Geochemistry, risk assessment, and Pb isotopic evidence for sources of heavy metals in stream sediments around the Ulukışla Basin, Niğde, southern Turkey

Authors: ABDURRAHMAN LERMİ, EMMANUEL DAANOBA SUNKARI

Abstract: Concentrations of selected elements (Al, Fe, Mn, Mo, As, Cd, Cu, Cr, Ni, Co, Pb, Sb, and Zn) and Pb isotope ratios were determined in 53 sediments from Alihoca, Gümüş, Horoz, and Çakıt streams around the south-central Taurides (Ulukışla Basin), Niğde, which is a known mining province in Turkey. Several pollution and risk assessment indices were used to assess possible heavy metal pollution in the stream sediments and the associated potential ecological risks. Concentrations of As, Cd, Cu, Cr, Ni, Co, Pb, Sb, and Zn were elevated in the streams located near ancient mines, active mines, and slag piles in the area, suggesting an influence from mining activities. The pollution assessment indices indicated that the sediments were significantly polluted by As, Cd, Sb, Zn, and Pb and moderately polluted by Cu, Ni, Cr, and Co. The sediments show very high potential ecological risk with As, Cd, Sb, and Pb as the principal contributors. Ni, Cr, As, Pb, Zn, and Cd exceeded the probable effect concentrations in most of the samples implying that their concentrations may frequently affect sediment-dwelling organisms. Multivariate statistical analyses indicate that the accumulation of heavy metals in the stream sediments is due to an interplay of anthropogenic activities (mining and agrochemical application) and geogenic processes (weathering of bedrocks and supergene alteration of base metal-rich mineralization). Pb isotopic tracing indicates that total Pb in the sediments (²⁰⁶Pb/²⁰⁷Pb = 1.09-1.29) is primarily from weathering and dissolution of ultrapotassic rocks (²⁰⁶Pb/²⁰⁷Pb up to 1.20) and galena (²⁰⁶Pb/²⁰⁷Pb up to 1.21) from the Pb-Zn-Au deposits in the area with some anthropogenic input from mine slag piles (²⁰⁶Pb/²⁰⁷Pb = 1.10).

Keywords: Heavy metals, stream sediments, risk assessment, Pb isotopic tracing, Ulukışla Basin, southern Turkey

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