摘要:

Cypermethrin (40 EC Ripcord®, 1.0 g a.i./L aqueous dilution) was applied to the basal 1 m of elm tree trunks to runoff for control of elm bark beetles at two different application times and sites. The initial residues ofcis‐A,trans‐C,cis‐B, andtrans‐D cypermethrin isomers in litter were 54 to 141, 41 to 125, 47 to 88, and 32 to 62 μg/g, respectively, depending on the application time, and dissipated to below detection limits at 341 d after application. Total cypermethrin residues in soil fluctuated from below detection limits to 10 μg/g during the experimental period. Dissipation half‐lives ofcis‐A,trans‐C,cis‐B, andtrans‐D in soil fortified in the laboratory and held under field conditions were 409 to 453, 277 to 286, 345 to 473, and 249 to 263 d, respectively. The trans‐cypermethrin isomers dissipated more quickly in soil than thecis‐isomers, and cypermethrin at higher concentrations dissipated more slowly than at lower concentrations.

ISSN:0360-1234    

DOI:10.1080/03601239809373149

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A phosphotriesterase (PTE) capable of hydrolyzing organophosphate esters was purified fromEscherichia colistrain DH‐5α carrying a clonedopdgene fromFlavobacterium.The effects of pH, temperature and metal ion concentrations on enzyme stability and activity were investigated. Optimum conditions for PTE's catalytic activity were determined to be 35°C and pH 8.5. Protein‐metal equilibrium binding experiments showed that PTE could accommodate two equivalents of Co2+or Zn2+ions. PTE protein was found to have higher affinity for Co2+. In addition, Co2+was found to possess the most positive effects in maintaining and restoring PTE's stability and catalytic activity when compared to other divalent metal ions. Assessment of the feasibility of PTE operation in a practical environment was performed in a system designed to mimic a continuously stirred tank reactor (CSTR) with different solution compositions in the flow reservoir. PTE was deactivated in 24 hours when the inflow solution contained5%ethanol or 1 mM EDTA, while it retained one third of its initial activity in a deionized water stream. When the inflow solution contained 1 mM Co2+, PTE was found to retain activity throughout the 24‐hour experiment.

ISSN:0360-1234    

DOI:10.1080/03601239809373150

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The role of microorganisms in the degradation of carbosulfan (2,3‐dihydro‐2,2‐ dimethyl‐7‐ benzofuranyl‐ (di‐n‐butyl)‐ aminosulfenyl methylcarbamate), an analogue of carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofiiranyl‐N‐methyl carbamate) was studied by selective enrichment of microorganisms degrading either or both insecticides by repeated application of the insecticides, individually or in combination to flooded soil. Soil suspension from the pots treated with carbosulfan and carbofuran, individually or in combination collected after two applications, effected distinctly more rapid hydrolysis of carbosulfan than did the suspension from untreated pots or the uninoculated medium. The rate of hydrolysis was further accelerated by soil suspensions collected after six applications of the insecticides in the order carbosulfan treated > carbofuran treated > carbosulfan + carbofuran treated. The ability of treated and untreated suspension to degrade carbofuran was also studied. The rate of degradation of carbofuran by the suspension was in the order carbofuran retreated > carbosulfan + carbofuran retreated > carbosulfan retreated soil. Further involvement of microorganism in the rapid degradation of carbosulfan was confirmed by testing the degradation in sterilized and nonsterilized enrichment culture.

ISSN:0360-1234    

DOI:10.1080/03601239809373151

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Changes in microbial numbers and activities in two non‐flooded soils treated with bensulfiiron‐methyl at 16 and 160 μg/kg were studied after 1 and 4 weeks of incubation under laboratory conditions. In addition to herbicide persistence, six general and functional microbial groups (numbers of culturable aerobic and anaerobic bacteria, aerobic N2fixers, autotrophic nitrifiers, aerobic and anaerobic cellulolytic microorganisms) and two activities (respiration and nitrification) were also studied. With respect to microbial numbers, only cellulolytic microorganisms in soil which had never been previously treated with pesticides significantly decreased in number. Only the higher dose of bensulfiiron‐methyl in the second soil (which had previously received bensulfuron treatment) substantially inhibited nitrification, possibly because of the greater persistence of the herbicide in the soil. Soil respiration (CO2emission) was not influenced by the herbicide in any of the samples. The half‐life of the herbicide in the soils studied was 1 to 3 weeks. Persistence was greater in the soil with pH 5.5, a condition which is known to favor abiotic degradation. The lower persistence of the herbicide in the other soil, which was alkaline and which contained more microflora, could be attributed to a higher rate of biodegradation. The data suggest that concentrations of bensulfuron‐methyl greater than those present under normal agricultural practice can alter some aspects of the structure and activity of the soil microbial community, and that the persistence of the herbicide can be low even in the absence of leaching and runoff.

ISSN:0360-1234    

DOI:10.1080/03601239809373152

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The residue levels of DDE, DDT, Dieldrin, Endosulfan and Lindane were determined in beans, maize and wheat samples collected from local markets in northern Tanzania. All residue levels were far below the FAO/WHO standards. No significant correlations were detected among the pesticides studied or between pesticides and the fat content of the commodities.

ISSN:0360-1234    

DOI:10.1080/03601239809373153

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of two sublethal fenitrothion concentrations (0.02 and 0.04 mg/L) on the energy metabolism of the european eelAnguilla anguillaand its recovery from intoxication was investigated. Analysis of various parameters such as glycogen, proteins and total lipids was made on liver and muscle eel tissues after 2, 8, 12, 24, 32, 48, 56, 72 and 96 hr of fenitrothion (0,0‐dimethyl 0–3‐methyl‐4‐nitrophenyl phosphorothioate) exposure. Subsequently, the fish were allowed recovery periods of 8, 12, 24, 48, 72, 96, 144 and 192 hr in clean water, and the same parameters were again evaluated. The results obtained during the exposure to the pesticide as well as during the recovery phase were used to calculate the caloric content in both tissues ofA. anguilla. Areduction in energy reserves in the selected tissues was observed after exposure to both fenitrothion concentrations and the caloric content in those animals was lower than in the controls. Most of the metabolic disorders did not persist after allowing recovery in clean water during a week.

ISSN:0360-1234    

DOI:10.1080/03601239809373154

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Acute toxicity of a neem pesticide (Vepacide‐Tech) was studied in male Wistar rats by oral (single) intubation for 7 days. Vepacide was found to be moderately toxic to rat based on LD50value. Subacute toxicity of Vepacide‐Tech was also studied in male rats by oral (multiple) intubation of low (80 mg Kg‐1day‐1), medium (160 mg Kg‐1day‐1) and high dose (320 mg Kg‐1day‐1) for 90 days. High dose caused a significant decrease in Cytochrome P‐450 (Cyt.P‐450) concentration at 45 and 90 days and the medium dose caused same effect at 90thday in liver and lung. Kidney showed similar effect at 90 days by the three doses. Cytochrome b5(Cyt. b5) concentration was significantly decreased in liver, lung and kidney at 45 and 90 days at medium and high doses. Brain Cyt.b5concentration was decreased on 90thday at high dose. Cytochrome P‐450 reductase (Cyt.P‐450 reductase) concentration was decreased significantly in liver and brain at 45 and 90 days, respectively at medium and high doses. The withdrawal study (28 days) has shown significant recovery. These results demonstrate that low levels exposure of Vepacide may have significant effect on the xenobiotic detoxification mechanism of different tissues of rat.

ISSN:0360-1234    

DOI:10.1080/03601239809373155

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Cadmium content of 97 samples of some edible wild mushrooms, corresponding to 13 different species, was determined by graphite furnace atomic absorption spectrophotometry. Influence of some factors (species and ecology, morphological portion, and traffic pollution) and the importance of mushrooms as a dietary source of this heavy metal have been studied. Saprophite species showed higher levels than mycorrhizal ones (p < 0.001), with some exceptions such asBoletusandAmanita.The hymenophore was always the morphological portion which contained the highest cadmium levels (p < 0.001). Traffic pollution was not a significant factor for the cadmium accumulation in fungi. The samples ofAgaricus macrosporusshowed the highest mean levels (68.96 and 36.84 ppm dry matter (d. m.) for hymenophore and the rest of the fruit‐body, respectively). The average cadmium content of the samples, with the exception ofA. macrosporus,was 0.96 for hymenophore and 0.53 ppm d.m. for the rest of the fruit‐body; and the range was between 0.18–4.32 and 0.10–1.91 ppm d.m. for hymenophore and the rest of the fruit‐body. The concentration levels were compared to literature data and levels set by legislation, and the contribution of mushrooms to the weekly intake of cadmium per person was calculated. The possible health risk for the consumer is pointed out.

ISSN:0360-1234    

DOI:10.1080/03601239809373156

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A mathematical model taking into account source depletion with time and the actual thickness of manure layer was derived to evaluate indoor inhalation exposure dynamics to three selected odor causing volatile organic compounds (VOC‐odors) ofp‐cresol, toluene, and xylene volatilization from stored pig slurry. The model assumes that pig slurry is undisturbed and the VOC‐odors released in a contaminated layer and transported through a clean layer as well as a manure‐air interface boundary. The model simulates time‐dependent volatilization, the depletion of source contaminant via both volatilization and degradation, and could be used with a contaminated zone of finite thickness. For a given VOC‐odor, the predicted total exposure and resulting manure cleanup criteria can be a large variability depending on the model whether a finite or infinite manure layer thickness was considered. Results obtained from model comparisons suggest that the model incorporating depth‐varying of manure layer and contaminant source depletion is more suitable to evaluate the VOC‐odor exposure dynamics in swine housing bioclimate.

ISSN:0360-1234    

DOI:10.1080/03601239809373157

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A closed‐loop anaerobic digestion system consisting of a leachbed (LB) and an upflow anaerobic sludge blanket (UASB) was tested as an alternative for the disposal of poultry mortalities. This paper compares the performances of three LB‐UASB treatment systems with different initial moisture contents in the LBs. Each LB was loaded with one chicken and 5, 10 or 18 liters of water. The LBs initially carried out the hydrolysis/acidification phase while the UASBs the methanogenesis phase. Due to repeated inoculation by the UASBs, the LBs with 10 and 18 liters of water started producing methane on day 5, while the one with 5 liters of water on day 19. However, methane production rates were low before day 40 for the LB with 10 liters of water and day 60 for the other LBs. Methane production gradually improved as the LBs continued to receive ungranulated sludge from the UASBs. The LBs eventually became balanced methane reactors. Continued balanced fermentation in the LBs resulted in leachates with very low substrate concentrations that could no longer support high‐rate methanogenesis in the UASBs. Consequently, methane production rates from the UASBs decreased quickly while that from the LBs reached peak levels. Cumulative methane production from each LB eventually exceeded that from its connecting UASB. After 118 days of digestion, 414, 437 and 470 liters of methane were produced from the three systems, respectively. Cumulative methane production from the LBs with 5 and 18 liters of water accounted for 63% of the total methane produced from their respective systems. The LB with 10 liters of water produced 75% of the total methane from that system. Methane yields ranged from 0.485 to 0.554 m3(Kg TS)1. About 86% of the initial dry weight was biodegraded. All three systems performed very well with little operational problems. Overall, the system that started with 10 liters of water in the LB performed the best. Strategy for enhancing system performances and implementing farm applications are discussed.

ISSN:0360-1234    

DOI:10.1080/03601239809373158

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor