Potentially Toxic Elemental Dispersion from the Brick Kilns: Preliminary Exploration of Mechanistic Pathways.

Abstract

This study investigates the contamination status and dispersion of 11 potentially toxic elements by exploring the potential mechanistic pathways by analyzing 60 samples (coal, ash, topsoil, and subsoil) from and around the coal-based brick kilns by neutron activation analysis. The mean_n=10 concentrations (μg g^-1) of scandium (Sc: 3.85), zinc (Zn: 79.21), Antimony (Sb: 4.06), and cesium (Cs: 4.81) in coal samples and manganese (Mn: 488), antimony (Sb: 10.9), and cesium (Cs: 20.3) in ash samples were 2.8-4.3 times and 1.1-2.5 times higher than world average values, respectively. In soil samples, average_n=40 abundances (μg g^-1) of chromium (Cr: 109), zinc (Zn: 144), arsenic (As: 8.98), rubidium (Rb: 113), antimony (Sb: 2.29), and cesium (Cs: 14.3) are 1.1-5.7 times higher than the crustal values. Additionally, geo-environmental indices showed that cesium (Cs) and chromium (Cr) had undergone severe modification relative to the crustal value, and the corresponding soil samples were moderately contaminated. The positive matrix factorization (PMF) model reveals that aerodynamic transportation contributes 22% to the elemental transportation of manganese, titanium, and iron throughout the soil profile in distant soil. In comparison, hydrodynamic transportation contributes 25% for As, Zn, and Sc in both topsoil and subsoil in the nearby soil. However, the combined process of bio-geo-accumulation, hydrodynamic leaching, and aerodynamic convection mechanisms contributes 53% of the dispersion and distribution of cesium (Cs), cobalt (Co), rubidium (Rb), and chromium (Cr) in the ambient pedosphere around the brick kilns which local geology, soil properties, solubility, and weathering can further influence. Our research findings contribute to advancing scientific approaches for investigating soil contamination, including the mechanistic pathways of potentially toxic elements and the risks associated with brick kilns.