Influence of deforestation on the mercury air/soil exchange in the Negro River Basin, Amazon

An investigation of air/surface exchange of mercury, performed at the Negro River Basin, (Amazonian region) in January 2003 and January 2004, is presented. Five sites were investigated: a flooding primary forest, a non-flooding primary forest and three deforested areas. The fluxes were estimated by using a dynamic flux chamber with sampling times varying between 6 and 12 h. The average mercury flux in deforested sites (13.7±10.3 pmol m−2 h−1) was significantly higher than in forest sites (0.1±1.8 pmol m−2 h−1). Our results showed that deforestation could be responsible for significantly increasing soil Hg emissions, mainly because of the high soil temperatures reached in deforested sites. Atmospheric gaseous mercury concentrations were generally low when compared with background areas from the Northern hemisphere. The average atmospheric Hg concentrations were 1.4±0.9 and 0.4±0.2 ng m−3 for forest and deforested sites, respectively.