Circumpolar measurements of speciated mercury, ozone and carbon monoxide in the boundary layer of the Arctic Ocean 1State key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
2Department of Chemistry, Göteborg University, 41296 Göteborg, Sweden
3CNRS/Université Joseph Fourier – Grenoble 1, Laboratoire de Glaciologie et Géophysique de l'Environnement, 54 Rue Molière, 38400 St Martin d'Hères, France
4Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
Received: 19 August 2009 – Published in Atmos. Chem. Phys. Discuss.: 05 October 2009 Abstract. Using the Swedish icebreaker Oden as a platform, continuous measurements of
airborne mercury (gaseous elemental mercury (Hg0), divalent gaseous
mercury species HgIIX2(g) (acronym RGM) and mercury attached to
particles (PHg)) and some long-lived trace gases (carbon monoxide CO and
ozone O3) 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 Göteborg, 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° to 90° N.
Revised: 10 May 2010 – Accepted: 10 May 2010 – Published: 01 June 2010
During the North Atlantic transect, concentration levels of Hg0, CO and
O3 were measured comparable to typical levels for the ambient
mid-hemispheric average. However, a rapid increase of Hg0 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 Hg0, reflecting a strong disequilibrium.
Heading through the sea ice of the Arctic Ocean, a fraction of the strong
Hg0 pulse in the water was transferred with some time-delay into the
air samples collected ~20 m above sea level. Several episodes of
elevated Hg0 in air were encountered along the sea ice route with
higher mean concentration (1.81±0.43 ng m−3) compared to the
marine boundary layer over ice-free Arctic oceanic waters (1.55±0.21 ng m−3). In addition, the bulk of the variance in the temporal series of
Hg0 concentrations was observed during July. The Oden Hg0
observations compare in this aspect very favourably with those at the
coastal station Alert. Atmospheric boundary layer O3 mixing ratios
decreased when initially sailing northward. In the Arctic, an O3
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 O3 mixing ratios was measured returning to initial levels
of the expedition (>30 ppbV). Ambient CO was fairly stable (84±12 ppbV) during the expedition. However, from the Beaufort Sea and moving
onwards steadily increasing CO mixing ratios were observed (0.3 ppbV day−1). On a comparison with coeval archived CO and O3 data from
the Arctic coastal strip monitoring sites Barrow and Alert, the observations
from Oden indicate these species to be homogeneously distributed over the
Arctic Ocean. Neither correlated low ozone and Hg0 events nor elevated
concentrations of RGM and PHg were at any extent sampled, suggesting that
atmospheric mercury deposition to the Arctic basin is low during the Polar
summer and autumn.
Citation: Sommar, J., Andersson, M. E., and Jacobi, H.-W.: Circumpolar measurements of speciated mercury, ozone and carbon monoxide in the boundary layer of the Arctic Ocean, Atmos. Chem. Phys., 10, 5031-5045, doi:10.5194/acp-10-5031-2010, 2010.