Mortality response and LC50 values for juvenile and adult crayfish, Procambarus clarkii exposed to Thiodan (insecticide), Treflan, MSMA, Oust (herbicides) and Cutrine-Plus (algicide)

Toxicities of three herbicides (Treflan, MSMA and Oust), an algicide (Cutrine-plus) and an insecticide (Thiodan) to juvenile (3.0-3.4 cm) and adult (9.0-10.0 cm) crayfish, Procambarus clarkii, were determined by 96 h static bioassays. Freshly prepared 0.01% and 1.0% aqueous stock solutions of these pesticides were diluted to desired concentrations. Mortalities were recorded each day up to 96 h. Aged tap-water was used for preparing all test solutions. Per cent mortalities were analyzed for linear regression and LC(50) values were computed by probit analysis. LC(50) values for juvenile P.clarkii in the descending order of toxicity were: 24 ppb Thiodan, 13 ppm Treflan, 101 ppm MSMA, 461 ppm Cutrine-plus, 12,174 ppm Oust; and for adults these values were: 423 ppb Thiodan, 26 ppm Treflan, 1019 ppm MSMA and 2945 ppm Cutrine-plus. No LC(50) values for adult crayfish could be computed for Oust herbicide which caused no mortalities up to 60,000 ppm concentration. Comparing the overall toxicities of these pesticides, Thiodan was the most toxic to all crayfish; followed by Treflan, MSMA, Cutrine-plus and Oust. Oust was more than 1/2 million times less toxic than Thiodan to juvenile crayfish. Published LC(50) values indicate that freshwater crayfish are more tolerant than marine decapods, Crangon septemspinosa and Mysidopsis bahia, to Thiodan insecticide and Treflan herbicide.     

A biological loss of endosulfan and related chlorinated organic compounds from aqueous systems in the presence and absence of oxygen.

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.     

Bioconcentration and depuration of endosulfan sulfate in mosquito fish (Gambusia affinis)

Endosulfan is an insecticide which has been widely used in agriculture. The technical grade material consists of two isomers (alpha and beta). Under natural environmental conditions, endosulfan is metabolized through oxidation and the main metabolite in the environment is endosulfan sulfate. Most ecotoxicology research has been conducted with technical grade endosulfan to determine effects on non-target aquatic organisms. Little data on the effects of endosulfan sulfate on aquatic organisms are available in the literature. This study characterizes endosulfan sulfate bioconcentration and depuration in mosquito fish (Gambusia affinis). During the study, G. affinis was exposed to an environmentally relevant endosulfan sulfate concentration of 0.25 μg L⁻¹ for 5 weeks (uptake phase) followed by a 3-week period (depuration phase) in clean water. This study found that G. affinis bioconcentrated endosulfan sulfate. During the exposure phase, fish tissue concentrations of endosulfan sulfate increased with time up to 730 μg kg⁻¹ dw or 215 μg kg⁻¹ ww. The bioconcentration data followed Michaelis-Menten kinetics better than the one-compartment first order kinetics (1-CFOK). Using these models, the bioconcentration factors for endosulfan sulfate-exposed G. affinis were from 687 to 888  L kg⁻¹ in wet weight or 2263 to 2936 L kg⁻¹ in dry weight. During the depuration phase, endosulfan sulfate concentrations in tissue significantly decreased and the data followed first order kinetics. The half-life of endosulfan sulfate in G. affinis was about 9 d. There was no significant difference in standard length or weight between control and exposed fish. The growth data followed the von Bertalanffy growth model. However, the condition factor of exposed fish increased with time during the exposure phase.     

Enrichment and isolation of endosulfan-degrading microorganism from tropical acid soil

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the enrichment and isolation of a microbial culture capable of degrading endosulfan with minimal production of endosulfan sulfate, the toxic metabolite of endosulfan, from tropical acid soil. Enrichment was achieved by using the insecticide as sole sulfur source. The enriched microbial culture, SKL-1, later identified as Pseudomonas aeruginosa, degraded up to 50.25 and 69.77 % of α and β endosulfan, respectively in 20 days. Percentage of bioformation of endosulfan sulfate to total formation was 2.12% by the 20th day of incubation. Degradation of the insecticide was concomitant with bacterial growth reaching up to an optical density of 600 nm (OD600) 2.34 and aryl sulfatase activity of the broth reaching up to 23.93 μg pNP/mL/hr. The results of this study suggest that this novel strain is a valuable source of potent endosulfan–degrading enzymes for use in enzymatic bioremediation. Further, the increase in aryl sulfatase activity of the broth with the increase in degradation of endosulfan suggests the probable involvement of the enzyme in the transformation of endosulfan to its metabolites.     

The histopathological effects of thiodan on the liver and gut of mosquitofish, Gambusia affinis

Thiodan (33.7% endosulfan), a polychlorinated cyclodiene insecticide, was evaluated for its histopathological effects on mosquitofish, Gambusia affinis, by light microscopy. Fish were exposed to doses of 0.00 (control), 1.00, 2.50, and 5.00 microg/L on days 7, 14, 21, and 30. No histopathological effects were apparent at control group. The histopathological alterations were characterized as oedema, degeneration, accumulation of lymphocytes in the lamina propria, disintegration of villuses, pycnotic state of nuclei, and necrosis in gut; degeneration, hypertrophy, sinusoids enlargement, hemorrhage, pycnosis position of nuclei, vacuolization of cell cytoplasm, infiltration of mononuclear lymphocyte, and congestion in liver. These alterations were time- and dose-dependent.     

Assessment of the impact of pesticide residues on microbiological and biochemical parameters of tea garden soils in India

The main aim of this study was to assess the impact of pesticidal residues on soil microbial and biochemical parameters of the tea garden soils. The microbial biomass carbon (MBC), basal (BSR) and substrate induced respirations (SIR), beta-glucosidase activity and fluorescein diacetate hydrolyzing activity (FDHA) of six tea garden soils, along with two adjacent forest soils (control) in West Bengal, India were measured. The biomass and its activities and biochemical parameters were generally lower in the tea garden soils than the control soils. The MBC of the soils ranged from 295.5 to 767.5 micro g g(- 1). The BSR and SIR ranged from 1.65 to 3.08 mu g CO2-C g(- 1) soil h(- 1) and 3.08 to 10.76 micro g CO2-C g(- 1)h(- 1) respectively. The beta-glucosidase and FDHA of the soils varied from 33.3 and 76.3 micro g para-nitrophenol g(- 1) soil h(- 1) and 60.5 to 173.5 micro g fluorescein g(- 1)h(- 1)respectively. The tea garden soils contained variable residues of organophosphorus and organochlorine pesticides, which negatively affected the MBC, BSR, SIR, FDHA and beta -glucosidase activity. Ethion and chlorpyriphos pesticide residues in all the tea garden soils varied from 5.00 to 527.8 ppb and 17.6 to 478.1 ppb respectively. The alpha endosulfan, beta endosulfan and endosulfan sulfate pesticide residues in the tea garden soils ranged from 7.40 to 81.40 ppb, 8.50 to 256.1 ppb and 55 to 95.9 ppb respectively. Canonical correlation analysis shows that 93% of the total variation was associated with the negative impact of chlorpyriphos, beta and alpha endosulfan and endosulfan sulfate on MBC, BSR and FDHA. At the same time ethion had negative impact on SIR and beta-glucosidase. Data demonstrated that the pesticide residues had a strong impact on the microbial and biochemical components of soil quality.     

The fate of endosulfan in water

Although the use of endosulfan to control cotton pests has declined, this insecticide still has widespread application in agriculture and can contaminate riverine systems as runoff from soil or by aerial deposition. The degradation of endosulfan in pure water at different pH values of 5, 7 and 9 and in river water from the Namoi and the Hawkesbury rivers of New South Wales (NSW), Australia, was studied in the laboratory. Endosulfan transformation into endosulfan sulfate in river water using artificial mesocosms was also investigated. The results show endosulfan is stable at pH 5, with increasing rates of disappearance at pH 7 and pH 9 by chemical hydrolysis. Incubation of endosulfan with river water at pH 8.3 resulted in the disappearance of endosulfan and the formation of endosulfan diol due to the alkaline pH as well as formation of endosulfan sulfate. Although the degradation of endosulfan by Anabaena, a blue-green alga, did not result in the transformation of endosulfan to endosulfan sulfate, we conclude that other microorganisms catalyzed the formation of the sulfate. Significant conversions of endosulfan into endosulfan sulfate were also reported from associated field studies using artificial mesocoms containing irrigation water from rivers inhabitated by micro-macro fauna. From these results, we conclude that the presence of endosulfan sulfate in river water cannot be used to distinguish contamination by runoff from soil from contamination by aerial drift or redeposition.     

Endosulfan and quinalphos residues and toxicity to soil microarthropods after repeated applications in a field investigation

Endosulfan (1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-en-2,3-ylenedimethylsulphite) and quinalphos (O,O-diethyl O-quinoxalin-2-yl phosphorothioate) persistence and their effect on soil microarthropods were studied after repeated applications in cotton fields. Dissipation behavior of insecticides after repeated applications was observed from 78 to 292 days after the first insecticide treatment. At any given time the concentrations of endosulfan beta residues were always higher as compared to endosulfan alpha. From 78 to 85 days, 5.0% and 20.4% decrease in alpha and beta endosulfan residues was observed, respectively. Endosulfan beta isomer decreased up to 93.0% in 292 days. Endosulfan sulfate was detected as a major metabolite in the soil samples. Total endosulfan residues decreased by 86.6% from 78 to 292 days. The amounts of quinalphos residues were less as compared to endosulfan at any given time. The residues observed after 78 days of application were 0.88 ng g-1 d wt. soil. At the end of 145 days, a 35.0% decrease in quinalphos residue was observed, which decreased further by 50.9% in 292 days. Among the soil microarthropods studied, Acarina was more sensitive to the applied insecticides as compared to Collembola. Three days after the last treatment, up to 94.5% (p < 0.01) and 71.2% (p < 0.05) decrease in Acarina population was observed in endosulfan and quinalphos treated fields, respectively, compared to control field. In general, no noticeable change in Collembola population was observed after the insecticide treatments.     

The Fate of Endosulfan in Water

Although the use of endosulfan to control cotton pests has declined, this insecticide still has widespread application in agriculture and can contaminate riverine systems as runoff from soil or by aerial deposition. The degradation of endosulfan in pure water at different pH values of 5, 7 and 9 and in river water from the Namoi and the Hawkesbury rivers of New South Wales (NSW), Australia, was studied in the laboratory. Endosulfan transformation into endosulfan sulfate in river water using artificial mesocosms was also investigated. The results show endosulfan is stable at pH 5, with increasing rates of disappearance at pH 7 and pH 9 by chemical hydrolysis. Incubation of endosulfan with river water at pH 8.3 resulted in the disappearance of endosulfan and the formation of endosulfan diol due to the alkaline pH as well as formation of endosulfan sulfate. Although the degradation of endosulfan by Anabaena, a blue-green alga, did not result in the transformation of endosulfan to endosulfan sulfate, we conclude that other microorganisms catalyzed the formation of the sulfate. Significant conversions of endosulfan into endosulfan sulfate were also reported from associated field studies using artificial mesocoms containing irrigation water from rivers inhabitated by micro-macro fauna. From these results, we conclude that the presence of endosulfan sulfate in river water cannot be used to distinguish contamination by runoff from soil from contamination by aerial drift or redeposition.     

Organochlorine contaminants in complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs from Belize

Seven complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs were collected in northern Belize and examined for organochlorine (OC) pesticide residues. The primary OC detected, p,p-DDE, was found in every egg analyzed (n=175). Other OCs detected included p,p-DDT, p,p-DDD, methoxychlor, aldrin, and endosulfan I. Concentrations of individual OCs ranged from 4 ppb (ng chemical/g egg wet weight) to greater than 500 ppb. A statistical evaluation of p,p-DDE levels in three complete clutches was used to derive the minimum number of eggs needed from a clutch to precisely determine the mean p,p-DDE concentration representative of that clutch. Sample sizes of 8 (80% confidence level) and 11 (90% confidence level) were determined to yield an accurate estimate of contaminant levels in a full clutch of eggs. The statistically recommended sample size of 11 eggs (at 90% confidence level) was successfully tested on the four additional clutches.     

Enhanced degradation of carbofuran in Pacific Northwest soils

Persistence of 14C-carbonyl carbofuran was measured in Pacific Northwest soils that had received 1-14 applications of the insecticide for root weevil control on perennial crops. Insecticide decay curves were obtained in nonautoclaved soil and several autoclaved soil samples from previously-treated fields and in nonautoclaved soils from paired control sites not previously treated with carbofuran. The insecticide usually degraded faster in soil from previously-treated fields than in soil from corresponding control fields. Among 26 previously-treated fields, the pseudo half-life (time for 50% loss) of carbofuran was less than one wk in 11 soils, 1-3 wks in 8 soils and greater than 4 wks in the remaining soils. Among the nontreated control fields the pseudo half-life was greater than 2 wks in all cases and greater than 15 wks in 5 of the soils. The carbofuran decay curve always possessed an initial lag phase where soil mixing enhanced insecticide decline. Carbofuran degraded very slowly in autoclaved soil samples. The half-life of carbofuran exceeded 16 wk in all autoclaved soils tested and in most instances 85-90% of the original dosage remained when the tests were terminated 112 days after treatment. These results provided evidence that many of the soils which received applications of carbofuran over the past several years have developed a capacity to degrade carbofuran very rapidly.     

Biodegradation of endosulfan by Mortieralla sp. strain W8 in soil: Influence of different substrates on biodegradation

To examine the bioremediation potential of Mortierella sp. strain W8 in endosulfan contaminated soil, the fungus was inoculated into sterilized and unsterilized soil spiked with endosulfan. Wheat bran and cane molasses were used as substrates to understand the influence of different organic materials on the degradation of endosulfan in soil. Strain W8 degraded α- and β-endosulfan in both sterilized and unsterilized soil. In unsterilized soil with wheat bran+W8, α- and β- endosulfan were degraded by approximately 80% and 50%, respectively after 28 d incubation against the initial endosulfan concentration (3 mg kg(-1) dw). The corresponding values for α- and β-endosulfan degradation with wheat bran only were 50% and 3%. Endosulfan diol metabolite was detected after 14 d incubation in wheat bran+W8 whereas it was not found with wheat bran only. Production of endosulfan sulfate, the main metabolite of endosulfan, was suppressed with wheat bran+W8 treatment compared with wheat bran only. It was demonstrated that wheat bran is a more suitable substrate for strain W8 than cane molasses. Wheat bran+W8 is a superior fungus and substrate mix for bioremediation in soil contaminated with endosulfan.     

Endosulfan and Quinalphos Residues and Toxicity to Soil Microarthropods after Repeated Applications in a Field Investigation

Endosulfan (1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-en-2,3-ylenedimethylsulphite) and quinalphos (O,O-diethyl O-quinoxalin-2-yl phosphorothioate) persistence and their effect on soil microarthropods were studied after repeated applications in cotton fields. Dissipation behavior of insecticides after repeated applications was observed from 78 to 292 days after the first insecticide treatment. At any given time the concentrations of endosulfan β residues were always higher as compared to endosulfan α. From 78 to 85 days, 5.0% and 20.4% decrease in α and β endosulfan residues was observed, respectively. Endosulfan β isomer decreased up to 93.0% in 292 days. Endosulfan sulfate was detected as a major metabolite in the soil samples. Total endosulfan residues decreased by 86.6% from 78 to 292 days. The amounts of quinalphos residues were less as compared to endosulfan at any given time. The residues observed after 78 days of application were 0.88 ng g^?1 d wt. soil. At the end of 145 days, a 35.0% decrease in quinalphos residue was observed, which decreased further by 50.9% in 292 days. Among the soil microarthropods studied, Acarina was more sensitive to the applied insecticides as compared to Collembola. Three days after the last treatment, up to 94.5% (p < 0.01) and 71.2% (p < 0.05) decrease in Acarina population was observed in endosulfan and quinalphos treated fields, respectively, compared to control field. In general, no noticeable change in Collembola population was observed after the insecticide treatments.     

Assessment of the impact of pesticide residues on microbiological and biochemical parameters of tea garden soils in India

The main aim of this study was to assess the impact of pesticidal residues on soil microbial and biochemical parameters of the tea garden soils. The microbial biomass carbon (MBC), basal (BSR) and substrate induced respirations (SIR), β -glucosidase activity and fluorescein diacetate hydrolyzing activity (FDHA) of six tea garden soils, along with two adjacent forest soils (control) in West Bengal, India were measured. The biomass and its activities and biochemical parameters were generally lower in the tea garden soils than the control soils. The MBC of the soils ranged from 295.5 to 767.5 μ g g^{? 1}. The BSR and SIR ranged from 1.65 to 3.08 μ g CO₂-C g^{? 1} soil h^{? 1} and 3.08 to 10.76 μ g CO₂-C g^{? 1}h^{? 1} respectively. The β -glucosidase and FDHA of the soils varied from 33.3 and 76.3 μ g para-nitrophenol g^{? 1} soil h^{? 1} and 60.5 to 173.5 μ g fluorescein g^{? 1}h^{? 1}respectively. The tea garden soils contained variable residues of organophosphorus and organochlorine pesticides, which negatively affected the MBC, BSR, SIR, FDHA and β -glucosidase activity. Ethion and chlorpyriphos pesticide residues in all the tea garden soils varied from 5.00 to 527.8 ppb and 17.6 to 478.1 ppb respectively. The α endosulfan, β endosulfan and endosulfan sulfate pesticide residues in the tea garden soils ranged from 7.40 to 81.40 ppb, 8.50 to 256.1 ppb and 55 to 95.9 ppb respectively. Canonical correlation analysis shows that 93% of the total variation was associated with the negative impact of chlorpyriphos, β and α endosulfan and endosulfan sulfate on MBC, BSR and FDHA. At the same time ethion had negative impact on SIR and β -glucosidase. Data demonstrated that the pesticide residues had a strong impact on the microbial and biochemical components of soil quality.     

Dissipation, half-lives, and mass spectrometric identification of endosulfan isomers and the sulfate metabolite on three field-grown vegetables

Endosulfan 3 EC, a mixture of α- and β-stereo isomers, was sprayed on field-grown pepper, melon, and sweet potato plants at the recommended rate of 0.44 kg A.I. acre(-1). Plant tissue samples (leaves, fruits, or edible roots) were collected 1 h to 30 days following spraying and analyzed for endosulfan isomers (α- and β-isomers). Analysis of samples was accomplished using a gas chromatograph (GC) equipped with a mass detector in total ion mode. The results indicated the formation of endosulfan sulfate as the major metabolite of endosulfan sulfite and the relatively higher persistence of the β-isomers as compared to the α-isomer. The initial total residues (α- and β-isomers plus endosulfan sulfate) were higher on leaves than on fruits. On pepper and melon fruits, the α-isomer, which is the more toxic to mammals, dissipated faster (T(1/2) = 1.22 and 0.95 d, respectively) than the less toxic β-isomer (T(1/2) = 3.0 and 2.5 d, respectively). These results confirm the greater loss of the α-isomer compared to the β-isomer, which can ultimately impact endosulfan dissipation in the environment. Additionally, the higher initial residues of endosulfan on pepper and sweet potato leaves should be considered of great importance for timing field operations and the safe entry of harvesters due to the high mammalian toxicity of endosulfan.     

Enhanced degradation of carbofuran in pacific northwest soils

Abstract

Persistence of ¹⁴C‐carbonyl carbofuran was measured in Pacific Northwest soils that had received 1–14 applications of the insecticide for root weevil control on perennial crops. Insecticide decay curves were obtained in nonautoclaved soil and several autoclaved soil samples from previously‐treated fields and in nonautoclaved soils from paired control sites not previously treated with carbofuran. The insecticide usually degraded faster in soil from previously‐treated fields than in soil from corresponding control fields. Among 26 previously‐treated fields, the pseudo half‐life (time for 50% loss) of carbofuran was < one wk in 11 soils, 1–3 wks in 8 soils and > 4 wks in the remaining soils. Among the nontreated control fields the pseudo half‐life was > than 2 wks in all cases and > than 15 wks in 5 of the soils. The carbofuran decay curve always possessed an initial lag phase where soil mixing enhanced insecticide decline. Carbofuran degraded very slowly in autoclaved soil samples. The half‐life of carbofuran exceeded 16 wk in all autoclaved soils tested and in most instances 85–90% of the original dosage remained when the tests were terminated 112 days after treatment. These results provided evidence that many of the soils which received applications of carbofuran over the past several years have developed a capacity to degrade carbofuran very rapidly.     

Assessment of the environmental persistence and long-range transport of endosulfan

Concentrations of the insecticide endosulfan (α- and β-isomer) and its degradation product endosulfan sulfate in air, seawater and soil are calculated with the global environmental fate model CliMoChem. As model input, physicochemical properties of all three compounds were assembled and a latitudinally and temporally resolved emission inventory was generated. For concentrations in air, model and measurements are in good agreement; a bimodal seasonality with two peaks in spring and fall as it is observed in Arctic air is reproduced by the model. For seawater, the agreement of model and measurements depends on the values of the hydrolysis activation energy of endosulfan used in the model; with relatively high values around 100 kJ/mol, model results match field data well. The results of this assessment of the levels, persistence, and global distribution of endosulfan are also relevant for the evaluation of endosulfan as a Persistent Organic Pollutant under the Stockholm Convention.     

Dissipation,half-lives,and mass spectrometric identification of endosulfan isomers and the sulfate metabolite on three field-grown vegetables

Endosulfan 3 EC, a mixture of α- and β-stereo isomers, was sprayed on field-grown pepper, melon, and sweet potato plants at the recommended rate of 0.44 kg A.I. acre^?1. Plant tissue samples (leaves, fruits, or edible roots) were collected 1 h to 30 days following spraying and analyzed for endosulfan isomers (α- and β-isomers). Analysis of samples was accomplished using a gas chromatograph (GC) equipped with a mass detector in total ion mode. The results indicated the formation of endosulfan sulfate as the major metabolite of endosulfan sulfite and the relatively higher persistence of the β-isomers as compared to the α-isomer. The initial total residues (α- and β-isomers plus endosulfan sulfate) were higher on leaves than on fruits. On pepper and melon fruits, the α-isomer, which is the more toxic to mammals, dissipated faster (T_1/2 = 1.22 and 0.95 d, respectively) than the less toxic β-isomer (T_1/2 = 3.0 and 2.5 d, respectively). These results confirm the greater loss of the α-isomer compared to the β-isomer, which can ultimately impact endosulfan dissipation in the environment. Additionally, the higher initial residues of endosulfan on pepper and sweet potato leaves should be considered of great importance for timing field operations and the safe entry of harvesters due to the high mammalian toxicity of endosulfan.     

Assessment of insecticide contamination in runoff and stream water of small agricultural streams in the main soybean area of Argentina

The first- and second-order streams, Brown and Horqueta, respectively, which are located in the main area of soybean production in Argentina were examined for insecticide contamination caused by runoff from nearby soybean fields. The insecticides most widely used in Argentina (chlorpyrifos, cypermethrin and endosulfan) were detected in sediments, suspended particles and water. Highest concentrations in suspended particles were 318 microg/kg for endosulfan in the stream Horqueta, while 226 microg/kg chlorpyrifos and 13.2 microg/kg cypermethrin were measured in the stream Brown. In the Horqueta stream 150 and 53 microg/kg chlorpyrifos and cypermethrin were detected in runoff sediments, respectively. Whereas cypermethrin concentrations in the suspended particles were relatively low, levels in the floodwater of Brown reached 0.7 microg/l. The highest chlorpyrifos concentration in floodwater was 0.45 microg/l in Brown. However, endosulfan was not detected in the water phase. In runoff water the highest concentrations measured were 0.3 microg/l for chlorpyrifos in Horqueta and 0.49 microg/l for cypermethrin in the Brown stream. On five sampling dates during the pesticide application period in Brown stream (2002/2003) the concentration of chlorpyrifos and cypermethrin in runoff and/or floodwater exceeded the water quality criteria for freshwater mentioned in this study. In three cases this insecticide concentration was measured in stream water, indicating an acute risk to aquatic life. The acute toxicity-exposure-ratio (TER) for chlorpyrifos and cypermethrin also shows an acute risk for aquatic invertebrates in the Brown stream. In the Horqueta chlorpyrifos concentrations in the runoff exceeded the safety levels three times during the application period (2001/2002), potentially endangering the aquatic fauna. Effects on aquatic macroinvertebrates after insecticide contamination were reported in earlier studies in Horqueta stream.     

Insecticide residues in cotton crop soil

Dimethoate, monocrotophos, triazophos, deltamethrin, cypermethrin and endosulfan were applied to a cotton crop soil located at Nurpur village, Punjab, India. The insecticides were applied sequentially at recommended dosages in cotton fields by foliar application in 1995, 1996 and 1998. Soil samples were collected from the cotton crop farms and extracted with acetone. The extracted material was analysed by a gas liquid chromatograph (GLC) equipped with an 63Ni electron-capture detector (ECD-63Ni). Recovery data was obtained by fortifying soil with insecticide. The average recoveries from the fortified soil samples were 76-92% for organophosphorous compounds and 90-98% for synthetic pyrethroids and organochlorines. The results showed that the insecticide residues under study were present in the range of 1.16 to 41.97 ng g(-1) d.wt.soil. The pattern of dissipation of the insecticides used was similar for the duration of the crop. Half lives of the insecticides ranged from 7 to 22 days. Except endosulfan none of the other insecticides used were leached below 15 cm. Endosulfan was found to be rapidly degraded in the soil and formed a sulfate metabolite. Persistence and dissipation pattern in soils with history of exposure to the insecticide compared to non-history soils were similar.