城市河道氧调控对沉积物-水界面还原性硫产生过程的影响及机制研究

The enrichment of reduced sulfur in urban river is a main reason for black-odour water formation. Except for the anaerobic pathway, the pathway of reduced sulfur production under aerobic conditions was often neglected. Therefore, extensive oxygen regulation cannot solve the black-odour water problem in urban river for existence of aerobic conditioned reduced sulfur production process. In addition, long-term maintaining of high dissolved oxygen level is not economic and sustainable in terms of energy consumption. Research on the effects and mechanism of the dissolved oxygen concentration on the production of reduced sulfur at sediment-water interface, is helpful to optimize dissolved oxygen regulation. The optimization could achieve the best balance between treatment effect and energy consumption during the restoration of black-odour water by oxygen regulation. A dissolved oxygen gradient simulation experiment will be conducted on urban river water and sediment in this research. Measures such as pore waters acquired with membrane equilibrium, chemical sequential extraction, inhibition of enzyme activity and high throughput sequencing will be adopted. Through this study, the distribution pattern of reduced sulfur in water and sediment will be revealed, and effects and microbial mechanism of oxygen regulation on the generation process of reduced sulfur at sediment-water interface will be investigated. The research results will help to determine the dissolved oxygen range to limit the formation of reduced sulfur in urban river. These will provide new viewpoints for the precise regulation of black-odour substance in urban river.

城市河道还原性硫的富集是其黑臭化的主要原因。除厌氧产生途径，还原性硫在好氧条件下的产生常被忽略，粗放式氧调控难以彻底消除城市河道黑臭问题。此外，维持高溶氧水平固然能短期内取得较好的治理效果，但极大增加了能耗和经济成本，不具有可持续性。研究沉积物-水界面溶氧水平与还原性硫生成之间的关系及机制，有助于优化溶氧范围和氧调控力度，使处理效果和能耗之间达到最佳平衡。本研究以城市河道水体/沉积物为对象，采用溶氧梯度模拟实验，通过膜平衡法间隙水获取、硫形态提取、酶活性抑制与高通量测序等技术手段，研究水体与沉积物中还原性硫的分布规律，阐明氧调控对沉积物-水界面还原性硫产生过程的影响及其微生物机制。研究结果有助于确定限制城市河道还原性硫产生的溶氧范围，将为城市河道黑臭物质的精细化控制提供新的观点和依据。

本项目围绕“通过分析城市河道沉积物中∑S2‒产生途径及产∑S2‒微生物对氧调控的响应特征，确定限制城市河道水体沉积物中∑S2‒产生的溶氧范围”这一核心科学问题，针对广州市城市河涌水体沉积物开展系列研究工作，取得以下主要结论：.1）城市河涌表观黑臭程度与河涌沉积物中硫化物含量直接相关。本研究测定的河涌沉积物中硫化物含量为0.028~1.43 μg/g，其中黑臭程度较高的H1和H2河涌沉积物中的硫化物含量要显著高于黑臭程度较低的H3和H4，并且沉积物硫化物含量在夏季要高于冬季。同样的，H1和H2的硫化物产生速率要显著高于H3和H4，且夏季的硫化物产生速率要明显高于冬季。此外，相比硫酸盐还原菌，产甲烷菌代谢含硫有机质主导了河涌沉积物中硫化物的产生。2）不同黑臭程度的河涌沉积物具有显著不同的硫酸盐还原菌和产甲烷菌群落特征。优势的硫酸盐还原菌属主要为Desulfobulbus、Desulfotignum、Desulfosarcina、Desulfococcus、Desulfogranum等；优势的产甲烷菌属主要包括Methanobacterium、Methanobrevibacter和Methanosphaera。这些优势的属在不同河涌沉积物中的相对丰度都有较明显的差异。产甲烷菌群和硫酸盐还原菌群对河涌沉积物硫化物积累和产生速率的相对重要性分别为55.7%和68.4%，44.3%和31.6%。其中，Methanobacterium和Methanomassiliicoccus，Syntrophobacter和Desulfosarcina分别是贡献度最高的产甲烷菌和硫酸盐还原菌类群。3）调控实验表明，升温能显著促进硫化物产生速率，并且产甲烷菌介导的硫化物产生对温度更为敏感。pH值对硫化物产生速率的影响是非线性的，当pH在7左右时能够最大程度的限制硫化物的产生，并且碱性环境比酸性环境更能促进硫化物的产生。沉积物硫化物产生速率随溶解氧的升高显著降低，并且抑制效果与原位硫化物产生速率有直接关系，溶解氧为1 mg/L时就能对原位活性较低的沉积物产生抑制，而原位活性较高的沉积物在溶解氧为3 mg/L的时候能被有效抑制。此外，产甲烷菌介导的硫化物产生对溶解氧的抑制作用更为敏感。本研究揭示了城市河涌沉积物中硫化物产生的主导途径及相关微生物群，阐明了关键影响因素，加深了对黑臭控制机制的认识。