Heavy metal enrichments in rural environment soils, pollution dynamics, source identification, and the role of subsurface mineralizations

Abstract

Abstract This study employed a multifaceted analytical approach, incorporating spatial distribution mapping, integrated pollution indexes, multivariate statistical methods, and geochemical comparative analyses to investigate the geochemical characteristics of heavy metals (HMs), determine the distribution of HMs, assess soil contamination levels, and elucidate the origins of HMs enrichment in soils. Notable concentrations of HMs in 719 soil samples were recorded, with levels reaching up to 33 ppm for arsenic, 114 ppm for cobalt, 746 ppm for copper, 2384 ppm for nickel, 53 ppm for lead, 128 ppm for vanadium, and up to 290 ppm for zinc. Various pollution indexes, including the degree of contamination (Cd), modified degree of contamination (mCd), ecological soil pollution index (ESPI), and pollution load index (PLI), were calculated to delineate the levels of contamination. The index calculation results of soil samples revealed that 3.3%, 0.7%, 0.3%, and 0.6% of the samples were contaminated with HMs on the basis of the Cd, mCd, ESPI, and PLI, respectively. The results of the correlation analysis demonstrated consistent and strong positive relationships between the pollution indexes, with a correlation coefficient greater than 84.4% at a significance level of 0.01. These findings also provided valuable insights for environmental risk assessment. The present study emphasized that anthropogenic sources are linked primarily to agricultural practices and former mining activities, while geogenic sources are primarily associated with weathering, oxidation, and hydrothermal processes occurring in local rocks and subsurface mineralizations.