Pesticide residues in foodstuffs in England and Wales. Part II: Inorganic bromide ion in cucumber,tomato and self-blanching celery grown in soil fumigated with bromomethane,and the ‘natural’ bromide ion content in a range of fresh fruit and vegetables

Surveys of inorganic bromide ion residues in tomatoes, cucumbers and selfblanching celery, commercially produced in England following soil sterilisation with bromomethane, have been carried out since 1979. The mean bromide ion level in 29 late-season cucumber samples was approximately 28 mg kg⁻¹ and ranged up to 109 mg kg⁻¹. Analysis of 242 tomato samples gave estimated mean bromide ion levels per plant ranging from 6 to 187 mg kg⁻¹ in fruit picked throughout the season from seven holdings, on six of which bromomethane had been used fairly recently prior to planting. A statistically significant fall in bromide levels over the growing season was shown on four of the sites. In 38 samples of self-blanching celery, the mean bromide ion level was 104 mg kg⁻¹ even though the mean interval between fumigation and planting was in excess of 1 year. Retail surveillance indicated that a large number of crops are likely to have bromide ion levels below 10mg kg⁻¹.     

Build-up and subsequent decline of residues of quintozene and hexachlorobenzene in lettuce in sequential crops

The build-up and decline of quintozene and hexachlorobenzene residues in protected lettuce, resulting from one to five treatments of the soil (each of 35 g m-2) with a quintozene formulation, have been studied. Residue levels were monitored in each experimental crop during growth until harvest. Residues in the soil at harvest were also determined. Quintozene residues in the harvested lettuce were in the range < 0.02–0.80 mg kg^?1 and those of hexachlorobenzene were in the range < 0.02–0.05 mg kg^?1 (expressed on a fresh weight basis). Residue levels in the soil were 5.4–231 mg kg^?1 for quintozene, and 0.20–5.4 mg kg^?1 for hexachlorobenzene (expressed on a dry weight basis). Under the experimental conditions of the trial there was no significant build-up of quintozene or hexachlorobenzene in harvested lettuce, even after five treatments to the same site.     

Residues in apples and sweet cherries after methyl bromide fumigation

Methyl bromide fumigations are used to treat apples, Malus domestica Borkh, and sweet cherries, Prunus avium (L), before export to Japan. In order to expand existing markets, additional cultivars are being prepared for export to Japan. As part of the approval process, residue analyses must be conducted and residues must be at acceptable levels. Five apple cultivars (‘Braeburn,’ ‘Fuji,’ ‘Gala,’ ‘Jonagold,’ and ‘Granny Smith’) were fumigated at 40 g m⁻³ for 2 h at 10 °C, and six sweet cherry cultivars (‘Brooks,’ ‘Garnet,’ ‘Lapin,’ ‘Rainier,’ ‘Sweetheart,’ and ‘Tulare’) were fumigated for 2 h with 64 g m⁻³ at 6 °C, 48 g m⁻³ at 12 °C, 40 g m⁻³ at 17 °C, and 32 g m⁻³ at 22 °C. Three replicates of fruit from each fumigation were analyzed for methyl bromide and bromide ion residues periodically with time. Methyl bromide residues for both apples and cherries were the highest immediately after fumigation, but rapidly declined so that only ‘Braeburn’ had residues >8 µg kg⁻¹ after 13 days and, except for ‘Lapin,’ all cherries were <1 µg kg⁻¹ after seven days. Average bromide ion residues were between 3.3 and 4.9 mg kg⁻¹ among apple cultivars, and between 3.7 and 8.0 µg kg⁻¹ among cherry cultivars. Published in 2000 for SCI by John Wiley & Sons, Ltd     

Permethrin and deltamethrin residues on lettuce

Permethrin and deltamethrin, two synthetic pyrethroid insecticides, are registered in several countries for use on lettuce. Both chemicals were applied on autumn and spring grown lettuce in the glasshouse. When applied at the normal prescribed dose rates of 25 and 12.5 g a.i. ha^?1, < 1 mg kg^?1 of either compound was found in the lettuce at harvest, even when applied only a few days before harvest. The total amount of active ingredient applied was too low to reach the 1 mg kg^?1 level when evenly applied on marketable lettuce heads weighing about 200 g each. Applying a higher dose than 25 g permethrin a.i. ha^?1 or 12.5 g deltamethrin a.i. ha^?1, or applying two applications in the 2 weeks prior to harvest, may well result in residue levels higher than the maximum residue limit of 1 mg kg^?1 for permethrin and certainly higher than the maximum residue limit of 0.2 mg kg^?1 for deltamethrin, which is more persistent.     

Uptake of phorate by lettuce

Following experimental and commercial applications to soil of a granular formulalation of phorate (O,O-diethyl S-ethylthiomethyl phosphorodithioate), residues in the soil and in lettuce were determined by gas-liquid chromatography. When applied by the bow-wave method as a continuous logarithmically-changing dose ranging from approximately 0.9 to 16.0 kg a.i. ha^?1, the proportional rate of oxidation in soil of phorate sulphoxide to phorate sulphone was inversely related to dose. Ten weeks after application, total phorate residues in the soil had declined by about 35% at all dose levels. Residues in mature lettuce, from the 1-5 kg ha^?1 dose-range, comprised the parent and oxygen analogue sulphoxides and sulphones; the relative proportions of the individual metabolites were independent of dose. Over this dose-range, total residue concentrations in the crop became proportionally slightly greater with increasing dose. When single doses of 1.1, 2.0 or 2.2 kg a.i. ha^?1 were applied at drilling, the total residue concentrations in the lettuce declined from 5 mg kg^?1 in seedlings from some treatments to <0.05 mg kg^?1 at harvest. In plants raised in peat blocks containing 10 or 20 mg a.i. per block, however, residues in seedlings totalled 45-47 mg kg^?1 and declined to only 0.7 mg kg^?1 at harvest. It was concluded that bowwave applications of phorate when field-sowing lettuce were unlikely to lead to unacceptable residues in the harvested crop, but that residues in lettuce raised in phorate-treated peat blocks may be unacceptably high.     

The effect of initial concentration of carbofuran on the development and stability of its enhanced biodegradation in top‐soil and sub‐soil

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     

Organophosphorus and synergised synthetic pyrethroid insecticides as grain protectants for stored sorghum

A field experiment was carried out on bulk sorghum stored for 26 weeks in concrete silos in South Queensland. No natural infestation occurred. Laboratory bioassays of treated grain, in which malathion-resistant strains of insects were added to grain samples, indicated that all the treatments were generally effective. Deltamethrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), fenitrothion (12mg kg⁻¹)+fenvalerate (1 mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), and fenitrothion (12mg kg⁻¹)+phenothrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) controlled typical malathion-resistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst) and Ephestia cautella (Walker). Pirimiphos-methyl (6mg kg⁻¹)+permethrin (1mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) allowed some survival of adults and progeny production by S. oryzae after 12 weeks, and by one strain of R. dominica throughout. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern on other cereal grains. Residues at the conclusion of the experiment were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

Effect of Biochar on Immobilization of Cadmium and Soil Chemical Properties

A pot experiment was conducted at Institute of Biotechnology and Genetic Engineering (IBGE), University of Agriculture Peshawar, Pakistan. To conduct the experiment, eight kilograms of air-dried soil were taken in each pot and the amendment biochar was added and mixed properly at different levels like 0%, 1%, 2% and 4% (w/w), respectively. All pots were spiked with Cd solution at the concentration of 10?mg kg^?1. The treatments were arranged in completely randomized design (CRD). Fourteen days old nursery plants of rice Oryza sativa L. were transplanted into pots. Five rice plants were grown in each pot. After transplantation of rice plant, the nitrogenous and phosphatic fertilizers (Urea and DAP) were incorporated at the standard rate. Standing water condition was kept for rice grown in pots. Rice plants were harvested after 70 days germination. Soil samples were collected from each pot after plant harvesting. After soil analysis, the given data elaborated that the concentration of Cd in soil was stabilized by the amendment from 8.7?mg kg^?1 (0%) to 4.2?mg kg^?1 (4%). Among the other soil parameters the minimum soil pH (7.31), EC (0.151?dSm^?1), soil organic matter (0.63%), N (0.13%), P (4.72?mg kg^?1) and K (55.6?mg kg^?1) were noted at 0% biochar application, while maximum pH (8.23), EC (0.231?dSm^?1), soil organic matter (1.67%), N (0.25%), P (8.96?mg kg^?1) and K (93?mg kg^?1) were found in the pot treated with 4% biochar. Hence, it was concluded that Cd was significantly immobilized with 4% biochar application.

     

Residues of synthetic pyrethroid insecticides on horticultural crops

Foliar applications of synthetic pyrethroids were made to several crops to determine residue levels at various intervals after application. On onions, residues of cypermethrin, permethrin and fenvalerate were negligible > 0.1 mg kg^?1, 7 days after application. On lettuce, residues of fenvalerate and permethrin were 0.8 mg kg^?1. On celery, residues of fenvalerate did not decline and ranged from 0.12 to 0.25 mg kg^?1 during the 14-day period. On green bush-beans, residues of permethrin and cypermethrin did not decline during the 14-day period and ranged from 0.1 to 0.6 mg kg^?1. By day 7, residues of cyfluthrin, cypermethrin, deltamethrin, fenvalerate and permethrin on strawberries were less than the acceptable maximum tolerance of 0.1 mg kg^?1 with the exception of cypermethrin, applied at the rate of 0.14 kg a.i. ha^?1 which gave a residue of 0.14 mg kg^?1.     

Fate of fluroxypyr in soil

Fluroxypyr-MHE (methylheptyl ester) was applied to small field plots containing Londo sandy loam soil. After 30 days, fluroxypyr had degraded to about 60% of the initial concentration, but was still the main component, while after 120 and 366 days the methoxypyridine metabolite was the main component in the soil. At 30, 120, and 366 days, lettuce, turnips, green beans, soybeans, and wheat were planted and grown with no observed injury. Residues of ¹⁴C in the edible crop fractions were indistinguishable from ¹⁴C in control plants exposed to ¹⁴CO₂, while residues in plant greens and chaff were low (0.1–0.2 mg kg^?1), with little evidence of fluroxypyr and no evidence of metabolite uptake. These results indicate that the methoxypyridine metabolite, if present in the soil, does not harm and is not taken up into the plants.     

The effect of the annual use of pesticides on soil microorganisms,pesticide residues in the soil and barley yields

A study has been made of the influence of pesticides used annually on soil microorganisms and crop yields. The persistence of these pesticides in the soil was also investigated. The herbicides MCPA, glyphosate, maleic hydrazide and tri-allate, and the insecticide parathion, were applied on experimental plots on which barley was grown during the years 1973-1981. The fungicide 2-methoxyethylmercury chloride was used every year for dressing the seeds grown in pesticide-treated plots. The pesticide treatments did not affect significantly the numbers of several groups of soil microorganisms. A slight increase was, however, observed in the nitrification activity in the soil. The barley yields were on average higher on pesticide-treated plots than on controls because of successful weed control. Pesticide residues in the soil were generally very low; for example, for parathion they were below 0.02 mg kg^?1 within 11 days, and for MCPA 0.06 mg kg^?1 within 7 days. However, the glyphosate residue was 1.6 mg kg^?1 in the autumn 2 days after the treatment, and the residue settled to a level of 0.2 mg kg^?1 during the following summer. No clear dependence was observed between the residue level and the time between treatment and sampling.     

In-vitro and in-vivo nematicidal activities of the cyclic dodecapeptide omphalotin A

Omphalotin A, a cyclic dodecapeptide produced by submerged cultures of the basidiomycete Omphalotus olearius, exhibited in-vitro and in-vivo nematicidal activity. Meloidogyne incognita was the most sensitive nematode. At 2.0 mg litre⁻¹, 50% of the nematodes were dead after one hour. Heterodera schachtii, Radopholus similis and Pratylenchus penetrans were affected at higher concentrations. Incorporated into agar, the compound prevented infection of cucumber seedlings by M. incognita at concentrations of 1 mg litre⁻¹ and higher. In glasshouse tests, complete protection of cucumbers and lettuce was achieved between 2.5 and 10 mg litre⁻¹. No insecticidal activity was observed when Plutella xylostella, Phaedon cochleariae or Spodoptera frugiperda were fed material containing 4 g kg⁻¹ of omphalotin A. © 1999 Society of Chemical Industry     

Morphological and physiological responses of the invasive weed Isatis tinctoria to contrasting light, soil-nitrogen and water

We evaluated the morphological and physiological responses to contrasting above- and below-ground resources for the invasive weed, Isatis tinctoria L. (dyer's woad). Plants were grown under low and high levels of light [shade (50% of ambient) and full sun], soil water (50 and 100 mL day⁻¹), and soil nitrogen (N) (0 and 20 mg N kg⁻¹ soil) in 8 L pots in 63 day glasshouse experiments conducted during winter and spring. Soil-N enrichment did not increase any of the growth variables (shoot and root dry mass, shoot:root ratio, leaf area, and specific leaf area) or physiological variables (stomatal conductance and ¹³C discrimination) in either experiment. The absence of plasticity in response to changes in soil-N supply suggests that I. tinctoria may survive and persist in nutrient-poor conditions by having low-N requirements, low-N productivity, or both. In contrast, plants compensated for shaded conditions by altering leaf area, specific leaf area, and shoot:root ratio to improve light capture. We discuss the potential mechanisms whereby response to these variable resources may be associated with a series of adaptations that favour the ability to tolerate and colonize harsh, nutrient-poor conditions, as well as invade shaded and undisturbed sites.     

城市污泥农用对油麦菜生理特性及品质的影响研究

通过盆栽试验研究了城市污泥农用对油麦菜生理特性和品质的影响。结果表明:(1)不同污泥用量对油麦菜吸收Zn、Cu、Pb、Cd、As、Hg、Ni的影响不显著。(2)第一期试验中,随污泥施用量的增加,所研究的油麦菜各指标呈现出先升高后降低的趋势:当污泥施用量在6 g·kg^-1时,发芽率达到最大,为93％;油麦菜根系总吸收面积和活跃吸收面积在污泥施用量9 g·kg^-1时达最大,分别为1.93 cm²·株^-1和0.88 cm²·株^-2;叶绿素a+b、可溶性糖含量最大值出现在污泥施用量为6 g·kg^-1的处理中,分别为1.39 mg·g^-1,7.90 mg·g^-1;可溶性蛋白含量最大值出现在污泥施用量为9 g·kg^-1的处理中,为25.38 mg·g^-1。(3)第二期残效试验中不同污泥处理的各项指标变化规律与第一期试验相似,但总体上不同处理各指标的测定值大干第一期试验,出现最大值的污泥处理量滞后。(4)通过对不同指标的综合分析,可以得出污泥有利于油麦菜生长和提高品质的最佳施用范围为6～9 g·kg^-1。     

Residues of carbofuran and 2,3-dihydro-3-hydroxy- 2,2-dimethylbenzofuran-7-yl methylcarbamate in the mushroom,agaricus bisporus,cultivated in casing soils treated with the insecticide

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.     

Efficacy of Surface Dust Treatments of Pirimiphos-Methyl and Etrimfos when Applied to Commercially Stored Wheat and Barley

Commercially stored wheat and barley were surface treated with dust formulations of pirimiphos-methyl and etrimfos at the manufacturer's recommended application rate. Samples were taken at four-weekly intervals for 32 and 16 weeks for wheat and barley respectively. Pesticide efficacy was determined using insect bioassays and chemical analysis of residues. There was no evidence to suggest a decline in residue levels of either pesticide over the experimental period. However, considerable variation was observed in the residue levels recorded at different sample points and also between residue levels recorded for the same point over the trial period. Control of susceptible strains of Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.) and Sitophilus granarius (L.) was achieved where recovered pesticide residues remained above 1 mg kg⁻¹ pirimiphos-methyl and 1·6 mg kg⁻¹ etrimfos.     

Dissipation rates of insecticides in six minor vegetable crops grown on organic soils in Ontario,Canada

Dissipation rates of diazinon, endosulfan, leptophos, methamidophos, methomyl, parathion and pirimicarb were studied on five minor vegetable crops, including cos and head lettuce, endive, cauliflower and Chinese cabbage. Residues from foliar treatment generally followed an exponential rate of decline. The number of days for residues to drop to below acceptable tolerances was highly dependent on the magnitude of the initial residue; large variations in initial residues were observed between years, between insecticides, and between crop types. Residues of five insecticides and two fungicides used in furrow treatments for onions intended for pickling were determined in the onions at harvest and after pickling. Fensulfothion and fonofos levels were below the accepted tolerance of 0.1 mg kg^?1 at harvest, while chlorfenvinphos, chlorpyrifos and ethion were present above this level; fungicide residues were not detected. Following pickling, only ethion residues were still present in the onions at levels greater than 0.1 mg kg^?1.     

Leaching of Methyl Isothiocyanate in Plainfield Sand Chemigated with Metam-Sodium

Soil column studies were undertaken to investigate the influence of soil water content and irrigation on leaching, distribution and persistence of methyl isothiocyanate (MITC) in a sandy soil chemigated with the soil fumigant metam-sodium. No leaching was obtained from columns at low water content (0·042 or 0·074 cm³ cm⁻³). However, 8·4 (±2·8), 34·2 (±7·4) and 119·4 (±8·3) μg of MITC leached from columns at 0·105, 0·137 and 0·168 cm³ cm⁻³ water content, respectively. Increased leaching resulted from sprinkler application of 25-mm of water to columns at 0·137 cm³ cm⁻³ water content. Leaching of MITC constituted only a small fraction of the amount applied even in the worst case. Methyl isothiocyanate persisted in soil for 15 days at 2°C in varying amounts under the different water regimes. Relatively high amounts of MITC residues (8–12 mg kg⁻¹ soil) were detected in the top 25-cm layer of all the soil columns. Degradation was the major pathway of dissipation for the chemical despite the soil water regime.     

Multiresidue method for captan,folpet, captafol,vinclozolin and iprodione on italian apples and pears by capillary gas–liquid chromatography with electron-capture detection

A method is described for the simultaneous determination of residues of five fungicides used for foliar treatment of apple and pear trees, and for postharvest application. After extraction, the mixture of these fungicides is cleaned-up on a ‘SEP PAK C₁₈’ cartridge and the components determined by gas-liquid chromatography with electron-capture detection. The minimum detectable amounts in apples and pears, on a fresh weight basis, were 0.005mg kg⁻¹ for vinclozolin, 0.010mg kg⁻¹ for captan, folpet and iprodione, and 0.020 mg kg⁻¹ for captafol. The percentage recovery for each fungicide (calculated by analysing four samples of untreated apples and pears, to which varying concentrations of each active ingredient had been added) varied for vinclozolin between 70.0 and 89.2, for captan between 72.0 and 83.8, for folpet between 73.0 and 93.0, for captafol between 70.8 and 91.8, and for iprodione between 75.1 and 97.1.     

Degradation of mecoprop at different concentrations in surface and sub-surface soil

Biodegradation of [ring-¹⁴C] mecoprop (2-(4-chloro-2-methylphenoxy)propionic acid) was determined in surface and sub-surface soil at concentrations of 0·0005, 0·05, 0·5, 5, 50, 500, 5000 and 25000 mg kg^-1. The kinetics of mineralisation were evaluated from the mineralisation rates as a function of time and by non-linear regression analysis. In the sub-surface soil, degradation was 6–8 times slower than in surface soil, but the shape of the curves was the same in both layers. At concentrations between 0·0005 and 0·5 mg kg^-1, in both surface and sub-surface soil, degradation was initially zero-order followed by first-order kinetics. At 5 to 500 mg kg^-1 in surface soil and 5 to 50 mg kg^-1 in sub-surface soil the degradation rate was initially either constant or decreasing followed by exponential degradation indicating increasing populations of mecoprop decomposers in the soil. At 5000 and 25000 mg kg^-1 in the surface soil and at 500, 5000 and 25000 mg kg^-1 in the sub-surface soil, the degradation was negligible, as determined by the percentage [¹⁴C] carbon dioxide evolved. By non-linear regression, the three-half order model was found to describe the mineralisation. © 1998 SCI