Atmospheric mercury over sea ice during the OASIS-2009 campaign

A Steffen,S Netcheva,R Ebinghaus,A Cole,U Friess,J Bottenheim,S Nghiem,T A Douglas,R Staebler,H Sihler

doi:10.5194/acp-13-7007-2013

Abstract

Abstract. Measurements of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected on the Beaufort Sea ice near Barrow, Alaska, in March 2009 as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) and OASIS-Canada International Polar Year programmes. These results represent the first atmospheric mercury speciation measurements collected on the sea ice. Concentrations of PHg averaged 393.5 pg m−3 (range 47.1–900.1 pg m−3) and RGM concentrations averaged 30.1 pg m−3 (range 3.5–105.4 pg m−3) during the two-week-long study. The mean concentration of GEM during the study was 0.59 ng m−3 (range 0.01–1.51 ng m−3) and was depleted compared to annual Arctic ambient boundary layer concentrations. It is shown that when ozone (O3) and bromine oxide (BrO) chemistry were active there is a positive linear relationship between GEM and O3, a negative one between PHg and O3, a positive correlation between RGM and BrO, and none between RGM and O3. For the first time, GEM was measured simultaneously over the tundra and the sea ice. The results show a significant difference in the magnitude of the emission of GEM from the two locations, with significantly higher emission over the tundra. Elevated chloride levels in snow over sea ice are proposed to be the cause of lower GEM emissions over the sea ice because chloride has been shown to suppress photoreduction processes of RGM to GEM in snow. Since the snowpack on sea ice retains more mercury than inland snow, current models of the Arctic mercury cycle may greatly underestimate atmospheric deposition fluxes because they are based predominantly on land-based measurements. Land-based measurements of atmospheric mercury deposition may also underestimate the impacts of sea ice changes on the mercury cycle in the Arctic. The predicted changes in sea ice conditions and a more saline future snowpack in the Arctic could enhance retention of atmospherically deposited mercury and increase the amount of mercury entering the Arctic Ocean and coastal ecosystems.

Highlights

Hydrology and Earth SystemMercury (Hg) is a toxic pollutanSt fcouiendnicnealsl compartments of the environment
The atmospheric mercury species measured during this campaign include gaseous elemental mercury (GEM), reactive gas phase mercury (RGM) and particulate mercury (PHg)
On March 25, during Event 3, open leads are closer at 12.5 km to the measurement and GEM is again depleted. These results suggest that both open leads and recently frozen sea ice are associated with GEM loss and with differences between reactive gaseous mercury (RGM) and PHg concentration levels

Summary

Introduction

Mercury (Hg) is a toxic pollutanSt fcouiendnicnealsl compartments of the environment. Its presence in the environment derives from both natural and anthropogenic sources. In a methylated form, mercury can be a neurotoxin taondwiislddliifsetriabnudtehdumwiatnhOsin. CTehecouassy,nsutneSmdecsrsiitesanncdrcuincegialhofowr it enters the protection of those living in them. The Arctic is vulnerable to mercury pollution and much has been published on its cycling in this unique environment (Steffen et al, 2008; Douglas et al, 2012b; Stern et al, 2012). The average northern hemispheric gaseous elemenStalomliedrcuErya(rGthEM) concentration has been reported to be approximately 1.7 ng m−3 in. 2003 (Slemr et al, 2003), with more recent reports showing

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Conclusion