PCBs and its coupling with eco-environments in Southern Yellow Sea surface sediments

In this paper, the spatial distribution and source of the PCBs in surface sediments of the Southern Yellow Sea (SYS) and influencing factors, such as the sediment characteristics (components, relative proportions and total organic carbon contents), and hydrodynamic conditions were analyzed. PCB concentrations in the surface sediments ranged from 518-5848 pg/g, with average values of 1715 pg/g decreasing sharply compared to last year. In the study area, the PCB pollution level in the middle area was the highest, followed by that of the east coast and the west coast, respectively. Although the PCB level in the coastal areas was lower than that in the middle areas, it was proven in our study that the Yellow Sea obtained PCBs by virtue of river inputs. There was a positive and pertinent correlation between the clay proportion and PCB concentrations, and the increase of the PCB concentrations was directly proportional to the increase of TOC contents, with r = 0.61, but it was contrary to the sediment grain size. Consequently, the factors controlling PCB distribution had direct or indirect relationships with sediment grain size; moreover, the hydrodynamic conditions determined the sediment components and grain size. In conclusion, hydrodynamic conditions of the Yellow Sea were the most important influencing factors effecting the distribution of PCBs in the surface sediments of the SYS. (C) 2007 Elsevier Ltd. All rights reserved.

一种先进的轻型水下机器人——金鱼Ⅲ号

本文叙及一种新的轻型水下机器人(亦称无人遥控潜水器或ROV)——金鱼Ⅱ号。概要地描述了它的主要技术特点,系统总体结构,简要工作原理,及其适用范围。文中以在丰满电站进行实际作业为例,说明了该型水下机器人的应用前景。

乌江流域水库水体中溶解性气态汞季节变化特征

选取乌江流域上两个典型的水库( 乌江渡水库和东风水库) 作为研究对象, 对不同季节水库水体中溶解性气态汞进行研究。结果显示: 两个水库溶解性气态汞均明显表现为上层水体﹥下层水体, 夏季﹥春季、冬季。水库中溶解性气态汞的含量受太阳辐射和水体中溶解性有机碳两个因素共同控制。

针式微萃取结合GC-IRMS测定水溶液中甲酸、乙酸的稳定碳同位素组成

甲酸和乙酸稳定碳同位素组成（δ^13C）的分析对环境、食品、制药和自然产品等的研究具有重要的应用价值。但目前尚缺乏有效的测定方法。本研究利用最近出现的针式固相微萃取技术（NeedlEX），以吹扫．捕集方式对水溶液中的有机酸进行了萃取，然后利用气相色谱．同位素比值质谱联用仪（GC—IRMS）对所萃取的有机酸分子进行了占δ^13C的测定。结果显示，质谱计的信号强度与水溶液中有机酸的浓度存在显著的线性相关关系（R^2〉0．99，P〈0．05），表明Needl EX对水溶液中有机酸具有稳定的萃取能力。在甲酸与乙酸含量分别不低于300μg／mL与200μg／mL的水溶液中，1000mL的吹扫体积可以使两者δ^13C多次分析结果的相对误差分别保持在3％和1％左右，且整个实验流程没有造成可检测的碳同位素分馏作用。低于这两个浓度界线，则分析误差随浓度的降低迅速增加。本研究虽然是针对水溶液中有机酸δ^13C的测定，其萃取方法对其他水溶性挥发和半挥发有机物δ^13C的分析也同样具有应用价值.

Low temperature specific heat and thermal stability of Fe-B ultrafine amorphous alloy particles

Fe-B ultrafine amorphous alloy particles (UFAAP) were prepared by chemical reduction of Fe3+ with NaBHO4 and confirmed to be ultrafine amorphous particles by transmission electron microscopy and X-ray diffraction. The specific heat of the sample was measured by a high precision adiabatic calorimeter, and a differential scanning calorimeter was used for thermal stability analysis. A topological structure of Fe-B atoms is proposed to explain two crystallization peaks and a melting peak observed at T=600, 868 and 1645 K, respectively.