【作者】 鲁成秀；

【导师】 成杰民；

【作者基本信息】 山东师范大学 ， 自然地理学， 2016， 博士

【摘要】 重金属因其毒性大、难以生物降解、易生物富集和放大等特点,成为湖泊水体中一类被广泛研究的污染物。沉积物-水界面的重金属过程十分复杂,涉及吸附/解吸、溶解/吸收、络合/解离等一系列的物理化学作用以及生物氧化、还原、甲基化等作用,是典型的生物化学过程。在富营养化的湖泊水体中,氮、磷和重金属污染往往同时存在,重金属的沉积物-水界面行为与富营养化程度密切相关,同时富营养化湖泊又富含各种有机质和数量众多、活性强的微生物。有机质的降解、微生物的新陈代谢都会影响到重金属的形态及行为。因此,开展富营养化湖泊沉积物-水界面重金属的迁移转化规律研究意义重大。本文在国家973计划项目子课题——富营养化湖泊复合污染机理及生态毒理效应(课题编号:2008CB418204)资助下,以太湖、南四湖、白洋淀三个不同富营养化湖泊沉积物为研究对象,采用野外现场采样、室内实验分析及模拟实验相结合的研究方法,对不同富营养化程度的湖泊沉积物污染状况进行分析和评价;在形态提取法分析重金属释放潜力的基础上,模拟动态和静态两种条件,探讨两种条件下不同富营养化湖泊沉积物中重金属的释放动力学特征及规律;通过灭菌和不灭菌模拟实验,探讨富营养化湖泊沉积物-水界面重金属释放的化学过程和生物化学过程,阐明微生物在沉积物中重金属释放过程中的作用,并通过沉积物粒径、营养盐水平以及水环境温度、pH值等影响因素的研究,进一步揭示重金属界面地球化学行为的过程与机理。主要研究结果如下:(1)根据本文在三个湖泊的采样点研究得知,三个湖泊上覆水体中TN、TP浓度分别在0.31-7.74 mg/L和0.014-0.482 mg/L,水体富营养化程度处于富营养到极富营养状态。沉积物中有机质、总氮、总磷含量分别在9.45-108.10 mg/g、0.58-4.82 mg/g、0.448-2.148 mg/g;太湖沉积物有机污染属于清洁状态,南四湖和白洋淀处于污染状态。(2)沉积物中重金属含量呈现Zn>Pb>Cu>Cd的分布规律,Cd污染最为严重,Cu、Zn污染较轻。从污染负荷指数看,白洋淀重金属污染最严重,南四湖次之,太湖最轻。重金属潜在生态危害分析表明,Cd的潜在危害最大,处于极高风险状态,pb、cu、zn的潜在生态危害状态均为轻微;不同湖泊沉积物中重金属的生态风险性从高到低的排序是南四湖>白洋淀>太湖。(3)重金属释放潜力分析表明,依据单一提取剂的方法,释放潜力最大的是cd,释放潜力最小的是zn;依据连续提取法,太湖沉积物中pb的释放潜力最大,太湖cu的释放潜力在三个湖泊中也最高。南四湖和白洋淀沉积物中cd释放潜力最大,但pb的释放潜力也不容忽视。分别将连续提取法各形态含量、单一提取法提取量与重金属污染负荷指数、潜在生态风险做相关分析发现:hcl提取态cu,dtpa提取态zn和pb,cacl2提取态cd与其活性态(弱酸提取态与可还原态之和)有良好的正相关关系,可以很好地表征其释放潜力。(4)模拟动态条件下,重金属cu、zn、pb、cd的释放可分为快速释放和释放平衡两个阶段。不同采样区cu的释放量差别不大,释放率在1.5%-2.5%,cd释放强度最大,释放率在10%-37%,pb的释放率0.8%-2.5%,zn的释放不足1%。释放动力学过程用elovich方程、双常数速率方程、伪二级动力学均能显著拟合,但以伪二级动力学方程拟合效果最好。从拟合特征值看,南四湖的生活污水区重金属释放强度较大,南四湖水生植被区释放强度最低。动态条件下重金属释放特征与单一浸提法、连续提取法实验结果相关性分析表明hcl提取法可以作为一种快速简便的方法表征cu、zn的释放量。(5)模拟静态条件下,重金属cu、zn的释放特征可分为缓慢释放、加速释放、释放平衡三个阶段,cu的平衡释放量在0.2mg/kg-0.3mg/kg,zn平衡释放量在0.3mg/kg-0.5mg/kg。pb在静态条件下的释放比cu和zn要快,平衡释放量在0.15mg/kg-0.45mg/kg。比较动态和静态两种条件下重金属释放特征,发现静态条件下重金属释放速率、释放强度较动态条件下小(zn除外,zn在静态条件下释放量比动态条件下高),释放过程更加复杂。由此,要防止湖泊水体沉积物悬浮带来的重金属释放的二次风险。(6)在重金属释放的影响因素研究中,沉积物粒径对重金属释放的影响是:沉积物中小粒径含量越多,比表面积越大,对重金属的吸附量大,重金属不易释放;富营养化湖泊中磷的含量对重金属有促进吸附,抑制释放的作用;微生物对沉积物中cu、cd和pb的释放起抑制作用,对zn的释放起促进作用;重金属的释放量随ph值的增加而降低;随温度的升高,cu释放量增加,但不明显,zn的释放则是在低温条件下释放量最大。(7)沉积物中溶解性有机质的光谱特征表明,在重金属释放过程中,沉积物中DOM含量呈现先降低后又增加的趋势,主要是类蛋白色氨酸减弱或消失,而后又重新生成类富里酸或类腐殖酸。更多还原

【Abstract】 Heavy metals in lake water body are widely researched pollutants due to their higher toxicity, lower biological degradability, and higher bioaccumulation. The processes of heavy metals on Sediment-Water Interface are complex, involving adsorption/desorption, dissolution/absorption, complexation/dissociation and a series of physical and chemical effects and biological oxidation, reduction, methylation and so on, and they are a typical biochemical processes. In Eutrophic lake water, it is noteworthy that nitrogen, phosphorus and heavy metals always exist at the same time, and there are close relationships between eutrophication and pollution. Besides, eutrophic lakes are rich in a variety of organic matters and a great number of microbes which have strong surface activity. The degradation of organic matter, microbial metabolism will affect the shape and behavior of heavy metals. For these reason, the research on migration and transformation of heavy metals in sediment-water interface of eutrophic lakes has important theoretical and realistic significance to solving the issue of eutrophication and heavy metal pollution.This paper was funded by the National Basic Research Program: “Water environmental quality evolution and water quality criteria in lakes”(2008CB418200). In this paper, three different rich eutrophic lake sediments of Tai lake, Nansi lake, and Bai Yangdian were studied as the research objects. Using the combination of research methods of wild field sampling, laboratory analysis and simulation experiment, the characteristics of sediment in eutrophic lakes were analyzed and evaluated. On the basis of the analysis of heavy metals’ release potential with extraction procedure, the simulation experiments of static and dynamic working conditions was carried out to explore the release kinetics characteristics of heavy metals in different eutrophic lake sediments. Through the comparison between sterilization and non-sterilization, we explored the chemical and biochemical process of heavy metals’ release on eutrophic lake sediment-water interface, and clarified the role of microorganisms in the sediment release process of heavy metals. Furthermore, through the study of the influence factors such as the particle size, nutrient level, eternal enviornment temperature, and p H, the process and mechanism of the geochemical behavior of heavy metals on the interfaces are further revealed.The main research results are as followed :(1) In the three lakes, the concentrations of TN and TP in the overlying water were 0.31-7.74 mg/L and 0.014-0.482 mg /L separately, it showed that the lakes were in highly eutrophic status. In sediments, the contents of organic matters, total nitrogen and total phosphorus were 9.54-108.10 mg/g, 0.58-4.82 mg/g, and 0.448-2.148 mg/g respecively. The organic pollution in Tai Lake was classified to clean status, while Nansi and Bai yangdian lakes were in pollution status.(2) The distribution rules of heavy metal contents in sediments were in the sequence of Zn>Pb>Cu>Cd. In these metals, Cd pollution was the most serious but Cu and Zn pollution is slighter. From the perspective of pollution load indexs, the heavy metal pollution in Bai yangdian was the most serious, Nansi Lake was secondary polluted, and Tai Lake was the lightest. Analysis on the potential ecological risk of heavy metals in lake sediment was: Nansi lake>Bai Yanydian> Tai Lake.(3) Based on a single method of extracting agent, heavy metals release potential analysis indicated the largest release potential was Cd, and the minimum was Zn. Based on continuous extraction method, Pd in the sediments of Taihu Lake had the greatest potential to release, and Cu had the highest potential in the three lakes. In Nansi and Bai Yangdian lakes, Cd had the greatest release potential, however the Pb’s potential could not be ignored. The correlation analysis for the single extraction amount, pollution load index and potential ecological risk of heavy metals shows that, Cu extracted by HCl,Zn and Pb extracted by DTPA, and the active fractions had positive correlations(represent the potential release).(4) Under the simulated dynamic condition, the release of heavy metals Cu, Zn, Pb and Cd can be divided into two phases which is called quick release and release balance. In different sampling areas, the release quantity of Cu had insignificant difference, with release ratio from 1.5% to 2.5%. The highest release intensity was Cd, and the release ratio was from 10% to 37%. For Pb, the release rate was from 0.8% to 2.5%, and for Zn, the release was less than 1%. The release kinetics process could significantly fit Elovich equation, double constant rate equation and pseudo secondary dynamics. But the pseudo secondary dynamics equation showed the best fitting effect. From the perspective of fitting characteristics value in Nansi Lake, it had the biggest intensity of heavy metals release in domestic sewage area, but had the lowest intensity in aquatic vegetation area. Based on the correlation analysis among heavy metal release characteristics in dynamic condition, the single extraction and continuous extraction experiments showed that HCl extraction method could be uesd as a kind of quick and easy characterization of the release quantity of Cu and Zn.(5) At the simulated static condition, the release characteristics of heavy metals Cu and Zn can be divided into three phases which is called slow release, accelerated release, and release balance. Balance release quantity of Cu is from 0.2 mg/kg-0.3 mg/kg, and Zn is from 0.3 mg/kg-0.5 mg/kg. Under the static condition, the release rate of Pb whose the balance release quantity of 0.15 mg/kg-0.45 mg/kg is faster than Cu and Zn. Through the comparison of heavy metals’ release characteristics between dynamic and static working conditions, it could be found that the release rate and intensity of heavy metals under the static condition is less than that in dynamic condition(except Zn, whose release quantity is higher under static conditions than that under dynamic condition). Furthermore, the release process was much more complicated.(6) Among the influence factors of heavy metal release, the size of sediment grain can affect the release of heavy metals: the more content of small size sediment is, the bigger of specific surface area to adsorbent to heavy metals is, so heavy metals are not easy to release. The contents of phosphorus in eutrophic lakes can promote the adsorption to heavy metals. Microorganisms have inhibitory effects on the release of Cu, Cd and Pb in sediments, but have promoting effect on the release of Zn. The release quantity of heavy metals decreases with the increase of p H value. When temperature rising, the release quantity of Cu increases, which is not obvious. On the contrary, Zn releases the largest quantity at low temperature.(7) Fluorescence spectrum of dissolved organic matter in sediments show that, DOM contents in the sediments show the tendency of first decreasing and then increasing in the process of heavy metal release. This is mainly attributed to the decreasing or disappearing of protein-like and the regenerating of the fulvic acid-like or humic acid-like.更多还原