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441.
442.
以钛酸四丁酯为前驱体,采用溶胶凝胶法,制备了CoO掺杂的TiO2光催化剂。利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见漫反射(UV—visDRS)对催化剂进行了分析、表征。以中压汞灯为光源,研究了亚甲基蓝(MB)在CoO/TiO2微粒水悬浮液中的降解动力学。结果表明:所制备的催化剂活性组分主要是锐钛矿型的二氧化钛和CoO固溶体,粒径为25~30nm,分布均匀。亚甲基蓝的光催化降解动力学满足一级动力学,在一定的浓度范围内,反应速率常数随初始浓度增大而减少,适当的掺钴量可以有效地提高TiO2光催化活性,其最佳掺杂量重量百分比为0.25%。 相似文献
443.
Steinman AD Biddanda B Chu X Thompson K Rediske R 《Environmental monitoring and assessment》2007,134(1-3):177-189
Groundwater withdrawal has major economic, social, and environmental implications. In Michigan, recent legislative activity
has begun to address the issue of groundwater sustainability. However, more hydrologic data are needed to help inform policy
and legislation. A study was conducted in Mecosta County, Michigan to: (1) determine if a relationship could be established
between land use/land cover and groundwater quality; and (2) develop a conceptual model for the shallow groundwater system
of the study region. In general, groundwater quality was good, with below detection levels of E. coli, low total bacterial counts, and relatively low nutrient concentrations. No statistically significant associations were found
between the bacterial numbers and either land use or the physical/chemical attributes measured, which may be because the scale
of our spatial analysis was too coarse to detect patterns. Finer-scale, localized processes may have a greater influence on
microorganism growth and abundance than coarser-scale, regional processes in this area. Our groundwater analysis suggested
that shallow groundwater flow paths are generally consistent with regional surface water flow networks, and that shallow groundwater
levels in most of the region have fluctuated within 1–2 m over the past 30 years, with no obvious increasing or decreasing
trend. 相似文献
444.
Photodecay of o-chloroaniline (o-ClA) in various combinations of UV sources, TiO2, and oxyhalogens was investigated. To improve the conventional photocatalytic process by using UV/TiO2, the addition of oxyhalogens (ClO3(-), BrO3(-) and IO3(-)) into UV/TiO2 system was studied and the effect in such addition is very encouraging for all the selected additives. Oxyhalogens are capable of deferring the electron-hole recombination of TiO2 which significantly improved its catalytic performance. The presence of IO3(-) in UV/TiO2 resulted in the fastest o-ClA decay among three oxhalogens at the same dosage. The decay of o-ClA in UV/TiO2/oxyhalogen process is characterized by a two-stage pseudo-kinetics, where a faster initial decay was followed by a retardation state. A mathematics model was successfully established for the prediction of the two-stage decay of o-ClA in UV/TiO2/IO3(-) with any designed [IO3(-)] concentration. 相似文献
445.
Photodegradation of the phenylurea herbicide monuron by using riboflavin (Rf), a sensitizer, was investigated by varying the doses of monuron and Rf in this work. An enhanced photochemical effect was observed in the process compared with the direct photolysis by using UV irradiation only. The reaction time was greatly shortened from more than 60 min (direct photolysis) to 8-30 min depending on the doses of initial concentration of monuron ([M]0) and Rf. A modified hyperbola model was found to be useful to determine the reaction kinetics and thereafter the performance on the photodegradation of monuron sensitized by Rf. Two measurable characteristic constants (initial decay rate and total removal index) were used to quantify the reaction. The maximum removal difference compared with the direct photolysis and Rf-sensitization was investigated. It was found that the improvement of the process depended on both the [M]0 and the doses of Rf. 相似文献
446.
Chu S Henny CJ Kaiser JL Drouillard KG Haffner GD Letcher RJ 《Environmental pollution (Barking, Essex : 1987)》2007,145(1):374-381
Current-use chlorophenoxy herbicides including 2,4-dichlorophenoxyacetic acid, dicamba, triclopyr, dicamba, dimethyl tetrachloroterephthalate (DCPA or dacthal), and the metabolite of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and the fungicide, chlorothalonil, were investigated in the eggs of osprey (Pandion haliaetus) that were collected from 15 sites from five study areas Puget Sound/Seattle area of Washington State, USA. DCPA differs from acidic chlorophenoxy herbicides, and is not readily hydrolyzed to free acid or acid metabolites, and thus we developed a new method. Of the 12 chlorophenoxy herbicides and chlorothalonil analyzed only DCPA could be quantified at six of these sites (2.0 to 10.3 pg/g fresh weight). However, higher levels (6.9 to 85.5 pg/g fresh weight) of the unexpected DCPA structural isomer, dimethyl tetrachlorophthalate (diMe-TCP) were quantified in eggs from all sites. diMe-TCP concentrations tended to be higher in eggs from the Everett Harbor area. As diMe-TCP is not an industrial product, and not commercially available, the source of diMe-TCP is unclear. Regardless, these findings indicate that DCPA and diMe-TCP can be accumulated in the food chain of fish-eating osprey, and transferred in ovo to eggs, and thus may be of concern to the health of the developing chick and the general reproductive health of this osprey population. 相似文献
447.
Dissipation of carbofuran and carbaryl on Oolong tea during tea bushes, manufacturing and roasting processes 总被引:1,自引:0,他引:1
Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranol-N-methylcarbamate) and carbaryl (1-naphthyl-N-methylcarbamate) are insecticides widely used in tea plantations. The objective of the present study was to evaluate the dissipation of carbofuran and carbaryl during the growth periods of Oolong tea, processing and roasting. Analysis of the residual insecticides was carried out using high-pressure liquid chromatography with a post-column fluorescence detector. Results showed that in the tea field carbofuran dissipated faster then carbaryl. Manufacturing processes of Oolong tea further reduced the carbofuran and carbaryl contents. The persistence of carbofuran and carbaryl was decreased with increasing roasting temperature. From the results, we conclude that the presence of carbofuran and carbaryl in tea can be reduced by proper field management, manufacturing and roasting processes. 相似文献
448.
通过室内培养和盆栽试验 ,研究了镧积累对红壤有效养分的影响。结果表明 ,镧积累降低了土壤有效氮、有效磷含量 ,有效氮、有效磷含量与镧浓度呈显著的负相关 ,镧对土壤有效钾的影响不明显。 相似文献
449.
450.