Experimental investigation of the scavenging of gaseous mercury by sea salt aerosol |
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Authors: | Elizabeth G Malcolm Amanda C Ford Tara A Redding Matthew C Richardson Brianna M Strain Scott W Tetzner |
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Institution: | (1) Department of Earth and Environmental Science, 1584 Wesleyan Drive, Virginia Wesleyan College, Norfolk, VA 23502, USA |
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Abstract: | Sea salt aerosol may be an important sink for reactive gaseous mercury (RGM) in the marine boundary layer, reducing ambient
RGM concentrations and transferring the mercury (Hg) to the oceans and coastal ecosystems. The goal of this study was to determine
the affinity of gaseous mercury for sea salt aerosol (SSA) by conducting adsorption experiments with sea salt-coated sampling
denuders. In the first set of experiments, ambient outdoor air was passed through denuders coated with either KCl, as in the
widely accepted method to sample RGM, or with NaCl, a primary component of sea salt aerosols. On the one sampling day in which
RGM was above the MDL, the NaCl coated denuders removed Hg from the ambient air, equivalent to 87% of the RGM in the air (as
determined by KCl denuders). For the second set of experiments HgCl2 generated in the laboratory was passed through denuders coated with KCl and either NaCl or sea salt. The NaCl denuders collected
an average of 99 ± 16% of the mercury that the KCl denuders collected. Newly coated sea salt denuders collected 88 ± 17% of
the amount of mercury that the KCl denuders collected, but interestingly the sea salt denuders capacity decreased with repeated
use. These experiments demonstrate that HgCl2, a major component of RGM has a strong affinity for NaCl and sea salt and is therefore likely to be scavenged by SSA. This
study adds to the growing evidence that RGM is scavenged by sea salt aerosols and therefore more quickly deposited to the
ocean and coastal environment. |
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