Release calculation and total mass estimation of toxic elements from black shales during weathering, Aq-Darreh Bala abandoned antimony mine area, Takab, NW Iran

Black shales of the abandoned antimony mine of Aq-Darreh Bala Village in northwest of Takabcity, northwest Iran, contain high concentrations of toxic elements, especially As (4403–11883ppm), Sb (405–1022 ppm) and Hg (30–58 ppm). Enrichment factor calculations revealed thatsome trace elements including As, Sb, Hg, Zn, U, Sr, Ni, V, Co, Cu, Mo, Ni, and Zr have beendepleted, while, Pb, Th, Ga, Rb, and Ta are enriched during weathering. Mass balancecalculation results show the highest release percents (% loss) belongs to Cd, Zn, U, Sr, Ni, V,Cu, As, Ti, Mo, Zr, Hg and Sb respectively. The highest weight amount of released elementsbelongs to As, Sb, Sr, Zn, Ni, V, Zr, Cu, U, and Hg respectively. As a result, it can be concludedthat the black shale outcrops in the Aq-Darreh Bala abandoned antimony mine area have a mainrole as a geogenic source in environmental contamination of downstream environments

Keywords:

Potentially toxic elements , weathering , black shale , abandoned mine , Takab , NW Iran