摘要:

A laboratory experiment was performed to study the role of microorganisms in producing the non‐extractable residues by anaerobically incubating cyanazine (2‐[[4‐chloro‐6‐(ethylamino)‐1,3,5,‐triazin‐2‐yl]‐amino]‐2‐methoxy‐l‐methylethyl)acetamide] and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methoxy‐l‐methylethyl)acetamide] in culture media that had been inoculated with sewage bacteria from anaerobic sludge. Based on the gas chromatographic analyses of extracts from the degradation, adsorption, and abiotic controls for the parent herbicide and its possible metabolites, this study provided the first direct evidence that bacterial biomass, rather than metabolism, was mainly involved in the formation of bound residues with cyanazine. Anaerobic bacteria appeared to be incapable of forming bound residues with metolachlor. The common phenomenon of age‐dependent extractability for bound residues was observed with cyanazine. These results imply that bacteria may adsorb pesticides selectively with preference for certain chemical structures over others.

ISSN:0360-1234    

DOI:10.1080/03601239809373126

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Aqueous association of several organic compounds to Aldrich humic acid (AHA) was determined by equilibrium dialysis or solubility enhancement. The effect of varying concentrations of AHA on chemical degradation was also determined in batch experiments. Atrazine and glucose mineralization was greater in the presence of AHA and the enhancement was attributed to enhanced cellular uptake. No AHA inhibition on naphthalene or quinoline biodegradation was observed.

ISSN:0360-1234    

DOI:10.1080/03601239809373127

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Streptomycessp. PS1/5 was able to degrade atrazine in soil while growing on a mixture of chitin and ground cornstalks as carbon and nitrogen source. The addition of triple superphosphate greatly stimulated the degradation of atrazine byStreptomycessp. PS1/5, while the addition of lime stimulated the degradation to a lesser degree. Ferrous sulfate had a small positive effect on atrazine degradation. Atrazine in soil was reduced from 20 g g‘1dry soil (20 ppm) to 6 ppm within 30 days in soil amended with 8% chitin, 2% cornstalks and 0.1% triple superphosphate and incubated at 25°C. The results indicate that it may be possible to use bacteria of the genusStreptomycesto degrade pesticide residues in contaminated soils.

ISSN:0360-1234    

DOI:10.1080/03601239809373128

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The adsorption isotherms of mecoprop [R,S‐2‐(4‐chloro‐2‐ methylphenoxy) propanoic acid] and dichlorprop [R,S‐2‐(2,4‐dichlorophenoxy)propanoic acid] on twelve calcareous soils were studied. All the isotherms fit the Freundlich equation. The distribution coefficients (Kf) were low and were only significantly related with the organic matter content of the soils. The main adsorption mechanism at the pH of these soils was found to be by cation bridging between the anionic forms of the two herbicides, and the external surfaces of the organic matter and/or negatively charged clay. The Koc values for mecoprop (R,S‐ MCPP) and dichlorprop (R,S‐ DCPP) adsorption predicted a high mobility of these herbicides in the soils. Their corresponding enantiomeric forms, R (biologically active) and S (biologically inactive) were adsorbed at the same ratio on these soils. The organic matter amended soils showed a significant increase on the retention capacity of both molecules.

ISSN:0360-1234    

DOI:10.1080/03601239809373129

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The lower Yakima Valley of Washington is a highly diversified irrigated agricultural region bordered by dryland wheat fields. Residues of herbicides sprayed in wheat can be atmospherically transported to susceptible nontarget crops in the valley. Nontarget crops may be exposed repeatedly to low levels of herbicide residues. The effects on grapes exposed to phenoxyacetate herbicide drift has been well documented, but the effects of comparatively newer wheat herbicides like sulfonylureas (SUs) are less known. Potential effects of repeated exposures of grapes to an SU herbicide were assessed in a simulated drift study. Grape vines of the cultivar “Lemberger”; were sprayed up to three times at a weekly interval with 1/100 (0.01X) of a field application rate of chlorsulfuron, which is a postemergence wheat herbicide. Thirty‐five days after the first application, photosynthesis and stomatal resistance of randomly tagged, fully expanded leaves were measured. Total leaf area and chlorotic leaf area were also measured on the same leaves. The percentage of chlorotic area was calculated to determine the correlation between chlorotic area and photosynthetic activity of the leaf. Foliar injury was indexed on a numerical scale and scored in three intervals over 120 days of growth.

ISSN:0360-1234    

DOI:10.1080/03601239809373130

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was undertaken to determine the bioconcentration‐elimination process of fenitrothion in the liver of the european eel(Anguilla anguilla).The animals were exposed to two sublethal fenitrothion concentrations corresponding to 1/5 and 1/10 of LC50 96‐h in a flow‐through test system. Uptake kinetics were determined from liver burdens measured at 2, 8, 24, 48, 56, 72 and 96 hours exposure. After pesticide exposure, animals were transferred to clean water for 72 hours. Fenitrothion elimination was determined after 12, 24, 48 and 72 hours of recovery period. The insecticide showed a high bioconcentration tendency. Steady‐state was reached after 48 hours exposure when the animals where exposed to the lowest concentration. This was followed with a rapid elimination process when the animals were transferred to clean water. Animals exposed to 0.04 ppm showed an early accumulation of the toxicant into the liver, and a steady‐state was reached after 8 hours. The elimination rate constant K2of 0.0096 h‐1and 0.06 h‐1were estimated from the data. The biotransformation rate of fenitrothion in the European eel were low as indicated by a relatively short half‐life (11.55 h) of the insecticide. An increase in the Hepatosomatic Index was observed after 96 hours of exposure, but no significant differences were found between control and exposed animals.

ISSN:0360-1234    

DOI:10.1080/03601239809373131

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Pinto beans (Phaselous vulgaris), sweet corn(Zea mays),and zucchini squash (Cucurbita pepo) were grown in a field pot study using alluvial floodplain soils contaminated with various radionuclides within Los Alamos Canyon (LAC) at Los Alamos National Laboratory, New Mexico. Soils as well as washed edible (fruit) and nonedible (stems and leaves) crop tissues were analyzed for tritium (3H), cesium (137Cs), strontium (90Sr), plutonium (238Pu and239,240Pu), americium (241Am), and total uranium (totU). Most radionuclides, with the exception of3H andtotU, in soil and crop tissues from LAC were detected in significantly higher concentrations (p <0.05) than in soil or crop tissues collected from regional background locations. Significant differences in radionuclide concentrations among crop species (squash were generally higher than beans or corn) and plant parts (nonedible tissue were generally higher than edible tissue) were observed. Most soil‐to‐plant concentration ratios for radionuclides in edible and nonedible crop tissues grown in soils from LAC were within default values in the literature commonly used in dose and risk assessment models. Overall, the maximum net positive committed effective dose equivalent (CEDE)—the CEDE plus two sigma for each radioisotope minus background and then all positive doses summed—to a hypothetical 50‐year resident that ingested 352 lb ([160 kg]; the maxiumum ingestion rate per person per year) of beans, corn, and squash in equal proportions was 74 mrem y‐1(740 μS y‐1). This upper bound dose was below the International Commission on Radiological Protection permissible dose limit of 100 mrem y‐1(1000 (μS y‐1) from all pathways and corresponds to a risk of an excess cancer fatality of 3.7 x 10s(37 in a million), which is also below the U.S. Environmental Protection Agency's guideline of 10‐4.

ISSN:0360-1234    

DOI:10.1080/03601239809373132

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0360-1234    

DOI:10.1080/03601239809373125

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor