Total gaseous mercury levels over the Northwestern Pacific Ocean and around Iceland: Oceanic, volcanic and geothermal influences

During the 5th China Arctic Research Expedition of the R/V Xuelong (June-September, 2012) total gaseous mercury (TGM) in the marine boundary layer along the route was measured. The spatial distribution of TGM was determined from Shanghai to the Bering Strait along the Northwestern-Pacific volcanic belt and around Iceland outside the Arctic Ocean. TGM ranged from 0.17 to 9.03 ng/m(3) with a mean of 1.86 +/- 1.21 ng/m(3) (median: 1.55 ng/m(3)). Several peaks along the cruise exceeded 4.0 ng/m(3). TGM means in leg1 and leg4 (near Japan) were 1.99 +/- 0.71 ng/m(3) and 2.56 +/- 1.39 ng/m(3), respectively. In leg2 and leg3 near the Kamchatka peninsula, TGM was 1.23 +/- 0.55 ng/m(3) and 2.78 +/- 1.42 ng/m(3), respectively. In leg5 near Iceland TGM was 1.39 +/- 1.02 ng/m(3) with relatively high value in Reykjavik harbor (mean: 1.91 +/- 1.27 ng/m(3)). Based upon backward air trajectory, trace gas CO, meteorological/hydrologic data, and volcanic degassing information, relatively greater TGM values were associated with the role of ocean emissions, volcanic, and other geothermal activities.