Toxicity bioassay of heavy metals in water using Tetrahymena pyriformis

The toxicities of five heavy metal compounds on the survival of the ciliated protozoan Tetrahymena pyriformis were determined. Three-day old cultured cells were exposed to five concentrations of each test compound in one or more of three water series; distilled, soft, and hard water. A culture of each sample was placed in a plastic petri dish and covered with mineral oil to prevent evaporation. The cells were counted initially, then again at 0·5 h, 1 h, 2 h, 1 day, 2 days, 3 days, and on the fourth day. Lethal threshold concentrations and tolerance limit medians were determined by graphic methods. On a weight bases cadmium was most toxic, followed in decreasing toxicity by mercury, cobalt, zinc, and lead. Compared to similar fish data, all heavy metals were more toxic to T. pyriformis except lead. The toxicity of lead in soft versus hard water exemplified an antagonistic effect with greater than seven times the amount of lead necessary in hard water to produce comparable mortality as lead in soft water. On the other hand, the toxicity of mercury is about twice as great in hard water as in soft water (a synergistic effect). T. pyriformis appears to be a more sensitive indicator than fish of heavy metal contamination of water. T. pyriformis bioassay should prove a good means of determining the existence of many water pollutants.     

The uptake of heavy metals by epiphytic bacteria on Alisma plantago-aquatica

Bacterial epiphytes on the surface of the fresh-water plant Alisma plantago-aquatica collected from a polluted river were found to be a major factor in contributing to the total metal concentrations of the plant. The removal of epiphytes from the leaf surface resulted in significant reductions in the concentrations of Cr (reduced by 15–50%), Cu (30–35%), Fe, Pb, and Zn (10–50%). While numbers of epiphytes and concentrations of heavy metals increased in samples collected from polluted water compared with from unpolluted water, the fraction of metals held by the epiphytes appeared to remain similar for all samples.     

魏秋良 虚怀谋大略

舍得—— 舍得舍得 先舍后得 不舍不得 大舍大德 记者：投资1600万元，征地60亩，如此大规模的扩大再生产，我想这绝不是魏总心血来潮。     

Particles and vegetation: implications for the transfer of particle-bound organic contaminants to vegetation

This paper presents a comprehensive review of the mechanisms responsible for the transfer of atmospheric particulate deposition and soil particulate re-suspension onto vegetation. The nature of atmospheric aerosols and dry/wet particulate deposition are reviewed, together with information from the literature on radionuclides as tracers of the air particle/soil particle to vegetation transfer processes. Information from these fields is used to make inferences about the potential significance of these pathways in supplying particle-bound semi-volatile organic chemicals (e.g. polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls) to vegetation. Retention of compounds on particles brought to the above-ground plant surfaces is discussed. In the absence of definitive field/experimental studies, calculations are made drawing on the literature data to estimate the contributions of atmospheric and soil particle-bound organic contaminants to the plant concentration. These show that depending on the site-specific, species-specific and compound-specific scenarios considered, particulate-bound inputs may be negligible or may dominate the supply of organic contaminants to the above-ground portion of plants. However, field/experimental studies and direct measurements are needed to provide reliable quantitative data on this topic.     

建筑门窗制作与安装工程的质量控制

门窗工程的质量已经影响了整个建筑物的工程质量.本文主要论述了门窗工程中制作与安装的质量控制.     

市场经济下的城市设计:实践基础、利益主体、实践平台

该文论述了竞争的市场经济环境与法治化的社会环境是市场经济下城市设计的实践基础,阐明了市场经济下城市设计实践的利益主体--政府、开发商与公众,并依据利益主体及城市设计师职能的不同,建构城市设计的实践平台.各利益主体与城市设计师组成城市设计实践团队,实践团队中城市设计师的作用在于协调各方利益,实现城市建设的经济效益、环境效益与社会效益的共赢.     

城建档案信息资源的开发

随着人类社会发展的日新月异,高新科技产业化的进程加快,现代科技在各行各业的渗透以及在全市、全国乃至全球范围的迅速扩散,人类正走向信息     

我国建设工程合同风险管理研究

改革开放以来，我国建筑业引入了竞争性的招投标制度，在建设项目的投资方和建设方之间建立起了承发包合同关系，这些改革极大地促进了我国建筑业的市场化水平，提高了建筑业的生产率。然而，合同履约不良的现象屡有发生，这直接影响了建设项目的投资控制、进度控制和质量控制，导致工程合同纠纷频繁、建筑业竞争无序。近来，一些地方甚至出现了严重的工程质量问题，工程拖欠款问题也积重难返。     

洛克忠告：制度必须简单而严肃

◇哲理故事◇在17～18世纪,英国的许多犯人被遣送到澳大利亚流放服刑,私营船主接受政府的委托承担运送犯人的任务。刚开始,     

A semiautomated procedure for the determination of phosphorus in water, waste waters and particulates

Improved procedures for the determination of total dissolved phosphorus (TDP), particulate phosphorus (PP) and dissolved inorganic orthophosphate (DP) are described. Organic particulate material is solubilized in 5 n NaOH, and phosphorus compounds are oxidized and mineralized to orthophosphate by persulfate digestion. DP is determined by an improved automated molybdenum blue procedure that does not require sample pH adjustment or a correction for silicate interference in the 0–50 mg Si 1^?1 range. The use of 36-position digestion racks allows 32 TDP or PP samples to be digested in ca. 1 and 4 h respectively. Detection limits in μg of phosphorus 1^?1 are DP, 2; TDP, 5; and PP. 1. Waste water samples were analyzed for TDP and PP by the nitric acid-sulfuric acid procedure and by the proposed method. There was no significant difference between the two sets of data (P > 0.45).