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- Title
National‐Scale Assessment of Total Gaseous Mercury Isotopes Across the United States.
- Authors
Tate, Michael T.; Janssen, Sarah E.; Lepak, Ryan F.; Flucke, Laura; Krabbenhoft, David P.
- Abstract
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 δ202Hg, but no consistent changes in other isotopes such as Δ199Hg and Δ200Hg were observed. Furthermore, δ202Hg 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. Plain Language Summary: A simple, economic total gaseous mercury analyzer was deployed across the United States to determine if atmospheric sources of mercury were distinguishable across regions and seasons using mercury stable isotope values. Results indicated that heavily contaminated sites and high elevation sites did have different mercury isotope values, but overall values across the country were similar. Further application of these measurements may aid in assessing the impact and changing sources of mercury because of federal and global initiatives, including the Minamata Convention on Mercury. Key Points: Mercury isotope values were measured on a national scale across a wide range of environmentsSource proximity and seasonal variables dictate Hg isotope values for total gaseous mercuryExtreme industrial contributions can be distinguished from background atmospheric mercury
- Subjects
UNITED States; MERCURY isotopes; AIR pollutants; ATMOSPHERIC mercury; EVIDENCE gaps; HAZARDOUS waste sites; STABLE isotopes; CATALYTIC reduction
- Publication
Journal of Geophysical Research. Atmospheres, 2023, Vol 128, Issue 8, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2022JD038276