Characterization of Heavy Metal Fractions in the Soil Developed on Volcanic Rocks of Karadağ Mountain, Turkey by Sequential Extraction

In this work, soil samples were taken from 15 different sites and the contents of Cd, Cr, Cu, Ni, Pb, and Zn in the mobile and residual fractions of the soils formed from the volcanic materials were determined by the sequential extraction procedure. The mobility of each metal was revealed by analysing fractions. The order of heavy metals in each fraction of Karadağ samples was: Cd: Acid and Water Soluble > Reducible > Oxidizable > Residual; Cr: Residual > Oxidizable > Reducible > Acid and Water Soluble; Cu: Residual > Oxidizable > Reducible > Acid and Water Soluble; Ni: Residual > Reducible > Oxidizable > Acid and Water Soluble; Pb: Reducible > Residual > Oxidizable > Acid and Water Soluble; Zn: Residual > Reducible > Oxidizable > Acid and Water Soluble. According to the results, while the concentrations of Cd and Pb in the mobile fraction were higher than those in the residual fraction, Cr, Cu, Ni and Zn were higher in the immobile fraction. When the higher mobility levels of Cd and Pb are evaluated in terms of environmental pollution and toxicity in soil, these metals have been found to have a higher potential risk than other metals. Cd and Pb are likely to be in close contact with plant roots and thus could potentially affect soil fertility. To avoid threats to productivity and food security in the long term, further trace metal inputs to soils in these areas should be avoided by agricultural management or other means.