title: Accumulation and oxidation of elemental mercury in tropical soils.
abstract: The role of chemical and mineralogical soil properties in the retention and oxidation of atmospheric mercury in tropical soils is discussed based on thermal desorption analysis. The retention of gaseous mercury by tropical soils varied greatly both quantitatively and qualitatively with soil type. The average natural mercury content of soils was 0.08 ± 0.06 μg g(-1) with a maximum of 0.215 ± 0.009 μg g(-1). After gaseous Hg(0) incubation experiments, mercury content of investigated soils ranged from 0.6 ± 0.2 to 735 ± 23 μg g(-1), with a mean value of 44 ± 146 μg g(-1). Comparatively, A horizon of almost all soil types adsorbed more mercury than B horizon from the same soil, which demonstrates the key role of organic matter in mercury adsorption. In addition to organic matter, pH and CEC also appear to be important soil characteristics for the adsorption of mercury. All thermograms showed Hg(2+) peaks, which were predominant in most of them, indicating that elemental mercury oxidized in tropical soils. After four months of incubation, the thermograms showed oxidation levels from 70% to 100%. As none of the samples presented only the Hg(0) peak, and the soils retained varying amounts of mercury despite exposure under the same incubation conditions, it became clear that oxidation occurred on soil surface. Organic matter seemed to play a key role in mercury oxidation through complexation/stabilization of the oxidized forms. The lower percentages of available mercury (extracted with KNO3) in A horizons when compared to B horizons support this idea.
authors.affiliation: Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Liliane Catone
authors.initials: LC
authors.lastname: Soares
authors.affiliation: Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil. Electronic address: fegreja@ufmg.br.
authors.forename: Fernando Barboza
authors.initials: FB
authors.lastname: Egreja Filho
authors.affiliation: Departamento de Ciências Exatas e Aplicadas, Instituto de Ciências Exatas e Aplicadas, Universidade Federal de Ouro Preto, 35931-008 João Monlevade, MG, Brazil.
authors.forename: Lucília Alves
authors.initials: LA
authors.lastname: Linhares
authors.affiliation: Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Cláudia Carvalhinho
authors.initials: CC
authors.lastname: Windmoller
authors.affiliation: Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil.
authors.forename: Maria Irene
authors.initials: MI
authors.lastname: Yoshida
mesh_terms: D000327:Adsorption; D000393:Air Pollutants / Q000032:analysis; D001938:Brazil; D004784:Environmental Monitoring / Q000379:methods; D005740:Gases / Q000032:analysis; D005843:Geography; D006863:Hydrogen-Ion Concentration; D008628:Mercury / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis; D010100:Oxygen / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*; D013054:Spectrophotometry, Atomic; D013696:Temperature; D014329:Tropical Climate
chemical_list: D000393:Air Pollutants; D005740:Gases; D009930:Organic Chemicals; D012987:Soil; D012989:Soil Pollutants; D008628:Mercury; D010100:Oxygen
keywords: Adsorption; Atmospheric mercury; Chemical transformations; Soil chemistry; Thermal desorption