Spatial distribution of heavy metals and sources of soil contamination in southern Konya (Turkey): Insights from geochemistry, Pb and Sr-Nd isotope systematics

Abstract

This geochemical study reports the concentrations, spatial distributions, and sources of heavy metals in soil samples from southern Konya. The investigation focused on topsoil (0-20 cm; n = 65), two soil profile (20-100 cm; n = 5), bedrock (n = 12) and stream sediment (n = 4) samples. A total of 70 soil samples were collected and in some samples determined to be enriched in Cd (5.38 ppm), Co (86.4 ppm), Cr (342 ppm), Cu (647 ppm), Fe (6.82%), Ni (755 ppm), Mn (2850 ppm), Zn (529 ppm) and As (89.8 ppm) relative to maximum allowable heavy metal concentrations in Turkey's soil. The heavy metals accumulated and enriched in stream sediments are mainly Cr, Ni, Co. The samples of soil profiles collected from different depths show commonly geogenic and partially anthropogenic effects. According to calculated geoaccumulation index (I-geo), enrichment factor (EF), and contamination factor (C-f) to evaluate possible metal enrichment in soil, the enrichment of heavy metals in the study area shows in the decreasing order of As > Ni > Cd > Co > Cr > Cu > Mn. The topsoil samples have CIA (Chemical Index of Alteration; 4.34-68.27) and CIW (Chemical Index of Weathering; 4.36-74.37) values ranged indicative of low-medium weathering. The Sr-87/Sr-86 and epsilon Nd values ranged from 0.705341 to 0.707491 and - 0.62 to - 4.95 in topsoil samples suggesting their bedrock sources. Lead isotopic data (Pb-207/Pb-206 = 0.816-0.852; Pb-208/Pb-206 = 2.000-2.242) of the topsoil and profile soil samples show mostly geogenic (natural), partially anthropogenic sources. Ni, Cr, Co, and Cu enrichments in soils and stream sediments are related extremely with weathering of ophiolitic rocks and partially with traffic and agricultural activities (fertilization, irrigation, etc.), while As and Cd enrichments in soils are related commonly with weathering of volcanic rocks and partially with similar human activities. The geochemical results of heavy metals, Pb and Sr-Nd isotope analyses indicate that the most important source of high amounts of As, Cd, Co, Cr, Ni, Cu, Mn in some of soils in southern Konya is dominantly geological materials (natural resources) and rarely human activities (anthropogenic).