Circumpolar measurements of speciated mercury, ozone and carbon monoxide in the boundary layer of the Arctic Ocean

Using the Swedish icebreaker Oden as a platform, continuous measurements of airborne mercury (gaseous elemental mercury (Hg super(0)), divalent mercury Hg super(II)(g) (acronym RGM) and mercury attached to particles (PHg)) and some long-lived trace gases (carbon monoxide CO and ozone O sub(3)) were performed over the North Atlantic and the Arctic Ocean. The measurements were performed for nearly three months (July-September, 2005) during the Beringia 2005 expedition (from Goeteborg, Sweden via the proper Northwest Passage to the Beringia region Alaska - Chukchi Penninsula - Wrangel Island and in-turn via a north-polar transect to Longyearbyen, Spitsbergen). The Beringia 2005 expedition was the first time that these species have been measured during summer over the Arctic Ocean going from 60 degree to 90 degree N. During the North Atlantic transect, concentration levels of Hg super(0), CO and O sub(3) were measured comparable to typical levels for the ambient mid-hemispheric average. However, a rapid increase of Hg super(0) in air and surface water was observed when entering the ice-covered waters of the Canadian Arctic archipelago. Large parts of the measured waters were supersaturated with respect to Hg super(0), reflecting a strong disequilibrium. Heading through the sea ice of the Arctic Ocean, a fraction of the strong Hg super(0)} pulse in the water was spilled with some time-delay into the air samples collected ~20 m a.s.l. Several episodes of elevated Hg super(0)(g) were encountered along the sea ice route with higher mean concentration (1.81 plus or minus 0.43 ng m super(− 3)) compared to the marine boundary layer over ice-free oceanic waters (1.55 plus or minus 0.21 ng m super(− 3)). In addition, an overall majority of the variance in the temporal series of Hg super(0) concentrations was observed during July. Atmospheric boundary layer {O sub(3)} mixing ratios decreased when initially sailing northward. In the Arctic, an O sub(3) minimum around 15-20 ppbv was observed during summer (July-August). Alongside the polar transect during the beginning of autumn, a steady trend of increasing O sub(3) mixing ratios was measured returning to initial levels of the expedition (>30 ppbv). Ambient CO was fairly stable (84 plus or minus 12 ppbv) during the expedition. However, from the Beaufort Sea and moving onwards steadily increasing CO mixing ratios were observed (0.3 ppbv day super(− 1)). On a comparison with coeval archived CO and O sub(3) data from the Ar