阳宗海表层沉积物砷形态的季节性变化及其对微藻毒性效应的影响

Arsenic is mainly concentrated in the surface sediments of Yangzonghai Lake after arsenic pollution treatment. Speciation of arsenic in high level in sediment easily changes with the seasonal variation of environmental conditions such as temperature, oxidation-reduction potential and releases again into water, and it is still a great threat to aquatic ecosystem. However, relevant research has been very limited. There is an urgent need to study the change of arsenic speciation driven by season variation and its toxic effect on microalgae. This project aims to study following contents through long-term field monitoring, sampling analysis and simulation experiments, including 1) the seasonal variation of arsenic speciation and valence in surface sediment in Yangzonghai Lake; 2) bioavailability of arsenic on dominant microalgae in sediment in different seasons; 3) toxic effect of arsenic in sediment on dominant microalgae in different seasons. Results of this project will contribute to further understanding and evaluation environmental behavior of arsenic pollution in the sediments in Yangzonghai Lake and the potential ecological risk after pollution controlling and provide scientific basis for the prevention and control of secondary pollution of arsenic in sediment.

阳宗海砷污染治理后砷主要富集在湖泊表层沉积物。表层沉积物中高浓度的砷的形态易随温度、氧化还原电位等环境条件的季节性变化而发生改变，并再次释放到水体中，对水生态系统潜在风险依然巨大，但相关研究还很有限，因此迫切需要研究季节变化驱动下沉积物砷形态的变化及其对微藻的毒性效应的影响。本项目拟通过野外长期监测、采样分析和模拟实验，研究(1) 阳宗海表层沉积物中砷形态与价态的季节性变化;(2)不同季节沉积物中砷的优势微藻生物有效性; (3) 不同季节沉积物中砷对优势微藻毒性效应的影响。项目的研究成果有助于深入了解和评估阳宗海在砷污染治理后沉积物中砷的环境行为及潜在的生态风险，为防治沉积物砷的二次污染提供科学依据。

为了解阳宗海在砷污染治理后沉积物中砷的赋存特征，以及湖泊沉积物中砷的生态风险，本项目对阳宗海表层水体和沉积物砷进行野外调研、测样分析和模拟实验的综合研究，研究结果表明：1）在阳宗海沉积物水界面As(Ⅲ)主要集中在北部和西南部，砷浓度最大可达46.6μg/L。沉积物水界面As(Ⅴ)浓度比As(Ⅲ)浓度低，分布于阳宗海中部较多。在表层水体中，As(Ⅲ)浓度高的区域为阳宗海北部。2）阳宗海沉积物中的砷主要以残渣态和有机物结合态为主，离子态砷、碳酸盐结合态砷、铁锰结合态砷含量非常低。3）在春、夏、秋、冬四个不同季节，沉积物水界面砷以As(Ⅲ)为主，表层水体中以As(Ⅴ)为主。不同季节条件的环境因子如温度、pH、氧化还原电位对水体和沉积物砷的形态影响不大，相关关系不显著。4）模拟实验结果表明，总体上低浓度的砷对大部分微藻具有一定的促进作用，高浓度的砷则对其产生抑制作用。500μg/L以下浓度的As(Ⅴ)对微囊藻无明显抑制作用，500μg/L As(Ⅴ)对小球藻有明显抑制作用。5）低砷沉积物同一季节条件下比高砷沉积物更有利于藻类的生长。在同一砷浓度条件下，模拟夏季环境条件比春、秋、冬季更有利于藻类的生长。.总体来看，目前阳宗海表层沉积物大部分砷为难溶态砷，砷对藻类的毒性效应并不显著，沉积物中赋存的砷生态风险很低。