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Mercury speciation in Pacific coastal rainwater, Monterey Bay, California

Citation

Conaway, CH and Black, FJ and Weiss-Penzias, P and Gault-Ringold, M and Flegal, AR, Mercury speciation in Pacific coastal rainwater, Monterey Bay, California, Atmospheric Environment, 44, (14) pp. 1788-1797. ISSN 1352-2310 (2010) [Refereed Article]

Copyright Statement

Copyright 2010 Elsevier Ltd. All rights reserved.

DOI: doi:10.1016/j.atmosenv.2010.01.021

Abstract

We measured mercury speciation in coastal rainwater samples from Monterey Bay, California in 2007–2008 to investigate the source of monomethylmercury (MMHg) in rainwater and determine the relative importance of wet atmospheric deposition of MMHg to coastal waters compared to other sources on the central Pacific coast. Total mercury (HgT) ranged from 10 to 88 pM, with a sample mean ± standard deviation of 33 ± 22 pM (volume-weighted average 29 pM). MMHg concentrations ranged from 0.12 to 2.3 pM with a sample mean of 0.7 ± 0.5 pM (volume-weighted average 0.68 pM). Reactive mercury (HgR) concentrations ranged from 0.87 to 47 pM, sample mean 7.8 ± 8.3 pM (volume-weighted average 6.1 pM). Acetate concentration in rainwater, measured in a subset of samples, ranged from 0.34 to 3.1 μM, and averaged 1.6 ± 0.9 μM (volume-weighted average 1.3 μM). Dimethylmercury (DMHg) concentrations were below the limit of detection in air (<0.01 ng m−3) and rainwater (<0.05 pM). Despite previous suggestions that DMHg in upwelled ocean waters is a potential source of MMHg in coastal rainwater, MMHg in rain was not related to coastal upwelling seasons or surface water DMHg concentrations. Instead, a multiple linear regression analysis demonstrated that MMHg concentrations were positively and significantly correlated (p = 0.002, adjusted R2 = 0.88) with those of acetate and HgR. These data appear to support previous suggestions that the aqueous phase methylation of Hg(II) by acetate may be the source of MMHg in rainwater, but imply that acetate concentrations in rainwater play a more important role relative to HgR than previously hypothesized. However, the calculated chemical speciation of Hg(II) in rainwater and the minimal predicted complexation of Hg(II) by acetate suggest that the aqueous phase methylation of Hg(II) by acetate is unlikely to account for the MMHg found in precipitation, or that the mechanism of this reaction in the atmosphere differs from that previously reported (Gardfeldt et al., 2003).

Item Details

Item Type:Refereed Article
Keywords:mercury, rainwater, acetate
Research Division:Environmental Sciences
Research Group:Environmental Science and Management
Research Field:Environmental Science and Management not elsewhere classified
Objective Division:Environment
Objective Group:Atmosphere and Weather
Objective Field:Atmospheric Processes and Dynamics
UTAS Author:Gault-Ringold, M (Dr Melanie East)
ID Code:125201
Year Published:2010
Web of Science® Times Cited:30
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2018-04-06
Last Modified:2018-05-04
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