Application of a teflon™ dynamic flux chamber for quantifying soil mercury flux: Tests and results over background soil

High precision and low blank contamination were achieved with a Teflon™ dynamic chamber for measuring, soil mercury flux. Using this chamber, background soil mercury flux averaged between 2 and 7 ng m−2 h−1 over forest soil, and between 12 and 45 ng m−2 h−1 over open field soil. Spatial heterogeneity of soil mercury flux at duplicate plots co-located within 2 m was small but significant, differing by 20–50%. Elevated mercury emission over field soil occurred in the presence of direct sunlight at the open field sites. Solar radiation, soil temperature and soil moisture were all significant factors effecting mercury emission from soil. Solar radiation affected the reduction of naturally occurring, inorganic soil mercury compounds to volatile elemental mercury (Hg°). We estimate that background soil accounts for the gross emission of 109 g yr −1 of Hg° to the atmosphere, with approximately two-thirds of this total from sunlight-exposed soil and the remainder from forest and other shaded-soil ecosystems.