UNCERTAINTY OF EXTREME FLOOD ESTIMATES INCORPRATING HISTORICAL DATA1

ABSTRACT: The ability to predict extreme floods is an important part of the planning process for any water project for which failure will be very costly. The length of a gage record available for use in estimating extreme flows is generally much shorter than the recurrence interval of the desired flows, resulting in estimates having a high degree of uncertainty. Maximum likelihood estimators of the parameters of the three parameter lognormal (3PLN) distribution, which make use of historical data, are presented. A Monte Carlo study of extreme flows estimated from samples drawn from three hypothetical 3PLN populations showed that inclusion of historical flows with the gage record reduced the bias and variance of extreme flow estimates. Asymptotic theory approximations of parameter variances and covariances calculated using the second and mixed partial derivatives of the log likelihood function agreed well with Monte Carlo results. First order approximations of the standard deviations of the extreme flow estimates did not agree with the Monte Carlo results. An alternative method for calculating those standard deviations, the “asymptotic simulation” method, is described. The standard deviations calculated by asymptotic simulation agree well with the Monte Carlo results.     

GROUND AND SURFACE WATER QUALITY IMPACTS OF NORTH CAROLINA SANITARY LANDFILLS1

ABSTRACT: Ground and surface water quality monitoring data from 71 municipal sanitary landfills in North Carolina were analyzed to determine the nature and extent of current contamination problems and identify any common characteristics associated with this contamination. A total of 322 surface and 411 ground water quality records were analyzed using the SAS data system. Almost all the landfill records included inorganic and heavy metal analyses while approximately half of the records also included organic analyses by CC/MS. Our analysis indicates that landfills are having measurable impacts on ground and surface water quality, but these impacts may not be as severe as is commonly assumed. Statistically significant increases were detected in the average concentrations in ground water and downstream surface water samples when compared to upstream surface water samples. The largest percentage increases were observed for zinc, turbidity, total organic carbon, conductivity, total dissolved solids, and lead. Violations of ground water quality standards for heavy metals and hazardous organic compounds were detected at 53 percent of the landfills where adequate data existed. The moat common heavy metal violations were for lead (18 percent), chromium (18 percent), zinc (6 percent), cadmium (6 percent), and arsenic (6 percent) (percentage of landfills violating shown in parenthesis). The organic compounds that appear to pose the greatest threat to ground water are the chlorinated solvents (8 percent), petroleum derived hydrocarbons (8 percent), and pesticides (5 percent). A comparison of monitoring data from sanitary landfills and secondary wastewater treatment plants suggests that the concentrations of heavy metal and organic pollutants discharged to surface waters from these two sources are similar.     

香港的策略性污水排放计划及其进展

为了保障香港市民的身体健康,保护鱼类及其他海洋生物并提高维多利亚港的水质,必须对香港的150万m3/d污水采取处理措施,介绍了策略性污水排放计划的产生及一期工程的进展情况.     

市场经济体制下的排污收费工作

在社会主义市场经济条件下，环保的根本出路在加强法制。应在当加强和完善排污收费法制建设的同时，深化改革，引入竞争机制，并把排污收费贯穿于环境监理的全过程。     

一起倾倒汽油导致的静电燃爆事故分析

分析了深圳龙岗发生的一起燃爆事故,疑因不规范操作产生的静电放电引起。针对GB12158对该类操作提出的要求,开展相关试验研究。塑料桶加注16 L汽油的过程中,塑料桶上的静电电位最高为4.7 kV。塑料桶与聚四氟乙烯板间相互摩擦,塑料桶上的最高电位为9.4 kV。不接地金属桶加注16 L汽油的过程中,金属桶上的最高电位为-15.4 kV。汽油加注过程中,不接地金属滤网上的最高电位为-1.91 kV。以上3种操作产生的静电皆可能引发静电放电,通过分析,深圳龙岗事故是由静电放电引发。     

现行城市机动车排放控制法律调整存在的不足与对策

针对目前中国城市机动车高速发展而带来了城市大气环境污染负面问题，分析了现阶段对城市机动车排放控制存在的法律责任界定不清、执法部门权责不明、市场机制运作不完善等缺陷，提出从法律视野进行调整，充分发挥法律的规制功能和权威力量，明确行政主管部门权责，健全机动车从生产-销售-回收以及与石油等部门的市场调节机制，最终促进城市机动车尾气排放得到有效的控制，营造良好的城市环境。     

试析环境保护手段

环境问题的外部性使得环境保护需要政府的介入;环境保护的手段按照是否影响成本收益可分为经济手段与非经济手段;通过比较不同环保手段的优缺点,分析如何进行环保制度安排来实施政策措施.     

低温等离子体水处理技术的应用及其反应器的研究

利用高压脉冲放电在水中产生高密度的低温等离子体来降解水中有机物、杀灭水中病毒细菌,是集电、化学氧化、光于一体的水处理高级氧化技术。并对该技术在水处理方面应用的原理、反应器的形式以及国内外的研究进展、成果、存在的问题进行探讨。并对该技术的应用进行了展望,这是一项新兴的并具有广阔前景的水处理技术。     

炼油污水达标排放存在问题与对策

针对洛阳石化总厂炼油污水影响达标的主要因素，进行了简要分析，并就解决COD、氨氮、悬浮物等问题的对策，提出了建议。     

对《超标环境噪声排污费征收标准》的异议

依据声级测量的误差分析，结合实例，对国家现行《超标环境噪声排污费征收标准》提出异议，建议取消１ｄＢ（Ａ）的超标收费规定、舍弃测量的小数值，并定义一个考虑污染范围的评价量以使收费更加合理。