Mercury in the snow and firn at Summit Station, Central Greenland, and implications for the study of past atmospheric mercury levels

[摘要] Gaseous Elemental Mercury (Hg° or GEM) was investigated at SummitStation, Greenland, in the interstitial air extracted from the perennialsnowpack (firn) at depths ranging from the surface to 30 m, duringsummer 2005 and spring 2006. Photolytic production and destruction of Hg° were observed close to the snow surface during summer 2005 and spring2006, and we observed dark oxidation of GEM up to 270 cm depth in June 2006.Photochemical transformation of gaseous elemental mercury resulted in diel variationsin the concentrations of this gas in the near-surface interstitial air, butdestruction of Hg° was predominant in June, and production was the mainprocess in July. This seasonal evolution of the chemical mechanismsinvolving gaseous elemental mercury produces a signal that propagatesdownward through the firn air, but is unobservably small below 15 m indepth. As a consequence, multi-annual averaged records of GEM concentrationshould be well preserved in deep firn air at depths below 15 m, andavailable for the reconstruction of the past atmospheric history of GEM overthe last decades.

[学科分类] 大气科学