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1.
Soils which have been pretreated with carbofuran can degrade the insecticide more rapidly than untreated soils, with a consequent loss of efficacy. In laboratory studies, soils pretreated with carbofuran were found to degrade the chemical more rapidly than soils which were not so pretreated. When pretreated soils were sterilised, the rate of carbofuran degradation was much reduced, indicating that most of it was due to microbial action. Incubation of pretreated soil with [phenyl-U-14C]carbofuran led to the rapid disappearance of the parent compound (3 % left after seven days). Most of the 14C was accounted for as bound residue after seven days, whilst smaller amounts were recovered as carbon dioxide, 3-hydroxycarbofuran, 3-ketocarbofuran, and an unknown metabolite. Incubation of pretreated soil with [carbonyl-14C]carbofuran led to rapid loss of the parent compound and the recovery of 73% of 14C as carbon dioxide by five days. Most of the bound 14C (>90%) arising from [phenyl-U-14C]carbofuran treatment of pretreated soil was extracted by 1 M sodium hydroxide and about half of the extracted 14C was precipitated with ‘humic acids’ after acidification. These and other results suggest that the major metabolic route for carbofuran in pretreated soils involves hydrolysis of the ester bond leading to (1) release of carbofuran phenol which rapidly binds to soil organic matter and, (2) release of the carbonyl moiety which quickly degrades to generate carbon dioxide.  相似文献   

2.
Carbofuran was incubated in top‐soil and sub‐soil samples from a pesticide‐free site at a range of initial concentrations from 0.1 to 10 mg kg−1. Amounts of the incubated soils were removed at intervals over the subsequent 12 months, and the rate of degradation of a second carbofuran dose at 10 mg kg−1 was assessed. An applied concentration as low as 0.1 mg kg−1 to top‐soil resulted in more rapid degradation of the fresh addition of carbofuran for at least 12 months. The degree of enhancement was generally more pronounced with the higher initial concentrations. When the same study was conducted in sub‐soil samples from the same site, an initial dose of carbofuran at 0.1 mg kg−1 resulted in only small increases in rates of degradation of a second carbofuran dose. However, degradation rates in the sub‐soil samples were, in many instances, considerably greater than in the corresponding top‐soil samples, irrespective of pre‐treatment concentration or pre‐incubation period. Initial doses of 0.5 mg kg−1 and higher applied to sub‐soil successfully activated the sub‐soil microflora. Application of the VARLEACH model to simulate carbofuran movement through the soil profile indicated that approximately 0.01 mg kg−1 of carbofuran may reach a depth of 70 cm 400 days after a standard field application. The results therefore imply that adaptation of the sub‐soil microflora (c 1 m depth) by normal field rate applications of carbofuran is unlikely to occur. In experiments to investigate this in soils exposed to carbofuran in the field, there was no apparent relationship between top‐soil exposure and degradation rates in the corresponding sub‐soils. The results further confirmed that some sub‐soil samples have an inherent capacity for rapid biodegradation of carbofuran. The high levels of variability observed between replicates in some of the sub‐soil samples were attributed to the uneven distribution of a low population of carbofuran‐degrading micro‐organisms in sub‐surface soil. There was no apparent relationship between soil microbial biomass and degradation rates within or between top‐soil and sub‐soil samples. © 2001 Society of Chemical Industry  相似文献   

3.
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   

4.
Tri-allate degraded faster in soil from a site (T1) that had received 1·7 kg ha?1 of tri-allate annually for 23 years than in soil from an adjacent site (TO) that had received no pesticide application. Soil from the untreated site, which had been removed to a glasshouse and treated three times per annum with tri-allate at 1·7 kg ha?1 for 7 years (T2), also showed faster degradation. Soil previously treated with tri-allate showed an increased degradation rate for carbofuran and EPTC but not for aldicarb. A further experiment, 2 years after the last treatment with tri-allate, showed that the enhanced degradation effect was still present. Degradation rates were always in the order T1 > T2 > T0 for tri-allate, EPTC and carbofuran. Half-life for degradation was reduced for tri-allate and carbofuran by approximately 40% in the previously treated soils and for EPTC by approximately 80% when compared with the previously untreated soil.  相似文献   

5.
Residues of iprodione and vinclozolin were measured following repeated application of the fungicides to a sandy loam soil in the laboratory. There was a progressive increase in rates of degradation with successive treatments. With iprodione, for example, the times for 50% loss of the first and second applications were about 23 and 5 days respectively. When treated for the third time, less than 10% of the applied dose remained in the soil after just 2 days. Similar results were obtained with vinclozolin in the same soil, and with both compounds in a second soil. In a third soil, which had relatively low pH, degradation of both compounds occurred only slowly and the rate of degradation of a second application was the same as that of the first. Degradation rates in this soil were increased by addition of 100 g kg?1 of a soil in which degradation occurred more readily, and they were markedly increased by addition of 100 g kg?1 of a soil in which enhanced degradation had been previously induced. Residues of both fungicides were also measured following repeated application in the field. When iprodione was applied to previously untreated plots, about 3% of the initial dose remained in the soil after 77 days. When applied to plots treated once before, less than 1% remained after 18 days, and when applied to plots treated twice previously less than 1% remained after 10 days. Similar results were obtained with vinclozolin. Enhanced degradation of subsequent soil treatments was also observed following a sequence of low-dosage sprays in the field.  相似文献   

6.
Prediction of the fate of pesticides in soil is of interest from an environmental (pollution) as well as an agricultural (efficacy, carryover) viewpoint. Two environmental parameters that control microbial degradation of pesticides in soil are moisture and temperature. This study was designed to quantify the impact of soil water content and temperature on microbial degradation rates of the insecticide carbofuran (2, 3-dihydro-2, 2-dimethylbenzofuran-7-yl methyl-carbamate). Carbofuran degradation was determined by monitoring the [ 14 C] carbondioxide production from soils amended with [carbonyl- 14 C]carbofuran. Soils were incubated at seven soil-water tensions over the range of 0–03 to 1–5 MPa, and at five temperatures (10°C to 30°C). The sigmoidal degradation kinetics observed from these incubations were modeled using a general saturation model. For the moisture experiments, maximum rate of hydrolysis and half-life (DT50) were accurately modeled by an exponential relationship. The response of carbofuran degradation to temperature was also well described by an exponential relationship, from which it was estimated that the Q10 associated with the maximum rate was 1.68, and the Q10 for DT50 was 1–89.  相似文献   

7.
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   

8.
丙硫克百威及其主要代谢物在棉田中的残留降解研究   总被引：2，自引：1，他引：2  
将20% 丙硫克百威乳油施于棉田, 采用气相色谱分析技术研究了丙硫克百威及其主要代谢产物在棉田中的残留降解情况。结果表明: 1) 丙硫克百威在棉田土壤和棉叶中可很快降解转化为克百威, 克百威在棉叶中的最大残留值出现在施药后当天, 在棉田土壤中出现在施药后3d, 说明丙硫克百威在棉叶中的降解速率快于在棉田土壤中; 2) 克百威可进一步转化为3-羟基克百威, 后者在棉叶和棉田土壤中的残留量表现为先升后降, 到第10 天才达最大值,明显滞后于克百威最大值出现的时间; 3) 丙硫克百威和克百威在棉叶和棉田土壤中的降解过程符合Ct= C0·e-kt方程, 它们在棉叶中的降解半衰期为3.6～4.4d, 在棉田土壤中则为10.4～11.9d; 4) 当丙硫克百威的用量按有效成份计为200～400g/hm2, 每季棉花施药3～4 次(每次间隔7d) , 最后一次施药距采收时间分别为20、30d时, 丙硫克百威(含克百威和3-羟基克百威) 在棉籽和棉田耕层土壤中的残留量均小于0. 5 mg/kg。  相似文献   

9.
The adsorption of carbofuran on soils from water‐methanol mixtures has been evaluated by batch shake testing. Two uncontaminated soils having different physicochemical properties were used in these experiments. The volume fraction of methanol in the liquid phase (fs) was varied from 0.25 to 1.0. Higher adsorption of carbofuran was observed in medium black (silt loam) soil than in alluvial (sandy loam) soil; calculated values of the Freundlich constant (Km) and distribution coefficient (Kd) showed that adsorption of carbofuran in both soils decreased with increase in fS values. The decreased carbofuran adsorption in methanol–water mixtures meant a greater potential of ground‐water contamination through leaching from potential sites. The data have been used to evaluate the co‐solvent theory for describing adsorption of carbofuran in methanol–water mixtures. The aqueous phase partition coefficient Kdw (mol g−1) normalized with respect to foc and the aqueous phase adsorption constant Kw for carbofuran were evaluated by extrapolating to fS = 0. © 2000 Society of Chemical Industry  相似文献   

10.
The movement of the organophosphate nematicide-insecticide ethoprophos (ethoprop; O-ethyl S,S-dipropyl phosphorodithioate) and the carbamate insecticide-nematicide carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yI methylcarbamate) was studied under steady-state flow in small-scale laboratory soil columns. Miscible displacement column experiments, mass balance calculations, and batch incubation studies furnished information on insecticide sorption and degradation processes that occur during transport through soil. Miscible displacement studies demonstrated that ethoprophos degradation could be described as first-order and that both insecticides exhibited non-equilibrium sorption. Both batch and miscible displacement results showed ethoprophos to be more strongly sorbed by soil than carbofuran. Measured equilibrium sorption coefficients were 1.29 cm3 g?1 for ethoprophos and 0.29 cm3 g?1 for carbofuran on a Riverhead soil (0.011 organic carbon fraction); 035 cm3 g?1 for carbofuran on Valois soil (0.016 organic carbon fraction); and 2.38 cm3 g?1 for ethoprophos on Rhinebeck soil (0.031 organic carbon fraction). Two solutions to the convection-dispersion equation, one that incorporated equilibrium sorption and another (bicontinuum model) that included a non-equilibrium sorption term, allowed quantitative evaluation of transport processes. The bicontinuum model used in conjunction with experimental batch and mass balance techniques provided estimates of insecticide sorption and degradation parameters.  相似文献   

11.
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   

12.
The persistence of carbofuran (2, 3-dihydro-2, 2-dimethylbenzofuran-7-yl methylcarbamate) and the β- and γ-isomers of HCH (hexachlorocyclohexane) applied to surface (oxidised) and sub-surface (reduced) layers of a flooded soil was studied using radiolabelled insecticides. In one experiment, these compounds were placed in the surface (2–5 mm) and sub-surface (10–15 cm) layers of 10-day flooded soil columns. HCH isomers were unstable under flooded soil conditions irrespective of their placement, but disappeared slightly faster when applied to the sub-surface layer, possibly due to the more reduced conditions prevailing. In contrast, sub-surface-applied carbofuran was more stable than surface-applied carbofuran. The decreased stability of surface-applied carbofuran may be due to a relatively higher pH in the surface layer and in the flood water which was in immediate contact with the surface layer. In another experiment, surface and sub-surface soil samples were collected from a rice field which had been flooded for 30 days. These soils were then again flooded under laboratory conditions prior to addition of carbofuran and β-HCH. Upon submergence, both surface and sub-surface soil samples attained almost equally reduced conditions. In flooded surface soil samples, more rapid degradation not only of carbofuran but also of β-HCH occurred, compared with similarly incubated sub-surface soil samples.  相似文献   

13.
The degradation in soil of the major constituents of a 1,3-dichloropropene-1,2-dich-loropropane nematicide has been studied under laboratory and outdoor conditions. In sealed glass containers, ( Z)- and ( E)-1,3-dichloropene- 2-14C were converted in soil into the corresponding 3-chloroallyl alcohols and these alcohols were in part strongly bound to the soil. The ( Z)- and ( E)-3-chloroacrylic acids were also found as minor products. More polar products were detected and these released the chloroacrylic acids in 20–30% yield upon hydrolysis. Although the 1,3-dichloropropenes were lost by volatilisation from soil stored in open glass jars outdoors, they also underwent degradation to the same products that were detected in sealed containers. There was evidence of only slight degradation of 1,2-dichloropropane- 2-14C (4 % or less of the applied radioactivity remained unextracted from a loam soil after 5 months). When soil treated with the 1,2-dichloropropane was stored outdoors in an open glass container, less than 1 % of the original radiolabel remained in the soil after 10 days under these conditions due to volatilisation of the applied material. In a separate experiment potatoes were grown in soil 6 months after treatment with a mixture of both ( Z)- and ( E)-1,3-dichloropropene- 2-14C and 1,2-dichloropropane- 2-14C. Although 5 % of the applied radiolabel remained in the soil at potato harvest the potato tubers contained only a very small residue (0.007 mg/kg).  相似文献   

14.
Abstract

An established banana field was treated by applying three compounds, fenamiphos, isazofos and carbofuran, to the soil around each mat. The tested compounds were found to reduce significantly soil and root nematode populations. The production cycle of the nematocide treatments was 24 days faster than that of the untreated control. Application of the above chemicals enhanced to the total production of banana. Carbofuran may be ranked top of these nematocides, followed by isazofos. Application of 2 g a.i. of carbofuran three times at intervals of 4 months, yielded 2.66 tonnes per acre more than that of the control.  相似文献   

15.
A study was conducted to relate the occurrence of accelerated pesticide biodegradation to the susceptibility of the pesticides to growth-linked degradation or cometabolism. The mineralization of 2,4-D was initially slow but then became rapid, and a second application was mineralized with no acclimation phase and more rapidly than the first. The numbers of 2,4-D-degrading micro-organisms increased markedly following its first application and then declined, but the population size increased after a second addition. Glyphosate was rapidly and extensively mineralized following the first and second applications to soil, and the abundance of organisms able to degrade it rose after the first addition and remained high before and following the second application. Propham (IPC) mineralization was detected only 15 days after its application but the degradation was rapid thereafter, and the second addition was rapidly and extensively mineralized with no acclimation phase. The population of propham-degrading micro-organisms was initially small, but increased markedy 10 days after the initial herbicide addition and was still large at the time of the second application. The rate of carbofuran biodegradation in the test soil was the same following the first and second applications, and the abundance of carbofuran-metabolizing microorganisms did not change appreciably as a result of soil treatment with the insecticide. Simazine mineralization was slow, although the rate was higher following the second addition; however, the number of simazine-degrading organisms did not increase appreciably. From 10 to 12% of the 14C from radiolabeled 2,4-D, propham, glyphosate or glucose was usually incorporated into the microbial biomass of soil but 0.82% or less of the 14C from simazine or ring- or carbonyl-labeled carbofuran was converted to biomass. It is suggested that pesticides that support microbial growth may be subject to accelerated biodegradation if the population remains large until the pesticide is applied again. Pesticides that do not support growth may not be subject to accelerated biodegradation.  相似文献   

16.
The rates of dissipation in soil and chloride-ion release, of the main components of dichloropropane-dichloropropene mixtures used as nematicides, were studied in sealed glass containers at different temperatures and moisture conditions. Half-lives of (Z)- and (E)-1,3-dichloropropenes at 20°C in soils were found to vary from 3 to 25 days; those of 1,2-dichloropropane and 2,3-dichloropropene were about four times and twice as long, respectively. The dissipation rates changed by a factor of about 2 per 10°C change in temperature. Judging from the release rates of waterextractable inorganic chloride in the soil (0-4% per week), the total degradation of all components applied at normal field rates was extremely slow. This indicated the formation of residues containing covalently bound chlorine. Only in ‘enrichment cultures’ was complete degradation indicated.  相似文献   

17.
Anaerobic degradation of the herbicide diuron, 3-(3,4-dichlorophenyl-1,1)dimethylurea, was studied. Enrichment cultures were established with seven different media in the presence of diuron (40 mg/liter). Media included combinations of sediment extract, mineral salts, and various organic amendments. Cultures were inoculated with aliquots of sediment collected from a pond previously treated with diuron and were maintained under an atmosphere of 95% N2 and 5% CO2. All enrichment cultures completely degraded diuron in 17–25 days. In all cultures showing diuron degradation, the product identified as 3-(3-chlorophenyl)-1,1-dimethylurea appeared in approximately stoichiometric amounts. Reinjection of diuron into each culture after 26 days resulted in rapid degradation of the parent herbicide with the appearance of proportionately more 3-(3-chlorophenyl)-1,1-dimethylurea. No other product was detected after 80 days in culture and the metachloro derivative was not degraded further during this time.  相似文献   

18.
Enhanced degradation of the fungicide vinclozolin was stimulated by multiple successive applications to a soil without any history of previous pesticide input. A vinclozolin-degrading bacterium isolated from this soil was identified as a strain of Pseudomonas putida. This organism metabolised vinclozolin as a source of carbon, but it would neither grow with nor transform any other closely related dicarboximide fungicides nor the degradation product, 3,5-DCA. The degradation of vinclozolin by cultures of P. putida St-1 was investigated under various culture conditions; biodegradation was optimal at 23°C, pH 6·5 and inoculum densities of 107 cells ml−1 but cultures would grow from as little as 100 cells ml−1. Amendments of the vinclozolin-degrading isolate to soil previously untreated with the fungicide caused rapid degradation of applied vinclozolin, whereas amendments of boiled cells, or viable cells grown in the absence of vinclozolin, produced no discernible effect on the rate of vinclozolin degradation.  相似文献   

19.
Residues of carbofuran ( 1 ) and 2,3-dihydro-3-hydroxy-2,2-dimethylbenzofuran-7-yl methylcarbamate ( 2 ) in and on mushrooms, cultivated on casing soils containing added carbofuran granular insecticide, were determined. The quantitative estimations in cleaned mushroom extracts were done on thin-layer plates using a cholinesterase inhibition method. Samples were analysed, which had been harvested at different times from cultures, to which different amounts of carbofuran were added. Residues in washed and unwashed mushroom samples were compared. Residues did not exceed 0.5 mg (carbofuran) kg?1 and 0.25 mg (compound 2 ) kg?1 for fresh unwashed mushrooms grown on casing soil treated with carbofuran granules 1 g (a.i.) m?2.  相似文献   

20.
Abstract

Studies have been carried out on the efficacy of carbofuran (Furadan 5G) in reducing the incidence of the major insect pests of maize in Nigeria. A single dose of 1.5 kg a.i./ha applied in the planting hole was found to reduce the incidence of spittle bug (Locris Maculata F.) and stem borers (Busseola fusca (Fuller) and Sesamia calamistis (Hmps.)) when compared with split applications of the same dose applied at planting and 40 days after planting. The number of damaged plants was reduced from 40% in the control to 11.7% in the treated plots. Yields of fresh maize cobs were also increased significantly in treated plots. A significant positive correlation was established between the mean number of stem borer larvae and mean percentage damage, and significant negative correlations between the mean yield and mean percentage damage and between the mean yield and mean number of stem borer larvae.  相似文献   

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