The effects of the coastal environment on the atmospheric mercury cycle

Abstract

[1] Atmospheric mercury (Hg) species were investigated on the east coast of Florida during June 2000. The site was impacted by air mass transport from the Atlantic Ocean and south Florida. Periods with atmospheric transport from the Atlantic were characterized by low concentrations of elemental gaseous Hg and inorganic divalent reactive gaseous mercury (RGM), demonstrating that the marine boundary layer was not a significant source of RGM to this coastal site as previous researchers have hypothesized. When anthropogenic impacts were observed at the site, indicated by elevated concentrations of gases including HNO 3 and SO 2 , RGM concentrations had higher daytime maximums. Particulate phase Hg concentrations were higher than can be explained by sea spray alone, as determined by chemical analysis of the seawater, suggesting that gaseous Hg is diffusing into the sea-salt aerosol. Although atmospheric Hg concentrations were not elevated, the observed scavenging of Hg gases by sea-salt aerosols indicates that Hg may be rapidly cycled at the atmosphere-ocean interface between gaseous, aerosol, and oceanic forms. Deposition of aerosol enriched in Hg via this process may constitute a significant global mercury flux to the oceans.

Mercury Sources to Lake Ozette and Lake Dickey: Highly Contaminated Remote Coastal Lakes, Washington State, USA

“…Continental flows brought occasionally enhanced RGM air masses (10 -20 pg/m 3 ), but were generally very low (< 2.0 pg/m 3 ). The low RGM concentrations are in contrast to similar studies at other coastal locations (Laurier and Mason 2007;Engle et al 2008;Malcolm and Keeler 2003). RGM measurements at CPO were not recorded during the summer months (June, July, August) when UV radiation and RGM would be expected to be at their highest.…”

“…In a study along the coast of Rhode Island, Malcolm et al (2003) hypothesized a mass transfer of atmospheric mercury to coarse sea salt particles to account for concentrations in particulates that could not be explained by mercury concentrations in seawater alone. Additionally, Engle et al (2008) found mercury concentrations in particulates to increase with proximity to the ocean.…”

“…Studies investigating mercury cycling and deposition at coastal environments have focused on in situ production of reactive gaseous mercury (RGM) and the role of sea salt aerosols on particulate deposition (Laurier and Mason 2007;Engle et al 2008;Malcolm and Keeler 2003). RGM is an important factor in evaluating atmospheric deposition as it is easily scavenged from the atmosphere via wet or dry deposition.…”

“…Land use activity leading to increased soil erosion can result in increased mercury export from watersheds, enhancing fluxes to waterbodies (Engstrom et al 2007;Grigal 2002). Additionally, marine atmospheric boundary layer processes influencing mercury speciation may have implications for enhanced loading in coastal settings (Malcolm and Keeler 2003).…”

A Re-Examination of Ambient Air Ozone Monitor Interferences

“…The authors' experimental observations suggest that the HSW and packed-bed Hopcalite scrubbers used in the UV-HSW, UV-Hop, and UV-Hop-N analyzers are very effective at removing Hg from the sample air at lower mixing ratios, although perhaps less so at the high Hg mixing ratio used for test A in which response ratios were reduced to 0.6 -0.7. 25,26 the O 3 artifact due to background Hg is much less than 1 ppb. In urban areas such as Toronto 27 and Tuscaloosa, AL, 28 the gas-phase Hg levels average up to 4 ng/m 3 (ϳ0.5 ppt), so the average O 3 interference should still be less than 1 ppb.…”