Shashi Singh | INDIAN AGRICULTURAL RESEARCH INSTITUTE, NEW DELHI, INDIA (original) (raw)
Papers by Shashi Singh
Pest Management Science, 2012
BACKGROUND: Pyrazosulfuron ethyl, a new rice herbicide belonging to the sulfonylurea group, has r... more BACKGROUND: Pyrazosulfuron ethyl, a new rice herbicide belonging to the sulfonylurea group, has recently been registered in India for weed control in rice crops. Many field experiments revealed the bioefficacy of this herbicide; however, no information is available on the persistence of this herbicide in paddy soil under Indian tropical conditions. Therefore, a field experiment was undertaken to investigate the fate of pyrazosulfuron ethyl in soil and water of rice fields. Persistence studies were also carried out under laboratory conditions in sterile and non-sterile soil to evaluate the microbial contribution to degradation. RESULTS: High-performance liquid chromatography (HPLC) of pyrazosulfuron ethyl gave a single sharp peak at 3.41 min. The instrument detection limit (IDL) for pyrazosulfuron ethyl by HPLC was 0.1 µg mL −1 , with a sensitivity of 2 ng. The estimated method detection limit (EMDL) was 0.001 µg mL −1 and 0.002 µg g −1 for water and soil respectively. Two applications at an interval of 10 days gave good weed control. The herbicide residues dissipated faster in water than in soil. In the present study, with a field-soil pH of 8.2 and an organic matter content of 0.5%, the pyrazosulfuron ethyl residues dissipated with a half-life of 5.4 and 0.9 days in soil and water respectively. Dissipation followed first-order kinetics. Under laboratory conditions, degradation of pyrazosulfuron ethyl was faster in non-sterile soil (t 1/2 = 9.7 days) than in sterile soil (t 1/2 = 16.9 days). CONCLUSION: Pyrazosulfuron ethyl is a short-lived molecule, and it dissipated rapidly in field soil and water. The faster degradation of pyrazosulfuron in non-sterile soil than in sterile soil indicated microbial degradation of this herbicide.
Pest Management Science, 2000
Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita... more Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita Kulshrestha, 1* Shashi B Singh,1 Shashi P Lal 2 and Nanjapur T Yaduraju 3 1Division of Agricultural Chemicals, Indian Agricultural ...
Pest Management Science, 2000
Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita... more Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita Kulshrestha, 1* Shashi B Singh,1 Shashi P Lal 2 and Nanjapur T Yaduraju 3 1Division of Agricultural Chemicals, Indian Agricultural ...
Journal of Environmental Science and Health, Part B, 2013
Metribuzin, a triazine herbicide, is poorly sorbed in the soils, therefore leaches to lower soil ... more Metribuzin, a triazine herbicide, is poorly sorbed in the soils, therefore leaches to lower soil profile. Fly ash amendment, which enhanced metribuzin sorption in soils, may play a significant role in reducing the downward mobility of herbicide. Therefore, the present study reports the effect of Inderprastha fly ash amendment on metribuzin leaching in three soil types. Fly ash was amended at 1, 2 and 5% levels in the upper 15 cm of 30 cm long packed soil columns. Results suggested a significant reduction in the leaching losses of metribuzin in fly ash-amended columns of all the three soil types and effect increased with increase in the level of fly ash. Even after percolating water equivalent to 362 mm rainfall no metribuzin was recovered in the leachate of 5% fly ash-amended columns. Fly ash application affected both metribuzin breakthrough time and its maximum concentration in the leachate. Further, it resulted in greater retention of metribuzin in the application zone and better effect was observed in the organic carbon poor soils.
Journal of Environmental Science and Health, Part B, 2013
This study reports the effect of fly ash amendment on persistence of metribuzin in three Indian s... more This study reports the effect of fly ash amendment on persistence of metribuzin in three Indian soil types. Fly ash [Inderprastha (IP) and Kota] was amended at 1, 2 and 5% levels. Metribuzin was more persistent in the flooded soils (predominantly anaerobic) than the nonflooded (aerobic) soils. Kota fly ash amendment to nonflooded soils slightly enhanced metribuzin persistence while IP fly ash reduced the herbicide persistence in nonflooded soils. In flooded soils both types of fly ash reduced metribuzin persistence, but the extent of the effect was specific to the soil and type of fly ash. A better effect was observed in low organic matter soils and IP fly ash was more effective than the Kota fly ash. The effect of fly ash amendment on metribuzin degradation in soils was more pronounced at higher dose of fly ash. No degradation of metribuzin was observed in the sterilized soils, both without and with fly ash, suggesting that degradation of metribuzin was microbial in nature. Deaminometribuzin was recovered as the only metabolite of metribuzin degradation.
Journal of Environmental Science and Health, Part B, 2013
Pyrazosulfuron-ethyl, a new herbicide belonging to the sulfonylurea group, is used for weed contr... more Pyrazosulfuron-ethyl, a new herbicide belonging to the sulfonylurea group, is used for weed control in rice crops growing in areas varying from acidic to alkaline soils. This study was undertaken to determine the degradation behaviour of pyrazosulfuron-ethyl in distilled water and buffer solutions at pH 4, 7 and 9. Degradation was pH-dependent and herbicide was least persistent in acidic pH followed by alkaline and neutral pH. The half-life of pyrazosulfuron-ethyl varied from 2.6 days (pH 4) to 19.4 days (pH 7) and half-life in distilled water was comparable to half-life at pH 7 buffer. HPLC analysis of different pH samples showed the formation of three metabolites viz., 5-(aminosulfonyl)-1-methyl-1H-pyrazole-4-carboxylic acid; ethyl 5-(aminosulfonyl)-1-methyl-1H-pyrazole-4-carboxylate and 2-amino-4,6-dimethoxy pyrimidine. The formation of pyrazosulfuron acid [5-([([(4,6-dimethoxy-2 pyrimidinyl)-amino]-carbonyl) amino]-sulfonyl)-1-methyl-1H-pyrazole-4-carboxylic acid] was not observed at any pH. The study indicated that the herbicide was least stable under acidic conditions and the predominant degradation route of pyrazosulfuron-ethyl in water is hydrolysis of sulfonamide linkage.
Journal of Environmental Science and Health, Part B, 2012
Sorption of metsulfuron-methyl and sulfosulfuron were studied in five Indian soils using batch so... more Sorption of metsulfuron-methyl and sulfosulfuron were studied in five Indian soils using batch sorption method. Freundlich adsorption equation described the sorption of herbicides with K(f) (adsorption coefficient) values ranging between 0.21 and 1.88 (metsulfuron-methyl) and 0.37 and 1.17 (sulfosulfuron). Adsorption isotherms were L-type suggesting that the herbicides sorption decreased with increase in the initial concentration of the herbicide in the solution. The K(f) for metsulfuron-methyl showed good positive correlation with silt content (significant at p = 0.01) and strong negative correlation with the soil pH (significant at p = 0.05) while sorption of sulfosulfuron did not correlate with any of the soil parameter. Desorption of herbicides was concentration dependent and, in general, sulfosulfuron showed higher desorption than the metsulfuron-methyl. The study indicates that these herbicides are poorly sorbed in the Indian soil types and there may be a possibility of their leaching to lower soil profiles.
Journal of Environmental Science and Health, Part B, 2008
… of agricultural and …, 2009
Studies were undertaken to analyze the residues of commonly used pesticides viz. chlorpyrifos, en... more Studies were undertaken to analyze the residues of commonly used pesticides viz. chlorpyrifos, endosulfan, dicofol, cypermethrin, fenvalerate, propargite, malathion, phorate, carbendazim, carbosulfan, thiamethoxam, and mancozeb in apple of integrated pest management (IPM) and non-IPM samples collected from the IPM and non-IPM fields of Shimla. We also present a method for the determination of these pesticides in apple samples. Residues of chlorpyrifos, endosulfan, dicofol, cypermethrin, fenvalerate, and propargite were analyzed by gas chromatography, while residues of carbendazim, carbosulfan, and thiamethoxam were analyzed by high-performance liquid chromatography. Residues of mancozeb were determined by a colorimetric method. Recoveries of all of the pesticides ranged from 61.30 to 95.46% at 0.1, 0.2, and 1.0 μg g -1 levels of fortification with relative standard deviations ranging between 0.8 and 8.7. Apples from IPM and non-IPM orchards were analyzed for these pesticides using a developed method. Except for carbendazim and chlorpyrifos, the residues of all of the pesticides analyzed were below detectable limits. Although residues of carbendazim and chlorpyrifos were below the prescribed limits of maximum residue levels in both IPM and non-IPM orchards, residues were lower in apples from IPM orchards.
Ecotoxicology and Environmental Safety, 2013
Field evaluation of two fly ashes (40t/ha) on persistence, mobility and bioactivity of metribuzin... more Field evaluation of two fly ashes (40t/ha) on persistence, mobility and bioactivity of metribuzin and metsulfuron-methyl was studied in soybean and wheat crops, respectively. Metribuzin was applied as pre-emergence at 0.5kg/ha, while metsulfuron-methyl was applied post-emergence at 8g/ha. Results suggested that metribuzin in surface (0-15cm) soil of fly ash unamended plots reached below detectable limit in 60 days, while herbicide persisted till 112 days in surface soil of fly ash amended plots. No metribuzin leached down to subsurface (15-30cm) soil in fly ash amended plots, while traces of metribuzin (0.6-1.2μg/kg) were recovered in subsurface soil of fly ash unamended plot. Metsulfuron-methyl in surface soil persisted till 15 days in control and 20 days in fly ash amended plots and no metsulfuron-methyl leached down to subsurface soil. Fly ash amendment had no adverse effect on the bioactivity of herbicides and yield of soybean and wheat. The study suggested that fly ash amendment to soil can be exploited to retain applied herbicides in surface soil.
Bulletin of Environmental Contamination and Toxicology, 2011
Persistence of azoxystrobin was studied in/on grapes when applied @ 150 g ai ha -1 (recommended d... more 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 present study is aimed at analysing and comparing different soil enzymes in soil samples of n... more The present study is aimed at analysing and comparing different soil enzymes in soil samples of native contaminated sites of a Mathura refinery and adjoining agricultural land. Enzyme activities are considered as indicators of soil quality and changes in biogeochemical function due to management or perturbations. Soil samples were collected from the premises and nearby area of Mathura refinery, India. Biological health parameters (dehydrogenase, aryl esterase, aryl sulphatase, β-glucosidase, alkaline phosphatase, acid phosphatase, lipase, laccase and catalase activity) were estimated in the soil samples. Among all the samples, sewage sludge soil showed maximum activity of enzymes, microbial biomass carbon and most probable number of polycyclic aromatic hy-P. Chaudhary · L. Nain (B)
Bulletin of Environmental …, 2011
An actinobacterium designated as PAH-13 was isolated from bitumen (heavy crude oil) soil collecte... more An actinobacterium designated as PAH-13 was isolated from bitumen (heavy crude oil) soil collected from Mathura refinery, India. The isolate was screened for its ability to degrade 34 ring PAH compounds (anthracene, fluorene, phenanthrene and pyrene) in minimal ...
Pest Management Science, 2011
Pyrazosulfuron-ethyl {ethyl 5-[(4,6-dimethoxypyrimidin-2-ylcarbamoyl)-sulfamoyl]-1-methylpyrazole... more Pyrazosulfuron-ethyl {ethyl 5-[(4,6-dimethoxypyrimidin-2-ylcarbamoyl)-sulfamoyl]-1-methylpyrazole-4-carboxylate} is a new rice herbicide belonging to the sulfonylurea group. This study reports the translocation of (14)C-pyrazosulfuron-ethyl to rice plants and its degradation in rice-planted and unplanted soil. Pyrazosulfuron-ethyl did not show any appreciable translocation to rice shoots, as (14)C-activity translocated to the aerial portion never exceeded 1% of the initially applied (14)C-activity over a 25 day period. Results suggested that the dissipation of pyrazosulfuron-ethyl from soils followed first-order kinetics with a half-life of 5.5 and 6.9 days in rice-planted and unplanted soils respectively. HPLC analysis of the organic extract of soil samples showed the formation of three metabolites, namely ethyl 5-(aminosulfonyl)-1-methyl-1-H-pyrazole-4-carboxylate, 5-[({[(4,6-dimethoxy-2 pyrimidinyl)-amino]-carbonyl} amino)-sulfonyl]-1-methyl-1H-pyrazole-4-carboxylic acid and 2-amino-4,6-dimethoxy pyrimidine, in both rice-planted and unplanted soils. The study indicates that pyrazosulfuron-ethyl was a short-lived compound in the soil and was degraded relatively faster in rice-planted soil than in unplanted soil. The herbicide did not show any appreciable translocation to rice plants.
Monatshefte Fur Chemie, 1986
Condensation of 2-hydrazino-4-methylquinoline (1) and acetylacetone gives a compoundA, which has ... more Condensation of 2-hydrazino-4-methylquinoline (1) and acetylacetone gives a compoundA, which has the structure of 3,5-dimethyl-1-(4-methylquinolino)-pyrazole (2) and not of 4-methylquinolino-(2,3—c)-3,5-dimethyl-1H-1,2-diazepine (3) assigned earlier. The structure2 was confirmed on the basis of1H-NMR,13C-NMR, IR spectral data and its unambiguous synthesis.
Synthetic Communications, 1987
Condensation of uracil derivatives (1,3,4) with acetone in the presence of triethylamine gave pyr... more Condensation of uracil derivatives (1,3,4) with acetone in the presence of triethylamine gave pyranopyrimidines (2,5,6).
Pest Management Science, 2012
BACKGROUND: Pyrazosulfuron ethyl, a new rice herbicide belonging to the sulfonylurea group, has r... more BACKGROUND: Pyrazosulfuron ethyl, a new rice herbicide belonging to the sulfonylurea group, has recently been registered in India for weed control in rice crops. Many field experiments revealed the bioefficacy of this herbicide; however, no information is available on the persistence of this herbicide in paddy soil under Indian tropical conditions. Therefore, a field experiment was undertaken to investigate the fate of pyrazosulfuron ethyl in soil and water of rice fields. Persistence studies were also carried out under laboratory conditions in sterile and non-sterile soil to evaluate the microbial contribution to degradation. RESULTS: High-performance liquid chromatography (HPLC) of pyrazosulfuron ethyl gave a single sharp peak at 3.41 min. The instrument detection limit (IDL) for pyrazosulfuron ethyl by HPLC was 0.1 µg mL −1 , with a sensitivity of 2 ng. The estimated method detection limit (EMDL) was 0.001 µg mL −1 and 0.002 µg g −1 for water and soil respectively. Two applications at an interval of 10 days gave good weed control. The herbicide residues dissipated faster in water than in soil. In the present study, with a field-soil pH of 8.2 and an organic matter content of 0.5%, the pyrazosulfuron ethyl residues dissipated with a half-life of 5.4 and 0.9 days in soil and water respectively. Dissipation followed first-order kinetics. Under laboratory conditions, degradation of pyrazosulfuron ethyl was faster in non-sterile soil (t 1/2 = 9.7 days) than in sterile soil (t 1/2 = 16.9 days). CONCLUSION: Pyrazosulfuron ethyl is a short-lived molecule, and it dissipated rapidly in field soil and water. The faster degradation of pyrazosulfuron in non-sterile soil than in sterile soil indicated microbial degradation of this herbicide.
Pest Management Science, 2000
Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita... more Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita Kulshrestha, 1* Shashi B Singh,1 Shashi P Lal 2 and Nanjapur T Yaduraju 3 1Division of Agricultural Chemicals, Indian Agricultural ...
Pest Management Science, 2000
Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita... more Page 1. Effect of long-term field application of pendimethalin: enhanced degradation in soil Gita Kulshrestha, 1* Shashi B Singh,1 Shashi P Lal 2 and Nanjapur T Yaduraju 3 1Division of Agricultural Chemicals, Indian Agricultural ...
Journal of Environmental Science and Health, Part B, 2013
Metribuzin, a triazine herbicide, is poorly sorbed in the soils, therefore leaches to lower soil ... more Metribuzin, a triazine herbicide, is poorly sorbed in the soils, therefore leaches to lower soil profile. Fly ash amendment, which enhanced metribuzin sorption in soils, may play a significant role in reducing the downward mobility of herbicide. Therefore, the present study reports the effect of Inderprastha fly ash amendment on metribuzin leaching in three soil types. Fly ash was amended at 1, 2 and 5% levels in the upper 15 cm of 30 cm long packed soil columns. Results suggested a significant reduction in the leaching losses of metribuzin in fly ash-amended columns of all the three soil types and effect increased with increase in the level of fly ash. Even after percolating water equivalent to 362 mm rainfall no metribuzin was recovered in the leachate of 5% fly ash-amended columns. Fly ash application affected both metribuzin breakthrough time and its maximum concentration in the leachate. Further, it resulted in greater retention of metribuzin in the application zone and better effect was observed in the organic carbon poor soils.
Journal of Environmental Science and Health, Part B, 2013
This study reports the effect of fly ash amendment on persistence of metribuzin in three Indian s... more This study reports the effect of fly ash amendment on persistence of metribuzin in three Indian soil types. Fly ash [Inderprastha (IP) and Kota] was amended at 1, 2 and 5% levels. Metribuzin was more persistent in the flooded soils (predominantly anaerobic) than the nonflooded (aerobic) soils. Kota fly ash amendment to nonflooded soils slightly enhanced metribuzin persistence while IP fly ash reduced the herbicide persistence in nonflooded soils. In flooded soils both types of fly ash reduced metribuzin persistence, but the extent of the effect was specific to the soil and type of fly ash. A better effect was observed in low organic matter soils and IP fly ash was more effective than the Kota fly ash. The effect of fly ash amendment on metribuzin degradation in soils was more pronounced at higher dose of fly ash. No degradation of metribuzin was observed in the sterilized soils, both without and with fly ash, suggesting that degradation of metribuzin was microbial in nature. Deaminometribuzin was recovered as the only metabolite of metribuzin degradation.
Journal of Environmental Science and Health, Part B, 2013
Pyrazosulfuron-ethyl, a new herbicide belonging to the sulfonylurea group, is used for weed contr... more Pyrazosulfuron-ethyl, a new herbicide belonging to the sulfonylurea group, is used for weed control in rice crops growing in areas varying from acidic to alkaline soils. This study was undertaken to determine the degradation behaviour of pyrazosulfuron-ethyl in distilled water and buffer solutions at pH 4, 7 and 9. Degradation was pH-dependent and herbicide was least persistent in acidic pH followed by alkaline and neutral pH. The half-life of pyrazosulfuron-ethyl varied from 2.6 days (pH 4) to 19.4 days (pH 7) and half-life in distilled water was comparable to half-life at pH 7 buffer. HPLC analysis of different pH samples showed the formation of three metabolites viz., 5-(aminosulfonyl)-1-methyl-1H-pyrazole-4-carboxylic acid; ethyl 5-(aminosulfonyl)-1-methyl-1H-pyrazole-4-carboxylate and 2-amino-4,6-dimethoxy pyrimidine. The formation of pyrazosulfuron acid [5-([([(4,6-dimethoxy-2 pyrimidinyl)-amino]-carbonyl) amino]-sulfonyl)-1-methyl-1H-pyrazole-4-carboxylic acid] was not observed at any pH. The study indicated that the herbicide was least stable under acidic conditions and the predominant degradation route of pyrazosulfuron-ethyl in water is hydrolysis of sulfonamide linkage.
Journal of Environmental Science and Health, Part B, 2012
Sorption of metsulfuron-methyl and sulfosulfuron were studied in five Indian soils using batch so... more Sorption of metsulfuron-methyl and sulfosulfuron were studied in five Indian soils using batch sorption method. Freundlich adsorption equation described the sorption of herbicides with K(f) (adsorption coefficient) values ranging between 0.21 and 1.88 (metsulfuron-methyl) and 0.37 and 1.17 (sulfosulfuron). Adsorption isotherms were L-type suggesting that the herbicides sorption decreased with increase in the initial concentration of the herbicide in the solution. The K(f) for metsulfuron-methyl showed good positive correlation with silt content (significant at p = 0.01) and strong negative correlation with the soil pH (significant at p = 0.05) while sorption of sulfosulfuron did not correlate with any of the soil parameter. Desorption of herbicides was concentration dependent and, in general, sulfosulfuron showed higher desorption than the metsulfuron-methyl. The study indicates that these herbicides are poorly sorbed in the Indian soil types and there may be a possibility of their leaching to lower soil profiles.
Journal of Environmental Science and Health, Part B, 2008
… of agricultural and …, 2009
Studies were undertaken to analyze the residues of commonly used pesticides viz. chlorpyrifos, en... more Studies were undertaken to analyze the residues of commonly used pesticides viz. chlorpyrifos, endosulfan, dicofol, cypermethrin, fenvalerate, propargite, malathion, phorate, carbendazim, carbosulfan, thiamethoxam, and mancozeb in apple of integrated pest management (IPM) and non-IPM samples collected from the IPM and non-IPM fields of Shimla. We also present a method for the determination of these pesticides in apple samples. Residues of chlorpyrifos, endosulfan, dicofol, cypermethrin, fenvalerate, and propargite were analyzed by gas chromatography, while residues of carbendazim, carbosulfan, and thiamethoxam were analyzed by high-performance liquid chromatography. Residues of mancozeb were determined by a colorimetric method. Recoveries of all of the pesticides ranged from 61.30 to 95.46% at 0.1, 0.2, and 1.0 μg g -1 levels of fortification with relative standard deviations ranging between 0.8 and 8.7. Apples from IPM and non-IPM orchards were analyzed for these pesticides using a developed method. Except for carbendazim and chlorpyrifos, the residues of all of the pesticides analyzed were below detectable limits. Although residues of carbendazim and chlorpyrifos were below the prescribed limits of maximum residue levels in both IPM and non-IPM orchards, residues were lower in apples from IPM orchards.
Ecotoxicology and Environmental Safety, 2013
Field evaluation of two fly ashes (40t/ha) on persistence, mobility and bioactivity of metribuzin... more Field evaluation of two fly ashes (40t/ha) on persistence, mobility and bioactivity of metribuzin and metsulfuron-methyl was studied in soybean and wheat crops, respectively. Metribuzin was applied as pre-emergence at 0.5kg/ha, while metsulfuron-methyl was applied post-emergence at 8g/ha. Results suggested that metribuzin in surface (0-15cm) soil of fly ash unamended plots reached below detectable limit in 60 days, while herbicide persisted till 112 days in surface soil of fly ash amended plots. No metribuzin leached down to subsurface (15-30cm) soil in fly ash amended plots, while traces of metribuzin (0.6-1.2μg/kg) were recovered in subsurface soil of fly ash unamended plot. Metsulfuron-methyl in surface soil persisted till 15 days in control and 20 days in fly ash amended plots and no metsulfuron-methyl leached down to subsurface soil. Fly ash amendment had no adverse effect on the bioactivity of herbicides and yield of soybean and wheat. The study suggested that fly ash amendment to soil can be exploited to retain applied herbicides in surface soil.
Bulletin of Environmental Contamination and Toxicology, 2011
Persistence of azoxystrobin was studied in/on grapes when applied @ 150 g ai ha -1 (recommended d... more 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 present study is aimed at analysing and comparing different soil enzymes in soil samples of n... more The present study is aimed at analysing and comparing different soil enzymes in soil samples of native contaminated sites of a Mathura refinery and adjoining agricultural land. Enzyme activities are considered as indicators of soil quality and changes in biogeochemical function due to management or perturbations. Soil samples were collected from the premises and nearby area of Mathura refinery, India. Biological health parameters (dehydrogenase, aryl esterase, aryl sulphatase, β-glucosidase, alkaline phosphatase, acid phosphatase, lipase, laccase and catalase activity) were estimated in the soil samples. Among all the samples, sewage sludge soil showed maximum activity of enzymes, microbial biomass carbon and most probable number of polycyclic aromatic hy-P. Chaudhary · L. Nain (B)
Bulletin of Environmental …, 2011
An actinobacterium designated as PAH-13 was isolated from bitumen (heavy crude oil) soil collecte... more An actinobacterium designated as PAH-13 was isolated from bitumen (heavy crude oil) soil collected from Mathura refinery, India. The isolate was screened for its ability to degrade 34 ring PAH compounds (anthracene, fluorene, phenanthrene and pyrene) in minimal ...
Pest Management Science, 2011
Pyrazosulfuron-ethyl {ethyl 5-[(4,6-dimethoxypyrimidin-2-ylcarbamoyl)-sulfamoyl]-1-methylpyrazole... more Pyrazosulfuron-ethyl {ethyl 5-[(4,6-dimethoxypyrimidin-2-ylcarbamoyl)-sulfamoyl]-1-methylpyrazole-4-carboxylate} is a new rice herbicide belonging to the sulfonylurea group. This study reports the translocation of (14)C-pyrazosulfuron-ethyl to rice plants and its degradation in rice-planted and unplanted soil. Pyrazosulfuron-ethyl did not show any appreciable translocation to rice shoots, as (14)C-activity translocated to the aerial portion never exceeded 1% of the initially applied (14)C-activity over a 25 day period. Results suggested that the dissipation of pyrazosulfuron-ethyl from soils followed first-order kinetics with a half-life of 5.5 and 6.9 days in rice-planted and unplanted soils respectively. HPLC analysis of the organic extract of soil samples showed the formation of three metabolites, namely ethyl 5-(aminosulfonyl)-1-methyl-1-H-pyrazole-4-carboxylate, 5-[({[(4,6-dimethoxy-2 pyrimidinyl)-amino]-carbonyl} amino)-sulfonyl]-1-methyl-1H-pyrazole-4-carboxylic acid and 2-amino-4,6-dimethoxy pyrimidine, in both rice-planted and unplanted soils. The study indicates that pyrazosulfuron-ethyl was a short-lived compound in the soil and was degraded relatively faster in rice-planted soil than in unplanted soil. The herbicide did not show any appreciable translocation to rice plants.
Monatshefte Fur Chemie, 1986
Condensation of 2-hydrazino-4-methylquinoline (1) and acetylacetone gives a compoundA, which has ... more Condensation of 2-hydrazino-4-methylquinoline (1) and acetylacetone gives a compoundA, which has the structure of 3,5-dimethyl-1-(4-methylquinolino)-pyrazole (2) and not of 4-methylquinolino-(2,3—c)-3,5-dimethyl-1H-1,2-diazepine (3) assigned earlier. The structure2 was confirmed on the basis of1H-NMR,13C-NMR, IR spectral data and its unambiguous synthesis.
Synthetic Communications, 1987
Condensation of uracil derivatives (1,3,4) with acetone in the presence of triethylamine gave pyr... more Condensation of uracil derivatives (1,3,4) with acetone in the presence of triethylamine gave pyranopyrimidines (2,5,6).