ISSN:0730-7268    

DOI:10.1002/etc.5620100401

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe sorption behavior of nonionic organic chemicals on humic acid‐modified silica was examined to assess its possible use as a simplified model of natural low organic carbon aquifer materials. Column and batch sorption experiments were conducted on humic acid‐coated silica (0.073% organic carbon), using tetrachloroethylene (PCE) and 1‐methylnaphthalene (MN). Batch kinetic experiments showed that equilibrium was attained rapidly for PCE (˜1 d), whereas several tens of days were required for MN. Batch experiment results indicated Freundlich (nonlinear) isotherm behavior when a wide concentration range was examined. Sorption coefficients derived from the column experiments were consistent with the batch‐derived Freundlich isotherms, illustrating the importance of isotherm type on breakthrough curves and solute transport in ground water. Similarities exist between the sorption behavior observed in this study and that of a number of natural aquifer materials. Humic acid‐modified silica serves as a simplified model for aquifer materials, which tend to be more complex and difficult to characterize and can be used to examine organic solute transport processes in gr

ISSN:0730-7268    

DOI:10.1002/etc.5620100402

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe ability of Fe oxides to adsorb phenol and various substituted phenols from dilute aqueous solution and from the vapor state was investigated, utilizing Fourier transform infrared (FTIR) spectroscopy to evaluate the type of surface complex formed. Adsorption from solution at pH 5.5 was weak (undetectable in the case of the unsubstituted phenol). There was some indication that quantity of adsorption was inversely related to the pKaof thep‐substituted phenols, with the most acidic phenols adsorbing the most strongly from solution. The FTIR spectra revealed that adsorption on goethite and amorphous Fe oxide from the vapor state tended to perturb vibrational bands sensitive to the phenolic OH group, an indication of bonding between surface Fe3+and the phenolic ligand. Depending on level of adsorption, both physically and chemically adsorbed phenols could be detected by FTIR with chemisorption being more in evidence on amorphous Fe oxide. Phenol that was 2,6‐methyl‐disubstituted failed to interact strongly with the goethite surface, suggesting that steric hindrance from groups adjacent to the phenolic group prevented inner‐sphere coordination of the phenols to surface Fe atoms. This steric effect was not evident for low levels of adsorption on amorphous Fe oxide, suggesting an important role of site geometry in limiting chemisorption. The strength of the Fe3+‐phenolic coordination bond was correlated to the pKaof the phenol, with more acidic phenols forming weaker CO bonds. The quantity of water present determined whether the phenols adsorbed at barely detectable or much higher levels, suggesting a competition between H2O and phenols for ligand positions of

ISSN:0730-7268    

DOI:10.1002/etc.5620100403

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractTheSalmonella typhimurium/mammalian microsome test has provided a simple and sensitive short‐term assay for the detection of environmental mutagens. Metabolic activation of precarcinogens is usually achieved by incubating the compound to be tested, the bacterial strain and mammalian liver homogenates with NADPH. The results presented here utilizeSalmonella typhimuriumstrain TA100, the precarcinogen 2‐aminofluorene and microsomal enzyme preparations prepared from liver homogenate of carp (Cyprinus carpio) taken from aquatic environments of northeastern Tennessee. Those environments range from virtually unpolluted to extremely polluted. The results show that the precarcinogen 2‐aminofluorene is activated either partially or totally in the presence of liver homogenates of carp taken from polluted aquatic environments (e.g., microsomal enzyme preparations made from rat liver with 2‐aminofluorene produced 808 revertants; whereas the liver preparations made from carp, taken from the Pigeon River, with 2‐aminofluorene produced 2,786 revertants). Revertant colony results correlated well with the degree of pollution within those waters. An increase (data were statistically different at the 0.05 level of significance) of TA100 revertant colonies was observed as aquatic contamination worsened. All data pairs of collecting sites in their order of increasing contamination, as well as those between collecting sites, were statistically different at the 0.05 level of sig

ISSN:0730-7268    

DOI:10.1002/etc.5620100404

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractNine benzoic acid hydrazides and carbazates were assayed for toxicity and teratogenicity by using early embryos of the frogXenopus laevis.The results of the 96‐h static tests were used for quantitative structure‐activity relationship (QSAR) analyses. Each compound induced the connective tissue defect osteolathyrism. Regression analyses indicated toxicity (LC50) and teratogenicity (EC50) were best correlated with the STERIMOL width parameterB1, but due to redundancy inB1values for the test chemicals and the relatively lowr2for the models, those equations should be used with caution. The mortality/malformation index (MMI) was negatively correlated with molar refractivity (MR). The relationships indicate that steric interactions may be important in explaining the variation in biological activity due to changes in chemical structure. Frog embryo teratogenesis assay:Xenopus(FETAX) may be useful in aquatic toxicology hazard assessment, evaluating developmental malformat

ISSN:0730-7268    

DOI:10.1002/etc.5620100405

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe aerobic biodegradation of methylene chloride was observed in a variety of surface soils including a sand, a sandy loam and a sandy clay loam, as well as a subsurface clay soil. Degradation was found to occur over concentrations ranging from approximately 0.1 ppm to 5.0 ppm. Degradation at higher concentrations was facilitated by the presence of an exogenous organic carbon source. No products other than carbon dioxide were detected in the biologically active microcosms. The time required for 50% disappearance of the parent compound varied over 100‐fold, ranging from 1.3 to 191.4 d. Preexposure of the soil to methylene chloride resulted in faster rates of degradation upon subsequent exposures. Methylene chloride degradation was also observed under anaerobic conditions in the sandy loam soil. In contrast to observations under aerobic conditions, a significant lag or acclimation period preceded biodegradation under anoxic conditions, and no loss of the parent compound was observed during the first 70 d. However, following the lag period, the rate of degradation was approximately 10‐fold higher under anaerobic conditi

ISSN:0730-7268    

DOI:10.1002/etc.5620100406

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractA study was conducted of the degradation of aniline‐humic acid and phenol‐humic acid complexes by sunlight and the subsequent mineralization by microorganisms. Irradiation of anilinehumic acid and phenol‐humic acid complexes in sunlight resulted in a loss of UV light absorbance and the formation of low‐molecular‐weight products. Sunlight irradiation of the aniline‐humic acid complexes had no effect on their subsequent mineralization. The rate and extent of mineralization of the phenol‐humic acid complexes were enhanced by sunlight irradiation. The mineralization of phenol‐humic acid complexes increased with integrated solar flux and was proportional to the percentage of the original complex that was converted to low‐molecular‐weight photoproducts. The effects of solar irradiation on molecular‐weight distribution of the complexes appear to be independent of the organic compound used to form the complex. The effects of irradiation on microbial mineralization of the complexes are different for differ

ISSN:0730-7268    

DOI:10.1002/etc.5620100407

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe magnitude of the binding interaction of dissolved organic matter with 2,2′,5,5′‐tetrachlorobiphenyl is affected by several environmental parameters: pH, ionic strength of the aqueous media, molecular weight and the source of the binding agent. Temperature has little effect. The binding constant for Aldrich humic acid is on the order of 1 × 105. Humic acids extracted from soil and water samples have lower binding capabilities than Aldrich humic acid (KDOCrange: 0.24 × 105‐0.64 × 105), whereas the fulvic acid and dissolved organic matter samples haveKDOCs near the method detection limit (0.086 × 105and 0.0076 × 105, respectively). Thermodynamic studies show the binding interaction to be entropy driven with ΔH° similar to that of van der Waals

ISSN:0730-7268    

DOI:10.1002/etc.5620100408

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effects of 100, 300 and 500 μg/ml of alachlor and metolachlor were investigated in cells ofAzospirillum brasilensegrown in chemically defined medium and dialyzed‐soil medium. Microorganisms cultured in the presence of alachlor showed lower nitrogenase activity and lower levels of ATP compared with control cells. However, the effects due to metolachlor disappeared after 48 h, showing thatAzospirillum brasilensecan tolerate high concentrations of that herbici

ISSN:0730-7268    

DOI:10.1002/etc.5620100409

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAn outdoor pen study was conducted with mallards (Anas platyrhynchos) to evaluate the effects of an 8‐d dietary exposure to methyl parathion (400 ppm) on egg laying and incubation when treatment was initiated at different times in the nesting cycle. Treatment groups were defined as egg laying (chemical initiated after fourth egg laid in nest), early incubation (initiated after day 4 of incubation), late incubation (initiated after day 16 of incubation) and control (no chemical). Forty‐eight pairs (12/group) were allowed to nest and hatch broods. In the egg laying group, daily egg production was reduced significantly during the treatment period compared to controls, but 4 of 10 hens resumed production post‐treatment. One of ten control hens abandoned its nest, whereas 17 of 23 hens in the early and late incubation groups either died or exhibited changes in incubation behavior, with 7 hens abandoning their nests and 6 displaying reduced nest attentiveness for one or more days during treatment. Reproductive parameters were not significantly different between treatment groups, but the number of hatchlings per nest was 61, 43 and 58% of controls for the egg laying, early incubation and late incubation groups, respectively. This study showed that nesting success may be impacted by short dietary exposures to methyl parathion, particularly during early incub

ISSN:0730-7268    

DOI:10.1002/etc.5620100410

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY