东南沿海地区燃煤电厂汞排放、迁移转化规律及其生态效应研究

Being one of the most toxic heavy metal pollutants in the environment, mercury(Hg) is a bioaccumulative neurotoxin that can enter terrestrial and aquatic ecosystems via atmospheric deposition, and therefore bears great ecological risks and high toxicity to human health. As one of the most remarkable anthropogenic mercury sources, the coal-fired power plant contributed significant mercury emissions to the atmosphere which has been widely concerned by governments and environmental protection organizations around the world. Therefore, investigations of mercury emission and deposition to surface environments from two coal-fired power plants in the southern east China, one is the Lanxi Power Plant which located in hills and the other one is Jiaxing Power Plant which located in plain, Zhejiang province, using mercury isotopes will be conducted. Characteristics of mercury emissions from coal burning in coal-fired power plants, the deposition of gaseous Hg on terrestrial ecosystems and its biogeochemical behavior, including transportation and transformation of Hg among the lithosphere, biosphere and hydrosphere, and the impact of mercury emission on food chain will be studied. Based on the above research, the biogeochemical cycling characteristics of mercury in atmosphere-soil-water-crop system will be identified. The results are expected to provide a theoretical support to global mercury cycle, as well as mercury pollution control of coal-fired power plants and the urban environmental protection.

汞是环境中一种生物毒性极强的重金属污染物，易在生物体内产生积累效应，严重威胁生态安全和人类健康。燃煤电厂作为最大的人为汞污染源之一，其汞排放问题受到各国政府和环保组织的日益关注。本项目选取东南沿海地区不同地形地貌（丘陵地区、平原地区）等环境条件下的两所燃煤电厂（浙江兰溪电厂和浙江嘉兴电厂）及其周边环境为对象，从燃煤电厂汞排放特征、气态汞在大气-陆地生态系统中沉降、迁移转化机理及燃煤汞排放对作物的影响等方面展开研究，明确不同地形和气候条件下燃煤电厂排放的汞污染物在大气-土壤-水-作物生态系统中的循环及转化特征。研究结果将为全球汞循环提供理论支撑，并为燃煤电厂汞污染控制和城市环境保护提供理论依据。

燃煤电厂是最大的人为汞污染排放源。本项目选取东南沿海地区两所典型燃煤电厂（浙江兰溪电厂和浙江嘉兴电厂）及周围环境作为研究对象，系统的研究燃煤电厂汞排放、迁移转化规律及其生态效应。主要研究结果如下：（1）通过连续四年的野外监测，初步探明：受主导风向和沉降的共同影响，电厂周围土壤中汞、铅、镉呈一定的空间自相关性；土壤中汞、铅、铬均以残渣态为主，而镉的生物有效态的比例超过50%，存在较大风险；利用铅同位素技术发现燃煤电厂对土壤铅污染贡献均值为65.65%，大气颗粒物（80.82%）对小麦籽粒铅的贡献远大于土壤铅（19.18%）。（2）电厂周围大气环境中PM2.5、PM10、TSP中汞的质量浓度远高于燃煤和灰飞，说明细颗粒物更容易富集汞，并通过干湿沉降，将大气中汞迁移沉降到地表环境中，电厂下风方向的降尘汞（99.51μg/m2·a）对地面汞的贡献率更高，降水中总汞浓度19.46ng/L，甲基汞浓度0.22ng/L。（3）受小型污染源和燃煤电厂影响，水体中甲基汞和总汞浓度均高于背景点，水体中汞的迁移主要靠颗粒态汞，甲基汞的迁移和浓度水平主要受溶解态甲基汞控制。（4）通过研究汞在植物-土壤之间的分布特征，发现农田湿地更有利于甲基汞的形成，汞主要富集在水稻和小麦的根部和蔬菜叶片，甲基汞主要在水稻籽粒和蔬菜叶片中富集。（5）通过调查当地居民的饮食和发汞发现，由于食物链的累积效应，年龄在0-17（HI>1）岁的高暴露人群（P95）存在健康风险，并且消化道摄入的贡献最高（99.94~99.95%）。（6）利用麦芽根制备的生物炭可通过还原土壤中有机官能团，降低土壤中汞的生物有效性，从而减少植物对汞的吸收，修复中低浓度汞污染土壤。通过上述研究，已发表有项目标注的SCI论文1篇及国内期刊论文2篇，申请专利共16项。