基于藻华暴发过程影响的湖泊中砷迁移转化及驱动机制

Algal bloom is an important inducement that cause deterioration of water quality in lakes of China. Algal bloom decomposition would promote arsenic (As) release by triggering anoxia in surface sediments; furthermore, the conversions between different As species depend on algal metabolism. The above processes result in the dynamic changes of As ecological risk. In this study, algal blooms will be selected as the entry point to analyze distributive changes of As combining field observation and indoor experiments. The objectives of this study are to determine the dynamic distribution characteristics of As and the main controlling factors during algal bloom process, and to identify main driving mechanism in transportation and transformation of As during rapid-, stationary- and decay stages of algal growth. Relevant results will contribute to fill the research gaps about regulation of algal blooms on As biogeochemical behavior, and will provide the data basis for the establishment of the association between algal blooms and As cycling. Meanwhile, the results will reveal controlling of algal blooms process on the distribution of As species posing different toxicities, favoring the prediction of As ecological risk in eutrophic lakes.

藻华暴发是我国湖泊水质恶化的重要诱因。藻华分解可通过触发表层沉积物缺氧状态促进砷的释放，而游离态砷的形态转化依赖浮游藻类的代谢；上述过程导致砷生态风险的动态变化。本研究以藻华暴发为切入点，结合实地观测与模拟研究，明确藻华暴发过程中砷的动态分布特征及其主控因素；识别藻华快速生长-稳定-衰亡阶段砷迁移转化的主要驱动机制；旨在填补藻华暴发在砷生物地球化学行为中调控作用的研究空缺，为藻华暴发过程与砷生物地球化学循环间关联的建立提供数据基础。同时，基于不同形态砷的毒性差异，揭示藻华暴发过程对水体砷形态分布的调控，为富营养化湖泊中砷生态风险的预判提供参考依据。

藻华暴发是我国湖泊水质恶化的重要诱因。藻华分解可通过触发表层沉积物缺氧状态促进砷的释放，而游离态砷的形态转化依赖浮游藻类的代谢；上述过程导致砷生态风险的动态变化。本项目以藻华暴发为切入点，以沉积物-水-浮游植物体系为研究对象，阐明了藻华暴发过程与沉积物-水界面氧/还状态耦合作用下环境体系中砷的动态变化特征，并结合宏观与微观层面识别了藻类不同生长阶段砷迁移转化的主要驱动机制，据此初步构建了藻华暴发过程与砷循环的关联，可为富营养化湖泊砷生态风险的预判提供参考依据。主要研究结果如下：.（1）研究发现水相中砷的浓度变化表现为藻类增殖-腐解期维持在相对高位、休眠期显著下降、复苏期又逐渐上升，从赋存形态来看，增殖期毒性更高的三价砷增加，砷生态风险相应升高；.（2）根据多介质砷形态变化及统计学分析，识别出藻类增殖-腐解期发生固相砷释放与水相砷还原/甲基化的主要驱动机制为界面有机物质的耗氧分解与藻类的砷代谢，而藻类休眠-复苏期的界面复氧诱发了游离态砷向沉积物的汇集；.（3）水相中砷还原及甲基化基因丰度在藻华发生过程中的变化与水相砷趋于一致，且水体中三价砷及藻类胞内甲基砷与砷还原、甲基化基因呈显著正相关，从分子层面反映出砷代谢基因对环境中砷行为的调控。