风浪扰动下南四湖沉积物Hg和Pb的动态迁移及其定量化研究

Dynamic transfer process and their environmental effects of pollutants at sediment-water interface have become the research hotspot in recent years. After wind-wave disturbance stopping, the heavy metals adsorped in the suspended matter might be redistributed and produce negetive effect on the ovlying water again during the depositon process of the suspended solid, while researches on transform of heavy metals between sinks and sources and their dynamic loadings now are little, and mainly focus on resuspension process, and less involved in sedimentation process. Such being the case, it will be more meaningful to conduct research combining the above two processes. In this study, taking Nanyang areas of Nansi Lake, highly polluted by Hg and Pb, as the research object, with the help of wind velocity tester, Y-shape sediment resuspension simulation apparatus,and the utilization of modern analysis methods of atomic fluorescence analysis, ICP-OES analysis and micro electrode analysis etc, the dynamic tranfer process of Hg and Pb at sediment-water interface under different winds and waves will be studied by simulating the resuspension and sedimentation behavior of intact sediment cores. Binding with the change of physical and chemical parameters in sediments-interstitial water-overlying water profile, the rules on dynamic transform of Hg and Pb and its mechanism are explored, and the dynamic internal Hg and Pb loadings under different winds and waves are evaluated. The results of this study will provide scientific basis for water quality protection and treatment of the east line for the national South-North Water Transfer Project.

沉积物-水界面污染物动态迁移过程及其环境效应近年来成为研究热点。风浪等动力扰动停止后，悬浮物沉降过程中，其吸附的重金属可能会进行再分配，对上覆水体产生二次影响。然而，目前关于重金属源/汇关系转换及其动态负荷的研究较少，且主要集中于再悬浮过程，而对于悬浮后的沉降过程则少有涉及，将两个过程结合起来进行研究更具意义。本项目拟以Hg和Pb污染较为严重的山东南四湖南阳湖区为研究对象，借助现场风速测定仪和Y型沉积物再悬浮模拟装置，利用原子荧光分析、ICP-OES分析和微电极测定等现代分析手段，通过对沉积物原柱样的再悬浮及沉降过程模拟，研究不同风浪扰动强度下该湖区典型重金属Hg和Pb在沉积物-水界面的动态迁移过程，结合沉积物-间隙水-上覆水剖面理化指标的变化，探讨Hg和Pb源/汇动态转化的规律及其驱动机制，并估算不同风浪作用下南阳湖区Hg和Pb的迁移量，为国家南水北调东线输水水质保障与治理提供科学依据。

随着对湖泊外源污染负荷控制力度的加大，来自湖体内部的内源负荷发生及贡献份额问题引起人们广泛关注，其中有关浅水湖的内源动态负荷成为了近些年来这一研究的重要热点。本研究以Hg和Pb污染较为严重的山东南四湖南阳湖区为研究对象，以现场不同风浪条件下悬浮物垂向分布为模拟切入点，在不破坏原状柱样沉积物理化性质的基础上，模拟不同风浪强度下湖泊水柱中Hg及Pb在颗粒物再悬浮和沉降过程中的变化行为，估算其不同风浪条件下的动态负荷。具体研究方法为：在南四湖南阳湖区风情统计基础上，确定风速过程和划分大中小风浪级别的风速范围，以河口区和湖心区为代表性区域，采用Y型再悬浮发生装置，研究风浪过程和沉降过程中水体悬浮物、Hg和Pb动态负荷的变化规律及其空间和季节性差异。主要研究结论如下：.在动力扰动阶段，水体悬浮物量随风浪过程呈增加趋势，其增量对风浪强度有正响应关系。南阳湖沉积物再悬浮特性区域差异明显，大风扰动下湖心区与河口区沉积物悬浮物增量分别为3203g/m2和1290g/m2。冬季水面大量菹草覆盖，沉积物再悬浮量冬季明显高于夏季。在动力沉降阶段，悬浮物含量普遍逐步减少，其中在最初4h下降最为显著。在不同风浪扰动条件下，南阳湖区表层沉积物侵蚀深度在0.09mm-13.73mm之间。Hg和Pb的动态含量在空间（湖区）上存在较大差异，泗河河口区沉积物、间隙水Hg含量较湖心区高，具有较高迁移性，在风浪扰动下，水柱中Hg浓度呈增加趋势，超过1ug/L，为劣Ⅴ类水质标准，存在较大生态风险；Pb含量相对较低，风浪等动力扰动下，水柱中Pb浓度均在10ug/L以下，为Ⅰ类水质标准，潜在风险较小。.