Springtime depletion of mercury in the European Arctic as observed at Svalbard

Abstract

This study was carried out to see whether the geographical extent of the mercury depletion events (MDEs), first seen at Alert in the Canadian High Arctic, is also covering Svalbard. Another goal was to determine the main reaction products from the MDE and their fate. Gaseous elemental mercury (GEM), total particulate mercury (TPM), reactive gaseous mercury (RGM) and total mercury in surface snow have been measured at the Zeppelin mountain during 2000. GEM has been measured with a high time resolution automatic monitor (Tekran 2537A) based on CV-AFS, TPM was sampled/measured using high volume samplers/CV-AFS and RGM was sampled with annular denuders and measured by CV-AFS (Gardis Hg-monitor). During spring of 2000, in the three-month period following polar sunrise, there were several episodic depletions in GEM concentration correlating well with the depletion of surface ozone. Measurements of RGM and TPM showed higher concentrations of these mercury species during the depletion period than during the rest of the year. Total mercury in surface snow showed a distinct increase from the polar night to the Arctic spring. MDEs are caused by the specific chemical and physical conditions observed in the Arctic during spring. GEM is oxidised and converted to more reactive forms (RGM and/or TPM), which have considerably higher deposition velocities than elemental mercury, leading to an overall enhanced deposition flux of mercury.