Tate Michael T, Janssen Sarah E, Lepak Ryan F, Flucke Laura, Krabbenhoft David P
Upper Midwest Water Science Center, U.S. Geological Survey, Madison, WI, USA.
Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency Office of Research and Development, Duluth, MN, USA.
J Geophys Res Atmos. 2023 Apr 20;128(8):1-15. doi: 10.1029/2022jd038276.
With the 2011 promulgation of the Mercury and Air Toxics Standards by the U.S. Environmental Protection Agency, and the successful negotiation by the United Nations Environment Program of the Minamata Convention, emissions of mercury (Hg) have declined in the United States. While the declines in atmospheric Hg concentrations in North America are encouraging, linking the declines to changing domestic and global source portfolios remains challenging. To address these research gaps, the U.S. Geological Survey initiated the first national-scale effort to establish a baseline of total gaseous mercury stable isotope values at 31 sites distributed across the United States. Results indicated that unique Hg sources, such as Hg evasion from an elemental Hg contaminated site or free tropospheric intrusions in high altitude sites, were distinguishable from background atmospheric values. Minor gradients were observed across the nation, with regions of heavy industrial activity demonstrating lower , but no consistent changes in other isotopes such as and were observed. Furthermore, was impacted by foliar uptake and senescence but trends varied between forested regions in the northeastern and midwestern United States. These data demonstrate regional emission sources and other environmental variables can impact total gaseous Hg (TGM) isotope values, highlighting the need to characterize atmospheric Hg isotopes over larger geographical areas to evaluate changes related to national and international Hg regulations.
随着美国环境保护局2011年颁布《汞及空气有毒物质标准》，以及联合国环境规划署成功协商签署《水俣公约》，美国汞（Hg）排放量有所下降。尽管北美大气汞浓度的下降令人鼓舞，但将这些下降与国内和全球源组合的变化联系起来仍具有挑战性。为填补这些研究空白，美国地质调查局启动了首次全国范围的工作，以在美国各地分布的31个地点建立气态总汞稳定同位素值的基线。结果表明，独特的汞源，如来自元素汞污染场地的汞逸出或高海拔地区对流层自由侵入，与大气背景值有所不同。在全国范围内观察到微小的梯度变化，重工业活动地区的汞含量较低，但未观察到其他同位素（如 和 ）有一致的变化。此外， 受叶片吸收和衰老的影响，但美国东北部和中西部森林地区的趋势有所不同。这些数据表明，区域排放源和其他环境变量会影响气态总汞（TGM）同位素值，凸显了在更大地理区域表征大气汞同位素以评估与国家和国际汞法规相关变化的必要性。
