US Geological Survey, 720 Gracern Road, Suite 129, Columbia, South Carolina 29210-7651, United States.
Environ Sci Technol. 2011 Mar 15;45(6):2048-55. doi: 10.1021/es103923j. Epub 2011 Feb 22.
We assessed methylmercury (MeHg) concentrations across multiple ecological scales in the Edisto (South Carolina) and Upper Hudson (New York) River basins. Out-of-channel wetland/floodplain environments were primary sources of filtered MeHg (F-MeHg) to the stream habitat in both systems. Shallow, open-water areas in both basins exhibited low F-MeHg concentrations and decreasing F-MeHg mass flux. Downstream increases in out-of-channel wetlands/floodplains and the absence of impoundments result in high MeHg throughout the Edisto. Despite substantial wetlands coverage and elevated F-MeHg concentrations at the headwater margins, numerous impoundments on primary stream channels favor spatial variability and lower F-MeHg concentrations in the Upper Hudson. The results indicated that, even in geographically, climatically, and ecologically diverse streams, production in wetland/floodplain areas, hydrologic transport to the stream aquatic environment, and conservative/nonconservative attenuation processes in open water areas are fundamental controls on dissolved MeHg concentrations and, by extension, MeHg availability for potential biotic uptake.
我们评估了在南卡罗来纳州的埃迪斯托（Edisto）和纽约州的上哈得逊（Upper Hudson）流域的多个生态尺度上的甲基汞（MeHg）浓度。在这两个系统中，河道外湿地/洪泛区环境是溪流生境中过滤甲基汞（F-MeHg）的主要来源。两个流域的浅水开阔水区的 F-MeHg 浓度较低，F-MeHg 质量通量呈下降趋势。在埃迪斯托，由于河道外湿地/洪泛区的增加和没有水坝，导致甲基汞浓度升高。尽管在上游边缘地区湿地面积大，F-MeHg 浓度高，但主要河道上的大量水坝有利于空间变异性，并降低了上哈得逊的 F-MeHg 浓度。结果表明，即使在地理、气候和生态条件多样的溪流中，湿地/洪泛区的生产、向溪流水生环境的水文输送以及开阔水区的保守/非保守衰减过程，都是控制溶解态甲基汞浓度的基本因素，进而也是控制甲基汞对潜在生物吸收的可用性的基本因素。
