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A carboxy methyl cellulose-nano organoclay (nano montmorillonite modified with 35-45 wt % dimethyl dialkyl (C 14 -C 18 ) amine (DMDA)) composite was prepared by solution intercalation method. The prepared composite was characterized by infrared spectroscopy (FTIR), X-Ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM). The composite was utilized for its pesticide sorption efficiency for atrazine, imidacloprid and thiamethoxam. The sorption data was fitted into Langmuir and Freundlich isotherms using linear and non linear methods. The linear regression method suggested best fitting of sorption data into Type II Langmuir and Freundlich isotherms. In order to avoid the bias resulting from linearization, seven different error parameters were also analyzed by non linear regression method. The non linear error analysis suggested that the sorption data fitted well into Langmuir model rather than in Freundlich model. The maximum sorption capacity, Q 0 (μg/g) was given by imidacloprid (2000) followed by thiamethoxam (1667) and atrazine (1429). The study suggests that the degree of determination of linear regression alone cannot be used for comparing the best fitting of Langmuir and Freundlich models and non-linear error analysis needs to be done to avoid inaccurate results., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In the present investigation, persistence of kresoxim-methyl (a broad spectrum strobilurin fungicide) was studied in water. Results revealed that kresoxim-methyl readily form acid metabolite. Therefore, residues of kresoxim-methyl were quantified on the basis of parent molecule alone and sum total of kresoxim-methyl and its acid metabolite. In water, influence of various abiotic factors like pH, temperature, light and atmospheric carbon dioxide level on dissipation of kresoxim-methyl was studied. The half life value for kresoxim-methyl and total residue varied from 1 to 26.1 and 6.1 to 94.0 days under different conditions. Statistical analysis revealed the significant effect of abiotic factors on the dissipation of kresoxim-methyl from water.

Persistence behavior of insecticides chlorpyriphos, profenofos, triazophos, cypermethrin, and deltamethrin following the use of three combination formulations Action 505 (chlorpyriphos + cypermethrin), Roket 44EC (profenofos + cypermethrin), and Anaconda Plus (triazophos + deltamethrin) was studied in cabbage following the spray application at the recommended and double doses. Bio-efficacy of these formulations was also evaluated against mustard aphids (Lipaphis erysimi Kaltenbach) and diamondback moth (Plutella xylostella L.). The residues of different insecticides persisted for 5-8 days at low dose and 8-12 days at high dose. The residues dissipated with time and 87-100% dissipation was recorded on the 8th day. The half-life values varied from 0.4 to 1.6 days. Based on the acceptable daily intake (ADI) values, a safe waiting period of 1 day has been suggested for the formulations Action 505 and Roket 44EC and 3 days for Anaconda Plus at the recommended dose of application. Action (1.6 L/ha) treatment was found to be the best as it significantly reduced the diamondback moth (DBM) (~60%) and aphid population (~70%) besides giving the highest yield (170% increase over control).

The present study evaluated rice husk ash (RHA) as an adsorbent for simultaneous removal of a mixture of seven different pesticides (alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, β-endosulfan, and p,p'-DDT) and two metabolites (p,p'-DDE and endosulfan sulfate) from water. The adsorbent RHA was prepared in the laboratory and characterized by techniques such as X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectrometry. Adsorption kinetics were well described by the pseudo-second-order kinetic model. The Freundlich isotherm model fitted the equilibrium data better than the Langmuir model, and the maximum sorption capacity varied from 0.078 to 0.166 mg/g. The column elution studies showed that 10 L of mixed pesticide-contaminated water (0.05 mg/L) can be treated with only 10 g of RHA at a removal efficiency of 90%. The results implied that RHA can be used as a low-cost, easily available, and efficient adsorbent for the simultaneous removal of pesticides from contaminated water.

In the present investigation, persistence of kresoxim-methyl (a broad spectrum strobilurin fungicide) was studied in two different soil types of India namely Inceptisol and Ultisol. Results revealed that kresoxim-methyl readily form acid metabolite in soil. Therefore, residues of kresoxim-methyl were quantified on the basis of parent molecule alone and sum total of kresoxim-methyl and its acid metabolite. Among the two soil types, kresoxim-methyl and total residues dissipated at a faster rate in Inceptisol (T1/2 0.9 and 33.8d) than in Ultisol (T1/2 1.5 and 43.6d). Faster dissipation of kresoxim-methyl and total residues was observed in submerged soil conditions (T1/2 0.5 and 5.2d) followed by field capacity (T1/2 0.9 and 33.8d) and air dry (T1/2 2.3 and 51.0d) conditions. Residues also dissipated faster in 5% sludge amended soil (T1/2 0.7 and 21.1d) and on Xenon-light exposure (T1/2 0.5 and 8.0d). Total residues of kresoxim-methyl dissipated at a faster rate under elevated CO2 condition (∼550μLL(-)(1)) than ambient condition (∼385μLL(-)(1)). The study suggests that kresoxim-methyl alone has low persistence in soil. Because of the slow dissipation of acid metabolite, the total residues (kresoxim-methyl+acid metabolite) persist for a longer period in soil. Statistical analysis using SAS 9.3 software and Duncan's Multiple Range Test (DMRT) revealed the significant effect of moisture regime, organic matter, microbial population, soil type, light exposure and atmospheric CO2 level on the dissipation of kresoxim-methyl from soil (at 95% confidence level p<0.0001)., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Contamination of drinking water sources with agrochemical residues became a major concern in the twenty-first century. Coagulation-flocculation is the most widely used water-treatment process, but the efficiency to remove pesticides and other organic pollutants are limited compared to adsorption process. Thus, simultaneous action of adsorption on normal bentonite or organo-modified montmorillonite clays [modified with octadecylamine (ODA-M) and octadecylamine + amino-propyltriethoxysilane (ODAAPS-M)] followed by coagulation-flocculation by alum and poly aluminium chloride has been evaluated for removal of 10 different pesticides, namely atrazine, lindane, metribuzin, aldrin, chlorpyriphos, pendimethalin, alpha-endosulphan, beta-endosulphan, p,p'-DDT, cypermethrin and two of its metabolites, endosulphan sulphate and p,p'-DDE, from water. The coagulation without integration of adsorption was less effective (removal % varies from 12 to 49) than the adsorption-coagulation integrated system (removal % varies from 71 to 100). Further, coagulation integrated with adsorption was more effective when organically modified montmorillonite was used as adsorbent compared to normal bentonite. The removal efficiency of organic clay depends upon the concentration of pesticides, doses of clay minerals, and efficiency was more for ODAAPS-M as compared to ODA-M. The combination of ODAAPS-M-clay with coagulants was also used efficiently for the removal of pesticides from natural and fortified natural water collected and the results exhibit the usefulness of this remediation technique for application in water decontamination and in treatment of industrial and agricultural waste waters.

The dissipation of pyraclostrobin, a strobilurin fungicide, in soil was found to be influenced by soil moisture, organic matter content and microbial population. Among the different moisture regimes, dissipation was faster under submerged condition (T1/2 10 days) followed by field capacity (T1/2 28.7 days) and in dry soil (T1/2 41.8 days). Use of sludge at 5 % level to Inceptisol favoured a faster dissipation of pyraclostrobin, whereas a slower rate of dissipation was observed in partial organic matter removed soil as compared to normal soil. Slower rate of dissipation was also observed in sterile soil (T1/2 47 days) compared to normal soil. Pyraclostrobin dissipated faster in Vertisol (T1/2 21.8 days) than in Inceptisol (T1/2 28.7 days). No significant difference in the dissipation rate was observed at 1 and 10 μg g(-1) fortification levels.

Removal of mixed pesticides, namely alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, β-endosulfan, p,p'-DDT and two metabolites p,p'-DDE and endosulfan sulphate from aqueous solution by batch adsorption onto three commercial organo-modified montmorillonite clays [modified with octadecylamine (ODA-M), modified with dimethyl- dialkylamine (DMDA-M) and modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M)] were investigated. Effect of process variables, mainly contact time and initial concentration of mixed pesticides, on adsorption phenomenon were evaluated. To understand the adsorption kinetic pseudo-first-order and pseudo-second-order models were tested. The pseudo-second-order model provided the best fit for explaining adsorption kinetics, on the basis of high correlation coefficient (r) and normalized percent deviation values. The adsorption equilibrium was explained by the Freundlich isotherm (r = 0.951-0.992). High values (0.17-0.52 mg g⁻¹) of Freundlich constant (K(f)) indicated higher affinity of pesticides towards all three organoclays, as a result of hydrophobic interaction between the adsorbent/adsorbate systems. Pesticides with high octanol-water partition coefficient (K(ow)) and low water solubility showed faster adsorption with higher K(f) values as compared to the pesticides with low K(ow) and high water solubility. The order of organoclays for removal efficiency of mixed pesticide was ODAAPS-M > DMDA-M > ODA-M. These findings may find application to decontaminate or treat mixed pesticide contaminated industrial/agricultural waste waters.

Persistence of cypermethrin, deltamethrin, profenofos, and triazophos in cauliflower curd was studied, following application of two premix formulations viz: Roket 44EC (profenofos 40 % + cypermethrin 4 %) and Anaconda Plus 36EC (triazophos 35 % + deltamethrin 1 %) at recommended (1.0 L ha(-1)) and double doses (2.0 L ha(-1)). In the case of Roket 44EC, residues of cypermethrin dissipated with the half-life values of 1.5-2.1 days, whereas residues of profenofos dissipated with the half-life of 2.9-3.3 days on cauliflower curd. In the case of Anaconda, residues of triazophos and deltamethrin dissipated from curd with the half-life values of 2.6-3.0 and 2.2-2.6 days, respectively. Both the combination mix significantly reduced the aphid population up to 14 days after spray and increased the yield by 155-160 % over control. Anaconda (2.0 L ha(-1)) treated plots yielded the highest number of marketable curds. Based on risk assessment analysis, safe waiting period of 3 and 5 days has been suggested for Roket 44EC and Anaconda Plus 36EC, respectively, in cauliflower at recommended dose of application.

Pyraclostrobin is a new broad-spectrum foliar applied and seed protectant fungicide of the strobilurin group. In this paper, adsorption-desorption of pyraclostrobin has been investigated in three different soils viz. Inceptisol (sandy loam, Delhi), Vertisol (sandy clay, Hyderabad) and Ultisol (sandy clay loam, Thrissur). Effect of organic matter and clay content on sorption was also studied in Inceptisol of Delhi. Leaching potential of pyraclostrobin as influenced by rainfall was studied in intact soil columns to confirm the results of adsorption-desorption studies. The adsorption studies were carried out at initial concentrations of 0.05, 0.1, 0.5, 1 and 1.5 μg mL(-1). The distribution coefficient (Kd) values in three test soils ranged from 4.91 to 18.26 indicating moderate to high adsorption. Among the three test soils, adsorption was the highest in Ultisol (Kd 18.26), followed by Vertisol (Kd 9.87) and Inceptisol (Kd 4.91). KF value was also highest for Ultisol soil (66.21), followed by Vertisol (40.88) and Inceptisol (8.59). S-type adsorption isotherms were observed in all the three test soils. Kd values in organic carbon-removed soil and clay-removed soil were 3.57 and 2.83 respectively, indicating lower adsorption than normal Inceptisol. Desorption studies were carried out at initial concentrations of 0.5, 1 and 1.5 μg mL(-1). Desorption was the greatest in Inceptisol, followed by Vertisol and Ultisol. Amounts of pyraclostrobin desorbed in three desorption cycles for different concentrations were 23.1-25.3%, 9.4-20.7% and 8.1-13.6% in Inceptisol, Vertisol and Ultisol respectively. Desorption was higher in clay fraction-removed and organic carbonremoved soils than normal Inceptisol. Desorption was slower than adsorption in all the test soils, indicating hysteresis effect (with hysteresis coefficient values varying from 0.05 to 0.20). Low values of hysteresis coefficient suggest high hysteresis effect indicating easy and strong adsorption, and slow desorption, of pyraclostrobin in soils. Higher hysteresis coefficient values in organic carbon removed soil (0.25-0.30) and clay fraction removed soil (0.28-0.36) as compared to normal Inceptisol soil suggest relatively weak adsorption and easy desorption of pyraclostrobin. Results of regression analysis suggest that the organic matter and pH of the soil play a major role in adsorption of pyraclostrobin. Leaching studies were carried out in intact soil columns in Inceptisol. The columns were leached with different amounts of water simulating different amounts of rainfall. The results suggest that most of the pyraclostrobin residues will remain present in the top soil layers even under high rainfall conditions and chances of pyraclostrobin moving to lower soil depth are almost negligible.

Persistence behavior of three combination mix formulations of insecticides viz. chlorpyriphos + cypermethrin (Action-505), profenofos + cypermethrin (Roket 44EC) and triazophos + deltamethrin (Anaconda) and their bioefficacy against melon fruitfly were studied in bittergourd fruits following spray application. Half-life values of the constituent insecticides calculated from first order dissipation kinetics were ~2-3 days. Based on acceptable daily intake values, safe waiting period of 3-days is suggested for all the three combination mix formulations at recommended dose of application. Anaconda (1 L/ha) was found to be most effective against Melon fruitfly as it gave 11.72 % (number/number) and 10.93 % (weight/weight) damage as compared to control 41.13 % and 41.16 %, respectively. Anaconda at lower and higher dose (1 and 2 L/ha) was not significantly different. Rocket (2 L/ha) and Action 505 (2 L/ha) were also found effective.

A bottleneck in crosstalk and QC research has been the quantification of diverse chemotypes in small amounts of tissue. An LC-UV method for estimating 28 selected metabolites of the regulatory network underlying growth, development, maintenance, vital functions, defense reactions, and food quality is reported. The method was based on binary gradient resolutions of the analytes in an RP C18 column. The mobile phase comprised solvent A [water+0.1% trifluoroacetic acid (TFA)] and B (acetonitrile + 0.085% TFA at a flow rate of 1 ml/min. Twenty-three metabolites (selected amino acids, coenzymes, growth regulators, phenolic antioxidant, and water-soluble vitamins) were detected at 254 nm, and four fat-soluble vitamins at 280 nm. Jasmonic acid was quantified at 210 nm. The RSDs of peak area and retention time for each metabolite were <5.8%. The calibration graphs were linear with R2 values ranging from 0.98 to 0.99. The LODs (microg/mL) were about 0.01-1.0 for 23 metabolites quantified at 254 nm, 0.1-0.2 for fat-soluble vitamins, and 0.1 for jasmonic acid. The recoveries ranged from 80 to 105%, with RSDs of 2.8 to 11.2%. The method has been satisfactorily applied for determination of 28 metabolites from Cicer arietinum (L.) and Solanum lycopersicum (L.). It could be an alternative and competitive method of choice that can cheaply and easily perform routine analysis for food quality and targeted metabolomics of chickpea and tomato in response to stressors.

Persistence of cypermethrin, chlorpyriphos, and profenofos in tomato and soil were studied following application of two pre-mix formulations of insecticides viz. Roket 44EC (profenofos 40% + cypermethrin 5%) and Action-505EC (chlorpyriphos 50% + cypermethrin 5%) at recommended (0.8-1.0 L ha(-1)) and double dosage (1.6-2.0 L ha(-1)). In all the treatments residues persisted beyond 7 days in tomato fruits. Half-life values were calculated from first-order dissipation kinetics. In the case of Roket 44EC, residues of cypermethrin on fruits dissipated with half-life of 2.0-3.6 days, whereas residues of profenophos dissipated with the half-life of 2.2-5.4 days. In the case of Action-505EC, residues of chlorpyriphos and cypermethrin dissipated from fruits with the half-life values of 2.9-3.3 and 2.5-4.8 days, respectively. In soil, residues of profenofos persisted for 7-15 days, whereas residues of chlorpyrophos and cypermethrin persisted for 0-7 days only.

A gas chromatograph with electron capture detection method for estimation of selected metabolites--amino acids (free and bound), gamma-aminobutyric acid (GABA), salicylic acid (SA), and acetyl salicylic acid (ASA) from tomato--is reported. The method is based on nitrophenylation of the metabolites by 1-fluoro-2, 4-dinitrobenzene under aqueous alkaline conditions to form dinitophenyl derivatives. The derivatives were stable under the operating conditions of GC. Analysis of bound amino acids comprised perchloric acid precipitation of protein, alkylation (carboxymethylation) with iodoacetic acid, vapor-phase hydrolysis, and derivatization with 1-fluoro-2,4-dinitrobenzene in that order. The metabolites were resolved in 35 min, using a temperature-programmed run. The method is rapid, sensitive, and precise. It easily measured the typical amino acids (aspartate, asparagine, glutamate, glutamine, alanine, leucine, lysine, and phenylalanine) used for identification and quantification of a protein, resolved amino acids of the same mass (leucine and isoleucine), satisfactorily measured sulfur amino acid (methionine, cystine, and cysteine), and quantified GABA, SA, and ASA, as well. The developed method was validated for specificity, linearity, and precision. It has been applied and recommended for estimation of 25 metabolites from Solanum lycopersicum (L.).

Persistence of azoxystrobin was studied in/on grapes when applied @ 150 g ai ha⁻¹ (recommended dose) and 300 g ai ha⁻¹ (double the recommended dose) in three grapes growing states of India, namely Karnataka, Maharashtra and Tamil Nadu, in the year 2006-2007. A total of five sprays were given at an interval of about 15 days. Grapes and soil samples were collected after 5th spray, extracted and analysed by gas chromatography using electron capture detector. Half life of azoxystrobin on grapes varied from 5.4 to 11.2 days. Residues of azoxystrobin were much below the prescribed MRL (0.5 mg kg⁻¹) after 21 days. The dissipation of azoxystrobin in soil followed first order rate kinetics with an average half life of 8.1 days at the recommended dose of application.

The productivity of chickpea, Cicer arietinum (L.), and tomato, Solanum lycopersicum (L.), is adversely affected by root-knot nematode, Meloidogyne species. Nematode-resistant chickpea and tomato are lacking except for a few varieties and therefore grower demand is not met. The available nematicides, namely, carbosulfan, cadusafos, phorate, and triazophos, were, therefore evaluated for their efficacy and persistence in soil and crops to devise nematode management decisions. In alluvial soil, cadusafos was the most persistent nematicide followed by phorate, carbosulfan, and triazophos in that order. The percent dissipation of cadusafos was greater (P < 0.05) in chickpea than in tomato plots, which influenced its half-life in soil. Nematicide residues were differentially taken up by chickpea and tomato plant roots with active absorption continuing for up to 45 days. Cadusafos and triazophos were absorbed to greater extent (P < 0.05) in tomato than in chickpea. The translocation of residues to shoot was highest by day 15 for cadusafos and at day 45 for other nematicides, with carbosulfan residues translocated the most. Nematicide residue concentrations in shoots never exceeded those in roots, with residues in both roots and shoots persisting beyond 90 days. Nematicide residues in green seeds of chickpea and tomato fruits were all below the Codex/German MRLs of 0.02, including the Indian tolerances of 0.1 microg/g in fruits and vegetables. Cadusafos was found to be the most effective nematicide followed by triazophos against Meloidogyne incognita and reniform nematode, Rotylenchulus reniformis . Application of cadusafos (Rugby 10 G) or, alternatively, spray application of triazophos (Hostathion 40 EC) in planting furrows, both at 1.0 kg of active ingredient/ha, followed by light irrigation is recommended for the effective control of M. incognita and R. reniformis infestations on chickpea and tomato.

Metabolism of (14)C-azoxystrobin was studied in water at pH 4, 7 and 9. The study suggested that volatilization losses of azoxystrobin were very low (3%) during 130 days of incubation. Only 2.5-4.2% of azoxystrobin was mineralised to CO(2) and pH of water did not have much effect on rate of mineralisation. The dissipation of azoxystrobin in water of all the three pHs followed first order kinetic with half-life values ranging from 143 to 158 d; degradation was the fastest at pH 9. Azoxystrobin acid, a major metabolite, was detected 4-7 day onwards and its concentration increased up to 130 days. The formation of azoxystrobin acid was more and faster under alkaline (pH 9) condition than neutral (pH 7) or acidic (pH 4) conditions.

Background: The root-knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood, is an important plant pathogen damaging to tomato. Continuous use of resistant tomato cultivars and nematicides for its effective management might lead to resistance break-up or nematicide failure. Genetic variability and virulence in M. incognita on susceptible Pusa Ruby tomato were analysed by bioassay, esterase and DNA polymorphism after a 5 year weekly exposure to carbofuran, carbosulfan, cadusafos and triazophos at 0.0125, 0.0250 and 0.0500 microg g(-1). Virulence in M. incognita after a 5 year multiplication on resistant tomatoes was assessed., Results: The nematicidal treatments resulted in the development of virulent M. incognita populations. Their invasion potential increased significantly after continuous exposure to low concentrations of the nematicides. Also, growing resistant tomato cultivars for ten successive seasons resulted in a 6.6% increase in the invasion potential. These virulent populations exhibited 1-3 additional esterase and DNA bands compared with untreated populations., Conclusion: A 5 year exposure of M. incognita to sublethal concentrations of nematicides or resistant tomato cultivars exerted enough selection pressure to cause genomic alterations for virulence development. Isozyme markers can be used for rapid and precise diagnostics of field populations by advisory services, enabling judicious remedial management decisions., ((c) 2009 Society of Chemical Industry.)

Persistence and efficacy of bifenthrin (25 and 50 g ai ha(-1)), fipronil (50 and 100 g ai ha(-1)) and indoxacarb (70 and 140 g ai ha(-1)) has been studied in okra fruits. The initial deposits varied from 0.259-0.382 microg g(-1) at low and 0.461-0.688 microg g(-1) at high rate of application. The residues persisted upto 10 days with half-life of 1.32-1.58 days for bifenthrin, 0.65-1.12 days for fipronil and 0.58-1.02 days for indoxacarb. Based on ADI, the suggested waiting period was 1 day for bifenthrin and indoxacarb and 3 days for fipronil. All the insecticides were found effective against leafhopper and shoot and fruit borer.

Persistence of two neonicotinoids viz thiacloprid and acetamiprid in soil as affected by UV and sunlight exposure was studied. Treated soil was placed in petri-plates, brought to field capacity moisture and then exposed to UV and sunlight. Dissipation for both the pesticides followed monophasic first order kinetics under sunlight, however under UV-light biphasic dissipation was recorded. Residues of acetamiprid and thiacloprid in soil dissipated with half-lives of 11.1 and 12.8 days under UV light and 25.1 and 19.1 days under sunlight, respectively. Residues of both the neonicotinoids dissipated quickly under UV light as compared to sunlight. Exposure of thin film of acetamiprid and thiacloprid to UV and sunlight revealed that acetamiprid is more photo labile than thiacloprid. More than 95% acetamiprid dissipated within 24 h as compared to approximately 70% dissipation observed for thiacloprid.

Persistence and leaching of thiamethoxam in soil were studied under laboratory conditions. The persistence studies carried out at two fortification levels and under three moisture regimes revealed that thiamethoxam persisted beyond 90 days in all the treatments with half-life varying from 46.3 to 301.0 days. Under dry conditions, the dissipation was faster at 10 mg kg(-1) level as compared to 1 mg kg(-1), whereas the reverse trend was observed under field capacity moisture and submerged conditions. The effect of moisture was prominent and longer persistence was observed under dry conditions (t1/2 200.7-301.0 days) followed by field capacity moisture (t1/2 91.2-94.1 days) and submerged condition (t1/2 46.3-75.3 days). The leaching experiment carried out under laboratory conditions showed that on leaching the soil column with water equivalent to 65 cm rainfall, 66-79% of the applied thiamethoxam was recovered from leachate and no residues were detected in soil. Results showed that thiamethoxam has a potential to leach down under heavy rainfall conditions.

Investigations were undertaken to study the adsorption-desorption, persistence and leaching of thifluzamide (2',6'-dibromo-2-methyl-4'-trifluoromethoxy-4-trifluoro methyl-1,3-thiazole-5-carboxanilide) in an alluvial soil under laboratory conditions. The adsorption-desorption studies were carried out using batch equilibration technique. The results revealed high but weak adsorption of thifluzamide in alluvial soil with K(F) value of 9.62 and 'n' value of 0.63. About 47-62% of the adsorbed amount got desorbed in four desorption cycles, which further substantiate the hypothesis of weak binding. The hysteresis coefficient varied from 0.19 to 0.40. Persistence studies carried out at three concentration levels (0.1, 1.0 and 10.0 microgg(-1)) and under three moisture conditions (air-dry, field capacity moisture and submerged) revealed that thifluzamide is a persistent chemical and only 19.5-54.0% dissipation was recorded on 90th day. However, it appears that aerobic microbes are more efficient in degrading thifluzamide than anaerobic microbes. The preliminary leaching studies carried out in the laboratory revealed that thifluzamide was moderately mobile in alluvial soil. Only small amounts (<1%) were recovered from leachate fractions whereas major portion remained in 0-15 cm soil depth.

Persistence as affected by rate of application and moisture regimes and leaching of beta-cyfluthrin was studied in alluvial soil under laboratory conditions. The effects of rate of application and moisture regimes on persistence were studied by incubating fortified soil at 0.1, 1.0 and 10.0 mg kg(-1) under air-dry, field capacity and submerged moisture regimes. The initial deposits of 0.09, 1.11 and 10.1 mg kg(-1) dissipated with time and 78.4-100% loss was recorded at 90 days. The half-life values varied from 7.8 to 41.8 days. The rate of dissipation decreased as the rate of application increased under field capacity and submerged conditions. However, under air-dry conditions, the effect was less pronounced, and half-life values showed a reverse trend. Persistence of beta-cyfluthrin under different moisture regimes followed the trend: air-dry > field capacity > submerged. The trend could be attributed to the effect of moisture on number and type of microbes. Leaching was studied in a packed soil column under saturated flow conditions. beta-Cyfluthrin was found to be highly immobile in alluvial soil. No residues were detected in any leachate fraction under the experimental conditions. In column soil, residues were detected at 0-10 cm depth and the major amount (>99%) was recovered from 0-5 cm depth. Although beta-cyfluthrin showed moderate persistence in alluvial soil, the possibility of its leaching to ground water is negligible as a result of its immobility.

Investigations were undertaken to determine the adsorption-desorption, persistence and leaching of dithiopyr (S,S'-dimethyl 2-difluoromethyl-4-isobutyl-6-trifluoromethyl pyridine-3,5-dicarbothioate) in an alluvial soil under laboratory condition. The adsorption-desorption studies were carried out using batch equilibration technique. The mass balance studies showed that 83-97% of the pesticide was recovered during adsorption-desorption studies. The results revealed strong adsorption of dithiopyr in alluvial soil with Kd values ranging from 3.97-5.78 and Freundlich capacity factor (KF) value of 2.41. The strong adsorption was evident from the hysteresis effect observed during desorption. The hysteresis coefficients ranged from 0.17-0.40. The persistence studies were carried out at two concentrations (1.0 and 10.0 microg g(-1) level) under field capacity moisture and submerged condition by incubating the treated soil at 25 +/- 1 degrees C. In general, dithiopyr persisted beyond 90 days with half-life varying from 11.5-12.9 days under different conditions. The rate of application and moisture regimes had no overall effect on the persistence. The leaching studies carried out in packed column under saturated flow condition revealed that dithiopyr was highly immobile in alluvial soil. Only small amounts (0.02-0.04%) were recovered from leachate whereas major portion (99.9%) remained in top layer of the soil column. The data suggest that strong adsorption of dithiopyr will cause a greater persistence problem in the soil. However, the chances of its movement to ground water will be negligible due to its immobility.

Effect of concentration, moisture and soil type on dissipation of flufenacet from soil has been studied under laboratory condition. The treated soil samples (1 and 10 microg/g levels) were incubated at 25+/-1 degrees C. The effect of moisture was studied by maintaining the treated soil samples (10 microg/g level) at field capacity and submerged condition. In general, flufenacet persisted for 60-90 days at lower and beyond 90 days at high rate. The dissipation of flufenacet from soil followed first order kinetics with half-life (DT50) values ranging from 10 to 31 days. The dissipation of flufenacet was faster at low rate than high rate of application. The slow dissipation at high rate could be attributed to inhibition of microbial activity at high rate. There was little overall difference in rate of dissipation in Ranchi and Nagpur soil maintained at field capacity and submerged condition moisture regimes. In Delhi soil net dissipation was faster under field capacity moisture than submerged condition. Soil types greatly influenced the dissipation of flufenacet. Dissipation was fastest in Delhi soil (DT50 10.1-22.3 days) followed by Ranchi soil (DT50 10.5-24.1 days) and least in Nagpur soil (DT50 29.2-31.0 days). The difference in dissipation could be attributed to the magnitude of adsorption and desorption of flufenacet in these soils.

Adsorption-desorption of the herbicide flufenacet (FOE 5043) has been studied in five soils from different locations in India (Delhi, Ranchi, Nagpur, Kerala and Assam) varying in their physicochemical properties. The organic matter (OM) content varied from 0.072 to 0.864%, clay content from 2.5 to 43.7% and pH from 4.45 to 8.35. The adsorption studies were carried out using a batch equilibration technique. Ten grams of soil were equilibrated with 20 ml of aqueous 0.01 M CaCl2 solution containing different concentrations (0-30 mg litre-1) of flufenacet. After equilibration, an aliquot of supernatant was taken out for analysis. During desorption, the amount withdrawn for analysis was replenished with fresh 0.01 M CaCl2 solution and further equilibrated. Desorption studies were carried out with the 30 mg litre-1 concentration of flufenacet only. The adsorption studies revealed that there was moderate to high adsorption of flufenacet considering the comparatively low organic carbon content in the five test soils. Average Kd values ranged from 0.77 to 4.52 and Freundlich KF values from 0.76 to 4.39. The highest adsorption was observed in Kerala soil (OM 0.786%; clay 25%; pH 4.45) followed by Ranchi, Nagpur and Delhi soils, and the lowest in Assam soil (OM 0.553%; clay 2.5%; pH 6.87). The trend in adsorption could be attributed to the chemical nature of flufenacet and the physicochemical properties of the soil such as pH, OM and clay contents. OM and clay contents were positively correlated whereas pH was negatively correlated. Soils having low pH, high OM and high clay contents showed higher adsorption. Desorption studies revealed that there was a hysteresis effect in all the soils. Hysteresis coefficient values (ratio of n(ad) and n(des)) varied from 0.09 to 0.45. The study implies that, because of its moderate to high adsorption, flufenacet is likely to persist in soil for some time. However, the possibility of its movement by leaching or surface run off is less.

Multiple residues of organochlorine insecticides were monitored in the agricultural fields near Farrukhabad in the vicinity of the River Ganga in northern India for one year (1991-1992). Almost all soil samples were found to be contaminated with residues of hexachlorocylohexane (HCH) and dichlorodiphenyl-trichloroethane (DDT). Residues of aldrin and endosulfan were also detected in a large number of samples. Heptachlor residues were scarcely detected. Alpha-HCH, pp'-DDT and alpha-endosulfan were found to dominate over the other isomers/metabolites of HCH, DDT and endosulfan, respectively. The average concentration of dieldrin was more than that of aldrin. The concentrations of residues progressively increased up to a depth of 1 m.

Residues of several organochlorine insecticides were monitored in the ground water from a rural area near Farrukhabad in the vicinity of the Ganga River in northern India for one year (1991-1992). Almost all the samples were found to be contaminated with residues of Hexachlorocyclohexane (HCH) and Dichloro-diphenyl-trichloroethane (DDT). Residues of Aldrin, endosulfan and heptachlor were also detected in a large number of samples. The concentrations of aldrin residues greatly exceeded the WHO guideline value for drinking water, concentrations of heptachlor and DDT residues also occasionally exceeded the specified limits. Migration of pollutants through ground water recharge with polluted Ganga River water and monsoon rains carrying undergraded residues downwards from the soil surface are throught to be important sources of insecticide contamination of ground water in the region.

Multiple residues of organochlorine insecticides were monitored in Ganga river water in the district of Farrukhabad in northern Indian for one year (1991-1992). Almost all the samples were found to be contaminated with residues of HCH and DDT. Residues of aldrin, endosulfan and heptachlor were also detected in a larger number of samples. Alpha-HCH, pp'-DDT and alpha-endosulfan were found to dominate over the other isomers of HCH, DDT and endosulfan, respectively. Enhanced percentage of beta-HCH suggests accumulation of this isomer in the aquatic environment. The average concentration of aldrin was more than that of dieldrin. Aldrin residues often exceeded the WHO guideline value for drinking water and the concentration of heptachlor occasionally exceeded the specified limits.