贵州湖泊沉积物中硫与重金属和营养盐耦合循环的微生物地球化学过程及其水质影响

Lakes in Guizhou Province have long been polluted by acid deposition, industrial and agricultural waste water and domestic sewage, which leads to the complex pollution of SO42-, heavy metals and nitrogen-phosphor nutrients in the lakes. At present, studies on the geochemical processes of coupling cycles of sulfur, heavy metals and nutrients and water quality effects in sedimentary environments of lakes in Guizhou Province are limited. Selecting Caohai lake, Hongfeng lake, Baihua lake and Aha lake as study subject, this project will collect samples of sediments and water at different time and space, and sulfur forms and isotopic compositions, the dominant group, quantity and functional activity of sulfate-reducing bacteria, and the contents of heavy metals and nutrients will be analyzed in lake sediments. Combining the measurement of dissolved oxygen, pH, organic matter, dissolved metals and water chemistry compositions, the water pollution will be evaluated based on the forms and contents of sulfur, heavy metals and nutrients in lake sediments and overlying water. The aim of this project is to elucidate the relationships between sulfate reduction drived by sulfate-reducing bacteria and fixation, dissolution and mobilization of heavy metals and nutrients in lake sedimentary environments and their effects on water quality. The research results are finally used to scientifically evaluate the environmental pollution and potential water quality effects, and then provide scientific basis for pollution control and ecological rehabilitation of lakes in Guizhou Province.

贵州湖泊长期受到酸沉降及工农业和生活污水的污染，呈现SO42-、重金属和氮磷营养盐的复合污染。目前对贵州湖泊沉积环境硫与重金属和氮磷营养盐耦合循环的微生物地球化学过程及其水质影响还缺乏研究。本申请拟以贵州草海、红枫湖、百花湖和阿哈湖为研究区域，采集不同时间和空间的沉积物和水样品，通过对沉积物硫形态和同位素组成、硫酸盐还原菌优势类群与数量和功能活性、重金属和营养盐形态、活性及释放条件的分析和评价，结合对溶解氧、pH、有机质等环境参数以及溶解态重金属和水化学组成的分析测定，探讨硫酸盐还原菌驱动的SO42-还原与重金属和氮磷营养盐固定、溶解、释放等涉及其形态和活性演变过程之间的内在联系，阐明SO42-还原与重金属和营养盐耦合循环的内在机制及水质影响，全面系统地评估贵州湖泊SO42-与重金属和营养盐污染的生态环境危害和潜在影响，以期为贵州湖泊的污染治理和生态修复提供基础科学依据。

草海是贵州唯一天然形成的浅水湖泊。红枫湖、百花湖、阿哈水库是贵州典型的亚深水型水库，是贵州水资源利用的主要形式之一。以硫循环研究为主线，通过对四个湖泊不同季节水体和沉积物中硫形态及其同位素变化、重金属空间分布和氮磷的分布对比，发现沉积物中的高浓度SO42-不是来自水体SO42-的向下扩散，而是来自黄铁矿的氧化。沉积物孔隙水中的高SO42-含量指示向水体扩散的趋势。本研究中的湖库有机质含量高，SO42-丰富，观测到的SO42-和硫化物之间的硫同位素分馏值之差不超过10‰，应该是硫化物氧化与SO42-还原之间内部循环造成的，这也说明了SO42-和硫化物之间的循环转化比较强烈，掩盖了SO42-异化还原形成的硫化物这一过程的真实分馏之间的差异。从SO42-和硫化物（AVS和FeS2-S）含量及其同位素比值的空间分布特征可以证实SO42-异化还原反应发生位置的季节性变化。对SO42-、AVS、FeS2、8种重金属、TN、TP及SRB类群及丰度的研究，可以发现湖泊沉积物中SO42-含量异常丰富，加之有机质丰富，则SRB驱动SO42-异化还原反应，带动了重金属和TN及TP的释放与循环。SO42-异化还原反应能够促使沉积物中氮磷的释放，这有可能加剧湖库水体的富营养状况。所研究的四个湖泊存在硫—重金属—氮磷营养盐的复合污染。污染的来源是沉积物内源，因此，今后这些湖库的水质治理和整体环境的改善，在控制外源输入的同时，更应关注沉积物内源的释放。沉积物环境硫—重金属—氮磷营养盐的耦合过程可导致水体缺氧、有毒气体（如H2S、CH4、N2O等）释放、有毒重金属溶解等一系列环境危害，这就需要在高硫、高重金属和富有机质的湖库环境中开展三者之间的相互影响与相互作用研究，也就为全面系统地评估贵州湖泊硫酸盐、重金属和营养盐耦合循环的水质影响及其生态环境危害指明思路，以求全面掌握湖库的污染态势，进而寻找治理环境污染的综合策略。