铁铝泥钝化沉积物重金属的机制与效应

The release of heavy metals from sediments can cause secondary pollution in lakes, destroying water environment and aquatic ecosystem. It is therefore an urgent issue to control the internal pollution of heavy metal in lake sediments. In this work, drinking water treatment residuals (WTR), a kind of safety by-products discharged from potable water production, is used as the adsorbent. The mechanism and effect of WTR on inactivation of heavy metals in the sediments of Lake Baiyangdian are investigated, for which Cd, Pb, Cr, Zn, As and Cu are analyzed by fractionation, microbiological analysis and ecotoxicity assay in laboratory- and field-scale tests. On one hand, the mechanism is determined by analyzing how each metal attaches to WTR and by clarifying how the competitive effects occur among multiple metals; on the other hand, the biological influences of WTR application are measured by examining the evolution of microflora and the reduction of toxicity to organisms in different trophic levels. From the perspectives of morphology, stability and toxicology, it is expected to bridge the gap between laboratory-based scientific development and real world field application of WTR. The in situ remediation method and technology could be established based on the long-term observation of the stability of heavy metals inactivation. The research will produce a win-win strategy for controlling heavy metal release from lake sediments by using WTR, as well as theoretical guidance and technical support for internal heavy-metal pollution control, water quality safety and water resources protection.

沉积物中重金属释放会对湖泊造成二次污染，破坏湖泊水环境和水生态，因此，有效控制湖泊内源重金属污染已经成为迫切需要解决的科学问题。本项目以给水处理过程的安全副产物（WTR）为吸附和钝化材料，研究其对沉积物中重金属的钝化机制与效应。以白洋淀沉积物中镉、铅、铬、锌、砷、铜为研究对象，采用分级提取、微生物分析和毒性检测等方法，通过室内实验和现场实验，探究WTR对不同重金属的吸附特征以及多种重金属竞争吸附的特点，确定WTR钝化沉积物重金属的作用机制；研究钝化前后沉积物微环境的演变特征以及不同营养级水生生物毒性的削减效果，确定WTR钝化沉积物重金属的生物效应。从形态学、稳定性和毒理学角度，揭示WTR钝化沉积物重金属的长期稳定性，并建立相应的原位修复技术方法。提出利用WTR控制沉积物重金属释放的“以废治废”的调控策略，为湖泊内源重金属污染控制、水质安全和水资源保护提供理论指导与技术支撑。

本项目以给水处理过程的安全副产物（WTR）为吸附和钝化材料，分别从单种和复合重金属污染的角度出发，确定了WTR对单种与多种重金属的吸附特征与机制。选取沉积物中Cd、Co、Cr、Pb和Zn为研究对象，考察了WTR对多种重金属的同步钝化，摸清了不同环境因子对钝化的影响，从重金属再分配、形态特征、浸出毒性及生物可给性等方面系统评估了钝化效果与稳定性。并且分别从微生态特征变化与不同营养级水生生物响应的角度，确定了WTR对沉积物微环境的影响以及沉积物钝化对生物毒性的削减与效应。主要成果有：.（1）WTR对单一或多种重金属的吸附效果与机制。WTR对Cd和Co的最大吸附量分别为35.4 mg/g和17.3 mg/g。被吸附的Cd主要以酸溶态和残渣态存在，形成Fe-O-Cd结构；Co以酸溶态为主，形成Fe(Al)-O-Co结构。不同pH、离子强度与有机酸条件下，均能较好的吸附重金属。竞争吸附过程中，出现“过饱和点”，Cd较Co优先吸附。.（2）WTR对沉积物中Cd、Co、Cr、Pb和Zn的钝化效果。钝化后，金属的释放量降低，Cd、Cr和Zn的残渣态比例升高，Cd和Pb生物可给性降低，Cd、Co、Cr、Zn浸出毒性降低40%以上。环境因子（腐殖酸、钾离子、钙离子、温度）对钝化过程中各金属的活性影响有一定差异，可能会造成Zn的释放（40%）。.（3）WTR应用对沉积物中微生物的影响。WTR应用会促使沉积物中总菌结构发生改变，提高它在沉积物中的丰度，但对它的多样性影响较小。同时会提高沉积物中AOB的丰度，有益于沉积物中好氧氨氧化作用的进行。.（4）WTR应用对不同营养级水生生物的影响。WTR修复前后沉积物对小球藻的生长表现出抑制作用，磷缺乏是抑制的主要原因，补充磷酸盐后抑制效应能快速消除；修复前后沉积物对大型蚤的生长和繁殖表现出促进作用；WTR不仅促进A. fischeri的发光和生长，而且降低了沉积物毒性。