Effect of antimonite mineralization area on heavy metal contents and geochemical fractions of agricultural soils in Gümüşhane Province, Turkey

In this study, the possible impacts of an antimonite mineralization area on agricultural lands with regard to heavy metal concentrations were examined. In this scope, surface soil samples (0–20 cm) were taken from a total of 27 locations including eleven from the Avliyana antimonite mineralization area (Torul, Gümüşhane-NW Turkey) and its surroundings, eleven from agricultural areas and five from the control area. Wet digestion method was used with aqua regia procedure for determining the total heavy metal (Cd, Cr, Cu, Ni, Pb, Zn) concentrations of the soil samples. The geochemical fractions of heavy metals in soil samples were determined by way of a sequential extraction procedure. The total heavy metal contents of the soils were determined as: Ni > Cr > Zn > Cu > Pb > Cd for control soils, Cr > Ni > Zn > Cu > Pb > Cd for agricultural soils and Zn > Cu > Ni > Cr > Pb > Cd for mining area soils. It was determined that especially the values of Zn (57.6 ± 6.2 μg/g) and Cu (52.4 ± 5.8 μg/g) were high at the mineralization area due to hydrothermal alterations that are effective in the formation of mineralization. It was put forth as a result of sequential extraction that the heavy metals examined excluding Pb were observed dominantly in the residual fraction for all data set. On the other hand, it was determined that the non-residual mobile fractions reached from 11% Cr to 78% Pb in control soils, from 20% Cd to 88% Pb in agricultural soils and from 24% Cd to 87% Pb in mineralization area soils. Contamination signals due to mineralization area were monitored by way of the metal content in mobile fractions. Even though the metal concentrations determined in short term are not alarming for agricultural production, signals were observed especially for Cd, Pb, Cu, Ni and Zn elements to be more mobile in mineralization area soils in the long term due to the impact of environmental factors thereby being carried over to and accumulating in agricultural soils. In conclusion, while it is expected that the metal inputs due to mineralization areas may increase in the future, it is suggested to include plant analyses in future studies for determining the impact of the amount of bioavailable metal.