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141.
Hu J Eriksson L Bergman A Jakobsson E Kolehmainen E Knuutinen J Suontamo R Wei X 《Chemosphere》2005,59(7):1043-1057
Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants and are increasingly turning up in the environment. Their structural similarities to polychlorinated biphenyls and thyroid hormones suggest they may be a risk to human health. The present study examines the reactivity of brominated diphenyl ethers (BDEs) on the basis of the electronic structures as calculated by semiempirical AM1 self-consistent field molecular orbital (SCF-MO) method. Frontier orbital energies were used to elucidate the reactivity of BDEs in electrophilic, nucleophilic and photolytic reactions. From an examination of the frontier electron densities, the regioselectivity, or orientation, of metabolic reactions of BDEs was predicted. Furthermore, satisfactory quantitative structure-activity (property) relationship (QSAR and QSPR) models were derived to calculate gas chromatographic and ultraviolet spectral properties and luciferase induction activities from the AM1-computed electronic parameters. 相似文献
142.
The paper presents a semi-continuous preexposure procedure (SCEP) for use with surface water batch simulation biodegradability tests at low test substance concentrations (0.1-100 microg/l). Simple one step batch tests are normally used first of all for determining "initial rates" characteristic of the water as sampled, as by contrast to "adapted" rates obtained as a result of exposure of the microbial community to the test compound. The aim of the SCEP is to facilitate this adaptation and to become able to estimate reproducible "adapted rates" representing a steady state situation. This is accomplished by maintaining the microbial diversity and a supply of test substance and natural substrates. Conducting a SCEP involves regular renewal of part (e.g. one third) of the test suspension (e.g. every two weeks) adding freshly collected natural water with test compound of the initial concentration. An example study was performed with aniline, 4-nitrophenol, 2,4-dichlorophenoxyacetic acid, 4-chloroaniline, and water from the urban river M?lle?. Following preadaptation lag phases were considerably reduced and much more reproducible than obtained with simple batch tests. In tests at 100 microg/l lag phases for aniline decreased from 5.2 to <1 day, 4-nitrophenol from 10 to <1 day, 2,4-dichlorophenoxyacetic acid from 24 to <1 day, and 4-chloroaniline from 88 to 9 days, respectively. Adapted rates obtained with the SCECP were roughly the same as final rates in simple batch tests with successful adaptation. The adapted rate constant is perceived as an inherent characteristic of the test compound at a specific concentration and under environmental influence (temperature, natural substrates, etc.) but with no simple links back to the original microbial population. By contrast, the initial rates in one step batch tests are determined also by the microbial population initially present in the water sampled. 相似文献
143.
Newcombe AC Gustafson DI Fuhrman JD van Wesenbeeck IJ Simmons ND Klein AJ Travis KZ Harradine KJ 《Journal of environmental quality》2005,34(3):1004-1015
The Acetochlor Registration Partnership conducted a prospective ground water (PGW) monitoring program to investigate acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)-acetamide] transport to ground water at eight sites. The distribution of soil textures among these sites was weighted toward coarser soil types, while also including finer-textured soils that dominate most corn (Zea mays L.)-growing areas of the United States. Each site consisted of a 1.2-ha test plot adjacent to a 0.2-ha control plot. Suction lysimeters and monitoring wells were installed at multiple depths within each test and control plot to sample soil-pore water and near-surface ground water. Irrigation was applied to each site during the growing season to ensure water input of 110 to 200% of average historical rainfall. Acetochlor dissipated rapidly from surface soils at all sites with a DT(50) (time for 50% of the initial residues to dissipate) of only 3 to 9 d, but leaching was not an important loss mechanism, with only 0.25% of the 15,312 soil-pore water and ground water samples analyzed containing parent acetochlor at or above 0.05 microg L(-1). However, quantifiable residues of a soil degradation product, acetochlor ethanesulfonic acid, were more common, with approximately 16% of water samples containing concentrations at or above 1.0 microg L(-1). A second soil degradation product, acetochlor oxanilic acid, was present at concentrations at or above 1.0 microg L(-1) in only 0.15% of water samples analyzed. The acetochlor PGW program demonstrated that acetochlor lacks the potential to leach to ground water at detectable concentrations, and when applied in accordance with label restrictions, is unlikely to move to ground water at concentrations hazardous to human health. 相似文献
144.
The investigation of 5547 prenatal diagnoses showed 31 unexpected structural chromosome rearrangements. These included 3 Robertsonian translocations, 14 reciprocal translocations and 14 inversions. A11 were balanced, including 5 de novo rearrangements. In 3 of these cases an induced abortion was performed and in 2 cases children without detectable malformations were delivered. 相似文献
145.
Leaching and crop uptake of nitrogen from nitrogen-15-labeled green manures and ammonium nitrate 总被引:1,自引:0,他引:1
Green manures can be used as an N source for agricultural crops as a substitute for inorganic N fertilizers. The effects of using green manures on leaching and uptake of N by spring barley (Hordeum vulgare L.) were evaluated in a 2-yr lysimeter study. Ryegrass (Lolium perenne L.) and red clover (Trifolium pratense L.) labeled with (15)N were applied in May of the first year at 160 kg total N ha(-1). Simultaneously, (15)NH(4)(15)NO(3) was applied at 80 kg N ha(-1) to additional lysimeters and others were left without N additions (control). During the second year, all lysimeters, except the control, received 80 kg N ha(-1) as unlabeled NH(4)NO(3). The cumulative, average loads of total N leached during the two years were: 37 (control), 62 (NH(4)NO(3)), 50 (ryegrass manure), and 73 (red clover manure) kg ha(-1). The differences among the treatments were not significant (P > 0.05), but the control had significantly smaller (P < 0.05) leaching loads than the treatments. About 24% of ryegrass- and red clover-derived N and 43% of NH(4)NO(3) were removed through spring barley grain and stover during the two growing seasons. Thus, the N use efficiency in barley was substantially larger when grown with inorganic N fertilizer than when grown with green manure. Viewed in combination with the tendency for larger N leaching loads under red clover manure, claims about water quality benefits of legume-based green manures should be evaluated with regard to the timing of N release and demand for N by the plant. 相似文献
146.
A method for direct detection of antibiotic resistance genes in soil samples has been developed. The tetracycline resistance gene, tet(M), was used as a model. The method was validated on Danish farmland soil that had repeatedly been treated with pig manure slurry containing resistant bacteria. The tet(M) gene was directly detected in 10-80% of the samples from the various farmland soils and could be detected in all samples tested after selective enrichment. To validate the obtained results, the method was applied to garden soil samples where lower prevalence of resistance was found. RESULT: A detection limit of 10(2)-10(3) copies of the tet(M) gene per gram of soil (in a Bacillus cereus group bacterium) was achieved. tet(M) gene was detected in soil samples with the highest prevalence on farmland treated with pig manure slurry. 相似文献
147.
Monte L Brittain JE Håkanson L Smith JT van der Perk M 《Journal of environmental radioactivity》2004,75(1):83-103
The present paper summarises the results of the review and assessment of models developed for predicting the migration of radionuclides from catchments to water bodies. The models were classified and evaluated according to their main methodological approaches. A retrospective analysis of the principles underpinning the model development in relation to experimental finding and results was carried out. It was demonstrated that most of the various conceptual approaches of different modellers can be integrated in a general, harmonised perspective supported by a variety of experimental evidences. Shortcomings and advantages of the models were discussed. 相似文献
148.
The presence of erm genes was investigated among macrolide-resistant Gram-positive bacteria isolated from soil samples collected from four Danish farms that had been treated with animal waste. Soil samples were collected before, a few days after spread and 1 1/2 months and 5 months later. In 33% (9/27) of these isolates, an erm gene was detected using PCR. Eight isolates were positive for erm(B) and one isolate was positive for erm(C). No isolates contained erm(A), erm(D) or erm(F). The positive isolates were identified to genus level. Two erm(B) positive isolates were identified as Enterococcus spp., and the erm(C)-positive isolate as a Streptococcus spp., probably indicating survival from animal waste. The remaining six erm(B) positive isolates all belonged to the Bacillus cereus group. The erm(B) gene has not previously been identified in B. cereus but is frequently found among enterococci. This result could indicate horizontal transfer from bacteria of animal origin to indigenous soil bacteria. 相似文献
149.
150.
Lotte Hatt Katarina Ravn Line Dahl Jeppesen Bolette Hestbek Nicolaisen Inga Baasch Christensen Ripudaman Singh Palle Schelde Simon Horsholt Thomsen Rikke Christensen Marianne Sinding Laura Vase Marianne Oestergaard Marie Bender Ruggard Hanne S. Jensen Helle Mogensen Niels Uldbjerg Naja Becher Sara Markholt Puk Sandager Lars Henning Pedersen Ida Vogel 《黑龙江环境通报》2023,43(7):854-864