Sources identification and health risk assessment of heavy metals in total suspended particulates (TSP) in a geochemical anomaly area influenced by historical indigenous zinc smelting activities.

Abstract

The superposition of heavy metals (HMs) from multiple anthropogenic sources in geochemical anomaly areas makes it difficult to discriminate prime sources in atmospheric HMs. This study utilized a combination of microscopic features, positive matrix factorisation, and Pb isotope fingerprints to trace the main sources of HMs bound to total suspended particulates (TSP) at a pollution site (Msoshui: MS) and control site (Lushan: LS) in northwestern Guizhou. The results reveal that the concentrations of Cd, Pb, Cr, As, Cu, Ni, and Zn in the TSP of LS are 3.97, 94.25, 2.93, 26.51, 3.15, 3.23, and 122.08 ng m^-3, respectively, in the 5 years from 2018 to 2022, compared to 20.15, 960.28, 4.20, 41.50, 7.72, 2.95, and 1614.50 ng m^-3 in that of MS. In comparison with other cities and remote areas, the concentrations of TSP-bound Cd, Pb, As, and Zn at MS and LS are high. The microscopic morphology shows that atmospheric particles of LS are primarily derived from mineral dust, whereas those of MS are mainly affected by multiple anthropogenic sources. The results of the positive matrix factorisation model (PMF) suggest that the predominant sources of TSP-bound HMs at MS are industrial sources, mixed sources (coal combustion and traffic sources), and mineral dust, reflecting the noticeable superposition of industrial sources compared to those at LS. The Pb isotope analysis demonstrates that TSP-bound Pb principally derive from surface soil (61.33%) and vehicle exhaust & dust from burning coal (38.67%) at LS, while it is mainly influenced by surface soil (29.21%), smelter dust (27.50%), and vehicle exhaust & dust from burning coal (43.29%) at MS. Moreover, it also indicates that the lingering effects of historical indigenous zinc smelting activities continue to impact the atmospheric and surface soil conditions in northwestern Guizhou Province. Risk assessment indicates that although the non-carcinogenic risk for each element is within acceptable limits, the total non-carcinogenic risk of HMs exceeds the minimal risk level, and Cd and As are the primary contributors.