Mobilization of small DNAPL pools formed by capillary entrapment

We performed an experimental study to quantify the critical conditions for the mobilization of small pools of dense nonaqueous phase liquids (DNAPLs) that may form at capillary-heterogeneity boundaries. A series of experiments were conducted in columns packed with uniform sands arranged to create capillary heterogeneities. DNAPL pools readily formed in these packings and were more easily mobilized than trapped DNAPL ganglia. A model was developed to describe the critical conditions for DNAPL pool mobilization. Pool mobilization was expected when a dimensionless pool trapping number N(T)p> 1 while mobilization was observed in our experiments when N(T)p>0.76+/-0.16 (+/- 95% confidence interval). The difference between the model prediction and the experimental observations was attributed to experimental error. Using this model for DNAPL pool mobilization, a simple numerical experiment was conducted to illustrate use of the model and to explore the effect of scale on the critical conditions for pool mobilization. With an increase in system scale flow bypassing around the DNAPL pool increased and the system-averaged conditions for the onset of mobilization changed: a greater system-average Darcy flux or lower interfacial tensions were required for DNAPL pool mobilization. This result illustrates the importance of system scale on mobilization of DNAPL pools in systems with capillary heterogeneities.     

硝化速率法用于活性污泥活性测试的研究

以城市污水厂回流污泥中的硝化细菌(氨氧化细菌和亚硝酸盐氧化细菌)为受试生物,HgCl2为标准毒性物质,通过对两组实验--氨氧化速率实验(NH 4-N→NO-2-N)和亚硝酸盐氧化速率实验(NO-2-N→NO-3-N)的研究表明,氨氧化细菌对HgCl2的灵敏度(IC50=0.034 mmol/L)明显高于亚硝酸盐氧化细菌(IC50=0.20 mmol/L).氨氧化速率法测试活性污泥活性时,使用NH 4-N或NO-X-N指标需要120 min或更长的时间,但使用NO-2-N指标仅需30 min就可完成测试,而且结果重现性要比NH 4-N和NO-X-N好,其变异系数CV为5.9 %.     

钢渣脱除烧结烟气中二氧化硫的实验研究

通过对钢渣的分析,确定了其作为脱硫剂的可能性.从钢渣在不同操作条件下脱硫的实验研究看,钢渣能有效地脱除烟气中的SO2,在湿润状态、低流速条件下,微细钢渣的脱硫能力较强,钢渣作为脱硫剂使用将具有良好的经济效益和环境效益.     

The study of fine and coarse particles, and metallic elements for the daytime and night-time in a suburban area of central Taiwan, Taichung

Daily average concentrations of fine and coarse particulates, and TSP samples have been measured simultaneously at daytime and night-time periods by using Universal and PS-1 sampler in a suburban area of central Taiwan from June to August 1998. The samples were analyzed by atomic absorption spectrometry to determine the fine and coarse particulate concentrations of metallic elements (Ca, Fe, Mn, Pb, Cu, Zn and Cr). The concentration of PM2.5 and TSP showed a decreased trend for the daytime period. The fine particle concentrations were about two times as that of coarse particulate concentrations. The averaged fine particulate concentrations at daytime are higher than at night-time. Ca and Fe were mostly in the coarse particulate mode. The correlation coefficients were 0.63 and 0.69 for elements Ca and Fe in the coarse particle mode for day and night periods. Pb showed a similar distribution ratio with Mn for the fine to coarse particle ratios at both day and night period. Pb and Mn are highly correlated for the day (R = 0.78) and night period (R = 0.61) at particle size <2.5 microm. Cu and Zn were mainly in fine particles at both day and night period. Fe and Ca consist of the major parts of all the elements. Elemental Mn is the lowest among the rest of the heavy metals.     

Sorption and desorption hysteresis of organic contaminants by kerogen in a sandy aquifer material

Sorption and desorption hysteresis of 1,2-dichlorobenzene, 1,3,5-trichlorobenzene, naphthalene, and phenanthrene were investigated for the Borden aquifer material with total organic carbon of 0.021% and the isolated natural organic matter (NOM). The isolated NOM is a kerogen type of organic matter with relatively low maturation degree and contained many different types of organic matters including vitrinite particles. The modified Freundlich sorption capacities (logK^′_f and logK^′_foc) are very close for the sorption of the four solutes by the isolated NOM and the original sand, respectively. Isotherm non-linearity (n value) and hysteric behaviors are related to solute molecular properties (e.g. K_ow and molecular size). Kerogen encapsulated by inorganic matrices in the original aquifer may not be accessed fully by solutes. The larger the hydrophobic organic chemical (HOC) (hydrophobic organic contaminant) molecule is, the lower accessibility of the HOC to kerogen. This study disputes widely held hypothesis that sorption to mineral surfaces may play a major role in the overall sorption by low TOC (e.g. 0.1% by mass) geomaterials such as Borden sand. It also demonstrates the importance of the condensed NOM domain, even at very low contents, in the sorption and desorption hysteresis of HOCs in groundwater systems.     

S絮凝剂急性和亚慢性毒性研究

对原水处理剂Ｓ絮凝剂进行了大鼠急性毒性和９０ｄ喂养试验。Ｓ絮凝剂大鼠经口半数致死量雄性为８７１０ｍｇ／ｋｇ，Ｂ．Ｗ．，雌性为１０９６５ｍｇ／ｋｇＢ．Ｗ．，属实际无毒类物质。９０ｄ喂试验结果表明，剂量≥０．８％，时对大鼠生长发育，血液学、生化学及病理组织学等各项指标水见有不良影响，Ｓ絮凝剂最大无作用剂量为０．８％，相当于实际作用量的１０００倍。     

水生毒理联合效应相加指数法

在水体中往往是多种污染物共存，它们彼此相互影响，产生协同、加合或拮抗作用。本文以联合效应相加指数法研究污染物对水生生物的毒性作用。     

面向可持续发展的水资源管理问题的探讨

可持续发展战略已引起世界各国的普遍重视和关注。本文从可持续发展的角度，对水资源的状况和水资源管理政策进行了分析，提出了二十一世纪面向可持续发展的水资源管理原则、管理模式和对策。论文的研究对改进我国的水资源管理具有重要意义。     

瓜尔豆胶废水预处理的方法研究

根据瓜尔豆胶在生产食品添加剂的过程中产生的废水COD的值高达216000mg/的特点，分别用如下方法进行处理①调pH=6．84，按0．5％质量比加入活性炭吸附荆，静止20天，此时去除率为87．7％；②用饱和硫酸铝2mL＋适量的聚丙烯酰胺絮凝，去除率为36．5％；③原液先蒸馏出1／4体积后在釜液中按3％的质量比加入Ca（OH）2，计算去除率为89．6％④利用铁炭屑以5：1的质量比形成微电池的方法作用两小时后再按3％的质量比加Ca（OH）2絮凝，此条件下去除率高达91．7％。经过比较得出第四种方法是最经济有效的，对该特种废水起到了很好的预处理作用。     

北京市轻型汽车尾气排放检测结果分析

对北京市566辆在用轻型车排放尾气进行了BASM检测，对不同厂牌的化油器车、化油器改造车和电喷车排放的HC、CO和NO平均浓度进行了比较，结果表明，化油器改造车3种污染物平均浓度比化油器车低50％左右，电喷车3种污染物平均浓度可比化油器车低80％左右。同时对几种车型的劣化规律进行了分析，发现化油器车的劣化关系离散性大，而另外两种技术的车辆的劣化关系呈收敛性，说明化油器车的污染物排放和保养关系密切，电喷车劣化规律明显优于化油器车和化油器改造车。实验结果为I／M实施提供了科学依据。