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141.
C. Radhakrishna Rao 《Environmental and Ecological Statistics》1994,1(1):7-19
Statistical methods as developed and used in decision making and scientific research are of recent origin. The logical foundations of statistics are still under discussion and some care is needed in applying the existing methodology and interpreting results. Some pitfalls in statistical data analysis are discussed and the importance of cross examination of data (or exploratory data analysis) before using specific statistical techniques are emphasized. Comments are made on the treatment of outliers, choice of stochastic models, use of multivariate techniques and the choice of software (expert systems) in statistical analysis. The need for developing new methodology with particular relevance to environmental research and policy is stressed.Dr Rao is Eberly Professor of Statistics and Director of the Penn State Center for Multivariate Analysis. He has received PhD and ScD degrees from Cambridge University, and has been awarded numerous honorary doctorates from universities around the world. He is a Fellow of Royal Society, UK; Fellow of Indian National Science Academy; Foreign Honorary Member of American Academy of Arts and Science; Life Fellow of King's College, Cambridge; and Founder Fellow of the Third World Academy of Sciences. He is Honorary Fellow and President of International Statistical Institute, Biometric Society and elected Fellow of the Institute of Mathematical Statistics. He has made outstanding contributions to virtually all important topics of theoretical and applied statistics, and many results bear his name. He has been Editor of Sankhya and theJournal of Multivariate Analysis, and serves on international advisory boards of several professional journals, includingEnvironmetrics and theJournal of Environmental Statistics. This paper is based on the keynote address to the Seventh Annual Conference on Statistics of the United States Environmental Protection Agency. 相似文献
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144.
西昌邛海水质现状调查分析 总被引:3,自引:0,他引:3
四川西昌的邛海水体中浮游植物群体组成以硅藻、绿藻及鼓藻为主,据1986~1991年连续监测结果表明,邛海水质总体处于贫营养状况,仅局部有富营养性藻类出现。 相似文献
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147.
天然有机物对零价铁去除水体中砷的影响研究 总被引:3,自引:0,他引:3
在研究零价铁对水体中砷去除动力学的基础上,着重探讨了天然有机物腐殖酸对零价铁除砷的影响.并对零价铁的腐蚀产物进行了分析.结果表明,水体中的砷可以通过在零价铁腐蚀产物上的吸附得到快速去除.腐殖酸显著降低了砷的去除率,这归因于腐殖酸与零价铁腐蚀产生的铁离子形成络合物,阻止了Fe(OH)3(或Fe(OH)2)沉淀的产生.腐殖酸浓度越高.砷的去除率越低.1.00 mg腐殖酸最多可以络合约0.75 mg铁离子.当铁离子与腐殖酸的络合达到饱和后,零价铁进一步腐蚀产生的铁离子可形成Fe(OH)3(或Fe(OH)2)沉淀,这些沉淀物可吸附水体中的腐殖酸和砷,从而加速砷的去除.冷冻干燥后的零价铁腐蚀产物的结构以无定型为主,含有少量的结晶化合物,包括γ-Fe2O3、γ-FeO(OH)和Fe3O4等.腐殖酸的存在可进一步增加腐蚀产物中的无定型成分.光电能谱(XPS)分析结果显示,吸附在腐蚀产物上的砷为5价,没有发现5价砷被还原成3价砷.在应用零价铁修复砷污染水体时,应考虑腐殖酸的影响. 相似文献
148.
Modeling watershed-scale effectiveness of agricultural best management practices to reduce phosphorus loading 总被引:1,自引:0,他引:1
Nalini S. Rao Zachary M. Easton Elliot M. Schneiderman Mark S. Zion David R. Lee Tammo S. Steenhuis 《Journal of environmental management》2009
Planners advocate best management practices (BMPs) to reduce loss of sediment and nutrients in agricultural areas. However, the scientific community lacks tools that use readily available data to investigate the relationships between BMPs and their spatial locations and water quality. In rural, humid regions where runoff is associated with saturation-excess processes from variable source areas (VSAs), BMPs are potentially most effective when they are located in areas that produce the majority of the runoff. Thus, two critical elements necessary to predict the water quality impact of BMPs include correct identification of VSAs and accurate predictions of nutrient reduction due to particular BMPs. The objective of this research was to determine the effectiveness of BMPs using the Variable Source Loading Function (VSLF) model, which captures the spatial and temporal evolutions of VSAs in the landscape. Data from a long-term monitoring campaign on a 164-ha farm in the New York City source watersheds in the Catskills Mountains of New York state were used to evaluate the effectiveness of a range of BMPs. The data spanned an 11-year period over which a suite of BMPs, including a nutrient management plan, riparian buffers, filter strips and fencing, was installed to reduce phosphorus (P) loading. Despite its simplicity, VSLF predicted the spatial distribution of runoff producing areas well. Dissolved P reductions were simulated well by using calibrated reduction factors for various BMPs in the VSLF model. Total P losses decreased only after cattle crossings were installed in the creek. The results demonstrated that BMPs, when sited with respect to VSAs, reduce P loss from agricultural watersheds, providing useful information for targeted water quality management. 相似文献
149.
The Avoidance Responses of Daphnia magna to the Exposure of Organophosphorus Pesticides in an On-Line Biomonitoring System 总被引:1,自引:0,他引:1
Zong-Ming Ren Zhi-Liang Li Jin-Miao Zha Kai-feng Rao Mei Ma Zijian Wang Rong-Shu Fu 《Environmental Modeling and Assessment》2009,14(3):405-410
In this study, avoidance behavior of the freshwater cladoceran Daphnia magna Straus was used as indicator to assess the early stress of accidental organophosphorus pesticide (OP) contamination. The
movement behavior was detected by a multi-species biomonitoring system. There was obvious concentration–response relationship
between the OP stress and the behavioral response even at sublethal exposure. A rising OP stress resulted in a significant
decrease of response time to escape (RTE; p<0.05). In comparison of different OPs, it was found that there was a power regression between RTE and the toxic unit of OPs.
Therefore, the avoidance behavior of D. magna was a sensitive indicator of sublethal OP stress, and the power relationship could be used to predict the early warning thresholds
of more OPs in the on-line biomonitoring system. 相似文献
150.
Zero-valent iron and iron oxide-coated sand as a combination for removal of co-present chromate and arsenate from groundwater with humic acid 总被引:1,自引:0,他引:1
The combination of zero-valent iron (Fe0) and iron oxide-coated sand (IOCS) was used to remove Cr(VI) and As(V) from groundwater in this study. The efficiency and the removal mechanism of Cr(VI) and As(V) by using this combination, with the influence of humic acid (HA), were investigated using batch experiments. Results showed that, compared to using Fe0 or IOCS alone, the Fe0-IOCS can perform better on the removal of both Cr(VI) and As(V). Metal extraction studies showed that As(V) was mainly removed by IOCS and iron corrosion products while Cr(VI) was mainly removed by Fe0 and its corrosion products. Competition was found between Cr(VI) and As(V) for the adsorption sites on the iron corrosion products. HA had shown insignificant effects on Cr(VI) removal but some effects on As(V) removal kinetics. As(V) was adsorbed on IOCS at the earlier stage, but adsorbed/coprecipitated with the iron corrosion products at the later stage. 相似文献