Grain size–dependent pollution levels in clastic sedimentary rocks, the example of the Eocene-aged sequence (NE Türkiye)

Abstract

This study describes the role of grain size in controlling the pollution levels in clastic sedimentary rocks, by presenting results from the Eocene sequence in NE Türkiye. The mean concentrations of the potentially toxic elements (PTEs) declined in order of Ni (179) > Zn (89.6) > Cu (62.5) > Cr (24.6) > As (15.9) > Pb (13.8) > Cd (0.21) > Hg (0.11) in the shale/marl and Ni (113) > Zn (48.2) > Cu (22.3) > Cr (21.7) > As (10.8) > Pb (7.4) > Hg (0.09) > Cd (< 0.1) the in sandstone. Among the PTEs, Ni, Cu, As, Cd, and Hg in the shale/marls, and Ni, As, and Hg in the sandstones were enriched to the upper continental crust. Based on the values of the enrichment factor shales/marls were “minor enrichment” to “very severe enrichment” with As and “moderate enrichment” to “moderately severe enrichment” with Ni, and the sandstones were “moderate enrichment” to “very severe enrichment” with As and “moderate enrichment to “moderately severe enrichment” with Ni, respectively. The potential ecological risk index indicated that the PTEs in the shale/marl samples have a moderate to considerable potential ecological risk and the sandstone samples pose a low to moderate potential ecological risk. In a shale sample, the hazard quotient_ing, and hazard index values of As were found to be greater than 1 for children. The carcinogenic risk index_ing values of As in the samples are higher than the acceptable level of risk for children. The multivariate statistical analysis summarized that PTE accumulation in the Eocene sedimentary sequence was related to anthropogenic, hydrothermal fluid, and lithological influence.