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1.
A laboratory study was conducted to determine the degradation rates and identify major metabolites of the herbicide metsulfuron-methyl in sterile and non-sterile aerobic soils in the dark at 20°C. Both [phenyl-U-14C]- and [triazine-2-14C]metsulfuron-methyl were used. The soil was treated with [14C]metsulfuron-methyl (0.1 mg kg−1) and incubated in flow-through systems for one year. The degradation rate constants, DT50, and DT90 were obtained based on the first-order and biphasic models. The DT50 (time required for 50% of applied chemical to degrade) for metsulfuron-methyl, estimated using a biphasic model, was approximately 10 days (9–11 days, 95% confidence limits) in the non-sterile soil and 20 days (12–32 days, 95% confidence limits) in the sterile soil. One-year cumulative carbon dioxide accounted for approximately 48% and 23% of the applied radioactivity in the [phenyl-U-14C] and [triazine-2-14C]metsulfuron-methyl systems, respectively. Seven metabolites were identified by HPLC or LC/MS with synthetic standards. The degradation pathways included O-demethylation, cleavage of the sulfonylurea bridge, and triazine ring opening. The triazine ring-opened products were methyl 2-[[[[[[[(acetylamino)carbohyl]amino]carbonyl]amino] carbonyl]-amino]sulfonyl]benzoate in the sterile soil and methyl 2-[[[[[amino[(aminocarbonyl)imino]methyl] amino]carbonyl]amino]sulfonyl]benzoate in the non-sterile soil, indicating that different pathways were operable. © 1999 Society of Chemical Industry  相似文献   

2.
Standing water from carbofuran-treated Azolla plots showing accelerated degradation was further enriched by five repeated transfers to carbofuran-supplemented mineral salts medium. This enrichment culture developed from standing water of carbofuran-treated Azolla plot can utilise carbofuran as sole source of carbon and nitrogen. The enrichment culture was able to hydrolyse nearly 100% of [ring-14C]carbofuran to carbofuran phenol in five days, which accumulated in the medium, while the carbamate side-chain in [carbonyl-14C]carbofuran was readily mineralized to [14C]carbon dioxide. Enrichment culture was able to degrade carbofuran up to 1000 µg ml−1 levels in mineral salts medium with ease. © 1999 Society of Chemical Industry  相似文献   

3.
Ammonium sulphate and urea, but not potassium sulphate, increased the persistence of carbaryl in a flooded laterite soil with a low native nitrogen content (0.04%), but not in an alluvial soil with a higher nitrogen content (0.11%). Thus, NH4+ but not SO42-, contributed to the increased persistence of carbaryl. Likewise, ammonium sulphate increased the persistence of carbofuran in the laterite soil, but not in the alluvial soil. Significant accumulations of 1-naphthol and 2,3-dihydro-2, 2-dimethylbenzofuran-7-ol (‘carbofuran phenol’), in soils treated with carbaryl or carbofuran, suggested hydrolysis as the major pathway of degradation. Treatment of the two soils with ammonium sulphate, urea or potassium sulphate led to a decrease in soil-bound residues and an increase in the respective hydrolysis products, compared with untreated soils. Sorption studies indicated that NH4+ and SO42- compete with carbaryl, 1-naphthol and carbofuran for sorption and exchange sites in the complex soil system. Evolution of [14C]carbon dioxide from ring-14C in carbaryl and carbofuran was negligible. Consequently, after 40 days, more than 50% of the 14C in [14C]carbaryl and [14C]carbofuran remained in the soils as hydrolysis products (1-naphthol or 2,3-dihydro-2,2-dimethylbenzofuran-7-ol) plus soil-bound residues.  相似文献   

4.
The biomineralization of [14C]glyphosate, both in the free state and as 14C-residues associated with soybean cell-wall material, was studied in soil samples from four different agricultural farming systems. After 26 days, [14C]carbon dioxide production from free glyphosate accounted for 34–51% of the applied radiocarbon, and 45–55% was recovered from plant-associated residues. For three soils, the cumulative [14C]carbon dioxide production from free glyphosate was positively correlated with soil microbial biomass, determined by substrate-induced heat output measurement and by total adenylate content. The fourth soil, originating from a former hop plantation, and containing high concentrations of copper from long-term fungicide applications, did not fit this correlation but showed a significantly higher [14C]carbon dioxide production per unit of microbial biomass. Although the cumulative [14C]carbon dioxide production from plant-associated 14C-residues after 26 days was as high as from the free compound, it was not correlated with the soil microbial biomass. This indicates that the biodegradation of plant-associated herbicide residues, in contrast to that of the free compound, involves different degradation processes. These encompass either additional steps to degrade the plant matrix, presumably performed by different soil organisms, or fewer degradation steps since the plant-associated herbicide residues are likely to consist mainly of easily degradable metabolites. Moreover, the bioavailability of plant-associated pesticide residues seems to be dominated by the type and strength of their fixation in the plant matrix. ©1997 SCI  相似文献   

5.
Ring- and carboxyl-labelled [14C]2,4-D were incubated under laboratory conditions, at the 2 g/g level, in a heavy clay, sandy loam, and clay loam at 85% of field capacity and 20 1C. The soils were extracted at regular intervals for 35 days with aqaeous acidic acetonitrile, and analysed for [14C]2,4-D and possible radioactive degradation products. Following solvent extraction, a portion of the soil residues were combusted in oxygen to determine unextracted radioactivity as [14C]carbon dioxide. The remaining soil residues were then treated with aqueous sodium hydroxide, and the radioactivity associated with the fulvic and humic soil components determined. In all soils there was a rapid decrease in the amounts of extractable radioacitivity, with only 5% of that applied being recoverable after 35 days. All recoverable radioactivity was attributable to [14C]2,4-D, and no [14C]-containing degradation products were observed. This loss of extractable radioactivity was accompanied by an increase in non-extractable radioactivity. Approximately 15% of the applied radioactivity, derived from carboxyl-labelled [14C]2,4-D, and 30% from the ring-labelled [14C]2,4-D was associated with the soil in a non-extractable form, after 35 days of incubation. After 35 days, less than 5% of the radioactivity from the carboxyl-labelled herbicide, and less than 10% of the ringlabelled material, was associated with the fulvic components derived from the three soils. Less than 5% of the applied radioactivities were identifiable with any of the humic acid components. It was considered that during the incubation [14C]2,4-D did not become bound or conjugated to soil components, and that non-extractable radioactivity associated with the three soil types resulted from incorporation of radioactive degradation products, such as [14C]carbon dioxide, into soil organic matter.  相似文献   

6.
The degradation of the wild oat herbicide flamprop-methyl [methyl DL -N-benzoyl-N-(3-chloro-4-fluorophenyl)alaninate] in four soils has been studied under laboratory conditions using 14C-1abelled samples. The flamprop-methyl underwent degradation more rapidly than its analogue flamprop-isopropyl. However, similar degradation products were formed, namely the corresponding carboxylic acid and 3-chloro-4-fluoroaniline. The latter compound occurred mainly as ‘bound’ forms although evidence was obtained of limited ring-opening to give [14C]carbon dioxide. The time for depletion of 50% of the applied herbicide was approximately 1-2 weeks in sandy loam, clay and medium loam soils and 2-3 weeks in a peat soil.  相似文献   

7.
In France, corn rootworm (Agriotes sp.) is controlled by applying insecticides such as carbofuran to the soil. In recent years, the failure of carbofuran to control this pest has been observed in the south-west area of France in continuous corn cropping. A soil survey was conducted in order to determine the main factors which could influence carbofuran degradation in various soils. Degradation estimates were based on measurement of the release of [ 14 C]carbon dioxide from [carbonyl- 14 C]carbofuran. The enhanced degradation of carbofuran observed in laboratory conditions corresponded to the growth of micro-organisms able to use carbofuran as sole carbon and nitrogen source. The size of this microbial population and the rates of carbofuran degradation were higher in the samples taken from plots with a history of carbofuran use than in samples from previously untreated plots. Abiological degradation was only observed in alkaline soil conditions. Statistical analyses showed that carbofuran-degrading activity was not related to any particular pedological characteristics.  相似文献   

8.
Enhanced biodegradation of ethoprophos was evident in a soil from a previously treated field in Northern Greece. However, enhanced biodegradation was specific to ethoprophos and there was no cross‐enhancement leading to rapid degradation for any of the other organophosphorus (cadusafos, fenamiphos, fonofos, isazofos) or carbamate (aldicarb, oxamyl) nematicides registered in Greece for the control of potato cyst nematodes. Studies with radio‐labelled ethoprophos showed that the adapted microflora in the soil from the previously treated field was able to degrade [propyl‐1‐14C]ethoprophos rapidly and mineralized about 60% of the initially applied nematicide. When [ethyl‐1‐14C] ethoprophos was applied, the reduction in extractable radioactivity in the previously treated soil was coupled with evolution of lower amounts of [14C] carbon dioxide and was similar to the amounts produced from the previously untreated soils. It is suggested that degradation of ethoprophos in the soil from the previously treated field proceeds via hydrolysis of the P‐S bond in the ‐S‐propyl moiety of the ethoprophos molecule, which is then further mineralized by the adapted micro‐organisms. Enhanced biodegradation of ethoprophos in this specific previously treated soil in Northern Greece and under the local environmental conditions was still evident two years after the last ethoprophos field application. It appears that, once established, enhanced biodegradation of ethoprophos can be quite stable. A possible solution to this problem might be the introduction of a rotation scheme where other nematicides like fenamiphos, cadusafos, aldicarb or oxamyl are used as alternatives with ethoprophos application restricted to only once every three or four years. © 2000 Society of Chemical Industry  相似文献   

9.
The effects of application rate, volume, solvent and soil moisture content on the kinetics of mineralization and degradation, of [14C] permethrin have been studied in a sandy loam soil under standard laboratory conditions. During the incubation period, up to 32 days, the temperature and moisture level of the soil were controlled. Apart from the effects of application rate, which have been widely reported, application volume had the most significant effect on mineralization rate and T1/2. [14C]Permethrin, at a level of a 1 mg kg?1 in the soil, applied in 100 μl of methanol, resulted in the evolution of 14% of the applied radiochemical as [14C] carbon dioxide over 30 days. The same level applied in 1000 μl mineralized at a faster rate, with 30% [14C]carbon dioxide evolved over 30 days. The test chemical applied to soil in methanol mineralized at a significantly faster rate than a similar concentration applied in ethanol. There was no significant difference when comparing applications made using acetonitrile with those using methanol or ethanol. The addition of formulation ingredients resulted in little or no variation in mineralisation rate compared to an equivalent application volume of methanol/water.  相似文献   

10.
[14C]Diflubenzuron is readily degraded in various agricultural soils and in hydro-soil; 50% of the applied dose of 1 mg kg−1 was metabolised in 2 days or less. The chief products of hydrolysis were identified as 4-chlorophenylurea and 2, 6-difluorobenzoic acid. A part of the radioactivity, increasing with incubation time, could not be extracted. Release from the soil of [14C]carbon dioxide, derived from both labelled phenyl rings, points to the ultimate mineralisation of diflubenzuron.  相似文献   

11.
2,6-Difluorobenzoic acid, one of the two primary diflubenzuron metabolites, is rapidly and completely degraded in soil. Times to 50% disappearance were 9 and 12 days in two agricultural soils. [14C]Carbon dioxide was an ultimate product of the ring-14C-labelled compound. A part of the radioactivity, increasing with time to one third of the applied dose of 1 mg kg?1, could not be extracted from the soil.  相似文献   

12.
The potential to mineralize 2,4‐dichlorophenoxyacetic acid (2,4‐D), mecoprop, isoproturon and terbuthylazine was studied in soil and aquifer chalk sampled at an agricultural field near Aalborg, Denmark. Laboratory microcosms were incubated for 258 days under aerobic conditions at 10 °C with soil and chalk from 0.15–4.45 m below the surface. The [ring‐U‐14C]‐labeled herbicides were added to obtain a concentration of 6 µg kg?1 and mineralization was measured as evolved [14C]carbon dioxide. The herbicides were readily mineralized in soil from the plough layer, except for terbuthylazine, which was mineralized only to a limited extent. In the chalk, lag periods of at least 40 days were observed, and a maximum of 51%, 33% and 6% of the added 2,4‐D, mecoprop and isoproturon, respectively, were recovered as [14C]carbon dioxide. Large variations in both rate and extent of mineralization were observed within replicates in chalk. No mineralization of terbuthylazine in chalk was observed. As a measure of the general metabolic activity towards aromatic compounds, [ring‐U‐14C]‐benzoic acid was included. It was readily mineralized at all depths. © 2000 Society of Chemical Industry  相似文献   

13.
The degradation of the wild-oat herbicide flamprop-isopropyl, [isopropyl (±)-N-benzoyl-N-(3-chloro-4-fluorophenyl)alaninate], in four soils has been examined under laboratory conditions with sampling times of up to 45 weeks after treatment. The major degradation product of [14C]flamprop-isopropyl in all soils at up to 10 weeks after treatment was the carboxylic acid (±)-N-benzoyl-N-(3-chloro-4-fluorophenyl)alanine. This compound in turn underwent degradation by loss of the benzoyl group and the propionic acid moiety, with evolution of [14C]carbon dioxide to form 3-chloro-4-fluoroaniline (CFA). The CFA was formed slowly in soil and occurred mainly as a bound form. There was evidence to show that the CFA was subsequently converted into other polar products. The time for depletion of 50% of the applied herbicide was approximately 10 weeks in sandy loam and medium loam soils, 11 weeks in a clay loam soil and 23 weeks in a peat soil.  相似文献   

14.
A 140-day laboratory incubation, using surface soil from a long-term soybean tillage study, evaluated tillage influence on [14C]metribuzin degradation. Higher plant residue conditions in no-tillage (NT) soil inhibited metribuzin mineralization to [14C]carbon dioxide as compared to metribuzin degradation patterns observed in conventional tillage (CT) soil. At 140 days, relative abundance of extractable 14C components in NT included polar metabolites > metribuzin = deaminated metribuzin (DA) = deaminated diketometribuzin (DADK), while in CT, components included metribuzin > polar metabolites > DADK?DA. Conditions in NT apparently inhibited polar 14C degradation, and resulted in its accumulation, while in CT polar 14C degradation proceeded relatively rapidly. For both NT and CT, more 14 C was measured in an unextractable fraction than in any other fraction. A greater portion of the unextractable fraction in NT was associated with decomposed plant residue than in CT. Surface accumulation of crop residue, such as occurs under NT, provided a soil environment which altered metribuzin degradation patterns.  相似文献   

15.
The degradation of bis(tri[1-14C]butyltin) oxide in two soils (1 mg tin kg?1) has been studied under laboratory conditions. Half of the applied compound disappeared from unsterilised silt loam and sandy loam in approximately 15 and 20 weeks, respectively; it disappeared also from the sterilised soils but to a lesser extent. The formation of small amounts of dibutyltin derivatives was established by thin-layer chromatography both in the unsterilised and sterile soils. The amount of unextractable radioactivity increased with time in the unsterilised and sterile soils. In the unsterilised soils 14C was released as [14C]carbon dioxide in amounts equivalent to 20% of the applied radioactivity for silt loam and 10.7% for sandy loam over a period of 42 weeks. Almost no [14C]carbon dioxide was released from the sterile soils, confirming microbial participation in the degradation of the compound in the unsterilised soils.  相似文献   

16.
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  相似文献   

17.
Insecticide wastes generated from livestock dipping operations are well suited for biodegradation processes since these wastes are concentrated, contained, and have no other significant toxic components. A field-scale biofilter capable of treating 15000-litre batches of dip waste containing the acaricide coumaphos was used to reduce the coumaphos concentration in two successive 11000-litre batch trials from 2000 mg litre-1 to 10 mg litre-1 in approximately 14 days at 25–29°C. Removal of coumaphos from the biofilter effluent is a function of both physical filtration and biodegradation by the biofilter. However, stoichiometric increases in chloride levels in the effluent as coumaphos concentrations decreased confirmed that coumaphos was being degraded by the biofilter rather than just being filtered out. In subsequent 5500-litre batch experiments, the addition of a vitamin supplement to the biofilter-treated dip resulted in a further decrease in coumaphos concentration to approximately 1 mg litre-1. Results from incubations of two representative Texas soils with biofilter-treated dip spiked with [benzo-U-14C] coumaphos revealed that 32–36% of the spiked [14C] coumaphos was mineralized in the soils after 110 days at 30°C. © 1998 SCI.  相似文献   

18.
Volatilization, mineralization, degradation and binding of soil-applied [14C]DDT were studied in three different soils from a tropical region of southern India subjected to solar irradiation and flooding for a period of 42 days. The soil types–red cotton soil, nursery soil and canal bank soil–differed in their organic carbon content, pH and texture. Under unflooded conditions, volatile losses were highest in the sandy canal bank soil. Flooding significantly enhanced volatilization, and this effect was maximal in the nursery soil, which had the highest organic carbon. The soils fully exposed to solar radiations in quartz tubes registered 1.5-1.8 times greater volatility. The volatilized organics contained appreciable quantities of DDE under both flooded and unflooded conditions. In addition, greater quantities of DDD volatilized from the flooded systems. The rate of formation of DDE was faster when soils were irradiated in quartz tubes. Mineralization remained minimal throughout the period of exposure and flooding the soil appeared to reduce further the [14C]carbon dioxide evolution. Canal bank soil exhibited the least mineralization and degradation. The data indicate that volatilization was significantly influenced by solar radiation and flooding to a much greater degree than by the differences in soil properties. Binding of DDT to soil was significantly increased by flooding the soil, thus leaving up to 33% of the initial DDT as bound residues in the nursery soil.  相似文献   

19.
Isolated rat hepatocytes were incubated for 4 hr with [phenyl-U-14C]2,4,5-trimethyl-N-phenyl-3-furancarboxamide ([14C]methfuroxam). 14C-Labeled metabolites were isolated by solvent extraction, column chromatography, and high-pressure liquid chromatography, and were then characterized by analysis of infrared and mass spectra. Metabolism of [14C]methfuroxam by isolated hepatocytes included: (1) hydroxylation of the 2-, 4-, and 5-methyl groups on the furan ring; (2) hydroxylation at the para position of the benzene ring; (3) combinations of 1 and 2; (4) the addition of a sulfur-containing adjunct to the methylfuran moiety; and (5) conjugation of 1–4. Rats given a single intragastric dose of [14C]methfuroxam excreted 56% of the 14C in the urine and 42% in the feces within 54 hr. Metabolism of [14C]methfuroxam by the intact rats included: (1) hydroxylation of the methylfuran moiety; (2) hydroxylation of the benzene ring; (3) the addition of S-methyl, methyl sulfoxide, and other sulfur-containing groups to methfuroxam; (4) combinations of 1–3; and (5) conjugation of 1–4.  相似文献   

20.
Increasing adsorption of [14C]-labelled carbendazim in soil took place within a few weeks of incubation and was greatest in soil with a high organic matter content. Carbendazim was slowly decomposed in soil, mainly by soil microorganisms. After 250 days of incubation in two unsterilised soils, 13 and 5% respectively of added [14C]-carbendazim was recovered compared with 70 and 50% respectively from sterile soils; 4–8% of added carbendazim was recovered as 2-aminobenzimidazole (2-AB) from both unsterilised and sterile soil. After 270 days' incubation, 33 and 9% of 14C was recovered as 14CO2 from soil supplied with [14C]-carbendazim (20 and 100 mg/kg) respectively. Degradation started more rapidly when carbendazim was added to soil preincubated with the fungicide but the degradation rate was very low in all cases, indicating that the compound is a poor microbial energy source and that the degradation is a co-metabolic process. 2-AB was found as a degradation product although it appeared to be unstable in soil, decomposing rapidly after a lag period of about 3 weeks; small amounts remained in the soil for several months, however, presumably adsorbed on soil particles.  相似文献   

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