Speciation and Photochemistry of Mercury in Rainwater |
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Authors: | Robert J Kieber Nichole E Parler Stephen A Skrabal Joan D Willey |
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Institution: | (1) Department of Chemistry and Biochemistry, University of North Carolina Wilmington, Wilmington, NC 28403-5932, USA |
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Abstract: | Mercury speciation was determined in rainwater from 76 storms in southeastern North Carolina between September 1, 2003 and
September 30, 2005. Volume-weighted average concentrations of total Hg (THg), total dissolved Hg (TDHg), particulate Hg (Hgpart) and dissolved monomethyl Hg (MMHg) were 45.5 pM, 34.8 pM, 12.0 pM and 1.1 pM respectively. TDHg accounted for 77% of THg
in precipitation which is similar to Cu but significantly higher than Cr or Fe. Concentrations of the various Hg species were
very similar during summer and winter indicating that there was not a dominant seasonal influence on Hg speciation in rainwater
at this location. THg, TDHg, and MMHg concentrations were also not significantly impacted by storm origin suggesting that
they are relatively well mixed regionally and that air mass back trajectory is not the dominant factor controlling their concentration
at this location. Concentrations of TDHg and Hgpart were inversely correlated in rainwater samples subjected to irradiation with simulated sunlight, suggesting the distribution
between dissolved and particulate Hg may be controlled by photochemical transformations. Unlike TDHg and Hgpart, no significant changes in MMHg were observed upon photolysis of rainwater indicating that its distribution is not significantly
driven by sunlight-mediated reactions, in contrast to what has been observed in surface waters. Results presented in this
study indicate that the speciation of Hg in rainwater is dynamic and is driven by a complex combination of natural and anthropogenic
processes as well as interactions with sunlight. |
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Keywords: | Rainwater Mercury speciation Photochemistry |
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