Aerobic soil metabolism of flupyrazofos

To elucidate the fate of flupyrazofos [O,O-diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl)phosphorothionate] in soil, an aerobic soil metabolism study was carried out for 60 days with [¹⁴C]flupyrazofos applied at a concentration of 0·38 μg g^-1 to a loamy soil. The material balance ranged from 103·5% to 86·9% and the half-life of [¹⁴C]flupyrazofos was calculated to be 13·6 days. The metabolites identified during the study were 1-phenyl-3-trifluoromethyl-5-hydroxypyrazole (PTMHP) and O,O-diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl)phosphate (flupyrazofos oxon), with maximum levels of 9·8% and 1·6% of applied radiocarbon, respectively. Evolved [¹⁴C]carbon dioxide accounted for up to 5·3% of applied radiocarbon and no volatile products were detected during the study. Non-extractable ¹⁴C-residue reached 31·6% of applied material at 60 days after treatment and radiocarbon was distributed almost evenly in humin, humic acid and fulvic acid fraction. © 1998 Society of Chemical Industry     

Photolysis of chlorsulfuron and metsulfuron-methyl in methanol

Photolysis of chlorsulfuron and metsulfuron-methyl was studied in methanol under UV light. Their rates of primary photolysis followed first-order kinetics. The main photoproducts were identified as 2-methoxy-4-methyl-1,3,5-triazin-6-amine, 2-chloro-benzenesulfonamide and methyl 2-(aminosulfonyl)benzoate, which entailed the cleavage of the two N–C ureic bonds. Further photolysis of benzenesulfonamide derivatives involved oxidation of −NH₂, cyclisation with loss of CH₃OH, and scission of the C–S bond A trace of methyl o-mercaptobenzoate was also detected. The corresponding photolysis pathways of chlorsulfuron and metsulfuron-methyl were tentatively proposed. © 1999 Society of Chemical Industry     

Fate of metsulfuron-methyl in soils in relation to pedo-climatic conditions

The dependence of the behaviour of metsulfuron-methyl on soil pH was confirmed during incubations under controlled laboratory conditions with two French soils used for wheat cropping. The fate of [¹⁴C] residues from [triazine-¹⁴C]metsulfuron-methyl was studied by combining different experimen-tal conditions: soil pH (8·1 and 5·2), temperature (28 and 10°C), soil moisture (90 and 50% of soil water holding capacity) and microbial activity (sterile and non-sterile conditions). Metsulfuron-methyl degradation was mainly influenced by soil pH and temperature. The metsulfuron-methyl half-life varied from five days in the acidic soil to 69 days in the alkaline soil. Under sterile conditions, the half-life increased in alkaline soil to 139 days but was not changed in the acidic soil. Metsulfuron-methyl degradation mainly resulted in the formation of the amino-triazine. In the acidic soil, degradation was characterised by rapid hydrolysis giving two specific unidentified metabolites, not detected during incubations in the alkaline soil. Bound residues formation and metsulfuron-methyl mineralisation were highly correlated. The extent of bound residue formation increased when soil water content decreased and was maximal [48 (±4)% of the applied metsulfuron-methyl after 98 incubation days] in the acidic soil at 50% of the water holding capacity and 28°C. Otherwise, bound residues represented between 13 and 32% of the initial radioactivity. © 1998 SCI     

Investigations on the metabolic fate of prochloraz in soil under field and laboratory conditions

The degradation of prochloraz in different soils was investigated in field and laboratory experiments. In laboratory degradation experiments in the dark, initial prochloraz concentrations decreased to 30–64% within 56 days, depending on temperature and soil pH. In neutral to basic soils, formation of up to 3.7% of the metabolite prochloraz-urea was observed. The rate of mineralization was strongly pH-dependent, not exceeding 3.2% in the acidic and 18.3% in the neutral to basic soils. Amounts of non-extractable residues ranged from 14 to 31%. Under field conditions, prochloraz disappeared much more rapidly with DT₅₀ values of 11–43 days. The metabolites prochloraz-formylurea and prochloraz-urea were found in significant concentrations. Laboratory experiments with fresh and sterilized soils under UV irradiation confirmed the enhancing effect of light on the formation of the primary metabolite, prochloraz-formylurea. The latter is hydrolysed to prochloraz-urea predominantly by microbial degradation. © 1999 Society of Chemical Industry     

甲磺隆和草甘膦对空心莲子草乙酰乳酸合酶活性和莽草酸含量的影响

为研究甲磺隆和草甘膦对空心莲子草的作用机理,探索其最佳的使用技术,采用有效成分为30 g/hm2和60 g/hm2 的甲磺隆处理空心莲子草,能明显抑制其茎和根乙酰乳酸合酶的比活性;有效成分为1537.5g/ hm2和3075g/ hm2 的草甘膦处理则能明显抑制空心莲子草莽草酸含量的积累;施用甲磺隆和草甘膦对空心莲子草生长的抑制作用随药剂浓度的提高而增大.二次施用草甘膦(间隔30天)的结果表明,低剂量处理对抑制空心莲子草根组织莽草酸含量的积累更明显.     

The effects of the herbicide metsulfuron-methyl on litter invertebrate communities in a coastal dune invaded by Chrysanthemoides monilifera spp. rotundata

We investigated the impacts of application of the sulfonylurea herbicide, metsulfuron-methyl, on soil and litter invertebrates in coastal vegetation where the weed Chrysanthemoides monilifera has invaded. We followed changes in litter invertebrates for 125 days following treatment to investigate direct toxic and indirect effects of treatment. Overall we found no effect of treatment on abundance, taxonomic richness or composition of litter invertebrates. In general, abundance and richness declined with time in both treated and untreated sites, suggesting that climatic factors were far more important in determining invertebrate communities than the effects of the treatment. Even changes in cover of vegetation as a result of death of the weed resulted in few measurable effects on invertebrates. It is concluded that metsulfuron-methyl had no impact on invertebrate communities up to 125 days following treatment.     

Degradation of primisulfuron-methyl and metsulfuron-methyl in soil

A newly developed chemical assay was used to determine the degradation in soil of two sulfonylurea herbicides, primisulfuron-methyl and metsulfuron-methyl, under both controlled and field conditions. The results from the chemical assay were compared with those from traditional bio-assays for determination of persistence in the field. Phytotoxic effects of these herbicides were not observed after 6 weeks following application to an acidic (pH 5.7) soil with high organic matter content (7.3% o.c). Half-lives of 13 to 29 days were measured for primisulfuron-methyl at different soil-water contents and temperatures while those for metsulfuron-methyl ranged from 8 to 36 days. The rate of degradation of metsulfuron-methyl was more sensitive to temperature than that of primisulfuron-methyl. Persistence in the field was shorter than expected considering the results from the controlled environment studies. However, determination of the persistence by both chemical assay and bioassay methods produced very similar results.     

Assessment of leaching potential of aldicarb and its metabolites using laboratory studies

The metabolites of pesticides can contaminate groundwater and pose a risk to human health when this water is used for drinking. This paper reports the results of a laboratory study on aldicarb and its main metabolites, aldicarb sulfone and aldicarb sulfoxide. Aldicarb and its metabolites showed K_oc values (6–31) which were lower than that of atrazine (55), indicating that they are very mobile in soil. They are less persistent than atrazine (DT₅₀ = 25 days), with DT₅₀ values from less than 1 day and up to 12 days. Aldicarb behaved as a non‐leacher, whereas its metabolites clearly showed the characteristics of leachers. Aged residue leaching experiments showed that aldicarb can occur at high concentrations in the leachate, together with its two metabolites. The leachate composition depends on the incubation time of the parent compound. Aldicarb and its metabolites can form various mixtures in groundwater on the basis of the time elapsing between the application of the insecticide and the first significant rainfall. This study confirms the characteristics of contaminants of aldicarb and especially its metabolites, as reported in the literature. © 2001 Society of Chemical Industry     

Variability of bioassays with metsulfuron-methyl in soil

A total of 74 independently run bioassays with soil incorporated metsulfuron-methyl from 12 different laboratories was analysed by a logistic dose-response curve to assess the precision of regression parameters and relate ED₅₀ to soil properties. The potency in terms of ED₅₀ of metsulfuron-methyl in Brassica rapa L., which was used by all laboratories, varied between 0.05 and 3.9 g a.i. ha^-1. ED₅₀ was negatively correlated with pH and positively correlated with organic matter. The majority of laboratories had ED₅₀ within the interval 0.1-1.0 g a.i. ha^-1. At one laboratory using three test species, the most sensitive species was Beta vulgaris L. followed by Brassica rapa L. and Lepidium sativum L. The coefficients of variation were smallest for the ED₅₀ and ED₉₀ response levels and largest for the ED₁₀. The slope of the response curves had considerably lower coefficients of variation than the EDs. The results are discussed in relation to a previous collaborative bioassay study. Finally it is suggested that standardization of bioassays with herbicides could be achieved in the same way as standardization of chemical analyses.     

Degradation of oxadiazon in Kalyani alluvial soil

Residual fate and behaviour of the herbicide oxadiazon in Kalyani soil, paddy straw and grain were studied under subtropical conditions, in West Bengal following application @ 1 kg and 2 kg ha⁻¹. Dissipation of oxadiazon in soil followed first-order kinetics and DT₅₀ values ranged from 44 to 45 days. Residues at harvest in paddy grains and straw were also studied. Degradation of oxadiazon after 60 days of incubation at 28(± 1) °C in alluvial soil at water holding capacity yielded 10 metabolites of which four were characterised by spectroscopy. © 1999 Society of Chemical Industry     

Translocation and degradation of pyrazosulfuron-ethyl in rice soil

BACKGROUND: 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 ¹⁴C‐pyrazosulfuron‐ethyl to rice plants and its degradation in rice‐planted and unplanted soil. RESULTS: Pyrazosulfuron‐ethyl did not show any appreciable translocation to rice shoots, as ¹⁴C‐activity translocated to the aerial portion never exceeded 1% of the initially applied ¹⁴C‐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. CONCLUSION: 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. Copyright © 2011 Society of Chemical Industry     

氟虫腈在三种土壤中的降解特性研究

实验室条件下,研究了氟虫腈在东北黑土、江西红壤和太湖水稻土中的降解特性。结果表明,氟虫腈在土壤中降解较慢,其在好气条件下的东北黑土、江西红壤和太湖水稻土中的降解半衰期分别为165、267和42 d,在渍水条件下的3种土壤中的降解半衰期分别为31、173和32 d。氟虫腈在pH 偏中性的太湖水稻土中降解最快;微生物对氟虫腈在土壤中的降解起主要作用;渍水条件有利于氟虫腈的降解,推测降解氟虫腈的微生物主要是厌氧菌属。     

甲磺隆结合态残留物对土壤微生物的影响

研究了不同处理土壤中结合态甲磺隆残留物对土壤微生物群落的影响。结果表明,在供试浓度下,土壤中甲磺隆结合态残留物的生态效应仍不容忽视,其对土壤细菌、真菌具有显著的刺激作用,而对土壤放线菌却有强烈的抑制作用,抑制率高达100%,至培养结束时(84 d)放线菌数量还未恢复到对照水平。但微生物反应程度在不同土壤、氮素水平及培养时间上皆存在一定的差异性。土壤微生物群落,尤其是放线菌可作为评价甲磺隆除草剂残留污染土壤生态环境效应的敏感指标。外源氮素(尿素)的添加,既能增加土壤微生物的数量,也能缓减结合态农药残留物对土壤放线菌的毒害效应。     

Influence of Portland cement amendment on soil pH and residual soil termiticide performance

Soil adjacent to new brick veneer work is likely to have a higher pH owing to the mixture of cement with the soil. In the Gainesville, FL, area, soil samples taken from such locations had a range of pH values from 9.0 to 10.1; similar soils used in bioassays had a pH of 5.6 before the addition of cement. Addition of 15 mg of Portland cement to 33 g of soil increased the pH to 6, and addition of 291 mg of Portland cement increased the pH to 9. The pH of soil amended with cement was stable for the first 5 months. After 10 months, soil pH values decreased from alkaline to near neutral in all cases. Eastern subterranean termite workers, Reticulitermes flavipes (Kollar), were exposed to the treated soil at pH 6-9 for 24 h, and percentage mortality was recorded at 5 days, 5 months and 10 months. Termite mortality significantly decreased at higher soil pHs for bifenthrin, chlorpyrifos, fipronil and imidacloprid treatments at 5 months and similarly for bifenthrin, permethrin, chlorpyrifos, fipronil and imidacloprid treatments at 10 months. There was an inverse linear relationship between soil pH and mortality. Increased soil pH diminished residual activity of termiticide in the following order: imidacloprid > fipronil > chlorpyrifos = bifenthrin > permethrin > cypermethrin.     

Combined application of cyanobacteria with soil fixing chemicals for rapid induction of biological soil crust formation

Combined applications of cyanobacteria with soil fixing chemicals were investigated to generate artificially induced biological soil crust (BSC). Polyvinyl alcohol (PVA) and Tacki-Spray (TKS7) chemicals composed of bio-polysaccharides and tackifiers were examined under laboratory conditions. Following singular applications of chemicals, the mean weight diameter values of soil treated with TKS7 were 1.4–2.5 times higher than those of soil treated with PVA and thus TKS7 was selected for further tests for application with cyanobacteria (Nostoc Vaucher ex Bornet &; Flahault, Phormidium Kützing ex Gomont, and Scytonema arcangeli Bornet ex Flahault). Combined application of cyanobacteria and different concentrations of TKS7 enhanced soil aggregate stability, resulting in mean weight diameter values of 0.58–0.69 mm and was comparable to TKS7 singular application (0.18–0.40 mm). Surface hardness values were also highly improved by the combined application of cyanobacteria with TKS7 (4.5 MPa) compared to singular treatment of cyanobacteria (2.3 MPa). In addition, superabsorbent polymer (SAP) was applied as a water-holding material and nutrient supplement in soil. The SAP promoted cyanobacterial cell growth under dry conditions. Chlorophyll a content of soil was improved by the addition of SAP (CST1: 2.93 µg g^?1) compared to singular treatment of cyanobacteria (C: 2.25 µg g^?1). These results suggest that combined application of cyanobacteria with TKS7 and SAP can induce BSC formation faster than singular application of cyanobacteria. The novel method presented herein can be applied to restoration of degraded soils in arid and semiarid areas.     

稻丰散在土壤和水中的降解及其在土壤中的吸附

在室内模拟条件下,研究了稻丰散在土壤和水中的降解及其在土壤中的吸附行为。结果表明:稻丰散的降解速率随土壤温度的升高和土壤含水量的增加而加快;微生物的存在有利于其在土壤中的降解;在20 ℃时,稻丰散在pH为5、7、9的水溶液中的降解半衰期分别为10.66、11.65和6.53 d。3种供试土壤对稻丰散的吸附均符合Freundich方程,且有机质含量越高,土壤对稻丰散的吸附越强。     

Characterization of propargyl bromide transformation in soil

Propargyl bromide is being investigated for its potential as a soil fumigant. Characterization of the fate of propargyl bromide in soil is important in determining both efficacy and the threat of environmental contamination. These experiments investigated some of the factors affecting the rate of propargyl bromide degradation in soil and quantified some of the products formed as a result of propargyl bromide degradation in four soils of differing composition and at three initial propargyl bromide concentrations. In all soils at all initial propargyl bromide concentrations, equimolar formation of Br- was observed during propargyl bromide degradation, but little propargyl alcohol (product of hydrolysis) was formed. The apparent first-order degradation coefficient (k) increased with decreasing initial propargyl bromide concentration in all soils, but the mass degraded per unit time increased with increasing propargyl bromide concentration. The rate of propargyl bromide degradation increased with increasing soil organic matter content, and the k value was correlated to the organic carbon content of the soil (correlation coefficient > 0.97 for all concentrations). Repeated application of propargyl bromide did not increase the rate of propargyl bromide degradation in soil. Addition of Br- did not affect the rate of propargyl bromide transformation in soil, so accumulation of Br- in the soil is not expected to impede propargyl bromide degradation.     

Isolation and characterisation of a bacterial strain degrading the herbicide sulcotrione from an agricultural soil

BACKGROUND: The dissipation kinetics of the herbicide sulcotrione sprayed 4 times on a French soil was studied using a laboratory microcosm approach. An advanced cultivation‐based method was then used to isolate the bacteria responsible for biotransformation of sulcotrione. Chromatographic methods were employed as complementary tools to define its metabolic pathway. RESULTS: Soil microflora was able quickly to biotransform the herbicide (DT₅₀ ≈ 8 days). 2‐Chloro‐4‐mesylbenzoic acid, one of its main metabolites, was clearly detected. However, no accelerated biodegradation process was observed. Eight pure sulcotrione‐resistant strains were isolated, but only one (1OP) was capable of degrading this herbicide with a relatively high efficiency and to use it as a sole source of carbon and energy. In parallel, another sulcotrione‐resistant strain (1TRANS) was shown to be incapable of degrading the herbicide. Amplified ribosomal restriction analysis (ARDRA) and repetitive extragenic palendromic PCR genomic (REP‐PCR) fingerprinting of strains 1OP and 1TRANS gave indistinguishable profiles. CONCLUSION: Sequencing and aligning analysis of 16S rDNA genes of each pure strain revealed identical sequences and a close phylogenetic relationship (99% sequence identity) to Pseudomonas putida. Such physiological and genetic properties of 1OP to metabolise sulcotrione were probably governed by mobile genetic elements in the genome of the bacteria. Copyright © 2011 Society of Chemical Industry     

敌草胺在土壤中的吸附及其与持久性和生物有效性之间的关系

土壤吸附是农药在环境中归趋的关键支配因素,也是支配农药在环境中的持久性和生物有效性的重要因素之一。该文采用高效液相色谱法研究了除草剂敌草胺在不同性质土壤中的吸附、持久性和生物有效性以及吸附与土壤持久性、蚯蚓生物有效性之间的关系。结果表明,在供试浓度范围内,采用批量平衡技术测定的敌草胺土壤吸附等温线可用Freundlich模型表征（r>0.99）,土壤有机质含量（PPt50）在61.3-97.6 d之间;微生物对敌草胺在土壤中的持久性影响显著,微生物降解是敌草胺在土壤环境中降解的主要途径,灭菌处理后其在土壤中的半衰期延长了2.09~3.65倍。蚯蚓Eisenia foetida对敌草胺的吸收和生物积累也主要取决于土壤性质,特别是土壤的有机质含量水平（Pr=-0.885,Pr=-0.796,Pt50=94.210-3.535 Kf和BAF=0.264-0.014 Kf,表明吸附系数可用作模型参数来评价敌草胺在土壤中的持久性和生物有效性。