Bioaccessibility of arsenic and other selective trace elements in soils around the mining areas of Bolivian Altiplano

• The occurrence of trace elements (TEs) in the soils from sites of historic and present activities both open pit (extracted Au, Ag) and underground mines (Ag, Zn, Pb, Sn) mining in Bolivian Altiplano and their toxicity is one of the major environmental concerns. The aim of this study is to assess the levels of toxic trace elements such as As, Cd, Pb and Zn in the soil and their bioavailability in three sub-basins along selected transects. A combination of DTPA, and sequential extraction procedure was adapted for assessment the As content in different fraction in the soils. The results showed that TE´s were mobilized under low pH in upstream segment, thus could be considered an important factor controlling their chemical behavior in these soils. In the downstream segment of the three sub-basins, the TE enrichments were related to an increased proportion of clay contents through adsorption processes. The bioavailable fractions of the TE´s in soils indicated considerable variability for As (< 2%), Cd (<32%), Cu (<9%), Ni (<11%), Pb (<5%) and Zn (<10%). By using As sequential extraction procedure found that the less than 11% of the total As is easily mobilized in soils, they are associated to fraction related to nonspecifically (F1) and specifically sorbed (F2) fraction, which could predict a helpful tool for environmental risk assessment of these trace element contamination on Bolivian Altiplano. Enrichment factors (EF) in the soils were significantly high for As and Cd, moderate for Pb and Zn, and low for Cu, Fe, Mn and Ni contents of TE´s were high in all crops along the studied transects, and the distribution followed the trend Zn>Cu>Pb>As>Ni>Cd. The bio-concentration factor (BCF) for As, Pb and Zn were lower (< 0.5) in all crops which indicate a limited bioavailability of these TE´s, except Cd that showed high BCF values in the study area. The bioavailable TE’s might take up by the crops and finally threat human health as potential impacts.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geokemi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geochemistry (hsv//eng)

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