陆源排放影响下水环境中氮污染的微生物消除途径与潜能研究

With the development of urbanization and industrialization in China, coastal water environment have been interfered by the land-sourced discharge, of which nitrogen is the primary pollutant. Therefore, the regional sustainable development is impeded. Microbial removal pathways and potential are the most significant mechanism for the nitrogen pollution control and removal in the discharge receiving environment, nevertheless the mechanism is usually ignored in the total pollutants reduction policy-making. The proposed project selects Hangzhou Bay as the research area to study on the microbial removal mechanism of nitrogen pollution in the human-interfered water environment. We plan to use environmental chemical analysis, molecular ecological technologies, and statistical methods to fulfill the following tasks: 1) collect the effluent and sludge samples from land-based sources (i.e. wastewater treatment plants) as well as the seawater and sediment samples from Hangzhou Bay, and analyze the community structures of nitrogen transformation microorganisms, nitrogen transformation activities and rates of these samples; 2) identify the significant impacts of land-sourced discharge on the microbial communities with nitrogen transformation functions as nitrification, denitrification, anammox, and dissimilatory nitrate reduction to ammonium (DNRA) in the bay, and then establish the relationship between the nitrogen transformation microorganisms and environmental factors; and 3) estimate the contribution of the major nitrogen transformation microorganisms to nitrogen pollution elimination in the bay, and further explore the regulatory mechanism of nitrogen pollution elimination in water environment. We will reveal the microbial potential of nitrogen pollution removal in the water environment under land-sourced discharge, and put forward the N-pollutants reduction requirement to land-based sources. The outputs of the project will provide scientific basis for the regional total N-discharge reduction and the bioremediation of eutrophic water environment.

随着我国城镇化和工业化的进程，陆源排放对近岸海域的环境污染愈加严重，尤以氮污染为首，严重制约了区域可持续发展。陆源氮污染物的排放总量控制决策，往往忽略了受纳水环境中氮污染的微生物消除途径与潜能。本项目选择严重富营养化的杭州湾为研究区域，联合使用环境化学分析、分子生态技术及统计学方法，开展水环境中氮污染的微生物消除机制研究。将采集陆地排放源（即废水处理系统）排水和污泥以及杭州湾海水和沉积物，分析样品中氮转化功能微生物的群落结构、氮转化活性及氮转化速率；解析陆源排放对湾内硝化、反硝化、厌氧氨氧化、硝酸盐异化还原到铵等功能菌群的影响，建立氮转化功能菌群与环境因子的相互关系；辨识主要氮转化功能微生物对海湾氮污染消除的贡献，探索水环境中氮污染消除的调控机制。研究将揭示受陆源排放影响下水环境中氮污染消除的潜力，提出陆源氮污染物的减排要求，为区域氮排放总量控制及富营养化水体修复提供科学依据。

本项目选取我国近海富营养化最为严重的海域之一——杭州湾为研究区域，结合环境理化分析、分子生物学技术及数理统计分析，系统解析了海湾内氮转化微生物丰度及活性的分布特征及关键影响因子；开展实验室微宇宙模拟实验，探讨了富营养条件下近海沉积物微生物群落的结构及氮转化功能对石油污染的响应特征。主要研究结论有：.（1）解析杭州湾沉积物氮转化微生物丰度的时空分布特征及其影响因素。结果显示，各功能基因存在不同的时空分布特征。时间尺度上，nirS基因丰度先升高后下降，nirK基因和nosZ基因丰度保持相对稳定，nrfA基因丰度先下降后升高，而hzo基因丰度存在较大幅度波动；空间尺度上，nirS和nirK基因丰度存在北部沿岸高于中部地区的趋势，hzo基因空间分布情况随年际变化波动，其他基因则不存在明显的空间分布规律。.（2）解析杭州湾沉积物反硝化速率的空间分布特征及其影响因素。结果显示，杭州湾无机氮脱除以反硝化作用为主；杭州湾沉积物潜在反硝化速率呈湾内向湾外递增、中部高于北岸的空间分布特征；反硝化速率与海水盐度和pH呈显著正相关，与海水硝酸盐浓度及沉积物C/N呈显著负相关，与反硝化功能基因nirS、nosZ及16S rRNA基因也呈显著正相关。.（3）阐明石油污染对近岸海域沉积物微生物群落结构的影响规律。结果显示，杭州湾石油烃类有机物是反硝化作用的重要碳源；与相对清洁的低污染区域相比，长期受陆源污染排放干扰、富营养化严重的近岸海域其微生物群落对石油污染更加敏感，石油污染加速了该地区微生物群落结构的演替过程。.（4）探究石油污染对近岸海域沉积物微生物氮转化功能的影响。结果显示，石油污染促进了反硝化等硝酸盐还原过程，增加了N2O的释放，抑制了硝化过程；同时还削弱了微生物氮循环功能基因之间的联系，且对高污染区的削弱作用更加明显，可能会影响富营养化海区的氮平衡。