太湖水体中的胶体态痕量金属及其影响因素研究

【作者】 张战平；

【导师】 楼章华； 朱广伟；

【作者基本信息】 浙江大学 ， 环境科学， 2006， 博士

【摘要】 胶体是物质的一种存在状态,在天然水体中是普遍存在的,并有着极其重要的环境意义,近年来越来越受到环境学界的广泛关注。本文利用目前国际上流行的切向流超滤(CFF)技术分离并获取了太湖水体中的胶体浓缩液,在研究其胶体有机碳(COC,1kD～1μm)的基础上对其水体中的胶体态痕量金属(Cd、Cu、Pb、Fe、Mn和Zn,1kD～1μm)进行了系统地、开创性地研究。本文的主要研究内容及结论如下: 1 探讨了太湖典型湖区的COC含量及其季节变化,揭示出:①作为浅水湖泊的太湖,其春季水体COC浓度为1.79mg/L～2.05m/L,比河流低,但比海洋、海湾及河口等水体高。太湖水体中的COC在总溶解有机碳(DOC)中的比例较低,仅为8.11%～22.13%。②作为藻型湖区的梅梁湾,其COC含量夏季最高,秋季最低,而作为草型湖区的贡湖湾,其COC含量在秋季最高,冬夏季较低,季节变幅较小;春季梅梁湾和贡湖湾COC含量没有大的差别,冬、夏季梅梁湾COC含量高于贡湖湾,秋季贡湖湾COC含量又高于梅梁湾。③浮游生物尤其是浮游植物的生命活动可能是太湖水体COC的主要来源。风浪的扰动作用对太湖表层水中的浮游生物现存量和悬浮物浓度有较大影响,进而可对表层水中COC含量产生直接或间接影响,在风速的衰减期,风浪的扰动作用和太湖表层水中COC含量存在一定的负相关关系。 2 探讨了太湖典型湖区胶体态痕量金属的含量及其季节变化,揭示出:①太湖春季水体中胶体态Cu、Zn、Pb、Fe、Mn和Cd的浓度分别为0.46～0.86μg/L、2.06～8.24μg/L、2.62～3.70μg/L、3.48～24.79μg/L、0.31～1.62μg/L和6.71～17.94ng/L,比海洋、小的河流及泻湖等水体高,但比大的河流低;平均分别占各自总溶解态的22.3%、26.3%、20.7%、58.9%、40.4%和59.2%;胶体态Cu、Pb、Fe、Mn和Cd平均分别占各自总量的17.4%、19.1%、55.1%、1.98%和52.8%,表明太湖水体中的胶体在痕量金属的生物地球化学循环中有着重要的意义。②太湖典型湖区水体中痕量金属的胶体态含量以及不同湖区之间的差异有较大的季节变化。梅梁湾胶体Pb含量在春季最高,夏季最低,其余的元素Cd、Cu、Fe、Mn和Zn的胶体态含量一般都是春季较低,而秋冬季较高:贡湖中胶体pb含量在春季最高,秋季最低,其余元素Cd、Cu、Fe、Mn和Zn的胶体态含量都是在冬季最高,其它更多还原

【Abstract】 Colloidal phase is an existing form of substances. In recent years, more and more environment scientists have focused on colloids in natural waters because their important environmental significances. In this paper, colloidal concentration was isolated from water samples of Lake Taihu by using cross-flow ultrafiltration(CFF) technique. And colloidal trace metals(1kD-1μm), such as Cd, Cu, Pb, Fe, Mn and Zn in Lake Taihu were inaugurally investigated based on the study of colloidal organic carbon(COC, 1kD-1μm) in it. This thesis includes the contents and conclusions as follows:1 Contents and seasonal changes of COC in typical lake zones of Lake Taihu were discussed in this paper. It was revealed that (a) COC concentration in Spring Lake Taihu, which is a large shallow lake, ranged from 1.79mg/L~2.05mg/L, accouting for 8.11%~22.13% of dissolved organic carbon(DOC). And COC concentration in Spring Lake Taihu was lower than those in rivers but higher than those in ocean and estuaries, (b) Contents of COC in Meiliang Bay, an algae lake zone of Lake Taihu, were highest in Summer and lowest in Autumn. But contents of COC in Gonghu Bay, a macrophyte lake zone of Lake Taihu, were highest in Autumn and lower in Summer and winter. There were no significant differences in COC concentration in Spring between the two zones. However, COC concentrations in the former were higher than those in the latter in Summer and Winter but lower in autumn, (c) Life activities of plankton, especially phytoplankton, may be the main sources of COC in Lake Taihu. And wind-wave disturbance can have direct or indirect effects on COC concentration in surface water of Lake Taihu because it can significantly influence the number of plankton and contents of suspended solids(SS) in surface water of Lake Taihu. In the period of wind attenuation, there was negative correlation relation between wind-wave disturbance and COC concentration in surface water of Lake Taihu to a certain extent.2 Contents and seasonal changes of colloidal trace metals in typical lake zones of Lake Taihu were discussed in this paper. It was revealed that (a) contents of colloidal trace metals in Spring Lake Taihu were 0.46-0.86 μg/L (22.3% of the totally dissolved partition) for Cu, 2.06-8.24 μg/L (26.3%) for Zn, 2.62-3.70 μg/L (20.7%) for Pb, 3.48-24.79 μg/L (58.9%) for Fe, 0.31-1.62 μg/L (40.4%) for Mn, and 6.71-17.94 ng/L (59.2%) for Cd. And averagely, the colloidal Cu, Pb, Fe, Mn, and Cd occupied 17.4%, 19.1%, 55.1%, 1.98%, and 52.8% of their total contents in lake water respectively. By comparison, contents of colloidal trace metals in Lake Taihu were higher than those in ocean, shorter rivers, and lagoons etc., but were lower than those in longer rivers. These indicated that the colloidal material in Lake Taihu was an important factor influencing the biogeochemical cycling of trace metals, (b) There were significant seasonal changes in contents of colloidal trace metals in typical zones of Lake Taihu, so were differences of contents of colloidal trace metals between different lake zones. As far as Meiliang Bay was concerned, contents of colloidal Pb were highest in Spring and lowest in Summer, and contents of colloidal Cd, Cu, Fe, Mn and Zn were lower in Spring and higher in Autumn and Winter. For Gonghu Bay, contents of colloidal Pb were highest in Spring and lowest in Autumn., and cotents of colloidal Cd, Cu, Fe, Mn and Zn were allhighest in Winter and lower in other seasons. Cotents of colloidal trace metals in Meiliang Bay were mostly higher than those in Gonghu Bay in each season, which may be due to the serious heavy metal pollution of Meiliang Bay. Moreover, proportions of colloidal Cd, Pb, Mn and Zn in each dissolved phase and total content in Meiliang Bay were all higher than those in Gonghu Bay. And differences of contents of colloidal trace metals between the two lake zones were insignificant in Spring except for Zn.3 In a process of wind wave, changes of concentrations of colloidal trace metals in Lake Taihu were discussed. And it was revealed that Contents of colloidal Mn, Cu and Pb were directly proportional to the intensity of the wave-wind disturbance. But Contents of the colloidal Zn were inversely proportional to it. However, contents of colloidal Fe were affected by COC primarily and the content of total Fe secondly. And they were fundamentally influenced by the wind-wave disturbance but had no evident and direct relation with it. Concentrations of colloidal Cd had no evident relation with contents of COC, total Cd concentrations and the wind-wave disturbance.4 Effects of hydrodynamic disturbance on contents of colloidal tace metals in Lake Taihu were studied simulatively. It was revealed that contents of colloidal trace metals in the overlying water were all increased continuously after disturbance began, being highest after 22 hours. Hereafter, contents of colloidal trace metals were fluctuantly decreased during the last period of disturbance and settlement except for Zn. The model experiment also indicated that contents of colloidal Cd in the overlying water were directly proportional to the intensity of hydrodynamic disturbance, which made up for the lack of field investigations. Contents of colloidal Cu, Pb and Mn in the overlying water were also directly proportional to the intensity of hydrodynamic disturbance to some extent. But there were no evident and direct relations between contents of colloidal Fe in the overlying water and the intensity of hydrodynamic disturbance. These verified the results of field investigations. The negative relation between contents of colloidal Zn and the intensity of wind-wave disturbance, which was found in the former field investigations, was also reflected to a certain extent in the model experiment.5 Influencing factors of contents of colloidal trace metals in Lake Taihu were also discussed in this paper. It was found that there were significant or extremely significant positive correlation between colloidal phase contents of trace metals and their total concentrations in Lake Taihu. These indicated that contents of colloidal trace metals in Lake Taihu were mainly controled by their total concentrations, which may be due to the higher contents of COC in Lake Taihu. As adsorbers, COC and inorganic colloids(mainly Fe and Mn oxide) also were not negligible factors. Wind-wave disturbance could have direct and indirect effects on contents of colloidal trace metals in Lake Taihu, and was a radical influencing factor.更多还原