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661.
Obst U 《Environmental science and pollution research international》2003,10(4):251-255
Surface waters have a great impact on ecology and life of man. Because of their current use and exploitation, chemical and biological pollution, as well as physical changes of rivers and lakes are common. Natural self-purification potential helps to compensate harms to a certain degree. Proposals are given to detect restrictions of the purification potential in time as well as to support and to enhance the natural purification potential. 相似文献
662.
Characteristics of MnO2 catalytic ozonation of sulfosalicylic acid and propionic acid in water 总被引:9,自引:0,他引:9
The characteristics of different types of MnO2 catalytic ozonation of sulfosalicylic acid (SSal) and propionic acid (PPA) have been investigated in this paper. The experimental results show the dependence of catalytic activity of MnO2 on organic compounds and the pH of solutions, but it is independent on the type of MnO2. For example, three types of MnO2 have not any catalytic activity when ozonation of PPA under the condition of this experiment. All MnO2 catalytic ozonation of SSal at pH=1.0 have a greater total organic carbon removal than ozonation alone has, however, at pH=6.8 and 8.5, catalytic efficiency is not observed. Furthermore, the batch experimental results indicate that there are no direct relationship between the activity of metal oxide catalytic decomposition of ozone and that of its catalytic degradation of organic compounds. 相似文献
663.
Patrick Martinez Donald K. Brandvold 《Atmospheric environment (Oxford, England : 1994)》1996,30(24):4177-4182
This research consists of a laboratory study and a field study. The laboratory research reports the formation of NOx from a point to plane corona discharge. Discharge polarity and relative humidity determined the amount of NOx that was produced. The positive point discharge caused more NOx to form than the negative point discharge. For both polarities NOx production showed a nonlinear increase with current. Relative humidity enhanced the NOx formation for both polarities. In each case, the amount of NOx formed was comparable to the quantity of N2O produced from corona discharge. The research also reports the results from a field study that measured the amounts of 03 and NO2 produced by corona discharge during a thunderstorm. The study found that the ambient concentrations of 03 and NO2 increased several fold due to corona discharge and returned to original levels after the thunderstorm. 相似文献
664.
In this paper, we present two years of seasonal nitric oxide (NO), ammonia (NH3), and nitrous oxide (N2O) trace gas fluxes measured in a recovering riparian zone with cattle excluded and adjacent riparian zone grazed by cattle. In the recovering riparian zone, average NO, NH3, and N2O fluxes were 5.8, 2.0, and 76.7 ng N m−2 s−1 (1.83, 0.63, and 24.19 kg N ha−1 y−1), respectively. Fluxes in the grazed riparian zone were larger, especially for NO and NH3, measuring 9.1, 4.3, and 77.6 ng N m−2 s−1 (2.87, 1.35, and 24.50 kg N ha−1 y−1) for NO, NH3, and N2O, respectively. On average, N2O accounted for greater than 85% of total trace gas flux in both the recovering and grazed riparian zones, though N2O fluxes were highly variable temporally. In the recovering riparian zone, variability in seasonal average fluxes was explained by variability in soil nitrogen (N) concentrations. Nitric oxide flux was positively correlated with soil ammonium (NH4+) concentration, while N2O flux was positively correlated with soil nitrate (NO3−) concentration. Ammonia flux was positively correlated with the ratio of NH4+ to NO3−. In the grazed riparian zone, average NH3 and N2O fluxes were not correlated with soil temperature, N concentrations, or moisture. This was likely due to high variability in soil microsite conditions related to cattle effects such as compaction and N input. Nitric oxide flux in the grazed riparian zone was positively correlated with soil temperature and NO3− concentration. Restoration appeared to significantly affect NO flux, which increased ≈600% during the first year following restoration and decreased during the second year to levels encountered at the onset of restoration. By comparing the ratio of total trace gas flux to soil N concentration, we show that the restored riparian zone is likely more efficient than the grazed riparian zone at diverting upper-soil N from the receiving stream to the atmosphere. This is likely due to the recovery of microbiological communities following changes in soil physical characteristics. 相似文献
665.
Olaguer EP 《Environmental science and pollution research international》2002,9(3):175-182
Dichloromethane, perchloroethylene, and trichloroethylene are commercially important chlorinated solvents whose health and environmental impacts are under scrutiny in the industrial world. Their distributions in the global atmosphere have been computed based on data from the Reactive Chlorine Emissions Inventory (RCEI) project using the Global Balance Environment (GLOBE) model, a 3-D radiative-dynamical-chemical model. Their atmospheric lifetimes, scaled to an observed methyl chloroform lifetime of 4.8 years, are 158 days, 105 days, and 4.3 days, respectively. They have strong interhemispheric gradients, with maximum zonal mean surface concentrations in the winter mid-latitude northern hemisphere of approximately 40 ppt, 9 ppt, and 2.5 ppt, respectively. Their spatial distributions show significant seasonal variability, and are sensitive to vertical mixing by cumulus convection and horizontal mixing by synoptic-scale turbulence. While the model interhemispheric exchange time (1.0 years) and computed atmospheric lifetimes are very sensitive to sub-grid scale diffusion, interhemispheric gradients of the chlorinated solvents are not. The simulated results suggest a greater importance for oceanic emissions of perchloroethylene and trichloroethylene than has previously been assumed. 相似文献
666.
667.
在调研了上海化学工业生产技术的基础上,针对目前污染严重的一些生产工艺提出了可替代的清洁生产技术。在洁净煤、环氧丙烷、碳酸二甲酯、聚醚、异丙苯、丙烯腈、丙二醇醚等项目方面提出了相应的建议。 相似文献
668.
Sergio Rodríguez Xavier Querol Andrés Alastuey Jesús de la Rosa 《Environmental Chemistry Letters》2007,5(1):1-7
This article synthesises the results obtained in several projects on atmospheric aerosol (particulate matter – PM) pollution
developed during the last years in the Western Mediterranean. It focuses on particulate matter sources and the strategies
for suitable monitoring in ambient air. The article has been structured in several sections that give response to the main
questions that prompted these studies. After analysing the main PM features in the Mediterranean, a brief review of the main
factors differentiating the particulate matter composition with respect to Central Europe is presented. Finally, the suitability
of the different metrics or parameters for monitoring ambient air PM levels in different types of environments is discussed.
Selected article from the 6th European Meeting on Environmental Chemistry, University of Belgrade, Serbia and Montenegro organized
by Prof. Dr. Branimir Jovancicevic (www.research.plymouth.ac.uk/ace). 相似文献
669.
Robert D. Gibbons 《Environmental and Ecological Statistics》1995,2(2):125-145
With increasing concern over chemicals that are potential health hazards at low levels, determination of limits of detection have undergone considerable scrutiny. Most traditional detection limit estimators suffer from extensive statistical and/or conceptual limitations. In this paper, traditional detection limit estimators are described and critically evaluated. Using the terminology of Currie (1968), methods are categorized into decision limits versus detection limits. The methods are further categorized into single concentration design versus calibration design methodologies. While the single concentration design methods are useful for fixing ideas and clarifying definitions, they are shown to be extremely limited in practice since dependence of variability on concentration can neither be estimated or incorporated. Calibration-based detection limit estimators are described, compared and contrasted. Generalizations to non-constant variance, multiple future detection decisions and simultaneous control of Type I and II errors are provided. The various calibration-based methods are illustrated using real data and experimental design issues for detection limit studies discussed. 相似文献
670.
Laboratory experiments have been carried out to investigate the effects of a sloping wall headland on the flow characteristics and the associated concentration distributions from a point source around the headland. A semi-conical headland with a slope of 1:2 was set up in a flow basin, 4.8 m long and 3.8 m wide. In this paper, the experimental results of a steady shallow-water current are reported. Three dimensional flow velocities in the basin were measured using Sontek-ADV instrument. The dye concentration levels in the basin were measured by two fluorometers. The experimental results showed a large-scale re-circulation region behind the semi-conical headland. The peak turbulence energy, at about 53% of the local kinetic flow energy, coincides with the region of high velocity gradient. Significant vertical flows were observed around the area near the downhill slope of the headland, with a maximum ratio of vertical to horizontal velocities being about 22%. Such relatively significant vertical scouring velocities, coupled with strong turbulence energy and high horizontal velocity gradients in the same region, could cause severe bed erosion. The experimental results have also been compared with the predicted results of a depth-averaged numerical model. The predicted eddy structure and the concentration distribution in the re-circulation area were found to compare favourably with the experimental results. However, the discrepancies in the flow velocities and the concentration levels near the headland were apparent. It was observed that the dye concentration continued to spread in the cross-stream direction after passing the headland, whereas only a limited extent of the lateral spreading was predicted by the numerical model further downstream of the headland. 相似文献