U.S. Geological Survey, California Water Science Center, 6000 J Street, Placer Hall, Sacramento, CA 95819, U.S.A..
U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, CA 95620, U.S.A.
Sci Total Environ. 2016 Nov 15;571:364-79. doi: 10.1016/j.scitotenv.2016.05.088. Epub 2016 Jul 2.
Widespread mercury (Hg) contamination of aquatic systems in the Sierra Nevada of California, U.S., is associated with historical use to enhance gold (Au) recovery by amalgamation. In areas affected by historical Au mining operations, including the western slope of the Sierra Nevada and downstream areas in northern California, such as San Francisco Bay and the Sacramento River-San Joaquin River Delta, microbial conversion of Hg to methylmercury (MeHg) leads to bioaccumulation of MeHg in food webs, and increased risks to humans and wildlife. This study focused on developing a predictive model for THg in stream fish tissue based on geospatial data, including land use/land cover data, and the distribution of legacy Au mines. Data on total mercury (THg) and MeHg concentrations in fish tissue and streambed sediment collected during 1980-2012 from stream sites in the Sierra Nevada, California were combined with geospatial data to estimate fish THg concentrations across the landscape. THg concentrations of five fish species (Brown Trout, Rainbow Trout, Sacramento Pikeminnow, Sacramento Sucker, and Smallmouth Bass) within stream sections were predicted using multi-model inference based on Akaike Information Criteria, using geospatial data for mining history and landscape characteristics as well as fish species and length (r(2)=0.61, p<0.001). Including THg concentrations in streambed sediment did not improve the model's fit, however including MeHg concentrations in streambed sediment, organic content (loss on ignition), and sediment grain size resulted in an improved fit (r(2)=0.63, p<0.001). These models can be used to estimate THg concentrations in stream fish based on landscape variables in the Sierra Nevada in areas where direct measurements of THg concentration in fish are unavailable.
美国内华达山脉的水系受到广泛汞（Hg）污染，这与历史上使用汞齐法提高金（Au）回收率有关。在内华达山脉西部斜坡和北加州下游地区，如旧金山湾和萨克拉门托河-圣华金河三角洲等受历史 Au 采矿作业影响的地区，Hg 被微生物转化为甲基汞（MeHg），导致 MeHg 在食物网中生物累积，增加了人类和野生动物面临的风险。本研究旨在基于地理空间数据，包括土地利用/土地覆盖数据和遗留 Au 矿的分布，开发一种预测溪流鱼类组织中总汞（THg）的模型。综合了 1980-2012 年间从加利福尼亚州内华达山脉溪流采集的鱼类组织和河床沉积物中的总汞（THg）和 MeHg 浓度数据与地理空间数据，以估算整个景观中的鱼类 THg 浓度。采用基于赤池信息量准则的多模型推断，利用采矿历史和景观特征以及鱼类物种和长度的地理空间数据，预测了溪流部分五种鱼类（褐鳟、虹鳟、萨克拉门托鱒、萨克拉门托吸盘鱼和小口黑鲈）的 THg 浓度（r(2)=0.61，p<0.001）。然而，包括河床沉积物中的 THg 浓度并没有改善模型的拟合度，而包括河床沉积物中的 MeHg 浓度、有机含量（灼烧损失）和沉积物粒径则可以改善模型的拟合度（r(2)=0.63，p<0.001）。这些模型可用于根据内华达山脉的景观变量来估算无法直接测量鱼类 THg 浓度的地区的溪流鱼类中的 THg 浓度。
