ISSN:0730-7268    

DOI:10.1002/etc.5620060501

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

ISSN:0730-7268    

DOI:10.1002/etc.5620060502

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractOxygen concentrations in ambient water do not influence the uptake and elimination rates of 2,2′,5,5′‐tetra‐ and 2,2′,4,4′,5,5′‐hexachlorobiphenyl in guppies (Poecilia reticulata) after aqueous exposure. It is concluded that both the bioconcentration kinetics and bioconcentration factors are independent of the ambient oxygen regime between 2.5 and 8.0 mg/L.Since it can be assumed that the volume of water passing over the gills increases proportionally with decreasing aqueous oxygen concentration, it is concluded that for the bioconcentration of extremely hydrophobic chemicals, such as polychlorinated biphenyls, the uptake efficiencies rather than the uptake rate constants are dependent on the aqueous oxygen concentration. The experimental results support the concept that the rate of diffusion of the hydrophobic chemicals inside the fish, and not the ventilation volume of contaminated water passing over the gills, dominates the rates of uptake

ISSN:0730-7268    

DOI:10.1002/etc.5620060503

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA method is presented for estimating the number of samples needed to evaluate pesticide leaching threats to ground water at a desired level of precision. Sample size projections are based on desired precision (exhibited as relative tolerable error), level of confidence (90 or 95%) and estimates of variability (expressed as the coefficient of variation) for selected pesticide and soil characteristics.Summary tables of descriptive statistics are provided as guides for projecting variability of various soil characteristics, pesticide properties (sorption, degradation), pesticide concentration profiles and inorganic solutes. These data were compiled through a comprehensive search of review articles and of reports of laboratory and field studies. The parameters selected are measurements generally required for conducting field pesticide leaching studies. They are also useful for evaluating ground water contamination by calibrating and conducting sensitivity testing with solute transport models. Coefficients of variation for selected soil characteristics were as follows: bulk density, 2 to 17%; organic matter, 42 to 125%; porosity, 4 to 18%; particle size distribution, 3 to 55%; hydrogen ion activity, 2 to 15%; 0.3 bar water content, 18 to 82%; 15 bar water content, 18 to 87%; saturated hydraulic conductivity, 48 to 320%; and infiltration rate, 40 to 97%.Coefficients of variation for selected pesticide characteristics were as follows: transformation rates, 7 to 202%; sorption coefficients, 34 to 56%; and pesticide concentration profiles, 40 to 450%. Variability of pesticide concentrations increased over time after the initial pesticide application. The coefficients of variation for inorganic solutes ranged from 19 to 127%.On the basis of these data, sample size estimates (for constant desired precision and confidence level) for characterizing selected soil characteristics generally are smaller than those required for estimating pesticide concentrations. Fewer samples are projected for estimating pesticide concentrations shortly after application, with progressive increases required in later sampling.

ISSN:0730-7268    

DOI:10.1002/etc.5620060504

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAzodyes dissolved in water containing humic acid (total organic carbon = 5 mg/L) and irradiated with a xenon tamp were transformed primarily by an indirect photoprocess involving1O2and/or oxyradicals. Dissociation of the phenolic/naphtholic OH groups of the dyes was the dominant factor in increasing indirect photolysis rates. Simplified structure‐activity relationships were developed based on pKaprediction methods and on the observation that the reactivities of the dissociated forms of all the dyes are nearly the same. Products of indirect photolysis could not be identified, but loss of color suggests cleavage of the azo linkage in nearly all cases. Aromatic amines are not likely to be forme

ISSN:0730-7268    

DOI:10.1002/etc.5620060505

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe photodegradation and degradation products of hexachlorocyclopentadiene (C‐56) in aqueous solutions were studied in the laboratory. In each case, the half‐life of C‐56 was less than 4 min when exposed to sunlight. At least eight degradation products were positively or tentatively identified: 2,3,4,4,5‐Pentachloro‐2‐cyclopentenone, hexachloro‐2‐cyclopentenone and hexachloro‐3‐cyclopentenone were the primary photodegradation products, and pentachloro‐cis‐2,4‐pentadienoic acid, Z‐ and E‐pentachlorobutadiene and tetrachlorobutyne were the secondary degradation products. Dissociation of the primary photolysis products may proceed through corresponding pentadienoic acids to form smaller molecular weight compounds such as pentachlorobutadiene isomers and tetrachlorobutyne. In addition, dimerization of 2,3,4,4,5‐pentachloro‐2‐cyclopentenone to form higher molecular weight compounds such as hexachloroindenone may present a minor route of degradation. The results also indicate that C‐56 is highly photoreactive and suggest a possible pathway for the compound's transformation in the

ISSN:0730-7268    

DOI:10.1002/etc.5620060506

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractExperiments were performed in order to better define the degradation mechanisms and kinetics for aldicarb and its two metabolites, aldicarb sulfoxide and aldicarb sulfone. The mechanisms studied were oxidation in surface soil and saturated zone soil samples, degradation in saturated zone soil samples and distilled water hydrolysis. The studies showed that soil is an important mechanistic factor, probably because surface catalysis occurs. Temperature and pH are important factors in determining degradation rates. The experiments seem to indicate that microbial oxidation is an important degradation mechanism in the surface soil, but the breakdown of aldicarb residues to noncarbamates is largely the result of chemical hydrolysis. The reduction of aldicarb sulfoxide to aldicarb was observed in the presence of limestone but only after an incubation period of two to six months. No reduction of aldicarb sulfone to aldicarb sulfoxide was observed in these experiments. The complexity of degradation is such that laboratory studies can augment but not replace well‐designed experiments conducted under actual field condition

ISSN:0730-7268    

DOI:10.1002/etc.5620060507

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA physiologically based human pharmacokinetic model of chemical intake via ingestion of food and water and inhalation of air is presented. The model takes the form of a series of algebraic equations that describe the steady state, constant exposure, transport rates and physiological distribution in arterial and venous blood, lung, fat, skin, muscle, liver, gut tissue, gut lumen and richly perfused tissues. It is assembled using the fugacity concept and is applied to a hexachlorobiphenyl and styrene. It is suggested that the model can be used to elucidate how tissue concentrations respond to these intake routes and thus should contribute to better assessment of the hazards or effects of exposure to organic chemicals on humans and other mammals.

ISSN:0730-7268    

DOI:10.1002/etc.5620060508

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractCucumber and lettuce are the biological test species recommended by the U.S. Environmental Protection Agency, the Food and Drug Administration and the Organization for Economic Cooperation and Development for toxicity testing and environmental assessment. Millet is a riverine species widely distributed in the Midwest. The Illinois State Water Survey has conducted several studies using this species and the results show the millet to be rather promising for toxicity testing.The objective of this study was to compare the responses of lettuce, cucumber and millet seeds to heavy metals, including Cd, Cr(VI), Cu, Mn, Ni and Zn. Lettuce was most sensitive to metal toxicity, while results for cucumber and millet were mixed. The millet seeds, however, did show a predictable pattern of response similar to their response to phenolic toxicity. There was a fairly good correlation between 50% effect concentrations and no observed effect concentrations for millet (R2= 0.858).Lettuce and millet seeds are recommended for use together in toxicity tests of unknown, complex hazardous substances.

ISSN:0730-7268    

DOI:10.1002/etc.5620060509

出版商:Wiley Periodicals, Inc.    

年代:1987

数据来源: WILEY