典型湖泊浮游生物与水体砷形态的时空变化及其耦合关系

Arsenic is an ubiquitous but toxic and carcinogenic element in the earth environment. Arsenic poisoning has been a major concern for its detritus effect to the environment and human health worldwide. Arsenic speciation determines the toxicity and is the key in understanding and controlling the arsenic poisoning and threat to human. Lakes act as the sinks of anthropogenic contamination, resulting in the elevation of various contaminants and eutrophication. Lakes also serve in numerous functions as drinking water sources, tourism, navigation, flood control, aquiculture, and so on. Arsenic toxicities vary with the speciation, and both inorganic and organic species of arsenic are found in lakes, mainly arsenate, arsenite, monomethylarsonic acid (MMA(V)) and dimethylarsinic acid (DMA(V)). In some cases, methylarsnic acid in +3 valence MMA(III) and DMA(III) are also present in lake waters, which have been reported to be even more toxic than arsenite to human, demonstrating genetic toxicity. Plankton is primary producer in lakes, algal bloom is widespread in many lakes in China due to eutrophication. The rapid growth of phytoplankton may take up large quantities of arsenate from waters and secrete arsenite and possibly methylarsnic (III) into waters again, consequently changing the speciation of arsenic in lake waters. In this project, some typical lakes from different regions of China, including Taihu,Chaohu,Dianchi and Yangzonghai will be selected for investigation for in a spatial-temporal varation view，field survey and sampling, in-situ monitoring and lab chemical and speciation analysis will be performed to reveal the constitution and abundance of plankton, arsenic contents and speciation in water and plankton, water quality parameters, eutrophication status and the synergetic effects between them in different season and different areas of the lakes. The in-situ field controlled experiments will be conducted to explore the behavior of arsenic uptake, transformation and metabolism of the typical plankton in different lakes. Data from field survey and experiments will be incorporated via methods of mathematical statistics, multivariate statistics, geo-statistics and GIS.spatial analysis to elucidate the coupling of plankton and arsenic speciation in the lakes. It is expected that the results of the project would contribute to both understanding the mechanism of arsenic speciation via metabolism by plankton and controlling the threat of arsenic to human health.

砷是一种有毒有害的元素；砷的毒性不仅取决于其总量，更决定于其形态。湖水中存在三价和五价的无机和甲基砷。湖泊浮游生物具吸收无机砷后在体内还原以及甲基化的能力，并可通过代谢作用将转化后的砷排出体外，进而改变湖泊水体中砷的形态分布。本项目选择我国不同地域的典型湖泊，包括太湖、巢湖、滇池和阳宗海，从时空变化的角度出发，采用野外调查采样、实地监测与室内化学与形态分析相结合，查明不同地域、不同季节、不同湖区浮游生物的组成与丰度、水体及浮游生物砷含量与形态、水质参数指标、水体富营养化指标等变化过程；采用野外现场人工添加砷的模拟实验研究各湖代表性浮游生物对砷的代谢作用；运用数理统计、多元统计、地统计学以及GIS空间分析方法研究湖泊浮游生物与水体砷形态分布的时空变化规律，揭示典型湖泊浮游生物与水体砷形态的耦合关系。研究成果对于认识湖泊富营养化与砷形态转化的关系以及控制砷健康危害具有理论与实际意义。

砷是一种有毒有害的元素，目前对砷在湖泊生态系统中的迁移、转化和生物富集行为知之甚少。本项目选择我国不同地域的典型湖泊，包括太湖、巢湖和滇池，从时空变化的角度出发，采用野外调查采样、实地监测与室内模拟实验相结合，查明不同地域、不同季节、不同湖区浮游生物的组成与丰度、水体及浮游生物砷含量与形态、水质参数指标、水体富营养化指标等变化过程；运用数理统计、多元统计、地统计学以及GIS空间分析方法研究湖泊浮游生物与水体砷形态分布的时空变化规律，揭示典型湖泊浮游生物与水体砷形态的耦合关系。结果表明，藻类显著影响湖泊水体中砷的含量和形态分布。太湖，巢湖和滇池的溶解态砷浓度为1.97（0.82-7.92）μg·L-1，总砷浓度为5.40（0.18-37.96）μg·L-1，砷在悬浮物与水之间的分配系数为4.58（3.19-6.28）, 砷在悬浮物中的含量显著高于水中，为24.7-516μg/g ；无论从丰度还是生物量，蓝藻都是三个湖泊中最主要的藻类，其次是绿藻和硅藻；三个湖中，藻类占了悬浮物很大的一部分，尤其是在滇池。藻在悬浮物中的占比，太湖冬季和夏季分别为 10.4%和7.1%，巢湖夏季为4.5%，滇池夏季为53.3%。太湖水体总砷和溶解态砷显示出显著的季节性差异，而悬浮物含量则无显著的季节性差异，其在冬季和夏季的平均含量分别为54.2和49.3 mg/L。三个湖中，水体总砷与悬浮物砷以及砷在悬浮物和水之间的分配系数呈显著的正相关。悬浮物中藻，尤其是蓝藻，显著影响砷在悬浮物和水相之间的分配。风浪扰动显著影响湖泊砷在悬浮物与水之间的分配系数，随着风浪作用的加强，溶解态砷和水体总砷浓度会升高2~3倍，相应的悬浮物总砷和分配系数有所降低，风浪作用可以降低悬浮物吸附砷的能力，进而促进砷从悬浮物中的释放，使水体中的溶解态砷增加。室内模拟实验结果显示，铜绿微囊藻、小球藻和硅藻具有很强的吸收富集和转化砷的能力；铜绿微囊藻的生长及胞内砷受到生长期、磷水平和As(V)水平的共同影响。在不同生长期时，铜绿微囊藻的生长代谢不同，从而使铜绿微囊藻的生长和胞内砷受到不同的影响而呈现出差异性；磷酸盐可抵消As(V)对铜绿微囊藻生长的抑制作用，同时也通过拮抗作用抑制As(V)进入藻细胞内，增加铜绿微囊藻对砷酸盐的耐性。