Five ARL Scientists Author Paper Examining Mercury Trends

March 2020

“Long-Term Observations of Atmospheric Speciated Mercury at a Coastal Site in the Northern Gulf of Mexico during 2007–2018” was recently published in a special issue of Atmosphere titled “Atmospheric Mercury: Sources, Sinks, and Transformations.” Authored by ARL’s Xinrong Ren, Winston Luke, Paul Kelley, Mark Cohen, and Ariel Stein, among others, the study presents measurements of atmospheric mercury collected at the Moss Point, Mississippi, Atmospheric Mercury Network site to examine their long-term trends. The authors also examined the relationships between mercury, trace gases, and meteorological parameters to develop source-receptor information for atmospheric mercury deposition to this sensitive coastal environment and to inform policies to reduce mercury loading.

Why study mercury?

Mercury is a potent neurotoxin – a chemical destructive to nerve tissue. The World Health Organization lists mercury among the top ten chemicals/groups of chemicals of major public health concern. High levels of mercury can harm vital organs in people of all ages, but it is particularly damaging to the development of fetuses, infants and young children.

Important conclusions

The study indicated that experiences at the monitoring site were impacted by local and regional mercury sources as well as global mercury cycle. Findings include:

• The concentrations of two forms of atmospheric mercury, gaseous elemental mercury (GEM) and gaseous oxidized mercury (GOM), have decreased while particulate-bound mercury (PBM) and mercury wet deposition increased slightly from 2007 to 2018.
• Lower GEM concentrations were observed in the early morning and are attributed to the absorption of GEM by surrounding plants, which is perhaps enhanced by chemical reactions on wet plant surfaces at night.
• Relationships between elevated GEM/GOM/PBM and wind direction indicate that mercury measurements at this site may be influenced by nearby mercury sources.
• Relationships among atmospheric mercury and other air pollutants suggest different sources of GOM, including direct emissions from mercury sources, photochemical production of GOM, and the air up higher with higher levels of GOM circulating down to the ground.

Water, aquatic grasses and trees on a distant shoreline under a blue sky with wispy clouds; a tall metal tower with steps to a platform from which metal cables extend down to the ground, collection units that appear to be metal boxes are mounted in multiple places near the top of the structure and a small metal trailer near the base sits inside wooden fencing with double doors open; a long, narrow wooden platform elevated several feet off the ground by wood and concrete pillars and a 6-step wooden staircase, five separate collection units are spaced at intervals along the length, the ground is gravel and weeds and the water’s edge and tree line are visible.
Around the Grand Bay Site: A view from the 10 meter measurement tower (top), the 10-m tower (middle) and precipitation collectors to measure mercury wet deposition and precipitation chemistry (bottom). Credit: NOAA