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991.
Hien PD Hiep HT Quang NH Huy NQ Binh NT Hai PS Long NQ Bac VT 《Journal of environmental radioactivity》2002,62(3):295-303
The 137Cs inventories in undisturbed soils were measured for 292 locations across the territory of Vietnam. The logarithmic inventory values were regressed against characteristics of sampling sites, such as geographical coordinates, annual rainfall and physico-chemical parameters of soil. The regression model containing latitude and annual rainfall as determinants could explain 76% of the variations in logarithmic inventory values across the territory. The model part was interpreted as the logarithmic 137Cs deposition density. At the 95% confidence level, 137Cs deposition density could be predicted by the model within +/- 7% relative uncertainty. The latitude mean 137Cs deposition density increases northward from 237 Bq m(-2) to 1097 Bq m(-2), while the corresponding values derived from the UNSCEAR (1969) global pattern are 300 Bq m(-2) and 600 Bq m(-2). High 137Cs inputs were found in high-rainfall areas in northern and central parts of the territory. 相似文献
992.
993.
Roger B. Long 《Journal of the American Water Resources Association》1981,17(5):904-906
994.
995.
Characterization and removal of dissolved organic matter (DOM) from landfill leachate rejected by nanofiltration 总被引:7,自引:0,他引:7
Dissolved organic matter (DOM) from wastewater rejected by nanofiltration from a landfill leachate treatment plant was fractionated into humic acid (HA), fulvic acid (FA) and hydrophilic (HyI) fractions. It was found that humic substances (HA and FA) composed 75% of the total dissolved organic carbon (DOC) concentration of the DOM, with an average molecular weight of about 1000 Da. Elemental analysis, infrared spectroscopy, UV-visible spectroscopy and acid-base titration observations showed that the HA and FA of the DOM exhibited lower fractions of condensed aromatic functional groups but larger fractions of acidic groups compared with other aquatic DOMs. The properties of HA and FA were similar, but HA exhibited more complete humification, while the HyI fraction had more acidic groups. An aminated polymeric adsorbent NDA-8 was used to adsorb the DOM in the wastewater along with primary coagulation. Results of bench-scale experiments indicated that the treatment process could effectively remove the DOM and heavy metals while desorption liquid was 10 times more condensed than raw wastewater. Results of desorption and reproducibility tests consolidated the strong application potential of this treatment process as an advanced landfill leachate treatment technology. 相似文献
996.
Sharon C. Long Jeanine D. Plummer 《Journal of the American Water Resources Association》2004,40(6):1433-1448
ABSTRACT: A renewed emphasis on source water protection and watershed management has resulted from recent amendments and initiatives under the Safe Drinking Water Act and the Clean Water Act. Knowledge of the impact of land use choices on source water quality is critical for efforts to properly manage activities within a watershed. This study evaluated qualitative relationships between land use and source water quality and the quantitative impact of season and rainfall events on water quality parameters. High levels of specific conductance tended to be associated with dense residential development, while organic carbon was elevated at several forested sites. Turbidity was generally higher in more urbanized areas. Source tracking indicators were detected in samples where land use types would predict their presence. Coliform levels were statistically different at the 95 percent confidence levels for winter versus summer conditions and dry versus wet weather conditions. Other water quality parameters that varied with season were organic carbon, turbidity, dissolved oxygen, and specific conductance. These results indicate that land use management can be effective for mitigating impacts to a water body; however, year‐ round, comprehensive data are necessary to thoroughly evaluate the water quality at a particular site. 相似文献
997.
998.
中国科学院自动化所陈龙教授,基于对电视监控技术的长期研究,推出了这篇力作.文章较为全面地概括了DVR的技术现状和发展动向,提出了颇有见地的见解:DVR有可能提升为数字监控主机;MPEG4压缩技术为DVR提供了新的用途;嵌入式网络型DVR正在出现等等.如果文中表述的观点和信息能够为企业或用户提供些许参考,那正是我们作者和编者所祈盼的. 相似文献
999.
Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments 总被引:118,自引:0,他引:118
Edward R. Long Donald D. Macdonald Sherri L. Smith Fred D. Calder 《Environmental management》1995,19(1):81-97
Matching biological and chemical data were compiled from numerous modeling, laboratory, and field studies performed in marine
and estuarine sediments. Using these data, two guideline values (an effects range-low and an effects range-median) were determined
for nine trace metals, total PCBs, two pesticides, 13 polynuclear aromatic hydrocarbons (PAHs), and three classes of PAHs.
The two values defined concentration ranges that were: (1) rarely, (2) occasionally, or (3) frequently associated with adverse
effects. The values generally agreed within a factor of 3 or less with those developed with the same methods applied to other
data and to those developed with other effects-based methods. The incidence of adverse effects was quantified within each
of the three concentration ranges as the number of cases in which effects were observed divided by the total number of observations.
The incidence of effects increased markedly with increasing concentrations of all of the individual PAHs, the three classes
of PAHs, and most of the trace metals. Relatively poor relationships were observed between the incidence of effects and the
concentrations of mercury, nickel, total PCB, total DDT and p,p′-DDE. Based upon this evaluation, the approach provided reliable
guidelines for use in sediment quality assessments. This method is being used as a basis for developing National sediment
quality guidelines for Canada and informal, sediment quality guidelines for Florida.
The methods and guidelines presented in this report do not necessarily represent the policy of the National Oceanic and Atmospheric
Administration, Environment Canada, or Florida Department of Environmental Protection. 相似文献
1000.
人操作者的手动控制能力在人机环境系统的工效研究中具有广泛的应用价值。本文研究了人操作者的手动控制能力,以跟踪时间、跟踪误差和失误率为评价指标;分析不同被控对象动力学特性对人操作者在两自由度跟踪能力的影响。 相似文献