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1.
The rate of loss of aldicarb sulphone was studied in incubation experiments on soils from four plough layers and two deeper layers. In all instances the loss could be described by first-order kinetics in the first period of two to three times half-life. However, in a clay loam soil and a greenhouse soil a faster degradation rate was observed after the first 56 and 112 days of incubation respectively. The half-lives of sulphone in plough layer soils at 15°C ranged from 18 days in a clay loam to 154 days in a peaty sand. Conversion in deeper layers was considerably slower than in the corresponding top layers of the soil profile. In a silty layer at 70 to 90 cm depth the half-life at 15°C was 46 days, whereas in a sand layer at 90–110 cm no clear loss was found during the 294 days of incubation.  相似文献   

2.
Aldicarb was incubated in seven soils at 15°C and its loss was well described by first-order kinetics. Rate constants varied between 0.078 day?1 in a peaty sand to 0.35 day?1 in a clay loam. The concentration-time relationships for aldicarb, its sulphoxide and its sulphone were approximated by a computation model which was used to analyse the importance of the various consecutive and simultaneous reactions. It was computed that 91 to 100% of the aldicarb would be oxidised to its sulphoxide.  相似文献   

3.
The loss of aldicarb sulphoxide was studied in incubation experiments with soil from four plough layers and two deeper layers. The loss during the 111 days of the experiment could be described by first-order kinetics. The half-lives at 15°C ranged from 20 days in a clay loam to 46 days in a peaty sand. The loss of sulphoxide in deeper layers was considerably slower than in the corresponding top layers of a soil profile. In soil from a silty layer at 70–90 cm depth the half-life was about 53 days. In soil from a sand layer at 90–110 cm depth a loss of only about 15% was measured after 111 days of incubation. First-order rate constants for sulphoxide conversion in a clay loam at 6, 15 and 25°C were found to be 0.009, 0.033, and 0.05 day?1 respectively; in a greenhouse soil these rate constants were 0.0052, 0.019 and 0.04 day?1 respectively. The fractions of aldicarb sulphoxide that were oxidised to sulphone at 15°C in soil from plough layers were computed to range from 0.52 to 0.76.  相似文献   

4.
Diphenamid (N,N-dimethyl-2,2-diphenylacetamide) in an aqueous solution in plastic bottles was partially detoxified when exposed to sunlight for 1 week. Varying spray volumes from 300 to 1,800 I/ha did not have an appreciable effect on the phytotoxicity of diphenamid, sprayed on a coarse or fine soil surface. The marked dissipation of diphenamid which occurred from the soil surface was attributed to photodecomposition and volatilization. Diphenamid phytotoxicity was greater when the first irrigation after spraying was applied in four increments of 100 m3/ha or two increments of 200 m1/ha than when it was applied in a single 400 m1/h watering; the latter caused more leaching of the herbicide. The diphenamid fraction leached out of a 4-cm soil layer increased as the organic matter content in the soil decreased, from 25% in peat (22.3% o.m.) to >88% in sandy loam (0.9% o.m.). The herbicidal activity remaining after leaching was lower in sandy loam and in peat than in soil with medium organic matter content (11.6% and 6.2%). Diphenamid degradation rate in soil at 50% field capacity moisture level, increased when temperature was increased from 10° to 30°C. After 4 months of incubation at 10°C, 40-50% of the original herbicide was detoxified, while at 20° and 30°C the loss exceeded 90%. Within the range of day-temperatures of 10° to 40°C in soil and of 10° to 35°C in nutrient solution, diphenamid phytotoxicity to tomato seedlings increased with temperature.  相似文献   

5.
The leaching of aldicarb and thiofanox in soils (sandy loam, silt loam and sandy clay loam), and their uptake by sugarbeet plants were studied. Three irrigation levels were maintained: half, normal and double dose. The residues were determined as the sum of the insecticidal metabolites (parent compound + sulphoxide+ sulphone) for both pesticides. Leaching was greatly influenced by the amount of water added and the soil type. Under normal conditions, leaching seemed to proceed very slowly, keeping the chemicals available for uptake by the root systems for a long time. The concentration of insecticide in the leaves was highest in beets grown on sandy loam and lowest in those grown on sandy clay loam. The quantity of irrigation did not influence the residue concentration in the leaves greatly, although its influence was obvious on the total residue present (μg per plant). Increasing the water dose always resulted in a higher total residue, and a greater plant weight. The breakdown in the soils was directly related to the water dose. The experiments show that thiofanox was more stable than aldicarb and was taken up by sugarbeet to a greater extent.  相似文献   

6.
Triazole fungicides are now widely used commercially and several are known to be persistent in soil. The degradation rates of five such fungicides were measured in laboratory tests with two soils over 720 days, with analysis of soil extracts by high-pressure liquid chromatography. Behaviour in a sandy loam and a clay loam were similar, and incubation of the compounds either singly or in admixture did not influence loss rates except for those of flutriafol which were lower in the latter. Triadimefon was quite rapidly reduced to triadimenol, though traces of the former were always found, indicating a possible redox equilibrium. Flutriafol, epoxiconazole and triadimenol (derived from triadimefon) were very persistent, breakdown following first-order kinetics with half-lives greater than two years at 10 °C and 80% field capacity. Propiconazole was moderately persistent, with a half-life of about 200 days under these conditions. Degradation rates increased about 3-fold as the temperature was increased from 5 to 18 °C, though decreasing soil moisture to 60% field capacity only slightly slowed degradation. The rate constants obtained are used in a companion paper describing field studies on these two soils to compare laboratory-measured degradation rates with losses in the field following commercial sprays. © 1999 Society of Chemical Industry  相似文献   

7.
The persistence of [14C]MCPA at a rate equivalent to 1 kg ha?1 was studied under laboratory conditions in a clay loam, heavy clay and sandy loam at 85% of field capacity moisture and 20±1°C both alone and in the presence of tri-allate, trifluralin, tri-allate and trifluralin, malathion, Vitaflow DB, malathion and Vitaflow DB, bromoxynil, bromoxynil and asulam, bromoxynil and difenzoquat, dicamba, dicamba and mecoprop, linuron, MCPB, metribuzin, propanil, TCA, benzoylprop-ethyl, diclofop-methyl, and flamprop-methyl. Except in the soils treated with asulam, the half-lives of [14C]MCPA in all three soil types were similar, being approximately 13±1 days, thus indicating that none of the other chemicals studied adversely affected the soil degradation of MCPA. In the asulam treated soils, the half-lives of the MCPA were about 3 days longer than in non-asulam treated soils; the effect was most marked in the clay loam.  相似文献   

8.
Aldicarb and its oxidation product aldoxycarb (aldicarb sulphone) were applied separately to columns of fallow, sandy loam soils under field conditions. The breakdown and movement of these compounds were monitored, as was the behaviour of aldicarb sulphoxide and aldoxycarb formed by oxidation of the applied aldicarb. The behaviour of these compounds was simulated by a computer model using laboratory data for adsorption and rates of degradation in soil. The model simulated the observed behaviour reasonably well, although redistribution of chemicals was often more rapid than predicted. Production of aldoxycarb from the sulphoxide was less in the field than was expected from the laboratory incubations. Accumulation of chemicals near the soil surface in dry periods was overestimated, indicating that the processes occurring under these conditions are not well described by the model. About 4 months after application, only aldoxycarb, in small amounts, remained in the soils.  相似文献   

9.
The persistence of [14C]sethoxydim (2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexene-1-one) at the 2 μg g?1 level was studied under laboratory conditions in three soils at 20°C and 85% of their field capacity moistures. Following extraction of the soils with methanol, the herbicide remaining was determined using radiochemical techniques. Loss of radioactivity was more rapid on moist clay loam and sandy loam, where the half-lives were 12 days, than on heavy clay in which the half-life was 26 days. Loss of radioactivity from air-dried soils (15% of field capacity) was negligible with over 94% of the applied activity being recovered after 28 days. The persistence of sethoxydim at a rate of 1 kg ha?1 was investigated under field conditions using small plots at three prairie locations for 3 successive years. Using an oat-root bioassay procedure, no residues were detected in the 0–10 cm depths of any soils, any year, in September following May treatments.  相似文献   

10.
Herbicide degradation in soils is highly temperature‐dependent. Laboratory incubations and field experiments are usually conducted with soils from the temperate climatic zone. Few data are available for cold conditions and the validation of approaches to correct the degradation rate at low temperatures representative of Nordic environments is scarce. Laboratory incubation studies were conducted at 5, 15 and 28°C to compare the influence of temperature on the dissipation of metribuzin in silt/sandy loam soils in southern and northern Norway and in a sandy loam soil under temperate climate in France. Using 14C‐labelled metribuzin, sorption and biodegradation were studied over an incubation period of 49 days. Metribuzin mineralisation and total soil organic carbon mineralisation rates showed a positive temperature response in all soils. Metribuzin mineralisation was low, but metabolites were formed and their abundance depended on temperature conditions. The rate of dissipation of 14C‐metribuzin from soil pore water was strongly dependent on temperature. In Nordic soils with low organic content, metribuzin sorption is rather weak and biodegradation is the most important process controlling its mobility and persistence.  相似文献   

11.
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   

12.
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   

13.
Fluroxypyr-MHE (methylheptyl ester) was added to four soils and incubated at 26 ± 1°C and approximately 0.1 MPa moisture. After initial rapid hydrolysis of the ester to fluroxypyr, fluroxypyr degraded with half-lives of 12, 12, 23, and 7 days in Barnes loam, Catlin silt loam, Hanford sandy loam, and Mhoon clay soils, respectively. Two metabolites (4-amino-3,5-dichloro-6-fluoro-pyridin-2-ol and 4-amino-3, 5-dichloro - 6 - fluoro - 2 -methoxypyridine) were identified, with the pyridinol at its maximum concentration after 2 to 4 weeks of incubation, and the methoxypyridine after 8 weeks. Degradation rates of fluroxypyr and its pyridinol were not significantly altered by diurnally varying soil temperature (21°C to 32°C) or moisture, nor by the presence of growing grass. Methoxypyridine dissipation was more rapid under greenhouse conditions, suggesting that laboratory studies underestimated the dissipation rate of this metabolite.  相似文献   

14.
A glass-lined trough was divided into six compartments by vertical transverse partitions and filled with soil to a height of 5 cm above the top of each partition. The base of the box and the surface of the soil sloped forwards one end with a gradient of 1 in 3·7. Dieldrin was applied (22 kg active ingredient/ha) to the soil surface in the uppermost compartment and the movement of dieldrin into leachate and down the slope was followed for 17 weeks. During this time 19·5 cm of rain fell. Less than 0·02% of the dieldrin appeared in the leachate and 99% of this was collected during the first 9 weeks, mainly from the uppermost compartment. Very little dieldrin moved down the slope and it was not detected in the leachate from compartments other than the treated one during 9–17 weeks after treatment. In other experiments, 3 cylinders were filled respectively with sandy loam, heavy clay loam and peat which were transferred from the field as intact cores. Three other cylinders were filled with soils of the same types but broken up. Approximately 2% of the dieldrin leached through one column but usually it was much less than 0·1%. The largest amounts of dieldrin were leached down columns of heavy clay loam, intermediate amounts down columns of peat, and least through sandy loam. Ten times as much dieldrin leached down the columns of intact soil as through those with broken soil. The results indicate that the movement of dieldrin from treated soil into water systems by leaching is limited and is unlikely to be a major pathway for the contamination of water.  相似文献   

15.
The breakdown of aldicarb and its oxidation products (the sulphoxide and the sulphone, aldoxycarb), under field conditions in 1976, were studied on three different types of soil (a sandy loam, a silt loam and a sandy clay loam that were normally cropped with sugarbeet). Residues were determined in leaves, stems, roots and soil, and related to aphid counts. Higher doses were needed on heavy soils in order to obtain a sufficient concentration in the leaves and thus provide an efficient treatment for aphid control. Weather conditions, especially rainfall, also affected the residue content. At harvest, the sugar beet tops used for fodder can contain residues which vary widely, depending on dosage, soil type and climatic conditions.  相似文献   

16.
The behaviour of the morpholine fungicide fenpropimorph applied to soil was investigated in a laboratory chamber. The volatility and metabolism of a 14C-labelled fenpropimorph formulation (Corbel®) was studied after application to three soils (sandy loam, loamy clay and loamy sand), simulating a four-day weather scenario in the volatilization chamber. Additional experiments were conducted under standard climatic conditions over a period of 24 h using sandy soils with different pH values. The results of the first experiments showed that most of the radioactivity applied remained in the soils as unchanged fenpropimorph four days after application. In the experiments with the sandy loam and loamy clay, less than 5% of the applied radioactivity was removed by volatilization whereas 11·4% volatilized from the surface of the loamy sand. The comparatively higher volatilization of the fungicide from the loamy sand was confirmed by the later experiments indicating that higher soil pH favoured volatilization of [14C]fenpropimorph from sandy soils. Thus 5·6% (pH 5·0), 18·9% (pH 5·8) and 28·3% (pH 6·6) of the radioactivity applied volatilized within one day after application. The overall recoveries were between 93·8% and 111·3% in these experiments. © 1998 SCI  相似文献   

17.
Mixtures of wet vegetable wastes (Brassica, carrot or onion) and dry onion waste were composted at 50 °C for 7 days. The incorporation of the raw or composted vegetable waste mixtures into sandy loam, silt and peat soils reduced the viability of sclerotia of S. cepivorum in glasshouse pot bioassays. The reduction in viability was dependent on waste type, rate of incorporation, duration of exposure and soil type. Onion waste was the most effective waste type in reducing sclerotia viability in all three soils. The Brassica and carrot wastes were as effective as the onion waste in silt soil but less effective in sandy loam and peat soil. A 50% w/w incorporation rate of the wastes gave the largest reduction in viability, with an increase in reduction over time. Composted onion waste reduced sclerotia viability under glasshouse and field conditions although the effect was smaller in the field. Composted onion waste incorporated into soil at 50% w/w reduced the incidence of Allium white rot on onion seedlings in glasshouse pot tests. Incidence and control of the disease differed with soil type. The most consistent control was achieved in peat soil whereas no control was observed in silt soil. Incorporation of the waste 2 months prior to sowing or transplanting reduced seedling emergence in sandy loam soil and growth in all three soil types. The potential for field application of composted vegetable wastes as a sustainable method for control of Allium white rot and waste disposal is discussed.  相似文献   

18.
The residues of aldicarb and of its main metabolites (aldoxycarb, 2-mesyl-2-methylpropionitrile, and 2-mesyl-2-methylpropan-1-ol) were measured, by a gas-liquid chromatographic procedure, in the leaves of ripe sugar beet plants from cultures made by several farmers. The sugar beet plants had been grown in normal fields and treated at sowing with aldicarb at the usual rate of 1 kg ha?1 in the form of ‘Temik’, the commercial formulation of aldicarb which contains 10% by weight of aldicarb. The samples of sugar beet plants were taken from three fields of different soil types. The residue concentrations, ranged in order of soil type, were: sandy loam > silt loam > clay.  相似文献   

19.
The persistence of bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), [14C]dicamba (3,6-dichloro-2-methoxybenzoic-7-14C acid) and propanil [N-(3,4-dichlorophenyl)propionamide] at rates equivalent to 1 kg ha?1, were studied under laboratory conditions in a clay loam, a heavy clay and a sandy loam at 85% of field capacity and at 20±1°C, both singly and in the presence of herbicides normally applied with these chemicals as tank-mix or split-mix components. The degradation of bromoxynil was rapid with over 90% breakdown occurring within a week in the heavy clay and sandy-loam soils, while in the clay-loam approximately 80% of the bromoxynil had broken down after 7 days. In all three soils degradation was unaffected by the presence of asulam, diclofop-methyl, flamprop-methyl, MCPA, metribuzin or propanil. Propanil underwent rapid degradation in all soil treatments, with over 95% of the applied propanil being dissipated within 7 days. There were no noticeable effects on propanil degradation resulting from applications of asulam, barban, bromoxynil, dicamba, MCPA, MCPB, metribuzin or 2,4-D. The breakdown of [14C]dicamba in a particular soil was unaffected by being applied alone or in the presence of diclofop-methyl, flampropmethyl, MCPA, metribuzin, propanil or 2,4-D. The times for 50% of the applied dicamba to be degraded were approximately 16 days in both the clay loam and sandy loam, and about 50 days in the heavy clay.  相似文献   

20.
Although glyphosate (N‐(phosphonomethyl)glycine) is one of the most frequently used herbicides, few controlled transport experiments in undisturbed soils have been carried out to date. The aim of this work was to study the influence of the sorption coefficient, soil‐glyphosate contact time, pH, phosphorus concentration and colloid‐facilitated transport on the transport of [14C]glyphosate in undisturbed top‐soil columns (20 cm height × 20 cm diameter) of a sandy loam soil and a sandy soil. Batch sorption experiments showed strong Freundlich‐type sorption to both soil materials. The mobility of glyphosate in the soil columns was strongly governed by macropore flow. Consequently, amounts of glyphosate leached from the macroporous sandy loam soil were 50–150 times larger than from the sandy soil. Leaching rates from the sandy soil were not affected by soil‐glyphosate contact time, whereas a contact time of 96 h strongly reduced the leaching rates from the sandy loam soil. The role of pH and phosphorus concentration in solution was relatively unimportant with respect to total glyphosate leaching. The contribution of colloid‐facilitated transport was <1 to 27% for the sandy loam and <1 to 52% for the sandy soil, depending on soil treatment. The risk for glyphosate leaching from the top‐soils seems to be limited to conditions where pronounced macropore flow occurs shortly after application. © 2000 Society of Chemical Industry  相似文献   

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