Atmospheric Environment 39 (2005) 7518–7528 Influence of deforestation on the mercury air/soil exchange in the Negro River Basin, Amazon Gabriella Magarelli, Anne He´le`ne Fostier à Institute of Chemistry, State University of Campinas (Unicamp), P.O.Box 6154, 13084-971, Campinas, SP, Brazil Received 24 January 2005; received in revised form 20 July 2005; accepted 20 July 2005 Abstract 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 (13.7710.3 pmol m 2 h 1 ) was significantly higher than in forest sites (0.171.8 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 1.470.9 and 0.470.2 ng m 3 for forest and deforested sites, respectively. r 2005 Elsevier Ltd. All rights reserved. Keywords: Mercury fluxes; Atmosphere–soil exchange; Flux chamber; Soil temperature 1. Introduction One of the most important characteristics of Hg, that differentiates it from other metals, is its capacity of being emitted or re-emitted to the atmosphere, mainly in its gaseous elemental form Hg 0 . Because of its properties of low chemical reactivity and low water solubility it presents an atmospheric residence time of about 1 year, allowing its dispersal and deposition in a global scale, resulting in the concept of ‘‘global pollutant’’ for this element (Schroeder et al., 1989). In the atmosphere, Hg 0 accounts for almost 98% of the total gaseous mercury (TGM) and it can participate in some processes and/or interactions of chemical, physical or photochemical natures, allowing its transfer to the aquatic and terrestrial compartments, as well as its possible conver- sion to methyl-mercury (MeHg), one of the most toxic Hg species. The property of MeHg to bio-accumulate up to a million of times along the aquatic food chain constitutes one of the main environmental concerns of mercury ecotoxicology, justifying the study of its biogeochemical cycle and, in particular, the processes of transfer of this element from aquatic and terrestrial ecosystems to the atmosphere (Schroeder and Munthe, 1998). It has been estimated that approximately 95% of the 200,000 tons of Hg mobilized since 1890 are currently accumulated in superficial deposits (‘‘Expert Panel’’, 1994). The re-emission of a portion of this supply would be equivalent to the total of the anthropogenic emissions of the United States (Porcella et al., 1996). Forests cover approximately 4  10 9 ha of the terrestrial surface (INPE, 2004) and the destination of the stored Hg, ARTICLE IN PRESS www.elsevier.com/locate/atmosenv 1352-2310/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2005.07.067 à Corresponding author. Tel.: +55 19 3788 3079. E-mail address: fostier@iqm.unicamp.br (A.H. Fostier).