Mercury in sediments from gold and copper exploitation areas in the Camaquã River Basin, Southern Brazil

Mercury fractionation in stream sediments from the Quadrilátero Ferrífero gold mining region, Minas Gerais State, Brazil

“…The field values of pH and Eh varied from 6.9 to 7.6 and from 184 to 281 mV, respectively. Within these intervals, the Hg 0 specie was expected to be predominate (Brookins 1988), as encountered in the present work and also observed in previous studies (CETEM 1992;Silva et al 1993;Pestana et al 2000). According to Lacerda and Salomons (1991), Hg found at processing sites is likely to occur in the metallic form.…”

“…Similar results were obtained in studies conducted in other gold mining regions of Brazil (Pestana et al 2000). Eh, pH and organic matter content proved to be important parameters, exerting control on the speciation of Hg and its distribution in aquatic environments.…”

“…These fractions correspond to the Hg associated to diverse sediment components such as Fe and Mn oxyhydroxides, a portion of organically bonded Hg which is exchanged through protonation of organic sites, and liberated from surface mineral sites where it is found strongly adsorbed (Pestana et al 2000). Since elemental mercury is sensitive to redox variations (Stein et al 1996), Hg 0 present in sediments may suffer oxidation, leading to the formation of Hg 2+ (Windmöller et al 1996;Wang et al 2003;Valle et al 2006), which presents great susceptibility to be absorbed by metallic oxihydroxides and organic superficies (Ribeiro et al 1999;Rytuba 2003;Sanei and Goodarzi 2006).…”

“…All analyzed samples showed very low levels of clay and organic material, confirming that the collected sediments had a low adsorption capacity. In its elemental form, mercury released from process sites showed relatively low solubility and mobility, tending to be concentrated in the vicinity of its release site signifying that Hg transport in aquatic mediums is controlled by sediment suspensions (Lacerda and Salomons 1991;Filho and Maddock 1997;Pestana et al 2000;Straaten 2000). In the present work, in spite of the considerable quantities of exchangeable and strongly bound Hg detected in the samples, it can be assumed that the low adsorption capacity of the evaluated sediments allowed that a large portion of Hg 2+ formed by oxidation of Hg 0 may be released.…”

Mercury speciation in soil in vicinity of coal beds using sequential extraction

“…Their general characteristics can be found in the related literature (Das et al 1995). Plenty of authors are now engaged in modifications of the various procedures (Bloom et al 2003;Boszke et al 2008;Davis et al 1997;Fernández-Martínez and Rucadio 2003;Han F et al 2006;Han Y et al 2003;Kucharski et al 2005;Lechler et al 1997;Neculita et al 2005;Pestana et al 2000;Renneberg and Dudas 2001;Sánchez et al 2005;Sladek and Gustin 2003;Wang et al 2003;Zagury et al 2006). The parameters of extraction such as extraction time, concentration of the solution, the ratio of the extractant to the sample, temperature or matrix effects are subjects for studies.…”