DocumThe effect of Amaranthus hybridus on fluoride removal by iron (III) salt...Hezron Mwakabona
The use of iron (Fe) (III) salts as fluoride coagulants in water is challenged by the requirement of high
pH for maximum efficiency. At their natural pH, these salts have low fluoride removal efficiency. This
study examines the effect of amaranth plants on enhancement of the defluoridation efficiency of Fe (III)
salts as coagulants. Amaranthus hybridus plants were suspended in fluoride water treated with varying
concentrations of Fe (III) with its roots immersed completely in fluoride water for varying time from 720
to 1440 min. The study shows that fluoride coagulation by Fe (III) in the absence of plants is limited to
10%, whereas when plants were introduced, it increased from 10 to 40%. These results suggest that
amaranth plants enhance the defluoridation efficiency of Fe (III). This enhanced removal may be
attributed to increased coagulation effected by exudates released by plant root which contain organic
compounds and CO2 or charged root surfaces by the formation of Fe (III) oxide film. The exact factor
that has a major contribution to enhanced removal observed remains to be subject of further studies.
In recent years, nanoparticles that have size of 1-100 nm is widely used for textile, pharmacy,
cosmetic and treatment of industrial wastewater. Producing and using of nanoparticles widely, causes
important accumulation in nature and toxicity on ecosystem. Knowledge of potential toxicity of nanoparticles is
limited. In this study, six different nanoparticles nano-zinc oxide, nano-silicon dioxide, nano-cerium oxide,
nano-aluminum oxide, nano-hafnium oxide, and nano-tantalum oxide which used commonly, were studied to
investigate toxic impacts on organisms. We studied nine different acute toxicity test (bacteria – Escherichia coli
(gram negative bacteria) ; bacteria – Bacillus cereus (gram positive bacteria) ; bacteria – Vibrio fischeri
(bioluminescences bacteria) ; methane Archae Bacteria ; yeast – Candida albicans ; mold – Aspergillus niger ;
algae – Chlorella sp. ; Crustacea – Daphnia magna ; lepistes - Poecillia reticula) for the effect of
nanoparticles to different trophic levels. In general, the most toxic nanoparticle is nano-zinc oxide and the least
toxic nanoparticle is nano-hafnium oxide. Among the used organisms in acute toxicity test; the most sensitive
organism is algae - Chlorella sp ;the most resistant organism is fish- Poecillia reticula.
Fertilizer plant waste carbon slurry has been investigated after some processing as an adsorbent for the removal of dyes and phenols using columns. The results show that the carbonaceous adsorbent prepared from carbon slurry being porous and having appreciable surface area (380 m2/g) can remove dyes both cationic (meldola blue, methylene blue, chrysoidine G, crystal violet) as well as anionic (ethyl orange, metanil yellow, acid blue 113), and phenols (phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol) fruitfully from water. The column type continuous flow operations were used to obtain the breakthrough curves. The breakthrough capacity, exhaustion capacity and degree of column utilization were evaluated from the plots. The results shows that the degree of column utilization for dyes lies in the range 60 to 76% while for phenols was in the range 53-58%. The exhaustion capacities were quite high as compared to the breakthrough capacities and were found to be 217, 211, 104, 126, 233, 248, 267 mg/g for meldola blue, crystal violet, chrysoidine G, methylene blue, ethyl orange, metanil yellow, acid blue 113, respectively and 25.6, 72.2, 82.2 and 197.3 mg/g for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol, respectively
pH effects on the adsorption of saxitoxin by powdered activated carbonhbuarque
Increasing occurrence of cyanotoxins in surface waters worldwide pose significant problems, including
those for drinking water utilities. In this study, the removal of saxitoxin (STX) from three different
powdered activated carbons (PACs) was studied. STX is one of the most toxic paralytic shellfish toxins
(PSTs), albeit not the most prevalent. The results showed that a wide range of non-electrostatic and
electrostatic interactions appeared to play a role in the sorption of STX on PAC, depending on the solution
pH, NOM concentration, and other factors. A bituminous coal-based PAC, that was studied in greatest
detail, showed a trend of increasing sorption capacity for STX with increasing pH. NOM appeared to
significantly inhibit adsorption when the pH was nearly neutral (e.g. 7.05), yet it had less effect at higher
pH levels of 8.2 and 10.7.
Phylogenetic Analysis of the Potential Microorganism for Remediation of Heavy...CSCJournals
The present research work has been carried out to study the waste disposal contaminated site for its physico chemical and microbial characterization and identification of potential microorganism capable of bioaccumulation and biodegradation of heavy metals. The ambient conditions present in the metal contaminated environment shows the values: pH(5.4),temperature(30°C), moisture(11.71%), nutrients; Nitrogen(0.2mg/l), phosphorus(22.65mg/l) and sulphur(559.3mg/l) respectively. The biological parameters studied indicate Dissolved oxygen (7.4mg/l), Biological oxygen demand (3.8 mg/l), Chemical oxygen demand (64.6 mg/l). The microbial consortium identified was found to survive and multiply in the present environmental conditions. Microbial consortium was sequenced and compared using Bioinformatics tools like BLAST, ClustalW and PHYLIP. In order to identify potential microorganism, microbial consortium was exposed to increasing concentrations of heavy metals viz 5mg/l, 25mg/l, 50mg/l, 100mg/l up to 800mg/l with special reference to Iron. At a concentration of 500mg/l, only one microorganism was found survived and multiplied. This shows that potential microorganism was only survived at higher concentration of iron. The 16SrRNA sequence and phylogenetic tree characterized the organism as Klebsiella pneumoniae, which was also confirmed by biochemical tests. The potential microorganism identified by BLAST technique can be used for remediation of the heavy metal from contaminated environment.
DocumThe effect of Amaranthus hybridus on fluoride removal by iron (III) salt...Hezron Mwakabona
The use of iron (Fe) (III) salts as fluoride coagulants in water is challenged by the requirement of high
pH for maximum efficiency. At their natural pH, these salts have low fluoride removal efficiency. This
study examines the effect of amaranth plants on enhancement of the defluoridation efficiency of Fe (III)
salts as coagulants. Amaranthus hybridus plants were suspended in fluoride water treated with varying
concentrations of Fe (III) with its roots immersed completely in fluoride water for varying time from 720
to 1440 min. The study shows that fluoride coagulation by Fe (III) in the absence of plants is limited to
10%, whereas when plants were introduced, it increased from 10 to 40%. These results suggest that
amaranth plants enhance the defluoridation efficiency of Fe (III). This enhanced removal may be
attributed to increased coagulation effected by exudates released by plant root which contain organic
compounds and CO2 or charged root surfaces by the formation of Fe (III) oxide film. The exact factor
that has a major contribution to enhanced removal observed remains to be subject of further studies.
In recent years, nanoparticles that have size of 1-100 nm is widely used for textile, pharmacy,
cosmetic and treatment of industrial wastewater. Producing and using of nanoparticles widely, causes
important accumulation in nature and toxicity on ecosystem. Knowledge of potential toxicity of nanoparticles is
limited. In this study, six different nanoparticles nano-zinc oxide, nano-silicon dioxide, nano-cerium oxide,
nano-aluminum oxide, nano-hafnium oxide, and nano-tantalum oxide which used commonly, were studied to
investigate toxic impacts on organisms. We studied nine different acute toxicity test (bacteria – Escherichia coli
(gram negative bacteria) ; bacteria – Bacillus cereus (gram positive bacteria) ; bacteria – Vibrio fischeri
(bioluminescences bacteria) ; methane Archae Bacteria ; yeast – Candida albicans ; mold – Aspergillus niger ;
algae – Chlorella sp. ; Crustacea – Daphnia magna ; lepistes - Poecillia reticula) for the effect of
nanoparticles to different trophic levels. In general, the most toxic nanoparticle is nano-zinc oxide and the least
toxic nanoparticle is nano-hafnium oxide. Among the used organisms in acute toxicity test; the most sensitive
organism is algae - Chlorella sp ;the most resistant organism is fish- Poecillia reticula.
Fertilizer plant waste carbon slurry has been investigated after some processing as an adsorbent for the removal of dyes and phenols using columns. The results show that the carbonaceous adsorbent prepared from carbon slurry being porous and having appreciable surface area (380 m2/g) can remove dyes both cationic (meldola blue, methylene blue, chrysoidine G, crystal violet) as well as anionic (ethyl orange, metanil yellow, acid blue 113), and phenols (phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol) fruitfully from water. The column type continuous flow operations were used to obtain the breakthrough curves. The breakthrough capacity, exhaustion capacity and degree of column utilization were evaluated from the plots. The results shows that the degree of column utilization for dyes lies in the range 60 to 76% while for phenols was in the range 53-58%. The exhaustion capacities were quite high as compared to the breakthrough capacities and were found to be 217, 211, 104, 126, 233, 248, 267 mg/g for meldola blue, crystal violet, chrysoidine G, methylene blue, ethyl orange, metanil yellow, acid blue 113, respectively and 25.6, 72.2, 82.2 and 197.3 mg/g for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol, respectively
pH effects on the adsorption of saxitoxin by powdered activated carbonhbuarque
Increasing occurrence of cyanotoxins in surface waters worldwide pose significant problems, including
those for drinking water utilities. In this study, the removal of saxitoxin (STX) from three different
powdered activated carbons (PACs) was studied. STX is one of the most toxic paralytic shellfish toxins
(PSTs), albeit not the most prevalent. The results showed that a wide range of non-electrostatic and
electrostatic interactions appeared to play a role in the sorption of STX on PAC, depending on the solution
pH, NOM concentration, and other factors. A bituminous coal-based PAC, that was studied in greatest
detail, showed a trend of increasing sorption capacity for STX with increasing pH. NOM appeared to
significantly inhibit adsorption when the pH was nearly neutral (e.g. 7.05), yet it had less effect at higher
pH levels of 8.2 and 10.7.
Phylogenetic Analysis of the Potential Microorganism for Remediation of Heavy...CSCJournals
The present research work has been carried out to study the waste disposal contaminated site for its physico chemical and microbial characterization and identification of potential microorganism capable of bioaccumulation and biodegradation of heavy metals. The ambient conditions present in the metal contaminated environment shows the values: pH(5.4),temperature(30°C), moisture(11.71%), nutrients; Nitrogen(0.2mg/l), phosphorus(22.65mg/l) and sulphur(559.3mg/l) respectively. The biological parameters studied indicate Dissolved oxygen (7.4mg/l), Biological oxygen demand (3.8 mg/l), Chemical oxygen demand (64.6 mg/l). The microbial consortium identified was found to survive and multiply in the present environmental conditions. Microbial consortium was sequenced and compared using Bioinformatics tools like BLAST, ClustalW and PHYLIP. In order to identify potential microorganism, microbial consortium was exposed to increasing concentrations of heavy metals viz 5mg/l, 25mg/l, 50mg/l, 100mg/l up to 800mg/l with special reference to Iron. At a concentration of 500mg/l, only one microorganism was found survived and multiplied. This shows that potential microorganism was only survived at higher concentration of iron. The 16SrRNA sequence and phylogenetic tree characterized the organism as Klebsiella pneumoniae, which was also confirmed by biochemical tests. The potential microorganism identified by BLAST technique can be used for remediation of the heavy metal from contaminated environment.
Triclosan Persistence in Environment and Its Potential Toxic Effects on AlgaeAJASTJournal
Triclosan (TCS) is widely used as an antibacterial agent in various industrial products, such as textile goods, soap, shampoo, liquid toothpaste and cosmetics, and often detected in wastewater effluent. Triclosan is highly toxic to aquatic animals, and is particularly highly toxic to the algae, which was used as a test organism in this study. Algae represent the first nutritional base on the aquatic food chain due to their ability to synthesize organic molecules using sunlight and carbon dioxide. Thus, the cultivation of algae has been an integral part for the production of commercially important species on aquaculture. This has been the reason to make great efforts in order to understand effect of triclosan to natural periphyton communities (algae). However, there is a paucity of data on the toxicity of triclosan and its effects on aquatic organisms. In this study, the toxicity of triclosan to a microalga was examined. The present investigation showed that “chlorophyll a” pigment in control algae was 5.92 mg/L and it decreased, when algae was treated with different concentration of triclosan (10-50 ppm). The study revealed that, as the concentration of triclosan increased then algae growth declined. It was observed that conductivity also increased because of decreased “chlorophyll a” and decreased phytoplankton levels. This result indicates that triclosan exerts a marked influence on algae, which are important organisms being the first-step producers in the ecosystem; therefore, the possible destruction of the balance of the ecosystem is expected if triclosan is discharged into the environment at high levels. The bioaccumulation of TCS in human impregnation from foodstuff exposure (in particular fish) and likely risk for human population also.
Application of Rapid Bioassay Method for Assessing Its Water Purification by ...IJERA Editor
Appreciated integral toxicity of four water samples taken from various sources, urban and rural environment,
and explored some of the properties of the reagent chemical purification of water - potassium ferrate K2FeO4.
These data allow suggesting for practical use test system based on bacterial luminescence for express evaluation
of the toxicity of chemical reagents used for water purification, selection of their effective concentrations and
optimal processing time of water samples.
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.
Concentration Distribution and Ecological Risk Assessment of Polycyclic Aroma...Scientific Review SR
The ecological risk assessment of 16 USEPA priority polycyclic aromatic hydrocarbon (PAHs) in water and sediments of Kolo creek, Niger Delta Nigeria was assessed the samples were collected from November, 2018 to June, 2019 from seven locations (A-G) along the creek. The samples were extracted using standard methods and analyzed using gas chromatography (model: HP5890 S). The concentrations of the PAHs in the water and sediment samples ranged between 0.000 - 9.239 µ/L and .002 – 374.35µg/Kg respectively. All the compounds analyzed were detected in all the sampling places, even area far from the flow stations. Hence, the urban runoffs, sewage discharges, and agricultural activities are implicated. Four rings hydrocarbon were present in higher concentration when compared to other PAHs in all sampling sites, with benz (a)anthracene having the highest values in both matrixes. Similarly, lower molecular weight (LMW) PAHs were present in lower concentrations in all sampling sites and they are known to exhibit higher lethal toxicity than the larger PAHs. HMW were present in high concentrations than LMW and are persistent in the environment as a result of their increase resistance to oxidation, reduction and vaporization as molecular weight increases. Similarly, The PAFs of the investigated creek is less than 5%, suggesting existences of minor ecological risks that are insignificance. However, the TEQs detected in high molecular weight showed that there is possibility of cancer to those who may be exposed to the bottom sediment. The indices measured in this habitat may put more pressures to the aquatic organisms and cause drastic changes to their ecosystem which may lead to species extinction.
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.
Microbial Decolorization of Leather Dye Effluentijtsrd
As we know 71% of Earths Surface is covered with water. Water is one of the most essential element for the persistence of life on this planet. Pure and contamination free water is the dire necessity of every living being present on Earth but today water pollution has posed great threat to the existence of life. The discharge of effluents from various industries into the water bodies are mainly responsible for water pollution specially effluents from leather industry are the most contaminating as along with the harmful chemicals they contain organic matter as well. The dyes disposed by the leather industry are the most harmful for the environment. The conventional physicochemical methods used for the treatment of leather dyes in the contaminated water i.e. coagulation, precipitation, oxidation etc have disadvantages and limitations. This study presents microbial decolorization of leather dye effluents from Shigella sp. isolated from effluent samples collected from leather industry. Different parameters such as temperature and pH were optimized for decolorization of Methylene Blue, Crystal Violet, EosinYellow, Safranine dyes by using bacterial isolates. Optimum temperature for decolorization was observed to be 300c, the optimum pH range for decolorization was found to be from pH6-pH8. All the samples were incubated at 30-°C 150 rpm. The decolorization was measured as decrease in absorbance maxima at 663 nm, 590 nm, 518nm, 530 nm for mehtylene blue, crystal violet, eosin yellow, safranine respectively. Dr. Jitender Kumar | Navleen Kaur Chopra"Microbial Decolorization of Leather Dye Effluent" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-5 , August 2017, URL: http://www.ijtsrd.com/papers/ijtsrd2405.pdf http://www.ijtsrd.com/biological-science/biotechnology/2405/microbial-decolorization-of-leather-dye-effluent/dr-jitender-kumar
combined toxicity and bioconcentration of fluoride and arsenic in african (3)IJEAB
Laboratory experiments were performed to examine the combined toxic effects of two important aquatic contaminants viz., arsenic and fluoride on African catfish, Clarias gariepinus. Additionally, the bio concentration factors (BCFs) of the two contaminants in tissues and blood of catfish were also determined. The LC50 for sodium fluoride and arsenic trioxide were determined to be 619.3 mg L-1, 30.3 mg L-1, respectively. Erratic swimming movements with hyperactivity, loss of equilibrium, augmented air gulping and decreased food consumption were observed in the experimental groups. In co-exposure groups of arsenic and fluoride, the concentration of fluoride in fish tissues increased with increasing water fluoride concentration in the test aquaria with significant differences (P<0.01)><0.05)>0.05) among the exposure groups. Arsenic was observed to exceedingly bioaccumulate and biomagnify in the tissues. Perhaps due to the complex formation of arsenic and fluoride the bio concentration of arsenic in tissues was observed to decrease with increasing water fluoride concentration and vice-versa. The study concludes that fluoride may interfere with the bio-concentration of arsenic.
Triclosan Persistence in Environment and Its Potential Toxic Effects on AlgaeAJASTJournal
Triclosan (TCS) is widely used as an antibacterial agent in various industrial products, such as textile goods, soap, shampoo, liquid toothpaste and cosmetics, and often detected in wastewater effluent. Triclosan is highly toxic to aquatic animals, and is particularly highly toxic to the algae, which was used as a test organism in this study. Algae represent the first nutritional base on the aquatic food chain due to their ability to synthesize organic molecules using sunlight and carbon dioxide. Thus, the cultivation of algae has been an integral part for the production of commercially important species on aquaculture. This has been the reason to make great efforts in order to understand effect of triclosan to natural periphyton communities (algae). However, there is a paucity of data on the toxicity of triclosan and its effects on aquatic organisms. In this study, the toxicity of triclosan to a microalga was examined. The present investigation showed that “chlorophyll a” pigment in control algae was 5.92 mg/L and it decreased, when algae was treated with different concentration of triclosan (10-50 ppm). The study revealed that, as the concentration of triclosan increased then algae growth declined. It was observed that conductivity also increased because of decreased “chlorophyll a” and decreased phytoplankton levels. This result indicates that triclosan exerts a marked influence on algae, which are important organisms being the first-step producers in the ecosystem; therefore, the possible destruction of the balance of the ecosystem is expected if triclosan is discharged into the environment at high levels. The bioaccumulation of TCS in human impregnation from foodstuff exposure (in particular fish) and likely risk for human population also.
Application of Rapid Bioassay Method for Assessing Its Water Purification by ...IJERA Editor
Appreciated integral toxicity of four water samples taken from various sources, urban and rural environment,
and explored some of the properties of the reagent chemical purification of water - potassium ferrate K2FeO4.
These data allow suggesting for practical use test system based on bacterial luminescence for express evaluation
of the toxicity of chemical reagents used for water purification, selection of their effective concentrations and
optimal processing time of water samples.
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.
Concentration Distribution and Ecological Risk Assessment of Polycyclic Aroma...Scientific Review SR
The ecological risk assessment of 16 USEPA priority polycyclic aromatic hydrocarbon (PAHs) in water and sediments of Kolo creek, Niger Delta Nigeria was assessed the samples were collected from November, 2018 to June, 2019 from seven locations (A-G) along the creek. The samples were extracted using standard methods and analyzed using gas chromatography (model: HP5890 S). The concentrations of the PAHs in the water and sediment samples ranged between 0.000 - 9.239 µ/L and .002 – 374.35µg/Kg respectively. All the compounds analyzed were detected in all the sampling places, even area far from the flow stations. Hence, the urban runoffs, sewage discharges, and agricultural activities are implicated. Four rings hydrocarbon were present in higher concentration when compared to other PAHs in all sampling sites, with benz (a)anthracene having the highest values in both matrixes. Similarly, lower molecular weight (LMW) PAHs were present in lower concentrations in all sampling sites and they are known to exhibit higher lethal toxicity than the larger PAHs. HMW were present in high concentrations than LMW and are persistent in the environment as a result of their increase resistance to oxidation, reduction and vaporization as molecular weight increases. Similarly, The PAFs of the investigated creek is less than 5%, suggesting existences of minor ecological risks that are insignificance. However, the TEQs detected in high molecular weight showed that there is possibility of cancer to those who may be exposed to the bottom sediment. The indices measured in this habitat may put more pressures to the aquatic organisms and cause drastic changes to their ecosystem which may lead to species extinction.
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.
Microbial Decolorization of Leather Dye Effluentijtsrd
As we know 71% of Earths Surface is covered with water. Water is one of the most essential element for the persistence of life on this planet. Pure and contamination free water is the dire necessity of every living being present on Earth but today water pollution has posed great threat to the existence of life. The discharge of effluents from various industries into the water bodies are mainly responsible for water pollution specially effluents from leather industry are the most contaminating as along with the harmful chemicals they contain organic matter as well. The dyes disposed by the leather industry are the most harmful for the environment. The conventional physicochemical methods used for the treatment of leather dyes in the contaminated water i.e. coagulation, precipitation, oxidation etc have disadvantages and limitations. This study presents microbial decolorization of leather dye effluents from Shigella sp. isolated from effluent samples collected from leather industry. Different parameters such as temperature and pH were optimized for decolorization of Methylene Blue, Crystal Violet, EosinYellow, Safranine dyes by using bacterial isolates. Optimum temperature for decolorization was observed to be 300c, the optimum pH range for decolorization was found to be from pH6-pH8. All the samples were incubated at 30-°C 150 rpm. The decolorization was measured as decrease in absorbance maxima at 663 nm, 590 nm, 518nm, 530 nm for mehtylene blue, crystal violet, eosin yellow, safranine respectively. Dr. Jitender Kumar | Navleen Kaur Chopra"Microbial Decolorization of Leather Dye Effluent" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-5 , August 2017, URL: http://www.ijtsrd.com/papers/ijtsrd2405.pdf http://www.ijtsrd.com/biological-science/biotechnology/2405/microbial-decolorization-of-leather-dye-effluent/dr-jitender-kumar
combined toxicity and bioconcentration of fluoride and arsenic in african (3)IJEAB
Laboratory experiments were performed to examine the combined toxic effects of two important aquatic contaminants viz., arsenic and fluoride on African catfish, Clarias gariepinus. Additionally, the bio concentration factors (BCFs) of the two contaminants in tissues and blood of catfish were also determined. The LC50 for sodium fluoride and arsenic trioxide were determined to be 619.3 mg L-1, 30.3 mg L-1, respectively. Erratic swimming movements with hyperactivity, loss of equilibrium, augmented air gulping and decreased food consumption were observed in the experimental groups. In co-exposure groups of arsenic and fluoride, the concentration of fluoride in fish tissues increased with increasing water fluoride concentration in the test aquaria with significant differences (P<0.01)><0.05)>0.05) among the exposure groups. Arsenic was observed to exceedingly bioaccumulate and biomagnify in the tissues. Perhaps due to the complex formation of arsenic and fluoride the bio concentration of arsenic in tissues was observed to decrease with increasing water fluoride concentration and vice-versa. The study concludes that fluoride may interfere with the bio-concentration of arsenic.
The IOSR Journal of Pharmacy (IOSRPHR) is an open access online & offline peer reviewed international journal, which publishes innovative research papers, reviews, mini-reviews, short communications and notes dealing with Pharmaceutical Sciences( Pharmaceutical Technology, Pharmaceutics, Biopharmaceutics, Pharmacokinetics, Pharmaceutical/Medicinal Chemistry, Computational Chemistry and Molecular Drug Design, Pharmacognosy & Phytochemistry, Pharmacology, Pharmaceutical Analysis, Pharmacy Practice, Clinical and Hospital Pharmacy, Cell Biology, Genomics and Proteomics, Pharmacogenomics, Bioinformatics and Biotechnology of Pharmaceutical Interest........more details on Aim & Scope).
All manuscripts are subject to rapid peer review. Those of high quality (not previously published and not under consideration for publication in another journal) will be published without delay.
In order to assessing whether algae can reduce the pollution concentration of the effluents by
absorbing the nutrients, it is found that effluents can effectively be treated by employing algal organisisms such
as Oscillatoria and Stigeoclonium species and these organisms are frequently found in the polluted waters and
they were recorded as pollution tolerant forms. In the laboratory procedures out of the several media tested
Modified CHU No. 10 medium was found to be quite suitable for both the test organisms. It was found that up to
87% and 85% of phosphate uptake was achieved by Oscillatoria and Stigeoclonium respectively with 13% and
16% increase of D.O. in the effluents by the tenth day. In case of organic matter Oscillatoria removed 73% and
Stigeoclonium 70% up to tenth day
Phytoremediation potential of native plant species for gaseous pollution from...Innspub Net
In developing countries, brick kilns are not well regulated by government agencies. As a result most of the time they are installed near to the cities to reduce transport cost. They use coal, waste plastic, scrap tires, etc as fuel. Brick kiln produces number of toxic pollutant like CO2, SOx, NOx, HF, etc. They produce tons of gaseous pollution which effect near and far settled human population. Phytoremediation is considered the most suitable option for developing countries because of low cost, eco-friendliness and easily manageable. In current study, the purpose was to identify tolerant plant species near the brick kilns by measuring air pollution tolerance index (APTI). Species of trees including Mangifera indica, Morus alba, Acacia nilotica, Eucalyptus globulus, Dalbergia sissoo and Moringa oleifera were selected for sampling. Samples were collected during July and December at 100m, 300m, 500m and 700m distance around the brick kilns from two selected sampling sites. Moringa oleifera (APTI=17.60) was identified as tolerant and a sink of hydrogen fluoride (HF). Whereas, Eucalyptus globules (APTI=9.91) was found sensitive, so it can be used as bio-indicator of HF. This study recommends the plantation of Moringa oleifera around brick kiln for HF phytoremediation.
Total phenolics and total flavonoids of extracts from freshwater Clam (Corbic...Innspub Net
The ethanol, ethyl acetate, and hexane extracts of the freshwater clam (Corbicula fluminea) were studied for the total phenolics and total flavonoids. Total phenolics and total flavonoids of the extracts were evaluated using Folin-Ciocalteau and Aluminum chloride colorimetric methods respectively. The findings showed that the total phenolics of the ethanol extract (1.67±0.28mg GAE/g of dried sample) were substantially higher than the total phenolics obtained from the ethyl acetate (0.70±0.00mg GAE/g) and hexane extracts (0.56±0.23mg GAE/g). While the total flavonoids in the ethyl acetate extract displayed a slightly higher total flavonoid (43.84±0.92mg QE/g of dried sample) relative to ethanol (30.41±1.34mg QE/g of dried sample) and hexane extracts (20.28±0.00mg QE/g of dried sample). Using ethanol, the highest yield for extraction was obtained. Ethanol is the best solvent among the three – ethanol, ethyl acetate, and hexane in terms of extraction yield and total phenolics. In addition, it can be inferred that the presence of significant amounts of phenolics and flavonoids suggests that freshwater clam is a promising source of antioxidants that provides nourishing proteins and oxidative stress remedies
this issue.
Climate Governance Initiative Australia
The AICD is the host of the Climate Governance
Initiative Australia which assists in supporting
our members in meeting the challenges and
opportunities of governing climate change risk.
As host of the Australian Chapter of the Climate
Governance Initiative, our members have
access to a global network of experts in risk
and resilience and to non-executive directors
who are leading their organisations’ governance
response to climate change.
The Climate Governance Initiative (CGI) is an
active and rapidly expanding network of over
20 bodies globally, whose Chapters promote the
World Economic Forum Climate Governance
Principles for boards and effective climate
governance within their jurisdictions. The
principles are set out in Appendix 2 of this guide.
The principles support directors to gain
awareness, embed climate considerations into
board decision making, and understand and act
upon the risks and opportunities that climate
change poses to their organisations.
CGI chapters have already been established
in many comparable countries, including the
UK, US (hosted by the National Association of
Corporate Directors), Canada (hosted by the
Institute of Corporate Directors) and France.
Australian Bushfire
and Climate Plan
Final report of the National Bushfire and Climate Summit 2020
The severity and scale of Australian bushfires
is escalating
Australia’s Black Summer fires over 2019 and 2020
were unprecedented in scale and levels of destruction.
Fuelled by climate change, the hottest and driest year
ever recorded resulted in fires that burned through land
two-and-a-half times the size of Tasmania (more than 17
million hectares), killed more than a billion animals, and
affected nearly 80 percent of Australians. This included
the tragic loss of over 450 lives from the fires and
smoke, more than 3,000 homes were destroyed, and
thousands of other buildings.
While unprecedented, this tragedy was not
unforeseen, nor unexpected. For decades climate
scientists have warned of an increase in climaterelated disasters, including longer and more
dangerous bushfire seasons, which have become
directly observable over the last 20 years. Extremely
hot, dry conditions, underpinned by years of reduced
rainfall and a severe drought, set the scene for the
Black Summer crisis.
Recommendations - The 3 Rs - Response,
Readiness and Recovery
There is no doubt that bushfires in Australia have
become more frequent, ferocious and unpredictable
with major losses in 2001/02 in NSW, 2003 in the
ACT, 2013 in Tasmania and NSW, 2018 in Queensland,
2009 Black Saturday Fires in Victoria and 2019/20 in
Queensland, NSW, Victoria and South Australia. We are
now in a new era of supercharged bushfire risk, forcing
a fundamental rethink of how we prevent, prepare for,
respond to, and recover from bushfires.
This Australian Bushfire and Climate Plan report
provides a broad plan and practical ideas for
governments, fire and land management agencies
and communities to help us mitigate and adapt to
worsening fire conditions. The 165 recommendations
include many measures that can be implemented right
now, to ensure communities are better protected.
How to work with petroleum hydrocarbon suppliers to reduce and eliminate cont...Turlough Guerin GAICD FGIA
Petroleum hydrocarbon suppliers affect a mine's goals for environmental performance because of the extensive reach of petroleum hydrocarbon products into the mining and minerals product life cycle, their impact on operational efficiencies, cost, and mine viability, and their potential for leaving negative environmental as well as safety legacies. The supplied petroleum hydrocarbon life cycle is a framework that enables structured engagement between supplier and customer on a range of environmental performance issues because it is an example of input into the mining industry that affects the entire mining and minerals processing an value chain. Engagement with suppliers in a proactive manner can be a risk management strategy. Questions for businesses to ask in relation to suppliers and their role in minimizing business risks and creating new value are offered (https://onlinelibrary.wiley.com/doi/full/10.1002/rem.21669).
Governments would get bigger bang for taxpayer
buck by instead spending more on upgrading existing infrastructure,
and on social infrastructure such as aged care and mental health care.
Choosing net zero is
an economic necessity
Australia pays a high price of a global failure
to deliver new growth in recovery. Compared
to this dismal future, Deloitte Access Economics
estimates a new growth recovery could
grow Australia’s economy by $680 billion
(present value terms) and increase GDP
by 2.6% in 2070 – adding over 250,000 jobs
to the Australian economy by 2070.
The world of venture capital has seen huge changes over the past decade. Ten years ago there were fewer than
20 known unicorns in the US5
; there are now over 2006
. Annual investment of global venture capital has increased
more than fivefold over the same period, rising to $264 billion by 2019. This investment has been dominated by the
tech sector harnessing digital frontiers to disrupt traditional industries – including cloud computing, mobile apps,
marketplaces, data platforms, machine learning and deep tech.7
It is an ecosystem that acts as the birthplace for
innovation and brands that can shape the future of consumerism, sectors and markets.
As COVID-19 has taken hold of the
world, the question of whether venture
capital, and early stage investing more
broadly, is backing and scaling the
innovations our world really needs has
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and biotech investing is an asset class
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This research represents a first-ofits-kind analysis of the state of global
climate tech investing. We define what
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2020s. Representing 6% of global
annual venture capital funding in 2019,
our analysis finds this segment has
grown over 3750% in absolute terms
since 2013. This is on the order of 3
times the growth rate of VC investment
into AI, during a time period renowned
for its uptick in AI investment.8
Looking forward can climate tech in the
2020s follow a similar journey to the
artificial intelligence (AI) investing boom
in the 2010s? The substantial rates of
growth seen in climate tech in the late
2010s, and the overarching need for
new transformational solutions across
multiple sectors of the economy,
suggests yes. The stage appears set
for an explosion of climate tech into the
mainstream investment and corporate
landscape in the decade ahead.
Nine shifts will radically change the way construction projects are delivered—and similar
industries have already undergone many of the shifts. A combination of sustainability
requirements, cost pressure, skills scarcity, new materials, industrial approaches, digitalization,
and a new breed of player looks set to transform the value chain. The shifts ahead include
productization and specialization, increased value-chain control, and greater customercentricity
and branding. Consolidation and internationalization will create the scale needed to
allow higher levels of investment in digitalization, R&D and equipment, and sustainability as well
as human capital.
Sustainable Finance Industry Guide
This industry guide provides information about sustainable finance in the built environment in Australia. It is designed to support investor understanding of Australia’s world-class rating tools and standards, and how these can be applied to direct more capital towards sustainable finance for our built environment. Included are insights that reflect lessons learnt when using a rating scheme to establish an investment framework, conduct
due diligence or report on an issuance.
Precincts to Support the Delivery of Zero Energy
This report frames the physical and organisational context for precinct action and identifies potential programs and government solutions that may be applied to better streamline the realisation of precinct-scale action to progress towards zero energy (and carbon) ready residential buildings within both new and existing precincts.
The report was developed based on a literature review and engagement with more than 80 stakeholders from industry, academia and government with the aim of identifying appropriate government action in the form of proposed solutions that may be applicable across Commonwealth, state and territory and/ or local governments.
The report has given focus to opportunities for precincts that are not already considered in the Trajectory to ensure that a wider system response is taken to considering the zero energy (and carbon) ready outcomes being sought.
When seeking funding, environmental and sustainability professionals must clarify how their role and the proposed project fit within the business' strategy.
This article provides a checklist for those seeking funding for sustainability and environmental projects.
The suggested questions will assist non-executive directors in evaluating sustainability-focused proposals.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
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We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
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Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
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Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
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Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
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;
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State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
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In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
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Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
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Mission to Decommission: Importance of Decommissioning Products to Increase E...
Abiological loss of endosulfan and related chlorinated organic compounds from aqueous systems in the presence and absence of oxygen
1. Environmental Pollution 115 (2001) 219–230
www.elsevier.com/locate/envpol
Abiological loss of endosulfan and related chlorinated organic
compounds from aqueous systems in the presence and absence of
oxygen
T.F. Guerin *
3/32 Wolli Creek Road, Banksia, Sydney, New South Wales 2216 Australia
Received 24 July 2000; accepted 25 January 2001
‘‘Capsule’’: Endosulfan, related OC pesticides, and major degradation products are studied in aquatic systems and factors
influencing persistence, and implications to biodegradation studies are explored.
Abstract
Endosulfan is a cyclodiene organochlorine currently widely used as an insecticide throughout the world. This study reports that
the endosulfan isomers can be readily dissipated from aqueous systems at neutral pH in the absence of biological material or
chemical catalysts, in the presence or absence of oxygen. The study showed that aldrin, dieldrin, and endosulfan exhibit bi-phasic
loss from water in unsealed and butyl rubber sealed vessels. Half-lives are substantially increased for endosulfan I when oxygen is
removed from the incubation vessel. The study conditions, where PTFE was used, were such that loss due to volatilization and
alkaline chemical hydrolysis was eliminated. Half-lives determined from these data indicate that the parent isomers are much less
persistent than the related cyclodienes, aldrin and dieldrin, confirming the findings of previous studies. The major oxidation product
of endosulfans I and II, endosulfan sulfate, is less volatile and can persist longer than either of the parent isomers. Endosulfan
sulfate was not formed in any of the treatments suggesting that it would not be formed in aerated waters in the absence of microbial
activity or strong chemical oxidants. Since endosulfan sulfate is formed in many environments through biological oxidation, and is
only slowly degraded (both chemically in sterile media and biologically), it represents a predominant residue of technical grade
endosulfan, which finds its way into aerobic and anaerobic aquatic environments. The data obtained contributes to and confirms
the existing body of half-life data on endosulfan I and II and its major oxidation product, endosulfan sulfate. The half-life data
generated from the current study can be used in models for predicting the loss of chlorinated cyclodiene compounds from aqueous
systems. The findings also highlight the importance of critically reviewing half-life data, to determine what the predominant processes are that are acting on the compounds under study. # 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Endosulfan; Degradation; Pesticide; Half-lives; Hydrolysis; Non-biological degradation; Bi-phasic loss; Persistence; Abiotic loss; Biodegradation; Endosulfan sulfate; Toxicity; Physico-chemical; Risk
1. Introduction
Endosulfan is a cyclodiene organochlorine possessing
a labile, cyclic sulfite diester group. Endosulfan is a
widely used agricultural chemical and it has been detected in an increasing number of environmental samples
in recent years (Guerin and Kennedy, 1991; Guerin,
1993; Mansingh and Wilson, 1995; Mansingh et al.,
1997; Miles and Pfeuffer, 1997; Guerin, 1999b). Of key
* Present address: Shell Engineering Ltd, NSW State Office, PO
Box 26, Granville 2142 NSW, Australia. E-mail address: turlough.
guerin@shell.com.au.
E-mail addresses: turloughg@hotmail.com, turlough.guerin@
bigpond.com (T.F. Guerin).
concern regarding its widespread distribution, particularly in water environments, is its high acute toxicity to
fish (Table 1). There are, however, relatively few studies
describing the fate of endosulfan in aquatic systems
(Greve, 1971; Walker et al., 1988; Peterson and Batley,
1991; Singh et al., 1991; Guerin and Kennedy, 1992;
Guerin, 1993; Peterson and Batley, 1993; Mansingh and
Wilson, 1995; Mansingh et al., 1997; Miles and Pfeuffer,
1997). In addition, it has not been extensively determined to what extent losses of the endosulfan isomers
result from chemical degradation as opposed to dissipation by other means, such as volatilization and
adsorption, in aqueous systems (Guerin and Kennedy,
1992; Guerin, 1993). Although there are a number of
reports describing biological oxidation of endosulfan to
0269-7491/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0269-7491(01)00112-9
2. 220
T.F. Guerin / Environmental Pollution 115 (2001) 219–230
Table 1
Overview of acute toxicity of key endosulfan compoundsa
Compound
Table 2
Liquid-phase physico-chemical properties of major endosulfan compounds
Toxicity LD50 (mg kgÀ1)
Insects
Endosulfan I
Endosulfan II
Endosulfan sulfate
Endosulfan diol
Fish
Birds
Mammals
5.5
9.0
9.5
>500
0.001–0.01b
0.001–0.01
0.001–0.01
1–10
26–1000
26–1000
–c
–
9.4–40
177
8–76
>1500
a
Summarized from the literature (Guerin, 1993; Anonymous,
1998).
b
The lower the lethal dose, i.e. LD50 value, the higher the toxicity.
c
–, indicates that there was no data available.
the sulfate, there is no clear evidence for its formation in
sterile soils or water (Guerin, 1993). This indicates that
living organisms may be necessary to bring about the
oxidation of endosulfan to form endosulfan sulfate in
the environment. Previous studies have also reported
that isomerization can occur between the parent isomers
in aqueous systems, with the reaction favouring formation of endosulfan I (a-endosulfan; Schmidt et al.,
1997).
The primary aim of the research described in this
paper was to determine the half-life of the parent endosulfan compounds in sterile aqueous solutions with and
without the presence of oxygen. A further aim was to
determine whether endosulfan sulfate could be formed
under these conditions.
2. Materials and methods
2.1. Chemicals
Endosulfan and its degradation products were a gift
from Hoechst, Germany. Aldrin and dieldrin were provided by Shell Chemicals, Australia. cis- and transAldrin diol were kindly provided by Shell Chemicals
Research, UK. Hexane (Nanograde) and methanol
(ChromAR) were purchased from Mallinckrodt Chemicals. The key physico-chemical properties of the endosulfan compounds are summarized in Table 2.
2.2. Incubation conditions in aerobic study
The pesticides, endosulfan I, II, aldrin and dieldrin and
the endosulfan degradation product, endosulfan sulfate
(100–500 ppm in 10 ml methanol) were added to either
Nanopure-filtered, distilled and deionized water, sterilized by autoclaving at 121 C for 20 min, or sterilized
100 mM potassium phosphate-buffered yeast mannitol
medium with filtered (45 m) soil extract (10% v/v of a 50
g lÀ1 soil in water extract; (Guerin, 1993) in 4 ml Wheaton vials, to give final amounts of 1–5 mg lÀ1. The headspace volume was 2 ml in the vials. The quantities of 1–5
Compound
Log Kow v.p. (Pa)a,b Hc
Solubility in
water (S) ppma
Endosulfan I
0.51
Endosulfan II
0.45
Endosulfan sulfate
0.48
Endosulfan diol
300.0
3.6
3.83
3.66
3.68
0.0004
8.0Â10À5
3.7Â10À5
2.3Â10À6
0.72
0.04
0.03
1.3Â10À4
a
Values reported are from the PhysProp and DATALOG Databases from Syracuse Research Corporation where available (Meylan
and Howard, 2000). Values for endosulfan diol are from elsewhere
(Guerin and Kennedy, 1992; Guerin, 1993).
b
Vapor pressure in units of Pa.
c
Henry’s constant (H)=v.p./S in units of Pa m3 molÀ1, calculated
from the v.p. and S data reported in this table.
mg lÀ1 pesticide used in this study reflects those commonly used in studies of the microbial degradation of
pesticides, and in aquatic toxicology, where bioassays
are performed. The medium was also sterilized by
autoclaving for 20 min at 121 C. It is also noted that the
quantities of added pesticide meant that these compounds were close to the limits of the solubility for these
compounds in the aqueous phase (Table 2). Duplicate
vials were made of unsilanized borosilicate glass and
prepared according to the protocol described (Guerin,
1993). The medium contents have previously been
described (Guerin, 1993). Vessels were sealed with either
Polytetrafluoroethylene (PTFE)-lined butyl rubber seals
(Wheaton, Millville NJ, USA supplied by Edwards
Instrument, Narellan, Australia) or non-PTFE-lined
butyl rubber stoppers. Duplicate vessels were kept at
30 Æ 0.5 C, in an incubator for 30 days. No further
attempt was made to artificially aerate the incubation
flasks during the course of the experiment, and sterile
air at atmospheric pressure from a laminar flow cabinet
was used as the gas atmosphere in the headspace of
the flasks. The media was kept sterile throughout the
experiment, and this was checked by heterotrophic plate
counts and microscopic examination (Guerin, 1993).
The pH of the media was adjusted to 7 Æ 0.05 with KOH
or HCl prior to dispensing into the incubation vessels.
Incubation vessels were kept in the dark.
Surface microlayer subsamples were also taken, in
triplicate, after 4 h (30 C) from vessels set aside especially to determine whether there was any difference in
pesticide concentration at the liquid–air interface. This
was performed by withdrawing a volume of 100 ml from
the surface, an amount equivalent to the top 0.9 mm
of the medium, using a pipette. The pipette was rinsed
with solvent and the medium extracted as previously
described (Guerin and Kennedy, 1992). An equivalent
volume removed from the medium bulk was also analyzed for pesticides.
3. T.F. Guerin / Environmental Pollution 115 (2001) 219–230
2.3. Incubation conditions in oxygen-limited study
3. Results and discussion
The incubations conditions were as before except
the incubation vessels were evacuated with N2 gas
at the commencement of the incubation period. Resazurin was added to the medium and this dye remained
in its reduced form throughout the entire incubation
period (i.e. clear) in all the incubation vessels.
221
3.1. Analysis using 0–30 day data
2.4. Extraction, recovery and analysis of parent
pesticides and degradation products
Duplicate incubation vessels containing the aqueous
media (2 ml) had their contents quantitatively transferred (i.e. sacrificed) into the reservoir of a 10 ml
liquid–liquid partitioning device (Mixxor1 by Genex)
and were extracted, recoveries determined, and analyses
conducted according to the method previously described (Guerin and Kennedy, 1992). Samples were
taken on days 0, 2, 4, 6, 8, 15 and 30. A total solvent
volume of 10 ml hexane/acetone/methanol/medium
(15:5:2:2) was also added to the Mixxor1 reservoirs.
The piston of the Mixxor1 was moved 60 times in its
reservoir to partition the pesticides into the solvent
phase. After the phases were allowed to separate ($1
min), the solvent layer was decanted off the aqueous
phase directly from the Mixxors1 into volumetric flasks
and the total volumes were made to either 10 or 25 ml
with hexane. Subsamples were dried with anhydrous
sodium sulfate prior to analysis by GC–ECD.
2.5. Analysis of data
Half-lives for all the compounds were determined.
The data analysis was conducted in three stages. During the initial data analysis (incorporating the data
collected at all sampling times, i.e. 0–30 days), the
square root of the correlation coefficient (r2) was determined from the log exponential decay plots i.e. log
100ÂC/Co vs t plots using the trend line function in
Microsoft Excel 2000 (Microsoft). In the second stage
of the analyses, data were analyzed, excluding the data
at day 15 and 30, to determine whether the pesticide
loss was bi-phasic, that is, exponential during the initial
phases of the experiment (0–8 days), followed by a later
linear phase (8–30 days). Where there was bi-phasic (i.e.
non-first-order or non-linear) loss occurring, evident
from the 100ÂlogC/Co vs t plots, 8–30 day data was
plotted and half-lives were also calculated using this
data. Multivariate analysis were conducted to compare
sets of data using the regression function in Microsoft
Excel 2000 (Microsoft). This generated P-values (5%
level of significance) for these comparisons. Univariate
analyses were conducted on individual treatments (e.g.
aldrin, unsealed, 0–30 days) to determine P values (5%
level of significance).
For each of the treatments, a line was plotted through
the data to determine whether the data collected at
all the sampling times fitted an exponential decay curve.
Since the concentration data was plotted as log values,
then an exponential decay plot would be a straight line
on such graphs.
The dissipation of aldrin and dieldrin from PTFE
sealed vessels observed the first order decay model. This
was also the case with the data from dissipation of
endosulfan I and II from the unsealed and PTFE sealed
flasks, and the dissipation of endosulfan sulfate from
unsealed, BRS and PTFE sealed flasks. This is illustrated in Fig. 1A–C.
These data indicated, however, that the first order
exponential decay model did not adequately describe the
losses of pesticide over the entire period of the experiment (0–30 days), particularly for losses of the more
volatile pesticides from the unsealed and butyl rubber
sealed vessels.
The dissipation of endosulfan I and II from water in
PTFE-sealed vessels (r2=0.93) and endosulfan sulfate
from water in unsealed vessels (r2=0.95) fitted the first
order decay model well, and therefore a single half-life
value was adequate to describe the loss of these compounds within these treatments. There was a significant
difference (P0.05) between the pesticide half-lives in
the butyl rubber sealed and PTFE-sealed flasks, and the
unsealed and PTFE-sealed vessels, but no differences
were measured between the butyl rubber sealed and the
unsealed vessels. The half-lives of the compounds in
each of the aerobic treatments are recorded in Table 3.
3.2. Analysis using 0–8 day data
The data that were obtained earlier in the trial (i.e. up
to the 8th day of incubation, only) for the unsealed and
BRS sealed treatments, generally showed larger r2
values and an improved fit to the first order exponential
decay model (compare columns 2, 3, 5, 6 in Table 3).
In the unsealed and butyl rubber sealed treatments, it
was found that data from the first 8 days fitted the
model of first order exponential decay better than data
from over the entire experiment (i.e. 30 days). These
findings indicated that the loss of pesticides from the
aqueous media, particularly in the butyl rubber-sealed
and the unsealed vessels, did display a first order exponential decay, but only over the initial phase of the
experiment. Volatilization from the unsealed vessels, and
absorption by butyl rubber in the butyl rubber sealed
vessels, could explain these losses early in the experiment.
As with the 0–30 day data, there was a significant difference (P0.05) between the pesticide half-lives in the
4. 222
T.F. Guerin / Environmental Pollution 115 (2001) 219–230
butyl rubber sealed and PTFE-sealed flasks, and the
unsealed and PTFE-sealed vessels, but no differences
were measured between the butyl rubber sealed and the
unsealed vessels. The 0–8 day data for aldrin, dieldrin
and endosulfan are plotted in Fig. 2A and B.
3.3. Analysis of 8–30 day data
When the 8–30 day data from the unsealed treatments
was analyzed, increased half-lives were obtained. These
half-lives increased from 0.5, 2, and 14 (for the 0–8 day
data), to 78, 46, and 29 days for aldrin, dieldrin, and
endosulfan I, respectively. These increased half-lives
reflected the predominant dissipation processes which
were acting on the compounds after the initial fast rate
of loss due to volatilization. These longer term rates of
loss reflecting the chemical degradation and slow desorption processes, showed that there was an 18–75Â
increase in the half-life length when data from 8–30 days
was considered. These slower processes were chemical
degradation and slow desorption of the compounds
from the glass and through the aqueous media, and
subsequent volatilization (Fig. 3).
3.4. Losses of aldrin and dieldrin
There were high rates of loss of aldrin and dieldrin
from both unsealed incubation vessels and flasks sealed
with butyl rubber when the 0–30 day data was considered. In the butyl rubber sealed vessels, aldrin and
dieldrin had largely disappeared at the 30th day, with
half-lives of 2.9 and 3.7 days, respectively. These results
were similar to the values of 0.5 and 2 days for half-lives
in the open flasks. The only difference in the pattern of
loss between these two treatments was that the initial
rate of dieldrin disappearance in the unsealed vessels
was slightly higher than in the butyl rubber sealed vessels. In contrast, when aldrin and dieldrin were incubated in similar sterile media or in water alone with
PTFE-lined butyl rubber seals, there was a considerably
slower rate of loss. The half-lives under these conditions
were 58 and 22 days, respectively.
Losses of aldrin and dieldrin were very low under
conditions of limited oxygen with half-life values of 134
and 46 days, respectively (Fig. 4A and Table 7).
The bi-phasic pattern of loss was particularly pronounced for aldrin, dieldrin and endosulfan I loss from
unsealed flasks (Table 4). A possible reason for this
non-first order loss could have been that a large proportion of pesticide was concentrated at the liquid–air
interface (surface microlayer) as previously reported
(Guerin and Kennedy, 1992). As a consequence, these
pesticides would be expected to volatilize early in the
experiment because of their close proximity to the liquid–
air interface. Peterson and Batley (1991) have also
suggested this mechanism as a reason for the loss of
Fig. 1. Dissipation of chlorinated compounds under oxygenated conditions (0–30 day data) (A) aldrin and dieldrin, (B) endosulfan I and
II, and (C) endosulfan sulfate.
endosulfan from aqueous media in laboratory experiments. After this surface quantity had entirely volatilized, further losses must have come from the solution
bulk through the process of diffusion. Therefore
another possible reason for this bi-phasic loss may be
due to a rim effect, where the more rapid diffusion
occurs at high adsorptions (i.e. at concentrations higher
than the compound’s solubility in the aqueous medium
5. 223
T.F. Guerin / Environmental Pollution 115 (2001) 219–230
Table 3
Half-lives (r2 values) in days for pesticide loss using the first order exponential decay model on data from various timesa
Compound
Unsealed (days)
0–30
Aldrin
Dieldrin
Endosulfan I
Endosulfan II
Endosulfan sulfate
a
b
13.6
2.8
25.8
18.0
37.3
BRS-sealed (days)
0–8
(0.37)
(0.65)
(0.83)
(0.90)
(0.95)
0.52
2.01
13.8
)200b
51.8
8–30
(0.73)
(0.98)
(0.89)
(0.001)
(0.48)
77.9
46.4
29.0
18.2
35.3
0–30
(0.55)
(0.90)
(0.93)
(0.91)
(1.0)
1.1
3.4
7.9
12.7
34.0
PTFE-sealed (days)
0–8
(0.79)
(0.94)
(0.83)
(0.83)
(0.5)
2.9
3.7
6.6
9.6
12.4
8–30
(0.98)
(0.98)
(0.96)
(0.96)
(0.78)
21.6
2.3
3.0
5.7
68.9
0–30
(0.71)
(0.99)
(0.66)
(0.63)
(0.18)
200b
75
21.7
24.2
102.5
0–8
(0.22)
(0.54)
(0.93)
(0.93)
(0.56)
57.8
21.8
13.8
36.2
65.1
(0.34)
(0.82)
(0.89)
(0.36)
(0.37)
Unsealed=cotton wool was used to stopper the flasks, BRS=butyl rubber sealed vessels, and PTFE=Teflon-lined butyl rubber seals.
Values of 200 and )200 days were given because of the relatively short time of the trials (30 days).
Fig. 2. Dissipation of chlorinated compounds under oxygenated conditions (0–8 day data) (A) aldrin and dieldrin, and (B) endosulfan I
and II.
early in the experiment) across the glass to the surface.
As the pesticide levels decrease in the vessels, the
amounts remaining after the initial high losses will more
closely approximate the upper limits of the compound’s
solubility. This may explain, at least in part, why the
pesticide loss is slower after 8–30 days incubation as
the forces of solubilization would tend to override those
exerted by volatilization (Guerin and Kennedy, 1992;
Guerin, 1993).
In the current study, approximately 40–50% of the
originally applied pesticides recovered from the vessels
containing aqueous medium (1–5 mg mlÀ1 originally
added), was found to be concentrated at the interfaces
of the system. Also, an attempt was made to subsample
the liquid–air interface and measure the pesticide concentration. However, there was no detectable difference
between the surface sample and that in the bulk of the
medium. Therefore, the pesticides must have accumulated at the liquid–glass interface only under these
conditions. Although it is possible that a slower rate
of hydrolysis could occur at this interface, insulated
from the effect of the hydroxyl ion, this is unlikely to
explain the increased half-lives for the endosulfan isomers reported in this study with effective sealing. A
similar increase in half-life was also observed for the
more stable compounds such as dieldrin, when the flasks
were sealed with PTFE.
This distribution to the glass-medium interface was
observed when the compounds under study were added
to either water or microbial growth media. An homogenous distribution of pesticide throughout the entire
system was achieved by adding 0.1% Tween 80. All of
the compounds studied were distributed throughout the
system in a similar fashion, and all responded similarly
to the detergent treatment in both the sterile distilled
water and growth medium. There was a greater distribution of all the pesticides to the liquid–glass interface in the vessels containing pure water. A similar effect
was observed by Peterson and Batley (1991) when they
subsampled from a larger total volume of water containing both endosulfan isomers at lower concentrations
(0.1 ppm) in polycarbonate vessels. These findings
and the results from the current study therefore illustrate the importance of avoiding subsampling when
analyzing aqueous extracts containing relatively high
concentrations of endosulfan and related cyclodienes.
The distribution of pesticides in aqueous systems is of
particular importance in microbial degradation studies
where the availability of the compound is likely to
affect its degradation. Thus, when the pesticide is added
in small amounts of solvent to the aqueous phase (as
has generally been reported in microbial pesticide
6. 224
T.F. Guerin / Environmental Pollution 115 (2001) 219–230
Fig. 3. Experimental vessel and graphical presentation of bi-phasic loss.
degradation studies, often followed by evaporation of
solvents with N2 gas), its distribution in the incubation
vessel will tend to be associated with the interfaces. The
geometry of the incubation vessel as well as the constituents of the medium will effect the pesticide distribution. In microbial degradation experiments, where
insoluble compounds are added in methanol or a similar
solvent, an apparent increase in pesticide concentration
with time will be observed in the bulk of the medium,
once exponential growth commences and lipids increase
in quantity. This effect may be overcome by completely
sacrificing the entire treatment incubation flasks at each
sampling time.
The inclusion of the very chemically stable cyclodienes,
aldrin and dieldrin, in PTFE-sealed vessels in this study
provided internal controls that indicated disappearance
predominantly from physical losses, thereby providing
the maximum limits of these processes in the system
studied. The experimental conditions were too mild and
the incubation period was too short to allow substantial
chemical degradation of these compounds. The persistence of aldrin and dieldrin in these incubations therefore
represents the maximum limits for either slow volatilization or other possible processes such as irreversible
binding to container surfaces. Thus, any differences
between the persistence of these internal controls and
that of the endosulfan compounds represents the actual
disappearance by chemical reaction. The very slow rate
of disappearance of aldrin and dieldrin in the PTFEsealed vessels in both water and growth medium confirmed that the system was well sealed.
3.5. Dissipation of endosulfan isomers
In both the butyl rubber sealed and the unsealed vessels, the endosulfan isomers were lost at fast rates. After
8 days of incubation, the calculated half-lives of endosulfans I and II in the butyl rubber sealed flasks were 7.9
and 12.7 days, respectively. When endosulfans I and II
were incubated in unsealed vessels, the half-lives varied
from 13.8 to 29 and 18 to )200 days, respectively. In
both the butyl rubber sealed and the unsealed flasks,
comparing 0–8 day data, endosulfan I loss was higher
than that of endosulfan II. This result reinforces previous findings that endosulfan I is more volatile than
endosulfan II (Goebel et al., 1982; Worthing and
Walker, 1987; Singh et al., 1991; Guerin and Kennedy,
1992; Guerin, 1993).
When the vessels were sealed with PTFE, rates of
disappearance for both isomers in both water and
7. T.F. Guerin / Environmental Pollution 115 (2001) 219–230
Fig. 4. Dissipation of chlorinated compounds under oxygen-limited
conditions (0–30 day data) (A) aldrin, dieldrin, endosulfan I and II
(1 ppm), and (B) endosulfan I and II (10 ppm), and (C) endosulfan
sulfate (5 and 50 ppm).
microbial growth medium were considerably lower
comparing 0–30 day data. The half-lives were 21.7 and
24.2 days for endosulfans I and II, respectively. Under
oxygen-limited conditions, the half-lives of endosulfan
I and II, were )200 and 58 days, respectively (Fig. 4A,
B and Table 7). The effect of PTFE sealing was to substantially reduce the volatilization of the parent compounds from the flasks.
225
It was clear from the butyl rubber sealed and unsealed
treatments that endosulfan I is more volatile than
endosulfan II. Given the relative chemical inertness of
the PTFE-sealed systems and that traces of endosulfan
diol were detected in the same system, it is reasonable to
conclude that both endosulfan isomers were chemically
degraded in the aqueous incubations. Based on this
data, endosulfan II may be more chemically labile than
endosulfan I.
In previous studies, it has been observed that endosulfan II also disappeared at a faster rate than endosulfan
I. Under aerobic conditions at a lower temperature of
22 C, the half-lives of endosulfans I and II in a potassium phosphate buffered, minimal salts medium (pH
6.5), were 88 and 40 days, respectively (Miles and Moy,
1979). In their paper no mention was made on how the
vessels were sealed. The half-lives of endosulfans I and
II in non-sterile seawater (pH 8.0) were 4.9 and 2.2
days, respectively (Cotham and Bidleman, 1989). These
incubations were carried out aerobically and at 20oC
under laboratory lighting. In another study, incubations in lake water showed that the half-life of endosulfan I was 35 days at pH 7 and 105 days at pH 5.5
(Greve, 1971). It was shown in the same study that
when iron hydroxide gel is mixed with water, the rate of
hydrolysis is considerably accelerated. Other researchers have reported half-lives of 10–43 days under controlled laboratory conditions, at pH values of 8.5
(Southan and Kennedy, 1995), and values of 3 days
for both isomers in laboratory water columns of unreported pH (Logan and Barry, 1996). Guerin (1999a)
has reported losses of endosulfan I under sterile anaerobic conditions, as part of a 30-day anaerobic biodegradation study, with losses of endosulfan I at 20, 10
and 2% (of that originally applied) when this compound was added at 1, 2, and 10 ppm, respectively,
indicating rates of loss are dependent on the mass of
added pesticide. The latter findings are consistent with
water insoluble pesticides desorbing from the glass surface into the medium. Also, in the Guerin (1999a) study,
when microorganisms were present, half-lives of endosulfan I varied between 5 and 15 days, substantially
increasing its loss. It has also been shown that endosulfan losses can be significantly minimized from water
solutions if the incubation vessels are sealed to prevent
volatilization (Guerin and Kennedy, 1992; Guerin,
1993). Several biodegradation studies in liquid culture
have demonstrated the importance of sealing incubation
vessels with Teflon or PTFE as previously discussed
(Guerin, 1995, and references cited therein). However,
not all biodegradation studies have employed PTFE
and this should be considered as a critical criterion
when reviewing and evaluating degradation data
reported in the literature. It was noted that there was no
interconversion between isomers under the conditions
described in the current study.
8. 226
T.F. Guerin / Environmental Pollution 115 (2001) 219–230
Table 4
Summary of bi-phasic loss data from trials with unsealed vessels
Phase of trial (days)
Main loss mechanisms
Relative rate of loss
Calculated half-lives (days)
Aldrin
Initial (0–8)
Latter (8–30)
Volatilization
Desorption, chemical degradation
The role of pH is important, particularly when the
rates of endosulfan loss are compared across different
studies. This is because the endosulfan isomers are susceptible to alkaline hydrolysis (Goebel et al., 1982).
Thus, rates of hydrolysis at pH 8 will be a $10 times
faster than the rates at pH 7. Some differences in the
half-lives previously reported may be due to differences
in temperature, which may also affect the hydrolysis
rates of pesticides. Since endosulfans I and II are volatile, the temperature at which the experiments are carried out is also very important.
In the current study there was no significant difference
(P0.05) in the degradation rates of either endosulfan
isomer comparing incubation in water and in the
microbial growth medium. This indicates that the soil,
peptone, or yeast extract and inorganic minerals had no
measurable effect on the persistence of the isomers.
3.6. Losses of endosulfan sulfate
In all of the experiments conducted, endosulfan sulfate was relatively stable and considerably more persistent than the parent isomers. The half-life of endosulfan
sulfate in the sterile water was calculated at 103 days
when sealed with PTFE compared with 30 days in the
unsealed vessels. Its persistence in the vessels sealed with
butyl rubber (10 day half life), compared with that in
the unsealed vessels (30 day half-life), was not significant, and this was likely to be due to the wide variation in the analysis of endosulfan sulfate data as
previously reported by (Guerin et al., 1992).
The data on the dissipation of endosulfan sulfate
from the PTFE-sealed vessels fitted the model of first
order exponential decay poorly, when all the sampling
times were analyzed. The very low r2 values obtained
with endosulfan sulfate in the PTFE-sealed vessels,
suggests little or no relationship between endosulfan
sulfate concentrations and time. However, from the
extraction and analysis of endosulfan sulfate previously
reported (Guerin and Kennedy, 1992), it is likely that
analytical error was also important and contributed to
the very low r2 values. Endosulfan sulfate was even
more stable under conditions of limited oxygen, with
half-lives typically )200 days (Fig. 4C and Table 5).
The results of the dissipation of endosulfan sulfate
therefore indicate a limitation of calculating the half-life
of this compound using the approach described here.
Fast
Slow
Dieldrin
Endosulfan I
0.52
77.9
2.01
46.4
13.8
29
This approach is more appropriate for determining the
half-lives of the parent isomers, where the differences
between the half-lives are not as great, and where analytical variation is low.
Miles and Moy (1979) have also reported on the persistence of endosulfan sulfate in aqueous media and
have given a value for its half-life, under the previously
described conditions, as 140 days. The reported persistence of endosulfan sulfate in the aqueous systems
studied in the current work, and from this report in the
literature, indicates that this endosulfan transformation
product is likely to remain in water environments much
longer than the parent isomers. It has previously been
shown not to be readily biodegradable. However, in real
environments, there may be other processes of endosulfan sulfate removal such as strong adsorption to soil
and sediment particles. It should be recognized that
because of the relatively short time frame of the trials,
the r2 values and corresponding half-life data for endosulfan sulfate, has been included in the data set for the
sake of completeness and these do not represent definitive values. Further research would be needed to determine definitive values for the persistence of this
compound in aqueous systems.
3.7. The role of volatilization in pesticide disappearance
From the increased losses in the open vessel incubations, it is evident that the endosulfan dissipation in
these treatments was primarily owing to volatilization.
The rates of volatilization of the endosulfan isomers
in the open-vessel experiments were similar to those
from the butyl rubber sealed experiments. These results
indicated that volatilization of these compounds from
the aqueous media has a similar effect as that of the
butyl rubber seals. Aldrin and dieldrin were also lost at
fast rates in similar incubations, confirming that
absorption into the butyl rubber seals was the major
cause of loss (Guerin and Kennedy, 1992). Extraction
and analysis of the butyl rubber seals after the incubation indicated that all the cyclodienes had become
absorbed into this sealing material.
No hydrolysis products of endosulfan, endosulfan
sulfate, aldrin or dieldrin were detected in hexane–
acetone extracts from the open or butyl rubber sealed
treatments. Thus, it is evident that the major cause of
dissipation of all compounds in the unsealed flasks was
9. 227
T.F. Guerin / Environmental Pollution 115 (2001) 219–230
Table 5
Half-lives for pesticide loss under oxygen-limited conditions using the first order exponential decay model (0–30 days)a
Compound
1 ppmb
10 ppmc
Half-life (days)
Aldrin
Dieldrin
Endosulfan I
Endosulfan II
Endosulfan sulfate
r2
Half-life (days)
r2
134
46
)200
58
)200
0.003
0.14
0.001
0.24
0.43
–
–
200
97
)200
–
–
0.001
0.71
0.01
a
PTFE-lined butyl rubber sealed vessel, evacuated 7Â prior to incubation (see methods); values 200 days were given because of the relatively
short time of the trials (30 days). Values of )200 indicated that the calculated half-lives were greater than 1000 days.
b
5 ppm of endosulfan sulfate was used because of its higher analytical detection limits.
c
50 ppm of endosulfan sulfate was used because of its higher analytical detection limits.
volatilization, and absorption in the butyl rubber sealed
flasks, rather than chemical degradation.
Volatilization from uninoculated controls in aerobic
microbial degradation studies is likely to be a significant
factor in overall pesticide disappearance in unsealed
systems, particularly with organochlorine pesticides
such as endosulfan. In one study, 30% of applied
endosulfan I was reported to have volatilized from a
seawater/sediment microcosm (sealed with polyurethane) during the first 4 days of the experiment
(Cotham and Bidleman, 1989). Others demonstrated
that polystyrene absorbed both endosulfan isomers
strongly, compared with glass (Peterson and Batley,
1991). The current findings therefore confirm these
findings, and illustrate the importance of sealing aqueous systems containing these compounds, with an inert
material such as PTFE.
The high volatilization rate of endosulfan I, is due to
its low water solubility and relatively high vapor pressure, or its high Henry’s constant. The ratio of liquidphase vapor pressure and solubility, or solid-phase
vapor pressure and solubility, provides a value for the
Henry’s constant. This relationship may be used to
show the difference in the relative rates of volatilization
of the parent endosulfan isomers and of the recalcitrant
cyclodienes, aldrin and dieldrin. In illustrating the
importance of the Henry’s constant of a compound, it is
convenient to introduce the concept of fugacity. The
fugacity is the escaping tendency of a compound from a
particular phase. This can be expressed mathematically
as f=C/Z. In this expression, f is the fugacity (units of
pressure Pa), C is the concentration (units of mol mÀ3)
and Z is the fugacity capacity (units of mol mÀ3 PaÀ1).
Each compound has its own fugacity and at equilibrium, compounds will accumulate in phases with
the lowest fugacity, or highest Z values. So in water, the
fugacity capacity is the inverse of the compound’s Henry’s constant (H) (Guerin and Kennedy, 1992). This is
described by the equation, Z=Zwater=1/H. The calculated fugacities of the cyclodiene compounds under
study are equivalent to their vapor pressure values in
the same phase because the concentration (C) is equal to
their water solubilities for the solid compounds.
In calculating the Henry’s constant, values for water
solubility and vapour pressure must be for the same
phase, that is, both for the liquid-phase or both for the
solid-phase. The values presented in Table 2 are for
the solid-phase for each of the pesticides.
Some of the behavior observed in the butyl rubbersealed and unsealed vessels can be accounted for by
differences in their calculated fugacities. The fastest
rates of disappearance from both of these treatments
were that of aldrin, which also had the lowest Z value,
or greatest fugacity. From the vapor pressure and solubility data obtained from the literature, endosulfan I has
a Henry’s constant of 0.72, approximately 18 times
that of endosulfan II (H=0.04), which correlates well
with the greater rate of disappearance from the nonPTFE-sealed vessels (consistent with volatilization and
absorption mechanisms of loss). Aldrin had the highest
Henry constant of 4.95, while dieldrin was lower at 0.53.
3.8. Detection and analysis of potential hydrolysis
products of endosulfan
Trace levels of the hydrolysis product, endosulfan
diol, were detected after 30 days incubation in flasks
containing either parent isomer of endosulfan at the
beginning of the experiment. The recovery treatments
showed that this degradation product was extracted
when spiked into zero time vessels. The identity of
endosulfan diol was confirmed using two different gas
chromatographic columns (Guerin and Kennedy, 1992).
The highest concentrations of endosulfan diol were
detected in the PTFE-sealed incubations. With endosulfan I, these concentrations were 0.08–0.1 ppm of
endosulfan diol after 30 days. This rate of endosulfan
diol formation correlates well for the calculated half-life
of endosulfan I of approximately 22 days in the sterile
media. This rate of formation, however, was not stoichiometric, as approximately 0.5 ppm of endosulfan
diol would have been expected to form over this period
10. 228
T.F. Guerin / Environmental Pollution 115 (2001) 219–230
if there was complete transformation. Some of the difference between the amount of endosulfan diol expected
and that which was observed, may have been due to the
reduced extraction efficiency of the endosulfan diol.
Higher concentrations of 0.1–0.15 ppm endosulfan diol
were detected in the endosulfan II incubations under the
same conditions, consistent with its lower chemical stability. Much lower amounts of endosulfan diol (0.01
ppm) were detected in the endosulfan sulfate incubations after 30 days, and then only in PTFE-sealed incubations. These findings correlate well with the observed
stability of this compound under these conditions.
The potential hydrolysis products of dieldrin, cis- and
trans-aldrin diol, were not detected in any of the treatment incubations containing dieldrin, although the
underivatized standard compounds were chromatographed successfully under the conditions described for
analyzing the parent compounds (Guerin et al., 1992).
Given the highly recalcitrant nature of dieldrin, and the
mild incubation conditions of water and growth medium, no hydrolysis products were expected to form.
Polytetrafluoroethylene (PTFE) exhibits chemical and
physical properties which, when coated onto butyl or
silicone rubber, make it suitable for sealing aqueous
media that is in contact with semi-volatile or hydrophobic compounds such a the cyclodiene pesticides.
These characteristics of PTFE are its high resistance to
heat, inertness to chemical attack over a wide range of
temperatures, low moisture absorption and permeability (0.01% in 24 h), high physical strength, very
high thermal stability, and flexibility. Because of
its high resistance to temperature, it is also autoclavable (Schlanger and Baumgartner, 1980; Guerin, 1993).
However, dry heat and radiation may also sterilize it.
These properties are listed in Table 6. Since this material
is impermeable to gases, including N2, O2, H2, and CO2,
it can also be used to maintain anaerobic conditions in
flasks containing media for the growth of microorganisms. Of these properties, its high chemical resistance is
of greatest importance in biodegradation studies as it
prevents absorption of the compounds under study, into
the sealing material.
4. Conclusions
This study reports that the endosulfan isomers can be
dissipated from simple aqueous systems at neutral pH in
the absence of biological material or chemical catalysts.
When the incubation vessels are sealed with PTFE, then
endosulfan II is more readily degraded than endosulfan
I, a phenomenon already observed in various aqueous
systems. The study also showed that under PTFE-sealed
conditions, but in oxygen-limited conditions, the halflives are more than doubled indicating that the parent
isomers of endosulfan are more stable under these conditions. This result is in contrast to that obtained in
unsealed systems, where the loss of endosulfan I is
greater than that of endosulfan II. Half-lives determined
from the data indicate that the parent isomers are much
Table 6
Physico-chemical properties of polytetrafluoroethylene (PTFE)
Inertness to chemical attack
Low moisture absorption and permeability
Impermeable to N2, O2, H2 and CO2
High physical strength and high thermal stability
Low coefficient of friction
Very low dielectric constant and excellent electrical insulator
Non-stick (anti-adhesion) surfaces
Flexible, making suitable for sealing vessels in biodegradation or dissipation studies
Table 7
Implications and recommendations from the current study
1.
The endosulfan isomers, like aldrin and dieldrin, volatilize readily from incubation vessels containing microbial growth media, which are
unsealed, or sealed with butyl rubber.
Published values for half-lives of volatile and semi-volatile values should be critically reviewed prior to use in modelling their degradation to
see whether the study has taken bi-phasic effects into account and use the data accordingly.
Biodegradation assays should include sterilized cells as a control to minimize glass surface binding effectsa.
Half-life values generated in the current study can be used in modelling the dissipation of the endosulfan and related compounds from
aqueous systems.
When endosulfan (or aldrin and dieldrin) are added to aqueous media at levels higher than their solubility in water, adsorption effects are
likely to retain the pesticide at the glass-media interfaces until microbial growth becomes significant, and causes it to desorb. Therefore in
sterile treatments, entire vessels should be extracted without prior subsampling, particularly with compounds that have low water solubility.
Anaerobic biodegradation assays should be sealed with Teflon-lined butyl rubber to avoid pesticide absorption, while maintaining an oxygen
impermeable seal.
2.
3.
4.
5.
6.
a
Particularly in aerobic studies where the medium surface has direct contact with the atmosphere through a cotton wool plug.
11. T.F. Guerin / Environmental Pollution 115 (2001) 219–230
less persistent than the related cyclodienes, aldrin and
dieldrin. However, the major oxidation product of
endosulfans I and II, endosulfan sulfate, is less volatile
and can persist longer than either of the parent isomers.
Endosulfan sulfate was not formed in any of the
treatments in the current study. This suggests that
endosulfan sulfate would not be formed in aerated
waters in the absence of microbial activity or strong
chemical oxidants. Since endosulfan sulfate is formed in
many natural environments through biological oxidation, and is only slowly degraded (both chemically in
sterile media and biologically), it represents a predominant residue of endosulfan in aerobic aquatic
environments.
Both the endosulfan isomers dissipated from the
incubation vessels at faster rates when the vessel was
sealed with butyl rubber, than when they were sealed
with PTFE. Conversely, the relatively inert PTFE seals
greatly reduced losses from volatilization and absorption, thus providing the necessary conditions for studying the chemical degradation of the cyclodienes.
Analysis of the data on the dissipation of the cyclodienes has indicated that the loss of the more volatile
cyclodienes, aldrin, dieldrin and endosulfan I, from
unsealed and butyl rubber sealed treatments, is bi-phasic.
The fact that there was very little difference between
the rates of dissipation of aldrin and dieldrin from
media sealed with butyl rubber and that which were
unsealed, showed that butyl rubber sealing was ineffective. As known from previous biodegradation studies,
such a rubber seal is therefore unsuitable for microbial
degradation studies when endosulfan or other volatile/
semi-volatile compounds are studied. Although butyl
rubber has a very low permeability towards oxygen, it
has a high affinity for organic compounds (e.g. hexane
and volatile organochlorine pesticides). Conversely,
PTFE, due to its very low coefficient of friction and
resistance to chemical reaction, has an extremely low
porosity to volatile/semi-volatile organic compounds.
PTFE-lined rubber therefore provides an ideal seal for
anaerobic degradation studies with compounds of high
volatility, for example see Guerin (1999a).
A significant finding was the complete absence of the
formation of endosulfan sulfate. This is a toxic degradation product (Table 1), and is the major oxidative
product of endosulfan in the environment. This was true
for both sterile incubations and incubations containing
soil extracts in the well defined liquid media used for
cultivating anaerobic and aerobic bacteria. From the
current study, it is unlikely that endosulfan sulfate
forms in naturally occurring waters under anaerobic
conditions, either with or without microorganisms present. However, endosulfan diol was formed in the sterile
incubations, indicating that this degradation product
may be formed in the absence of any microbial activity.
Furthermore, under the conditions described, there was
229
no interconversion between the parent isomers of endosulfan during the study period.
Further implications for studying the behaviour of
chlorinated organic compounds in aqueous systems are
also given (Table 7). It is imperative that in any aqueous
incubation containing volatile/semi-volatile organic
compounds, such as endosulfan, aldrin or dieldrin, special precautions must be taken to reduce volatilization.
An important demonstration in this study is that of the
necessity to seal aqueous incubation vessels with Teflonlined butyl rubber seals to prevent volatilization which
would have otherwise reduced the apparent half-lives of
the compounds under study. For these volatile organochlorines, unlined butyl rubber was shown to be ineffective as a vessel stopper, and may even enhance the
loss of these compounds from sterile aqueous media.
These findings are fundamental to the design of future
biodegradation experiments as losses of these compounds due to volatilization, as well as from chemical
hydrolysis, are also likely to occur. These losses can
confound the results of biodegradation experiments,
making it difficult to determine which losses are actually
a result of biological activity. Therefore, these findings
were applied to the design of experiments aimed at
determining the role of indigenous soil microorganisms
in the biodegradation of endosulfan under anaerobic
conditions and have allowed the biodegradation potential of indigenous populations of anaerobic microorganisms to be determined (Guerin, 1999a).
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