Morway Eric D, Thodal Carl E, Marvin-DiPasquale Mark
Nevada Water Science Center, U.S. Geological Survey, Carson City, NV 89701, USA.
National Research Program, U.S. Geological Survey, Menlo Park, CA 94025, USA.
Environ Pollut. 2017 Oct;229:1006-1018. doi: 10.1016/j.envpol.2017.07.090. Epub 2017 Aug 7.
The Carson River is a vital water resource for local municipalities and migratory birds travelling the Pacific Flyway. Historic mining practices that used mercury (Hg) to extract gold from Comstock Lode ore has left much of the river system heavily contaminated with Hg, a practice that continues in many parts of the world today. Between 1998 and 2013, the United States Geological Survey (USGS) collected and analyzed Carson River water for Hg and methylmercury (MeHg) concentrations resulting in a sixteen year record of unfiltered total mercury (uf.THg), filtered (dissolved) Hg (f.THg), total methylmercury (uf.MeHg), filtered MeHg (f.MeHg), and particulate-bound THg (p.THg) and MeHg (p.MeHg) concentrations. This represents one of the longest continuous records of Hg speciation data for any riverine system, thereby providing a unique opportunity to evaluate long-term trends in concentrations and annual loads. During the period of analysis, uf.THg concentration and load trended downward at rates of -0.85% and -1.8% per year, respectively. Conversely, the f.THg concentration increased at a rate of 1.7% per year between 1998 and 2005, and 4.9% per year between 2005 and 2013. Trends in flow-normalized partition coefficients for both Hg and MeHg suggest a statistically significant shift from the particulate to the filtered phase. The upwardly accelerating f.THg concentration and observed shift from the solid phase to the aqueous phase among the pools of Hg and MeHg within the river water column signals an increased risk of deteriorating ecological conditions in the lower basin with respect to Hg contamination. More broadly, the 16-year trend analysis, completed 140 years after the commencement of major Hg releases to the Carson River, provides a poignant example of the ongoing legacy left behind by gold and silver mining techniques that relied on Hg amalgamation, and a cautionary tale for regions still pursuing the practice in other countries.
卡森河是当地市政当局以及沿太平洋迁徙路线飞行的候鸟的重要水资源。历史上的采矿作业使用汞（Hg）从康斯托克矿脉矿石中提取黄金，这使得该河流系统的大部分区域都被汞严重污染，如今世界上许多地方仍在继续这种做法。1998年至2013年期间，美国地质调查局（USGS）收集并分析了卡森河水中汞和甲基汞（MeHg）的浓度，得出了16年的未过滤总汞（uf.THg）、过滤（溶解）汞（f.THg）、总甲基汞（uf.MeHg）、过滤甲基汞（f.MeHg）以及颗粒结合态总汞（p.THg）和甲基汞（p.MeHg）浓度记录。这是任何河流系统中最长的汞形态数据连续记录之一，从而提供了一个评估浓度和年度负荷长期趋势的独特机会。在分析期间，uf.THg浓度和负荷分别以每年-0.85%和-1.8%的速率呈下降趋势。相反，f.THg浓度在1998年至2005年期间以每年1.7%的速率增加，在2005年至2013年期间以每年4.9%的速率增加。汞和甲基汞的流量归一化分配系数趋势表明，从颗粒相到过滤相发生了具有统计学意义的转变。河流水柱中汞和甲基汞库中f.THg浓度加速上升以及从固相到水相的明显转变，表明下游流域汞污染导致生态状况恶化的风险增加。更广泛地说，在向卡森河大量释放汞开始140年后完成的16年趋势分析，为依赖汞齐化的金银开采技术留下的持续遗留问题提供了一个深刻的例子，也为其他国家仍在采用这种做法的地区敲响了警钟。
