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461.
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
462.
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
463.
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
464.
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
465.
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
466.
467.
468.
Results of the first comprehensive light pollution survey in Hong Kong are presented. The night-sky brightness was measured
and monitored around the city using a portable light-sensing device called the Sky Quality Meter over a 15-month period beginning
in March 2008. A total of 1,957 data sets were taken at 199 distinct locations, including urban and rural sites covering all
18 Administrative Districts of Hong Kong. The survey shows that the environmental light pollution problem in Hong Kong is
severe—the urban night skies (sky brightness at 15.0 mag arcsec − 2) are on average ~ 100 times brighter than at the darkest rural sites (20.1 mag arcsec − 2), indicating that the high lighting densities in the densely populated residential and commercial areas lead to light pollution.
In the worst polluted urban location studied, the night-sky at 13.2 mag arcsec − 2 can be over 500 times brighter than the darkest sites in Hong Kong. The observed night-sky brightness is found to be affected
by human factors such as land utilization and population density of the observation sites, together with meteorological and/or
environmental factors. Moreover, earlier night skies (at 9:30 p.m. local time) are generally brighter than later time (at
11:30 p.m.), which can be attributed to some public and commercial lightings being turned off later at night. On the other
hand, no concrete relationship between the observed sky brightness and air pollutant concentrations could be established with
the limited survey sampling. Results from this survey will serve as an important database for the public to assess whether
new rules and regulations are necessary to control the use of outdoor lightings in Hong Kong. 相似文献
469.
Hone-Jay Chu Liang-Cheng Chang Yu-Pin Lin Yung-Chieh Wang Yu-Wen Chen 《Environmental Modeling and Assessment》2010,15(3):211-221
This study designs a multipurpose urban shallow artificial lake, including water supply, flood detention, and water environment
preservation. It is expected to not only preserve a healthy water environment but to also retain water conservation and flood
detention. This study adopts system dynamics (SD) to analyze the relationship between different purposes of water resources
utilization. Furthermore, different operation strategies effects can be simulated by SD through a proposed urban multipurpose
shallow artificial lake system. The results demonstrate the dynamic effects of strategies managers propose such as demand
analysis, inflow control, and water quality improvement in this case study for Taiwan. SD aids lake system prediction and
understanding temporally in sequential planning for water supply, environmental preservation, and flood detention. The SD
model will hopefully serve as a reference to study different features before artificial lakes constructing. 相似文献
470.
Effects of land cover changes induced by large physical disturbances on hydrological responses in Central Taiwan 总被引:1,自引:0,他引:1
Nien Ming Hong Hone-Jay Chu Yu-Pin Lin Dung-Po Deng 《Environmental monitoring and assessment》2010,166(1-4):503-520
This study analyzes the significant impacts of typhoons and earthquakes on land cover change and hydrological response. The occurrence of landslides following typhoons and earthquakes is a major indicator of natural disturbance. The hydrological response of the Chenyulan watershed to land use change was assessed from 1996 to 2005. Land use changes revealed by seven remote images corresponded to typhoons and a catastrophic earthquake in central Taiwan. Hydrological response is discussed as the change in quantities and statistical distributions of hydrological components. The land cover change results indicate that the proportion of landslide relative to total area increased to 6.1% after the Chi-Chi earthquake, representing the largest increase during the study period. The study watershed is dominated by forest land cover. Comparisons of hydrological components reveal that the disturbance significantly affects base flow and direct runoff. The hydrological modeling results demonstrate that the change in forest area correlates with the variation of base flow and direct runoff. Base flow and direct runoff are sensitive to land use in discussions of distinction. The proposed approach quantifies the effect of typhoons and earthquakes on land cover changes. 相似文献