砷污染对高原湖滨湿地磷削减影响及调控过程研究

Phosphorus reduction by lakeshore wetland has been becoming a hot research direction over the world. It’s really valuable to pay attention to the efficiency of phosphorus reduction by lakeshore wetland under arsenic pollution for researchers; therefore, it would be focused on how arsenic pollution sediment affects the efficiency of phosphorus reduction by lakeshore wetland and the control methods in this research. The two key scientific problems need to be solved in the research as (1) what is the effect the arsenic-polluted sediment will take for the efficiency of phosphorus reduction by lakeshore wetland?(2) will the different effect happens for the efficiency of phosphorus reduction by lakeshore wetland under various arsenic forms and concentrations? Choosing the arsenic-polluted sediment lakeshore wetland (near the Lake of Yangzonghai) as typical object, the relevant research work will be operated for finding out the effect of phosphorus reduction by sediment and plant in arsenic-polluted sediment of lakeshore wetland and the effective control methods. Through field monitoring, inside simulating and site original checking trials, the conclusion results will be achieved on the efficiency of phosphorus reduction and changing characters by arsenic-polluted sediment of lakeshore wetland, and the effect factors will be determined. With the comparing, statistical and relative analysis methods, the efficiency of phosphorus reduction by the factors of environmental conditions (pH, DO, porous and particle-size degrading) and arsenic form and concentration of arsenic-polluted sediment will be disclosed, and its control factors will be found. The research predicted achievements will support for arsenic-polluted lakeshore wetland management and remediation designing.

湖滨湿地对磷的削减是目前国内外研究热点，砷污染对湖滨湿地磷削减效果的影响值得关注。本项目以砷污染底质湖滨湿地为研究对象，拟开展对磷削减的影响及调控过程研究，重点解决两个科学问题：（1）砷污染底质如何影响高原湖滨湿地植物和底泥对磷的削减？（2）如何调控砷污染底质高原湖滨湿地对磷削减过程？本研究以阳宗海砷污染底质湖滨湿地为典型研究对象，重点研究砷污染底质对湖滨湿地磷削减效果的影响并探索有效的调控方法。通过现场原位监测、室内模拟和野外原位验证等方法，在摸清砷污染底质湖滨湿地对磷削减效果及时空变化规律并判定影响因子的基础上，进行对比、统计和相关性分析，揭示微环境条件（pH值、DO和水文条件）、砷的形态和浓度等因子对湖滨湿地磷削减效果的影响，找出提高磷削减效率的调控因子，为砷污染湖滨湿地的治理与恢复重建提供技术支持。

研究结合野外调查和室内模拟实验，探析了阳宗海砷污染湖滨湿地水-沉积物中砷和磷时空分布特征、典型湿地挺水植物香蒲对砷的吸收分配及修复潜力和磷输入对沉积物砷形态转化及生态风险影响等，主要研究结果如下： .（1）阳宗海湖滨湿地水体中砷属内源污染。表层沉积物中总砷含量总体表现为湖心>湖滨>湖岸，垂直方向上表层含量高，沉积物砷形态主要以残渣态为主，从季节分布来看，弱酸提取态砷（F1）和氧化态砷（F3）存在差异性，湖滨湿地面临砷可能被再次释放的风险；.（2）水-沉积物中磷含量沿湖心至湖岸方向呈递减趋势，沉积物中总磷含量在垂直方向上的变化趋势表现为由表层至底层先增大后减小大的变化趋势，与阳宗海湖滨湿地受到的不同程度的污染有关，沉积物中磷形态含量主要以十钙磷为主。沉积物pH（S-pH）、溶解氧（DO）、电导率（TDS）对磷形态有较大影响，而S-pH、DO、氧化还原电位（Eh）对砷形态有较大影响；.（3）总体来看，湿地优势挺水植物香蒲地下部对As的吸收均高于地上部，从整体来看无幼苗期累积能力略弱于花果期，但明显强于枯黄期；香蒲生长前和后期根部是As的主要贮存部位，花果期香蒲体内As的积累量则地上部大于地下部；地上部不同部位对As的积累能力呈现出自下而上增加的规律，表明As被香蒲根部吸收后较难向地上部分转运，香蒲对As具有一定的累积能力，但非As超富集植物；.（4）沉积物中砷和磷的活性态及含量对其吸附磷的能力有重要影响，高活性成分的比例越大影响越大；沉积物中弱酸提取态砷、可还原态砷及上覆水-pH对沉积物吸附磷有重要贡献；上覆水磷浓度的升高能促进沉积物砷的释放，污染风险增加。磷的输入能显著增加沉积物中总磷的含量，生态风险也随之增加；.（5）磷的进入能够促使表层沉积物中砷的释放，能使沉积物总砷的浓度低于土壤环境质量标准值，降低砷的环境风险，沉积物对于污染物的蓄积具有重要意义。磷浓度达到40 mg/L，沉积物总磷达到重度污染水平；上覆水中磷对沉积物总磷的浓度有重要贡献。