富里酸对重金属在沉积物上吸附及形态分布的影响

以连续碱提取法获得的乌梁素海沉积物中的富里酸为基础,以原状沉积物和去除有机质沉积物为吸附剂,开展了富里酸对重金属在沉积物上吸附行为和形态分布的影响实验研究.结果表明,有机质的去除和富里酸的添加对沉积物吸附重金属均有一定影响;未添加富里酸条件下,有机质的去除对Cu~(2+)影响最大,可导致沉积物对Cu~(2+)的吸附率下降17.85%;随富里酸添加量的增加,2种沉积物对重金属离子的吸附率均逐渐降低,下降速率表现为Cu~(2+)?Cd~(2+)Zn~(2+)Pb~(2+);当富里酸添加量超过5%时,富里酸逐渐成为影响重金属离子吸附率下降的主导因素;随富里酸添加量的增加,原状沉积物和去除有机质沉积物中重金属的形态分布均有明显变化,添加富里酸增加了体系中H~+的浓度,H~+能够置换碳酸盐结合态金属,使碳酸盐结合态金属从沉积物中释放出来,从而导致重金属的碳酸盐结合态与富里酸添加量呈显著负相关,重金属的有机硫化物结合态含量与富里酸添加量呈显著正相关,Cd因亲有机性较弱,其有机硫化物结合态的含量最低且变化幅度最小.     

40.5kV真空灭弧室内部电场强度分布的仿真分析

40.5 kV/2.5 kA/63 kA真空灭弧室作为363 kV/5 kA/63 kA快速断路器串联模块的子单元,研究其内部电场强度分布以确保其绝缘性能,对于整套快速断路器装置的安全可靠运行尤为重要。根据实际参数搭建了40.5 kV真空灭弧室的基本模型,利用Ansoft 有限元计算仿真软件搭建了40.5 kV真空灭弧室的仿真模型,进行了电场强度分布的仿真计算,得到了灭弧室中的动触头台阶倒角区域、动触头倒角区域、静触头台阶倒角区域、静触头倒角区域的电场强度最大,最有可能发生击穿的结论。提出了通过改变台阶倒角和触头倒角以改善电场分布进行优化设计的建议,并利用Ansoft 仿真软件进行改变台阶倒角值和触头倒角值后的仿真计算,得到了触头台阶处倒角取值2mm、动静触头倒角2mm或3mm的设计较优,只设置1个触头片时触头倒角取值3 mm设计较优。     

Seasonal succession and diversity of phytoplankton in a eutrophic lagoon (Liman lake)

The seasonal succession, composition and diversity of phytoplankton in a eutrophic lagoon (Liman lake) were studied between January 2002 and November 2003. Samples were collected from surface water and deeper (1 m depth) at stations and species diversity (Shannon-Weaver, H) and evenness were calculated. Shannon Diversty was similar at Station 1 and Station 2. Minimum and maximum diversity values (0.101 and 0.765 bits. mm3) were recorded in June and July 2003 at Station 2. Cluster analysis and NMDS (Non metric multidimensial scaling) were applied to the phytoplankton community. The lagoon exhibits high conductivity (7211-10757 microScm(-1)), mean temperature of 17.7 degrees C, varying concentrations of dissolved oxygen (3.3-8.4 mg l(-1)). Light, temperature, rainfall, turbidity and salinity were expected to be the main factors affecting the seasonal succession. The seasonal succession of phytoplankton were similar at surface water and 1 m depth. A total of 130 taxa belonging to Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Dinophyta, Xantophyta, Chrysophyta and Cryptophyta divisions were identified. Pseudanabaena limnetica, Kirchneriella obesa, Kirchneriella lunaris, Ankistrodesmus falcatus and Ankistrodesmus spiralis were highly represented.     

山西关帝山神尾沟植物群落物种多样性与环境关系的研究I．丰富度、均匀度和物种多样性指数

以89个植物群落调查样地数据为基础,运用8个多样性指数对山西关帝山神尾沟物种多样性与环境之间的关系进行了分析.（1）群落总的表现为多样性和均匀度随海拔升高而下降,丰富度从1700m下降到2400m后开始升高;（2）群落不同层次表现为乔木层和灌木层多样性、丰富度和均匀度随海拔升高而下降,草本多样性和均匀度表现为上升趋势,丰富度下降到1900m后开始上升;（3）乔灌草三者多样性和丰富度指数值以及变化幅度都表现为草本层>灌木层>乔木层,三者均匀度相差不大;（4）群落不同坡向表现为阳坡多样性和丰富度都大于阴坡,均匀度相差不大.图6参7     

Spatial and Seasonal Variations of Disinfection Byproducts (DBPs) in Drinking Water Distribution Systems of Istanbul City,Turkey

This study presents the seasonal and spatial variations of trihalomethanes (THMs) and haloacetic acids (HAAs) in 30 sampling points within three water distribution systems of Istanbul City, Turkey. The effects of surface water quality, seasonal variation, and species differences were examined. The occurrence of chlorinated THMs and HAAs levels was considerably lower in the system in which raw water is subjected to pre-ozonation versus pre-chlorination. Seasonal analysis of the data indicated that the median concentration of four THMs (THM₄) was higher than nine HAAs (HAA₉) concentrations in all three distribution systems sampling points. For all distribution systems monitored, the highest median THM₄ and HAA₉ concentrations were observed in the spring and summer season, while the lowest concentrations of these disinfection byproduct (DBP) compounds were obtained in the fall and winter period. Due to the higher level of bromide in supplying waters of these two systems, moderate levels of brominated DBP species have been observed in the Kagithane and Buyukcekmece distribution systems districts. In fact, Spearman partial correlations (Spearman rank correlation coefficients [rs]) tend to be higher among analogues in terms of number and types of substituent, especially TCAA with TCM (rs 0.91), and DBAA with DBCM (rs 0.90). In contrast, the hydraulic (residence time and flow rate) and chemical mechanisms (hydrolysis, volatilization, and adsorption) affect the fate and transport of DBPs in distribution systems. Seasonal and spatial variations of DBPs presented in this study have important implications on regulatory issues and from an epidemiological point of view.