小球藻强化去除硒污染的作用机制及其对水体生态毒性效应的影响研究

High selenium (Se) levels in the wastewater from mining operations, petroleum refineries, and coal-fired power plants may pose a high risk to people and wildlife, even in the area where the soil is known to be lacking in selenium. While previous research has suggested Chlorella vulgaris was most effective in terms of Se volatilization and Se removal from the water column, nitrogen to phosphorus ratios and light/dark cycles also played an important role in the processes. Further experimental investigations are needed to estimate relationships between rates of selenium removal/volatilization and other important growing conditions. We propose new microcosm experiments in an environmental controlled laboratory to investigate effects of levels of selenium, sulfur, nitrogen, phosphorus, pH and carbon dioxide, and light/dark cycles on the efficiency of selenium removal/volatilization. The results will help recognize key influencing factors for Se removal/volatilization by C. vulgaris. Meanwhile, mesocosm experiments in the greenhouse will be necessary to verify the lab results to determine the ideal growing conditions to yield the highest rates of selenium removal/volatilization. To investigate toxic effects of selenium-laden C. vulgaris on aquatic life, cattail wetland mesocosms and tanks for freshwater bivalves, including Corbicula fluminea, Anodonta woodiana and Hyriopsis cumingii, will be set up and fed with algal cultures that contain various selenium species. Selenium speciation in tissues of cattails and bivalves, and soil will be determined using X-ray absorption spectroscopy (XAS) to evaluate the transfer of Se from C. vulgaris into the base of the aquatic food chain. Based on the results from the proposed microcosm and mesocosm experiments, the gap between research and practice will be bridged, leading to toxic free resolutions for designs and management of an algal pond for Se removal in the future.

矿产开发、炼油厂与火力发电厂排出的废水中，普遍检验出超标的硒浓度，让硒污染的问题不再局限于硒富集的地区。小球藻在前期研究已被证实为生物处理法中去除与挥发硒速率最高的物种，同时研究也确认其去除效率受到氮磷浓度比的与光照周期的影响。本申请课题将延续之前的研究，再进一步探讨影响小球藻除硒机制的关键环境因子，并研究小球藻体内挥发后残留的硒是否会通过食物链的传递，产生生物毒性放大的效应。在实验室内受控试验条件下，解析硒硫比、氮磷比、pH、光照周期、二氧化碳供应量调控与小球藻去除、生物转化与挥发硒酸盐与亚硒酸盐速率之间的相互关系。结合温室围隔试验，进一步验证实验室结果，并确认最适小球藻硒去除与挥发速率的生长环境条件范围;同时设置贝类养殖槽与香蒲微湿地槽，采用X光吸收光谱的技术，进一步解析小球藻体内不同形态的硒对于淡水贝类与水生植物的硒积累与毒害影响，为小球藻净化塘的优化设计和生态毒性调控管理。

针对小球藻除硒作用机制与生态风险开展研究，研究期间依次开展了实验室小试研究、围隔实验和中试研究，得到了不同硒硫比、氮磷比、光照条件、pH、二氧化碳供应量条件下小球藻对水中硒酸盐与亚硒酸盐的去除效率，阐明了环境因素对小球藻除硒路径——积累与挥发的影响；研究了含硒小球藻对滤食性生物河蚌的生态毒性，分析了河蚌对硒的摄入与净化规律；研究了含硒小球藻在潜流人工湿地系统中的归趋，并分析了水生植物中硒的化学形态；研究了硒在浮叶表面流人工湿地系统中的归趋，并细致分析了硒的食物链传递与生物转化，得到了有机硒的生物放大规律；分析了微生物作为碎屑食物链底层对硒的去除与植物残体投加的影响机制。通过上述研究，得到了小球藻去除硒的作用机制，明确了其对水生生态系统的潜在生态风险，为藻类净化塘的优化设计和工程调控管理提供了基础依据。最终，研究了含硒小球藻的燃烧处理、生物柴油提取与产氢，结合藻类硒形态的变化，从而为含硒藻类的资源化利用提供了数据支撑，有利于实现同时实现藻类对水体硒污染的去除与资源化利用。