a practical scale.
3) Since then, new thin-film composite membranes have been developed that can withstand a wider range of conditions and have improved water flux and solute separation, enabling many reverse osmosis applications including desalination, wastewater treatment, and food processing.
1) Arsenic contamination of groundwater in Southeast Asia affects tens of millions of people. The document examines the source and transport of arsenic in the Mekong Delta of Cambodia, which has experienced minimal human disturbance.
2) Field measurements show arsenic is released from near-surface river-derived sediments under anaerobic conditions and transported through the underlying aquifer over centuries to the river.
3) The rates of arsenic influx via sediment deposition and efflux via groundwater transport are comparable, indicating release from solids and transport through the aquifer are in balance.
Giant convecting mud balls of the early solar systemSérgio Sacani
Carbonaceous asteroids may have been the precursors to the terrestrial planets, yet despite their importance,
numerous attempts to model their early solar system geological history have not converged on a solution. The
assumption has been that hydrothermal alteration was occurring in rocky asteroids with material properties similar
to meteorites. However, these bodies would have accreted as a high-porosity aggregate of igneous clasts
(chondrules) and fine-grained primordial dust, with ice filling much of the pore space. Short-lived radionuclides
melted the ice, and aqueous alteration of anhydrous minerals followed. However, at the moment when the ice
melted, no geological process had acted to lithify this material. It would have been a mud, rather than a rock.
We tested the effect of removing the assumption of lithification. We find that if the body accretes unsorted chondrules,
then large-scale mud convection is capable of producing a size-sorted chondrule population (if the body
accretes an aerodynamically sorted chondrule population, then no further sorting occurs). Mud convection both
moderates internal temperature and reduces variation in temperature throughout the object. As the system is
thoroughly mixed, soluble elements are not fractionated, preserving primitive chemistry. Isotopic and redox heterogeneity
in secondary phases over short length scales is expected, as individual particles experience a range of
temperature and water-rock histories until they are brought together in their final configuration at the end of
convection. These results are consistent with observations from aqueously altered meteorites (CI and CM chondrites)
and spectra of primitive asteroids. The “mudball” model appears to be a general solution: Bodies spanning a
×1000 mass range show similar behavior.
This chapter discusses different types of flows through soils, including water, heat, electricity, and chemicals. It focuses on describing these flows, quantifying flow rates and how they change over time, and how the flows impact soil properties. Water flow is most extensively studied due to its importance for problems involving seepage, consolidation, and stability. Darcy's law describes water flow and relates flow rate to hydraulic conductivity, a soil-specific property that can vary significantly between soil types and even within a given soil deposit. The chapter reviews the physics of different flow types and coupled flows, and how flow rates relate to driving forces based on various flow laws. It also evaluates parameters that influence flow and their typical ranges of values.
DSD-INT 2019 Elbe Estuary Modelling Case Studies-StanevDeltares
Presentation by Emil Stanev (HZG Institute of Coastal Research, Germany), at the DANUBIUS Modelling Workshop, during Delft Software Days - Edition 2019. Friday, 8 November 2019, Delft.
The Boltysh crater fill sediments – a 500,000 year record of the lower DanianIain Gilmour
The document summarizes research on sediments from the Boltysh impact crater in Ukraine that preserve a 500,000 year record of the early Danian period. The continuous lacustrine sediments within the crater provide an expanded and detailed record of a negative carbon isotope excursion approximately 200,000 years above the Cretaceous-Paleogene boundary, correlating to the Dan-C2 excursion in the marine record. Changes in floral communities through the excursion reflect changing biomes from a rapidly warming climate during an early Danian hyperthermal event, followed by ecosystem recovery, analogous to other major climatic events in the geologic record. The timing of the excursion may correlate with the late stages of
This document summarizes research on radionuclide migration from the D1225 Shaft at Dounreay in the UK. Key findings include:
1) Four distinct zones of radioactive contamination have been identified, with Sr-90 dominating the bulk contamination signal. Cs-137 and Pu isotopes showed very limited mobility.
2) Contamination is associated with zones of higher permeability, especially along bedding planes with enhanced porosity from rock-water interactions.
3) Quantitative modeling shows the importance of different sorption mechanisms on various mineral substrates like clays and iron oxyhydroxides in controlling radionuclide migration.
4) Sr sorbs reversibly on clays while Cs sor
This document provides an overview of a reservoir engineering course focused on fundamental rock properties. It discusses key topics like porosity, saturation, wettability, capillary pressure, and how they are determined through laboratory core analysis. Porosity refers to the pore space available to hold fluids and is classified as absolute or effective porosity. Saturation represents the fraction of pore space occupied by a fluid. Capillary pressure describes the pressure differential between immiscible fluids based on interface curvature. Laboratory tests on core samples are used to characterize these important rock properties.
9 17 fujisawa et al -seags e journal 2013-06chakfarmer
The document discusses an experimental study that investigated the relationship between seepage force and the velocity of sand particles during sand boiling. The study used silica sand and measured the migration velocities of seepage water and sand particles by calculating discharge amounts. The results revealed that:
1) The equilibrium of forces (gravity, buoyancy, fluid-particle interaction) can be used to estimate velocities of sand particles subjected to upward seepage flow.
2) The seepage force needed for horizontal transport of sand tends to decrease as the velocity of sand particles increases.
3) Previous studies on seepage failure focused on critical hydraulic gradients or velocities, but this study provides insights into how sand transport develops during
Fluid saturations refer to the fraction of pore volume occupied by water, oil, or gas in a reservoir. The sum of all fluid saturations must equal 1. Fluid saturations can be measured directly from core analysis under reservoir conditions or indirectly from well log or capillary pressure analysis. Factors like drilling mud composition and changes in pressure/temperature can affect measured fluid saturations in cores. While core saturations may not accurately reflect reservoir saturations, they provide useful information on fluid contacts, minimum water saturations, and validation of indirect methods.
The document discusses using a geomechanical approach to obtain permeability coefficients (Cpx) from magnetic resonance sounding (MRS) data by relating Cpx to longitudinal seismic velocity (VL). Data from sites in Europe and Africa were used to develop a logarithmic relationship between Cpx and VL for confined aquifers. This approach needs further testing but shows promise as a robust method for hydrogeologists to estimate permeability when pumping tests are limited.
1. Laboratory column experiments were conducted to investigate pollutant leaching from waste rock at an abandoned mine in southwest England. Metals (Cd, Cu, Mn, Pb, Zn) and major ions were measured in leachate from the dynamic up-flow percolation tests.
2. The highest concentrations of Zn, Cu, and Cd in leachate occurred at low solid to liquid ratios. Concentrations decreased exponentially for most elements except Pb, which remained high. Batch extractions showed similar results except for some differences at high ratios.
3. Field measurements of shallow groundwater near the mine site showed Zn and Cd concentrations comparable to column experiments at high ratios. However, Pb and
SEG 2015 The solution of nongas bright-spot and nonbright-spot gas identifica...Abra(Jianli) Yang
This document discusses the challenges of identifying gas reservoirs using traditional bright spot analysis of seismic data. Specifically, it notes that bright spots can be caused by non-reservoir formations, brine zones, or low gas saturation zones rather than high gas saturation gas reservoirs. It proposes that elastic property analysis through pre-stack seismic inversion is a better solution, as high gas saturation reservoirs consistently exhibit low elastic properties like density and Poisson's ratio. The document presents multiple examples from the northern South China Sea where bright spots were found to not indicate gas, and elastic analysis correctly identified the reservoir properties. It concludes elastic prediction is an effective way to identify non-gas bright spots and non-bright spot gas reservoirs.
High-frequency monitoring of water fluxes hess-20-347-2016Meidan Winegram
Controlled drainage was introduced at an experimental field to assess its effects on water storage and nutrient transport. Monitoring before and after controlled drainage showed that it:
1) Reduced drain discharge and increased groundwater storage in the field.
2) Initially elevated drain overflow levels in early spring to maximize water storage.
3) Increased nitrogen concentrations and loads in drains, largely from one monitored drain.
4) Reduced phosphorus loads via drains due to reduced discharge, but this may be counteracted by higher groundwater levels and increased shallow groundwater and overland flow to surface water.
Settlement rates of invasive tunicates were observed over 4 weeks at different locations and depths in Pillar Point Harbor, California. Clod dissolution plates and settlement plates were used to measure flow rates and tunicate recruitment. Results showed no relationship between flow and settlement, but temperature increases, heavy algal growth, and predation on plates correlated with lower settlement. Further study of how temperature, competition, and predation impact recruitment is needed to better manage invasive tunicates.
Origin of water salinity in Annaba aquifer system, North-Eastern Algeria | JBESInnspub Net
The Annaba area hosts in its underground a water potential of great importance. In fact, it is one of the Algerian plains where groundwater is subject to over-pumping. Moreover, the expansion of farmlands and the development of the neighboring agglomerations required a massive pumping of water, thereby leading to the change in hydrodynamic regime of groundwater and to the degradation of its quality. On the basis of boreholes and physicochemical data, the three major factors responsible for the evolution of chemical quality of water observed at the aquifer were identified: (1) mineralization due to natural and anthropogenic processes (responsible for the increase in the contents of chlorides, sodium, calcium and magnesium), (2) the oxydoreduction conditions due to the passage of the water table from an unconfined aquifer or even semi-confined to a confined aquifer (responsible for the reduction of nitrates and (3) pollution of groundwater by nitrates in areas where the water table is shallow and in the absence of a protective clayey cover.
The document discusses using borehole-to-surface electromagnetic (BSEM) monitoring to track carbon dioxide sequestration in deep saline reservoirs. BSEM involves a borehole transmitter and surface receivers. It can accurately resolve fluid movement at depth compared to surface-only methods. The authors modeled BSEM over a 3D resistivity model of the Kevin Dome sequestration site. Inversion of simulated BSEM data accurately recovered the expanding CO2 plume at different radii, showing potential for EM monitoring of CO2 sequestration.
This document provides background information for a student project on saltwater intrusion detection methods. It includes:
1) An introduction that lists the student's name, number, and date of submission.
2) Overviews of various geophysical methods for detecting saltwater intrusion, including the theoretical principles and what to expect when applying each method to map the intrusion of saline water. The methods discussed are DC resistivity, ground penetrating radar, time domain electromagnetics, and audio magnetotellurics.
3) Context about the aquifers in the Perth Basin study area and details on the superficial aquifer, which is the target of the student's field work.
This document provides a basic overview of the fundamental rock properties. It delivers a detailed analysis of the basic reservoir rock properties like porosity, permeability, Fluid saturation , wettability, etc.
79307422 2-wettability-literature-survey-part-1Jonatan Sierra
This document summarizes literature on how the wettability of rock/oil/brine systems can be altered by core handling and experimental conditions. It discusses how wettability affects core analysis results and the need to restore cores to their native wetting state. The document also reviews methods for classifying wettability based on contact angle measurements and findings that many reservoirs exhibit intermediate or oil-wet properties rather than being strictly water-wet.
This study analyzed changes in thermokarst lakes near Chersky, Russia between 1965 and 2011 using historical photographs and satellite imagery. The total lake area increased by 2,801,400 square meters over this period. Specifically, the number of small lakes increased while the number of large lakes decreased. Additionally, small lakes made up a greater percentage of the total lake area in 2011 compared to 1965. This suggests climate change is contributing to the drainage of larger lakes and expansion of smaller, more numerous water bodies in the region.
This document summarizes a study of water quality and chemistry in a pond and wetland system on Railroad Branch in Vermont. Samples were taken from 7 sites, including the inlet and outlet of the pond, under various hydrologic conditions. Laboratory analysis found fluctuations in temperature, pH, dissolved oxygen, conductivity, and cation concentrations between sites. Results showed the wetland was able to regulate cation flow between the inlet and outlet. Organic constituents in the pond/wetland also appeared to influence acidity. The data provides insight into the biochemistry of the area and establishes a baseline for further study.
1) Reverse osmosis membrane technology has advanced significantly since the 1950s. Early membranes allowed separation of salt from water but had low water fluxes, making the process impractical.
2) In the 1960s, Loeb and Sourirajan developed asymmetric cellulose acetate membranes with higher water fluxes and separations, making reverse osmosis separation possible on a practical scale.
3) Since then, new thin-film composite membranes have been developed that can withstand a wider range of conditions and have improved water flux and solute separation, enabling many reverse osmosis applications including desalination, wastewater treatment, and food processing.
1) Arsenic contamination of groundwater in Southeast Asia affects tens of millions of people. The document examines the source and transport of arsenic in the Mekong Delta of Cambodia, which has experienced minimal human disturbance.
2) Field measurements show arsenic is released from near-surface river-derived sediments under anaerobic conditions and transported through the underlying aquifer over centuries to the river.
3) The rates of arsenic influx via sediment deposition and efflux via groundwater transport are comparable, indicating release from solids and transport through the aquifer are in balance.
Giant convecting mud balls of the early solar systemSérgio Sacani
Carbonaceous asteroids may have been the precursors to the terrestrial planets, yet despite their importance,
numerous attempts to model their early solar system geological history have not converged on a solution. The
assumption has been that hydrothermal alteration was occurring in rocky asteroids with material properties similar
to meteorites. However, these bodies would have accreted as a high-porosity aggregate of igneous clasts
(chondrules) and fine-grained primordial dust, with ice filling much of the pore space. Short-lived radionuclides
melted the ice, and aqueous alteration of anhydrous minerals followed. However, at the moment when the ice
melted, no geological process had acted to lithify this material. It would have been a mud, rather than a rock.
We tested the effect of removing the assumption of lithification. We find that if the body accretes unsorted chondrules,
then large-scale mud convection is capable of producing a size-sorted chondrule population (if the body
accretes an aerodynamically sorted chondrule population, then no further sorting occurs). Mud convection both
moderates internal temperature and reduces variation in temperature throughout the object. As the system is
thoroughly mixed, soluble elements are not fractionated, preserving primitive chemistry. Isotopic and redox heterogeneity
in secondary phases over short length scales is expected, as individual particles experience a range of
temperature and water-rock histories until they are brought together in their final configuration at the end of
convection. These results are consistent with observations from aqueously altered meteorites (CI and CM chondrites)
and spectra of primitive asteroids. The “mudball” model appears to be a general solution: Bodies spanning a
×1000 mass range show similar behavior.
This chapter discusses different types of flows through soils, including water, heat, electricity, and chemicals. It focuses on describing these flows, quantifying flow rates and how they change over time, and how the flows impact soil properties. Water flow is most extensively studied due to its importance for problems involving seepage, consolidation, and stability. Darcy's law describes water flow and relates flow rate to hydraulic conductivity, a soil-specific property that can vary significantly between soil types and even within a given soil deposit. The chapter reviews the physics of different flow types and coupled flows, and how flow rates relate to driving forces based on various flow laws. It also evaluates parameters that influence flow and their typical ranges of values.
DSD-INT 2019 Elbe Estuary Modelling Case Studies-StanevDeltares
Presentation by Emil Stanev (HZG Institute of Coastal Research, Germany), at the DANUBIUS Modelling Workshop, during Delft Software Days - Edition 2019. Friday, 8 November 2019, Delft.
The Boltysh crater fill sediments – a 500,000 year record of the lower DanianIain Gilmour
The document summarizes research on sediments from the Boltysh impact crater in Ukraine that preserve a 500,000 year record of the early Danian period. The continuous lacustrine sediments within the crater provide an expanded and detailed record of a negative carbon isotope excursion approximately 200,000 years above the Cretaceous-Paleogene boundary, correlating to the Dan-C2 excursion in the marine record. Changes in floral communities through the excursion reflect changing biomes from a rapidly warming climate during an early Danian hyperthermal event, followed by ecosystem recovery, analogous to other major climatic events in the geologic record. The timing of the excursion may correlate with the late stages of
This document summarizes research on radionuclide migration from the D1225 Shaft at Dounreay in the UK. Key findings include:
1) Four distinct zones of radioactive contamination have been identified, with Sr-90 dominating the bulk contamination signal. Cs-137 and Pu isotopes showed very limited mobility.
2) Contamination is associated with zones of higher permeability, especially along bedding planes with enhanced porosity from rock-water interactions.
3) Quantitative modeling shows the importance of different sorption mechanisms on various mineral substrates like clays and iron oxyhydroxides in controlling radionuclide migration.
4) Sr sorbs reversibly on clays while Cs sor
This document provides an overview of a reservoir engineering course focused on fundamental rock properties. It discusses key topics like porosity, saturation, wettability, capillary pressure, and how they are determined through laboratory core analysis. Porosity refers to the pore space available to hold fluids and is classified as absolute or effective porosity. Saturation represents the fraction of pore space occupied by a fluid. Capillary pressure describes the pressure differential between immiscible fluids based on interface curvature. Laboratory tests on core samples are used to characterize these important rock properties.
9 17 fujisawa et al -seags e journal 2013-06chakfarmer
The document discusses an experimental study that investigated the relationship between seepage force and the velocity of sand particles during sand boiling. The study used silica sand and measured the migration velocities of seepage water and sand particles by calculating discharge amounts. The results revealed that:
1) The equilibrium of forces (gravity, buoyancy, fluid-particle interaction) can be used to estimate velocities of sand particles subjected to upward seepage flow.
2) The seepage force needed for horizontal transport of sand tends to decrease as the velocity of sand particles increases.
3) Previous studies on seepage failure focused on critical hydraulic gradients or velocities, but this study provides insights into how sand transport develops during
Fluid saturations refer to the fraction of pore volume occupied by water, oil, or gas in a reservoir. The sum of all fluid saturations must equal 1. Fluid saturations can be measured directly from core analysis under reservoir conditions or indirectly from well log or capillary pressure analysis. Factors like drilling mud composition and changes in pressure/temperature can affect measured fluid saturations in cores. While core saturations may not accurately reflect reservoir saturations, they provide useful information on fluid contacts, minimum water saturations, and validation of indirect methods.
The document discusses using a geomechanical approach to obtain permeability coefficients (Cpx) from magnetic resonance sounding (MRS) data by relating Cpx to longitudinal seismic velocity (VL). Data from sites in Europe and Africa were used to develop a logarithmic relationship between Cpx and VL for confined aquifers. This approach needs further testing but shows promise as a robust method for hydrogeologists to estimate permeability when pumping tests are limited.
1. Laboratory column experiments were conducted to investigate pollutant leaching from waste rock at an abandoned mine in southwest England. Metals (Cd, Cu, Mn, Pb, Zn) and major ions were measured in leachate from the dynamic up-flow percolation tests.
2. The highest concentrations of Zn, Cu, and Cd in leachate occurred at low solid to liquid ratios. Concentrations decreased exponentially for most elements except Pb, which remained high. Batch extractions showed similar results except for some differences at high ratios.
3. Field measurements of shallow groundwater near the mine site showed Zn and Cd concentrations comparable to column experiments at high ratios. However, Pb and
SEG 2015 The solution of nongas bright-spot and nonbright-spot gas identifica...Abra(Jianli) Yang
This document discusses the challenges of identifying gas reservoirs using traditional bright spot analysis of seismic data. Specifically, it notes that bright spots can be caused by non-reservoir formations, brine zones, or low gas saturation zones rather than high gas saturation gas reservoirs. It proposes that elastic property analysis through pre-stack seismic inversion is a better solution, as high gas saturation reservoirs consistently exhibit low elastic properties like density and Poisson's ratio. The document presents multiple examples from the northern South China Sea where bright spots were found to not indicate gas, and elastic analysis correctly identified the reservoir properties. It concludes elastic prediction is an effective way to identify non-gas bright spots and non-bright spot gas reservoirs.
High-frequency monitoring of water fluxes hess-20-347-2016Meidan Winegram
Controlled drainage was introduced at an experimental field to assess its effects on water storage and nutrient transport. Monitoring before and after controlled drainage showed that it:
1) Reduced drain discharge and increased groundwater storage in the field.
2) Initially elevated drain overflow levels in early spring to maximize water storage.
3) Increased nitrogen concentrations and loads in drains, largely from one monitored drain.
4) Reduced phosphorus loads via drains due to reduced discharge, but this may be counteracted by higher groundwater levels and increased shallow groundwater and overland flow to surface water.
Settlement rates of invasive tunicates were observed over 4 weeks at different locations and depths in Pillar Point Harbor, California. Clod dissolution plates and settlement plates were used to measure flow rates and tunicate recruitment. Results showed no relationship between flow and settlement, but temperature increases, heavy algal growth, and predation on plates correlated with lower settlement. Further study of how temperature, competition, and predation impact recruitment is needed to better manage invasive tunicates.
Origin of water salinity in Annaba aquifer system, North-Eastern Algeria | JBESInnspub Net
The Annaba area hosts in its underground a water potential of great importance. In fact, it is one of the Algerian plains where groundwater is subject to over-pumping. Moreover, the expansion of farmlands and the development of the neighboring agglomerations required a massive pumping of water, thereby leading to the change in hydrodynamic regime of groundwater and to the degradation of its quality. On the basis of boreholes and physicochemical data, the three major factors responsible for the evolution of chemical quality of water observed at the aquifer were identified: (1) mineralization due to natural and anthropogenic processes (responsible for the increase in the contents of chlorides, sodium, calcium and magnesium), (2) the oxydoreduction conditions due to the passage of the water table from an unconfined aquifer or even semi-confined to a confined aquifer (responsible for the reduction of nitrates and (3) pollution of groundwater by nitrates in areas where the water table is shallow and in the absence of a protective clayey cover.
J. Sequeira Ocean Acidification SoA ReviewJohn Sequeira
This document summarizes research on ocean acidification and its effects. It discusses how increased CO2 absorption by oceans leads to acidification, affecting calcium carbonate availability and organisms that use it in shells and skeletons. While most research focuses on single species responses, one study found increased calcification in coccolithophores during winter when pH is lowest, contradicting hypotheses. Experts agree ocean acidification due to CO2 emissions will continue for centuries and exceed past rates, but have less consensus on specific biogeochemical issues.
This document describes numerical and analytical models used to study vertical solute transport processes in a domed peat bog in Switzerland. The models test the hypothesis that downward porewater flow from bog crests controls vertical solute distributions. The models show that before 7000 years ago, diffusion from underlying soils dominated solute transport. Between 7000-1250 years ago, both diffusion and downward advection influenced transport. After 1250 years ago, downward advection likely dominated as the bog dome grew and porewater flow patterns changed over time. Solute transport in peat bogs is controlled by both downward advection and upward diffusion, influenced by bog hydrology and stratigraphy.
DSD-INT 2019 Fine sediments - transport in suspension, storage and supply - F...Deltares
The transport of fine sediments in rivers is governed by complex interactions between sediment supply from basins, in-channel storage, and lateral storage in floodplains and off-channel areas. Experiments and modeling were used to investigate how sediment transport dynamics are influenced by the relative proportions of proximal in-channel sediments and distal incoming sediments, resulting in different types of hysteresis loops. Additional work examined how lateral embayments and their geometry affect hydrodynamics and sediment trapping, with higher trapping efficiencies found at intermediate discharges. Unsteady flows were shown to potentially re-mobilize sediments depending on embayment dimensions.
This document summarizes a study that monitored changing groundwater-surface water interactions during a drought in a Scottish montane catchment. Synoptic surveys were carried out along the stream network on four occasions as flows declined. Samples were analyzed for major ions, isotopes, and other tracers. Initial surveys showed relatively homogeneous stream chemistry from riparian peat soils. Later, stream chemistry became more enriched with weathering-derived solutes as groundwater dominance increased. However, these changes showed spatial variability, implying different groundwater sources influenced flows differentially during the recession. Isotope data also indicated some streams were influenced by evaporation from peat soils. The surveys inferred heterogeneous groundwater bodies contributed variably to flows,
Bridgewater (2013) Muddy River BiodiversityAngeline Chen
This study investigates the relationship between microbial biodiversity and sediment contamination in two ponds within the Muddy River system. Willow Pond downstream is known to be contaminated with oil, pesticides and heavy metals, while Ward's Pond upstream has little contamination. Sediment samples from both ponds will be analyzed chemically and microscopically to quantify contaminant levels and compare microbial populations. Previous studies have found microbial indicators can assess water quality and ecosystem health in a simple, inexpensive way. The researchers hypothesize microbial diversity will be lower in Willow Pond's more contaminated sediments.
This study monitored groundwater-surface water interactions during an unusual drought in the Scottish Highlands in 2013. Synoptic hydrogeochemical surveys were carried out as stream flows declined over several months. Initial surveys showed relatively uniform stream chemistry dominated by peat soils, but chemistry became more varied with weathering-derived solutes as groundwater contributions increased. Repeated surveys found an evolving chemistry as smaller, shallower groundwater stores depleted sequentially. Spatial variability in chemistry reflected differences in bedrock geology and drift deposits. The integrated data provided a new conceptual model of catchment groundwater-surface water systems that is more dynamic, with diverse montane groundwater bodies contributing differentially during recession.
This is a pamphlet I made for the Hui Aloha O Kiholo community group in Kona that describes the current findings of research I am conducting at Kiholo Bay.
Offshore fresh groundwater reserves as a global phenomenonCarlos Bella
There is mounting evidence that vast reserves of fresh and brackish groundwater exist below continental shelves around the world. These offshore fresh groundwater reserves (OFGRs) were formed when sea levels were lower during glacial periods, exposing continental shelf areas that became recharged with precipitation and glacial meltwater. While some OFGRs may still be connected to modern coastal groundwater systems, many appear to be relics of past hydrological conditions and are termed "palaeo-groundwater". The largest documented OFGR is below the New Jersey shelf, where freshwater has been found over 100km offshore. Global occurrences of OFGRs have also been identified through borehole and geophysical data in locations such as the North
Assessment of The Trophic Status of The Future Buk Bijela HPP Accumulationinventionjournals
Eutrophication is a natural process in which water bodies age, and transit from a low productive condition (oligotrophic) into a high productive condition (eutrophic). In such condition, a majority of organic substances that are produced in surface layers do not completely decompose, but settle on the bottom, where they decompose. An increased (artificial) input of nutrients significantly accelerates this process, disturbing the natural balance between the biomass production and mineralization, where the production considerably multiplies. This can lead to a successful decrease in oxygen concentration on the bottom of an eutrophic lake, and in more inconvenient cases even to an anaerobic condition. This can result in an increase in the concentrations of ammonium, iron, manganese, and other substances, as well as in the occurrence of hydrogen sulphide and methane, which has a negative impact on the quality, both from the aspect of biotope habitat and water usage possibilities.
This research article analyzes the concentration and isotope data for Li, Mg, Ca, Sr, and Ba in groundwater samples collected from coastal aquifers around the world to estimate the flux of these elements from groundwater discharge into the oceans. The authors find that groundwater-derived solute fluxes represent at least 5% of riverine fluxes for these elements. Additionally, the isotope signatures of Mg, Ca, and Sr from global groundwater discharge are distinct from average riverine values, while Li and Ba are isotopically indistinguishable from rivers. The magnitude and isotope compositions of global groundwater fluxes depend strongly on the distribution of coastal lithology included in flux models.
- The confined segment of the stream exported water and dissolved organic carbon consistently, while the unconfined segment stored these during high flows and exported them during low flows due to increased water residence times in floodplain water bodies.
- Rates of gross primary productivity and ecosystem respiration were generally lower and less variable at the outflow of the confined segment compared to the outflow of the unconfined segment, and rapidly increased in a floodplain side channel as it disconnected from the main channel.
- The study found that intermittent connectivity between rivers and their floodplains can optimize ecosystem metabolism by allowing storage of resources like dissolved organic carbon during high flows, and utilization of these resources during low flows when water residence times in flood
Modelling climate change impacts on nutrients and primary production in coast...Marco Pesce
The document describes an integrated modelling approach used to project the impacts of climate change on nutrient loadings and phytoplankton communities in coastal waters. The approach combines climate models, a hydrological model, and an ecological model. Climate models project increases in winter precipitation and summer temperatures. The hydrological model shows increases in winter nutrient loads and decreases in summer. The ecological model then projects changes in nutrient concentrations, phytoplankton biomass, and species composition in the coastal waters.
A Trophic State Index for LakesAuthor(s) Robert E. Carlson.docxransayo
A Trophic State Index for Lakes
Author(s): Robert E. Carlson
Reviewed work(s):
Source: Limnology and Oceanography, Vol. 22, No. 2 (Mar., 1977), pp. 361-369
Published by: American Society of Limnology and Oceanography
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A trophic state index for lakes'
Robert E. Carlson2
Limnological Research Center, University of Minnesota, Minneapolis 55455
Abstract
A numerical trophic state index for lakes has been developed that incorporates most
lakes in a scale of 0 to 100. Each major division (10, 20, 30, etc.) represents a doubling
in algal biomass. The index number can be calculated from any of several parameters,
including Secchi disk transparency, chlorophyll, and total phosphorus.
My purpose here is to present a new ap-
proach to the trophic classification of lakes.
This new approach was developed because
of frustration in communicating to the pub-
lic both the current nature or status of lakes
and their future condition after restoration
when the traditional trophic classification
system is used. The system presented here,
termed a trophic state index (TSI), in-
volves new methods both of defining
trophic status and of determining that status
in lakes.
All trophic classification is based on the
division of the trophic continuum, however
this is defined, into a series of classes
termed trophic states. Traditional systems
divide the continuum into three classes:
oligotrophic, mesotrophic, and eutrophic.
There is often no clear delineation of these
divisions. Determinations of trophic state
are made from examination of several di-
verse criteria, such as shape of the oxygen
curve, species composition of the bottom
fauna or of the phytoplankton, concentra-
tions of nutrients, and various measures of
biomass or production. Although each
changes from oligotrophy to eutrophy, the
changes do not occur at sharply defined
places, nor do they all occur at the same
place or at the same rate. Some lakes may
be considered oligotrophic by one criterion
and eutrophic by another; this problem is
1Contribution .
Samples were collected from four stations along the Rhode Island coast with varying depths and nutrient inputs. The Providence River estuary station exhibited the highest mean concentrations of organic matter and chlorophyll a, while Rhode Island Sound exhibited the lowest. Concentrations differed significantly between stations. Additionally, chlorophyll a and organic matter concentrations in Rhode Island Sound and Block Island Sound were higher than values from other nearby studies. The abundance of these variables in sediments relates to primary production levels in the overlying waters.
Inorganic and methylmercury do they transfer along a tropical coastal food ...racheltrans
This study evaluated methylmercury (MeHg) and inorganic mercury (Hginorg) concentrations in water, plankton, and fish from Guanabara Bay, a eutrophic coastal area in Brazil. The aims were to compare the trophic transfer and biomagnification of MeHg and Hginorg between different trophic levels in the food web, from plankton to predatory fish. Water, microplankton, mesoplankton, and muscle tissue from 7 fish species with different feeding habits were sampled. Results showed that MeHg concentrations and proportions increased with trophic level, while Hginorg decreased, indicating MeHg was the species that biomagnified. MeHg also reflected the vertical
The International Journal of Engineering and Science (The IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
The International Journal of Engineering and Science (The IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
2015 SEG NSAP conference_Vp in near waterbottom_CopyrightAlan FOLEY
The document discusses variations in compression (p-wave) velocities measured in near-seabed sediments. In unconsolidated sediments close to the seabed, p-wave velocities can be transmitted either through the pore fluid or sediment grains. Measurements typically only capture the faster fluid transmission velocity. Near the boundary of normal compaction, the fluid and grain velocities converge as effective stress increases. Care must be taken to use appropriate geophysical techniques to accurately measure changing p-wave velocities in these environments.
2015 SEG NSAP conference_Vp in near waterbottom_Copyright
Benoit-2009-Effect of Bioirrigat
1. Effect of Bioirrigation on
Sediment-Water Exchange of
Methylmercury in Boston Harbor,
Massachusetts
J A N I N A M . B E N O I T , * , †
D A V I D H . S H U L L , ‡
R E B E C C A M . H A R V E Y , ‡ , §
A N D
S A M U E L A . B E A L †
Chemistry Department, Wheaton College,
Norton, Massachusetts 02766, Department of Environmental
Sciences, Western Washington University,
Bellingham, Washington 98225-9181
Received December 18, 2008. Revised manuscript received
March 05, 2009. Accepted March 18, 2009.
Coastal marine sediments are important sites of methylmercury
(MMHg) production, and dissolved efflux provides an
important source of MMHg to near-shore, and possibly off-
shore, water columns and food webs. We measured the flux
of MMHg across the sediment-water interface at four stations
in Boston Harbor that span a range of infaunal population
densities and bioirrigation intensities. At each station we carried
out total MMHg flux measurements using core incubations
and collected near-surface pore waters to establish MMHg
gradients for diffusive flux calculations. The flux cores were also
imaged by CT scanning to determine the distribution of
infaunal burrows, and pore-water sulfide and 222
Rn profiles
were measured. Total MMHg fluxes, measured using core
incubations, ranged from -4 to 191 pmol m-2
d-1
, and total
MMHg fluxes were strongly correlated with burrow densities
at the stations. Estimated diffusive fluxes, calculated based on
MMHg concentration gradients below the sediment-water
interface, were much lower than total fluxes at three of the
stations, ranging from 2-19 pmol m-2
d-1
. These results indicate
that MMHg exchange may be significantly enhanced over
moleculardiffusioninbioturbatedsediments.Furthermore,burrow
density provides a strong predictor of total MMHg flux.
Pore-water exchange of both dissolved MMHg and 222
Rn, a
naturallyoccurringpore-watertracer,increasedacrosstherange
of observed burrow densities, suggesting that the presence
of burrows enhances both MMHg production and flux.
Introduction
The importance of estuarine and coastal marine sediments
as sites of net monomethyl mercury (MMHg) production
has been demonstrated in a number of environments
including the Patuxent River estuary (1), the Chesapeake Bay
(2), the Gulf of Trieste (3), Long Island Sound (4), and the Bay
of Fundy (5). Sediment-produced MMHg may be mobilized
across the sediment-water interface and become available
for bioaccumulation and biomagnification in pelagic food
webs. Although the source of MMHg to deep ocean fish is
not currently known, it has been estimated that MMHg
diffusion from coastal sediments is large enough to sustain
MMHg concentrations in marine fish (4). Therefore, it is
essential to adequately quantify MMHg fluxes to properly
assess all sources of MMHg to the near-shore, and possibly
off-shore, marine environments. Furthermore, a better
understanding of the controls on MMHg efflux will allow for
more effective management of the coastal zone.
Exchange of MMHg across the sediment-water interface
has been quantified from pore-water profiles assuming
diffusive transport (4, 6), with in situ benthic flux chambers
(7-10), and using sediment-core incubations (11-13). The
latter two methods quantify total (or actual) flux of MMHg,
whereas diffusion estimates only account for molecular
diffusive flux expected due to pore-water MMHg gradients
near the sediment-water interface. Total and diffusive fluxes
may differ markedly when the two are compared at the same
location.
Several studies of MMHg exchange using benthic flux
chambers indicate that diffusion-based rates may under-
estimate the flux of MMHg from estuarine and marine
sediments (8-10, 13). For example, Covelli et al. (8) found
thatbenthicfluxesofMMHgweregreaterthandiffusivefluxes
in the Gulf of Trieste throughout most of the year. Similarly,
Choe et al. (9) found that diffusive flux accounted for only
0.3-65% of the total MMHg flux in the San Francisco Bay-
Delta.Theyattributedthisdiscrepancytoadvectiveprocesses
such as biological irrigation, although they did not explore
this possibility explicitly. In Long Island Sound, Hammer-
schmidt and Fitzgerald (13) compared diffusive fluxes to total
fluxes in core incubations. They found that total flux was up
to four times greater than diffusive flux, and that total/
diffusive flux ratios were positively correlated with dissolved
oxygen (DO) concentrations in bottom waters, suggesting a
bioirrigation control. Finally, Point et al. (10) found that the
diffusive flux of MMHg represented only 1.5% of the total
MMHg flux measured in benthic chambers in Thau Lagoon,
andarguedthatthedifferencecouldbeattributedtoadvective
flux brought about by bioturbation/bioirrigation processes.
Other flux chamber studies have measured MMHg fluxes
that are lower than estimated diffusive fluxes of pore-water
MMHg (7, 9). Suppressed MMHg flux may result from
trapping of MMHg within an oxidized surface layer, as has
been observed in the Saguenay Fjord (14, 15). A geochemical
box model in this Fjord suggests that oxic sediments provide
an adsorptive barrier to exchange of dissolved MMHg across
the sediment-water interface. A redox control on MMHg
exchange is consistent with the diurnal variation in benthic
MMHg flux observed in Lavaca Bay (7) where benthic
chamber flux exceeded diffusive flux by a factor of 6 during
a 9-h dark period, but became negative during a 22-h light
period. The large flux in the dark was attributed to the onset
of anoxic conditions at the sediment-water interface when
oxygen production by photosynthetic organisms declined.
Work by Mason et al. (11) in Baltimore Harbor provides an
alternative explanation for enhanced MMHg flux under
anoxic conditions. In long-term (5-day) sediment-core
incubations they found that the flux of MMHg was unrelated
to the flux of Fe or Mn, and they suggested that enhanced
MMHg flux occurs due to direct release of MMHg produced
at the sediment-water interface, rather than release during
dissolution of Fe and Mn oxohydroxides. Covelli, et al. (12)
also observed increases in MMHg flux in core incubations
from Grado Lagoon after 10 days, when sulfide began to
* Corresponding author: phone 508-286-3966; fax 508-286-8278;
email: jbenoit@wheatonma.edu
†
Wheaton College.
‡
Western Washington University.
§
Current address: Department of Environmental Science and
Policy, Plymouth State University, Plymouth, NH 03264-1595.
Environ. Sci. Technol. 2009, 43, 3669–3674
10.1021/es803552q CCC: $40.75 2009 American Chemical Society VOL. 43, NO. 10, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3669
Published on Web 04/14/2009
2. build up in the overlying water, and they attributed this
increase to enhanced net methylation under anoxic condi-
tions and/or increased mobilization.
Since bioirrigation tends to enhance both penetration of
oxygen into the sediment pore water and exchange of
dissolved constituents out of the sediment, benthic mac-
rofauna might influence MMHg efflux in two distinctly
different ways. First, bioirrigation could decrease MMHg
efflux due to increased oxidation of the sediment-water
interface. On the other hand, ventilation of deep burrows
could facilitate transport of MMHg from where it is produced
below the sediment-water interface into the overlying water
column.Therefore,whenpredictingtherelationshipbetween
burrow density and MMHg flux it is reasonable to posit two
alternative hypotheses: (1) MMHg efflux will be negatively
correlated with burrow density, or (2) MMHg efflux will be
positively correlated with burrow density. In previous studies
in Boston Harbor, we established that increasing burrow
densities lead to an increase in the depth of the oxic and
suboxic zones, as indicated by pore water oxygen and sulfide
profiles(16),andanincreaseinradonfluxduetobioirrigation
(17). Therefore, the Harbor provides an ideal environment
to test these alternative hypotheses. In this study, we
compared diffusive and total fluxes of MMHg from Boston
Harbor sediments and related total MMHg fluxes to infaunal
burrow densities. We also compared the flux of a tracer of
pore water transport, 222
Rn, to MMHg flux to gain insight
about the impact of bioirrigation on MMHg production.
Experimental Section
Stations in Boston Harbor (Figure S1) were chosen to span
a range of infaunal population densities, based on our
previous investigation (16). The stations included BH04
(42°18.60′ N, 71°2.49′ W), QB01 (42°17.61′ N, 70°59.27′ W),
and BH08A (42°17.12′ N, 70°54.75′ W), all of which had been
sampled in summer 2003. For our current investigation a
fourth station, BH02 (42°20.63′ N, 71°00.12′ W), was sampled
to represent sediments with very dense infaunal populations.
Cores were collected from Boston Harbor sediments in July
2007 into acid-cleaned 12.7-cm diameter by 32-cm long
polycarbonate tubes by divers or by use of a HAPS bottom
corer. At each station four sets of triplicate cores were
collected for the following purposes: (1) total MMHg fluxes
andburrowdensities,(2)surfacebulk-sedimenttotalmercury
(HgT) and MMHg and pore-water MMHg for diffusive flux
estimates, (3) down-core pore-water 222
Rn profiles, and (4)
down-core bulk-sediment HgT/MMHg and pore-water sul-
fide profiles.
Total and Diffusive Fluxes. For the measurement of total
sediment-water exchange of MMHg, we used incubations
in core chambers similar in design to those described by
Giblin et al. (18) to measure nutrient exchange in Boston
Harbor and Hammerschmidt and Fitzgerald (13) to measure
Hg flux in New York/New Jersey Harbor. Our chambers
consisted of 12.7-cm (ID) by 32 cm long polycarbonate tubes
fitted with leak-proof bottoms and caps and equipped with
stirring motors and sampling ports. After cores were collected
in the chamber tubes, the chambers were sealed and
maintained at ambient temperature. In the laboratory, the
overlying water was replaced with bottom water from the
station, and chambers were incubated with gentle stirring at
ambient bottom-water temperatures. Overlying water was
collected periodically using peristaltic pumping and in-line
filtration through 0.2 µm polysulfone membranes in Teflon
filter units. Procedural blanks were determined using cham-
bers filled with bottom water, but without sediment. All
equipment was rigorously acid-cleaned and trace-metal-free
protocols were followed throughout the procedure. MMHg
exchange was calculated using the following equation:
F ) (Cf - C0)(V ⁄ A) ⁄ (tf - t0)
where Cf and C0 are the final and initial concentrations, tf
and t0 are the final and initial sampling times, V is the volume
of water overlying the core, and A is the surface area of the
core. Corrections were made for dilution by bottom water,
which was used to replace overlying water during sampling.
Bottom-water dissolved MMHg concentrations were below
the detection limit (<0.05 pmol/L) at all stations.
At the end of the incubation period, the flux cores were
imaged using a General Electric Lightspeed QX/i CT scanner,
and the density of burrows was determined by image analysis
(19, 20). This approach provides measurements of both flux
and burrow density in each of two cores at four stations, and
prevents the need to take averages for these two parameters
within stations.
Surface sediment porosity and pore-water concentrations
were used to calculate diffusive fluxes based on an ap-
proximation of Fick’s First Law. Diffusive flux of a dissolved
pore-water constituent is described as follows: F ) - φ Ds
dC/dz, where F is the flux of a solute with concentration C
and depth z, φ is the sediment porosity, and Ds is the
tortuosity-corrected molecular diffusion coefficient. Porosity
determination is described below. The tortuosity-corrected
molecular diffusion coefficient was estimated as Ds ) Dw/θ2
,
where Dw is the molecular diffusion coefficient for CH3HgSH0
in water at 25 °C, 1.2 × 10-5
cm2
s-1
(4), and θ is tortuosity
calculated using the relationship θ ) 1 - ln(φ2
) (21). The
value of dC/dz at the sediment-water interface was ap-
proximated as ∆C/∆z, the MMHg concentration gradient
between overlying water and pore water at 2 cm depth in the
sediment. This general approach has been used widely to
estimate diffusive fluxes in coastal sediments (e.g., 4, 7, 22),
although the gradient depth and choice of diffusing species
varies somewhat among investigators.
Ambient and Supported 222
Rn. Additional cores were
collected for 222
Rn analysis. These cores were sectioned into
2-cm increments immediately upon returning to shore.
Sections were transferred to glass jars containing 100 mL of
harbor water, and then the jars were sealed with airtight lids.
Rn-222 was sparged from samples and collected by cold
trapping following the methods of Mathieu et al. (23), and
222
Rn activities were measured using a DRC-MK10-2 scintil-
lationcounter(AppliedTechniques,Co.,Hendersonville,NC).
After the samples were purged of radon, 222
Rn was allowed
to grow in to reach secular equilibrium with its parent 226
Ra.
222
Rn was measured again to determine supported activity
duetodecayofambient226
Ra.The222
Rnsystemwascalibrated
with standards made from NIST traceable 226
Ra.
Mercury Determination. Cores were also collected for
down-core solid-phase MMHg measurements. These cores
were extruded and cut into 2-cm sections in an oxygen-free
glovebox. Pore waters were separated from these sections
for sulfide analysis (see below) using vacuum filtration in
disposable filter units with 0.2-µm polysulfone membranes.
The top 0-4 cm sections of three additional cores were used
for collection of pore waters for dissolved MMHg and solid-
phase HgT and MMHg determinations. In this case, acid-
cleaned filter units were used and blanks were produced by
filtering purified laboratory water through the acid-cleaned
filter units.
Mercury analyses were carried out as previously described
in Benoit et al. (16). Containers were rigorously acid cleaned,
and trace-metal-free protocols (e.g., (24)) were used during
all phases of sample handling, storage, and analysis. MMHg
concentrations in waters and sediments were determined
bydistillation(25),aqueous-phaseethylation,purgeandtrap,
gas chromatographic separation of ethylated species, py-
rolytic decomposition, and cold-vapor atomic fluorescence
(CVAFS) detection (26). HgT concentrations in sediments
3670 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 43, NO. 10, 2009
3. were determined by acid digestion, SnCl2 reduction, purge
and trap on gold, thermal desorption, and CVAFS detection
(27, 28). Accuracy of the methods was determined by analysis
of certified reference materials, PACS-2 (National Research
Council of Canada) for HgT and IAEA-405 (International
Atomic Energy Agency) for MMHg. We measured an average
(n ) 6) concentration of 3.16 ( 0.23 µg Hg g-1
in PACS-2,
which is within the reported range of 3.04 ( 0.20 µg Hg g-1
.
For IAEA-405, our measured average (n ) 9) concentration
of5.73(0.48ngHgg-1
(asMMHg)alsofellwithinthecertified
range of 4.96-6.02 ng g-1
. Sediments from these stations
were previously used in a side-by-side comparison of
distillation and nitric acid leaching as sample pretreatment
methods prior to MMHg analysis. Results showed insignifi-
cant artifactual MMHg production in these sediments during
distillation (16). Analytical uncertainties, determined using
triplicate sample measurements and expressed as % relative
standard deviation were as follows: 8.9% (n ) 5 triplicates)
for HgT and 8.7% (n ) 7 triplicates) for MMHg. Spike
recoveries for pore waters and flux samples were 100 ( 10%
(n ) 4). Detection limits for 2 g of wet sediment were 0.02
nmol g-1
for HgT and 0.05 pmol g-1
for MMHg. For 50 mL
of pore water or flux sample the MMHg detection limit was
0.05 pmol L-1
.
Ancillary Measurements. The pore waters collected for
sulfide determination were preserved in sulfide antioxidant
buffer (SAOB) and analyzed for total dissolved sulfide using
an ion-selective electrode. For our diffusion estimates,
porosity was determined from known masses of sediment
dried to constant weight in a 70 °C oven, using the following
equation:
φ ) (g water ⁄ 1.02 g mL-1
) ⁄ [(g water ⁄ 1.02 g mL-1
) +
(g dry sediment ⁄ 2.6 g mL-1
)]
Percent organic matter (%OM) was determined by measuring
the loss on ignition in dried samples combusted at 600 °C
for 8 h.
Results and Discussion
Sediment Profiles. Solid-phase MMHg (Figure 1) and pore-
watersulfide(Figure2)concentrationprofilesfollowapattern
we have observed in previous years (16). In our prior
investigation in Boston Harbor MMHg peaks occurred just
above the depth where dissolved sulfide reached ca. 10 µM.
We proposed a descriptive model in which MMHg peaks
occurinazoneofoptimalMMHgproductionthatisdelimited
at the top by the depth where sulfate reduction becomes
dominant and at the bottom by the depth where high sulfide
concentration becomes limiting to methylation (29, 30). We
foundthatthedepthsofpeakMMHgconcentrationincreased
with increasing burrow densities, and we concluded that
bioirrigation influences the down-core accumulation of
MMHg by changing the three-dimensional geometry of
sedimentredoxconditionsand/orbyincreasingMMHgefflux
(16). The solid-phase MMHg profiles at BH04, QB01, and
BH02, which had 300, 800 and 12,000 burrows m2
, respec-
tively, are consistent with our previous results and support
our model. We were unable to obtain sufficient pore water
from BH08A cores for sulfide analysis, because the sediments
at this station were very sandy and had much lower porosity
than the other stations (Table S1). The low organic matter
content limits the retention of MMHg, resulting in relatively
constant and low MMHg concentrations with depth.
MMHg Fluxes. The main goals of this investigation were
to compare diffusive and total fluxes of MMHg and to
determine the relationship between total MMHg fluxes and
burrow densities. The magnitudes of these two types of fluxes
varied widely among the four stations (Figure 3). Diffusive
fluxes of MMHg ranged from 2 ( 1 to 19 ( 8 pmol m-2
day-1
.
These fluxes are within the range of -10 to 440 pmol m-2
d-1
observed in a number of other estuarine and coastal
environments, as summarized in Table 1. Differences largely
reflect different pore-water gradients at the various study
locations, but may also be influenced by the choice of the
diffusing species, and hence, the molecular diffusion coef-
ficient used in the calculations. For example, Gill et al. (7)
estimated diffusive fluxes for MMHgCl to be about 6 times
FIGURE 1. Solid-phase sediment MMHg distributions at four
stations in Boston Harbor. Concentrations are expressed on a
dry weight basis.
FIGURE 2. Pore-water dissolved total sulfide profiles at three
stations in Boston Harbor. Undetectable concentrations are
plotted at the method detection limit, 0.005 µM.
FIGURE 3. Total and diffusive fluxes measured at four stations
in Boston Harbor. Averages from duplicate cores from each site
are shown, and error bars represent one standard deviation.
VOL. 43, NO. 10, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3671
4. higherthanfluxesforMMHgassociatedwithmacromolecular
organic matter.
In Boston Harbor, average total fluxes ranged from -4 (
5 to 191 ( 1 pmol m-2
d-1
, and they were much greater than
estimated diffusive fluxes at three of the four stations (Figure
3). A wide range of total fluxes have been measured in coastal
marine sediments (Table 1), and greater total flux has
generally been observed when both diffusive and total fluxes
have been measured. At BH04, the station with the highest
organicmattercontentandpore-watersulfideconcentrations
and the lowest burrow densities, the total flux was not
significantly different from zero although the estimated
diffusive flux was relatively large. The lack of a significant
total flux at this site suggests that over the time period of the
incubation(16h)oxygendidnotbecomesufficientlydepleted
at the sediment-water interface for enhanced flux to occur,
as has been observed in other coastal marine sediments
(7, 10-12). It appears that direct release of MMHg from the
sediment-water interface was not significant, even at our
most eutrophic station (BH04).
Oursamplingstationsincludedarangeofinfaunalburrow
densities, from 300-12,000 burrows m-2
at the sediment
surface (Table S1), enabling us to test our alternative
hypotheses about the effect of bioirrigation on MMHg flux.
There is a significant positive, linear correlation between
total MMHg fluxes and infaunal burrow densities (Figure 4).
This relationship supports the second alternative hypothesis,
and is consistent with the idea that burrows stimulate the
exchange of dissolved MMHg. This study underscores the
importance of measuring total fluxes in bioturbated sedi-
ments. The strong linear relationship between MMHg fluxes
and burrow densities indicates that sediments with dense
infaunal populations export MMHg more efficiently than
sediments with lower infaunal densities. This trend is
consistent with observations in Long Island Sound, where
flux enhancements (total:diffusive flux ratios) were positively
related to bottom-water dissolved oxygen concentrations,
and presumably to infaunal population densities (13).
Similarly, Point et al. (10) compared MMHg flux in benthic
chambers at stations in Thau Lagoon with 0 and 510
macrofaunal individuals m-2
, and found a 3-fold greater total
flux at the latter station. In Boston Harbor, average mac-
rofaunal population densities were also linearly related to
average MMHg fluxes across the stations (results not shown,
r2
) 0.94), confirming the relationship between burrow
densities and MMHg fluxes observed in individual cores
(Figure 4).
Examinationofthefluxof222
Rncanprovidefurtherinsight
into the effect of burrows on pore-water transport. Dissolved
gaseous 222
Rn is continuously produced in sediments from
the radiodecay of solid-phase 226
Ra and lost via radiodecay
to 218
Po. Since pore-water 222
Rn has no other significant
sources or sinks, deficits in measured pore-water 222
Rn
activity, relative to its supported activity from 226
Ra, can be
used to determine the 222
Rn flux. We measured ambient and
supported 222
Rn activity profiles at each of the stations (17)
and used the observed deficits to calculate average 222
Rn
fluxes (Figure 5). The flux of radon increases with increasing
burrow densities, indicating that sites with higher densities
of burrows have higher rates of bioirrigation. Observed 222
Rn
profiles can be explained with a transport control that
depends on diffusive exchange of dissolved pore-water
constituents across burrow walls and periodic flushing of
burrows (17). According to this model, as the number of
burrows increases, the surface area for exchange also
increases until a point is reached where the burrows are so
close together that the 222
Rn deficit zones around the burrows
fuse together. At this point, additional burrows fail to increase
TABLE 1. Summary of MMHg Diffusive (Fdiff) and Total (Ftotal) Sediment Flux Measurements in Estuarine and Coastal Marine
Environments (NA Means Not Available)
study area Fdiff (pmol m2
d-1
) Ftotal method Ftotal (pmol m2
d-1
) source
Gulf of Trieste, Italy -9-26 flux chambers -520-11,800 8
Lavaca Bay, TX 50-80 (open water) flux chamber 770/-1650 (light)/4150 (dark) 7
San Fransisco Bay-Delta, CA -4-440 flux chambers -92-850 9
Long Island Sound, USA 24-174 NA NA 4
Baltimore Harbor, MD NA core incubations <24-1440 after 16 h 11
Thau Lagoon, France 4 NA NA 32
Thau Lagoon, France NA flux chambers 94-300/-147 (light)/315 (dark) 10
Grado Lagoon -10-84 flux chambers 1050 7430 12
core incubations 170 (oxic)/2480 (anoxic)
NY/NJ Harbor, USA 13-17 (Feb) 54-86 (Aug) core incubations 39-55 (Feb) 71-92 (Aug) 13
Mugu Lagoon, CA 0.7-26 NA NA 33
Boston Harbor, MA 2-19 core incubations -4-191 this study
FIGURE 4. Relationship between total dissolved MMHg flux and
burrow density in Boston Harbor flux cores. The eight points
represent four stations with duplicate cores, each of which
provided measurements of both infaunal density and MeHg flux.
FIGURE 5. Relationship between average dissolved gaseous
222
Rn flux and average burrow density in Boston Harbor.
Averages from triplicate cores for radon and duplicate cores
for burrow density are shown, and error bars represent one
standard deviation.
3672 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 43, NO. 10, 2009
5. the 222
Rn flux, which approaches the depth-integrated rate
of 222
Rn production by its parent 226
Ra within the bioturbated
zone.
Mass balance considerations require that in the steady
state, net production of MMHg (the balance of methylation
and demethylation) must equal the total flux. The observed
increase in MMHg flux across the stations indicates that
greaternetmethylationmustoccuratthestationswithhigher
burrow densities. Enhanced fluxes could be driven by greater
net production with similar rates of bioirrigation, if more
concentrated pore water were exchanged at the more densely
populated stations. However, our results do not support this
possibility because pore-water MMHg concentrations do not
increase with increasing burrow densities (Table S1). Also,
since 222
Rn is a tracer of pore-water transport, the positive
relationship between 222
Rn flux and burrow density indicates
enhancedpore-waterexchangeatstationswithhigherMMHg
flux. Therefore, it is likely that the observed relationship
between MMHg flux and burrow density occurs due to a
combination of increased net MMHg production and en-
hanced bioirrigation.
There are several possible mechanisms for the observed
enhancement of net MMHg production at higher burrow
densities. Rapid bioirrigation may remove MMHg more
rapidly than it can be demethylated so that a greater
proportion of MMHg produced in the sediment is transferred
to the water column. Alternatively, burrow irrigation might
indirectly augment net MMHg production through the
stimulation of Hg-methylation. Bioirrigation can enhance
rates of microbial activity, sediment respiration, and organic
matter degradation (31) or increase the bioavailability of
Hg(II) by lowering pore water sulfide concentrations (29, 30),
and thus might boost rates of Hg methylation carried out by
sulfate-reducing bacteria. Further, sediments that support
high infaunal densities may also be favorable for large
populations of methylating bacteria. A third possible mech-
anismisareductioninthedensityoractivityofdemethylating
organisms due to changes in sediment characteristics caused
by bioirrigation. Our data do not enable us to differentiate
among the possibilities, and these mechanisms warrant
further investigation.
Implications. This study is the first to explicitly relate a
direct measure of bioirrigation intensity with MMHg efflux
from coastal marine sediments across a broad range of
benthic population densities. The results demonstrate that
MMHg flux from the subsurface can be stimulated by
macroinfauna, which have a 2-fold effect on MMHg cycling.
First, the presence of burrows influences the redox geometry
of the sediments and expands the zone of optimal Hg
methylation (16), thereby increasing net MMHg production.
Second, the penetration of burrows into the sediment allows
for efficient transport of MMHg from the regions where
maximum production occurs. The overall result is a signifi-
cant increase in total MMHg flux relative to molecular
diffusion in biorrigated sediments. These results indicate that
diffusive flux is not a good measure of sediment-water
exchange of MMHg in sediments inhabited by benthic
macroinfauna. Finally, the observed relationship between
burrow density and flux suggests that remediation efforts in
impacted estuaries that result in recolonization of previously
defaunated sediments may increase MMHg export to the
water column as sediments are recolonized.
Acknowledgments
We thank Anne Giblin, Chuck Hopkinson, Sam Kelsey, and
Jane Tucker of the Marine Biological Laboratory and the crew
of the R/V Aquamonitor of Battelle for assistance with field
sampling. We thank Tom Torgersen of the Marine Sciences
Department of the University of Connecticut for supplying
the transfer board and detectors for radon analysis. Funding
for this project was provided by MIT Sea Grant (5710001527).
Matching support was provided by the Massachusetts Water
Resources Authority, Wheaton College, and Western Wash-
ington University.
Supporting Information Available
A figure indicating the locations of the sampling stations in
Boston Harbor and a table of surface sediment and pore
water characteristics at the stations. This information is
availablefreeofchargeviatheInternetathttp://pubs.acs.org.
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