Abstract
Industrial activities have resulted in severe environmental contamination that may expose rural and urban populations to unacceptable health risks. For example, chlor-alkali plants (CAPs) have historically contributed mercury (Hg) contamination in different environmental compartments. One such site (a burden from the Soviet Union) is located in an industrial complex in Pavlodar, Kazakhstan. Earlier studies showed the CAP operating in the second half of the twentieth century caused elevated Hg levels in soil, water, air, and biota. However, follow-up studies with thorough risk characterization are missing. The present study aims to provide a detailed risk characterization based on the data from a recent site assessment around the former CAP. The ⅀HI (hazard index) ranged from 9.30 × 10−4 to 0.125 (deterministic method) and from 5.19 × 10−4 to 2.54 × 10−2 (probabilistic method). The results indicate acceptable excess human health risks from exposure to Hg contamination in the region, i.e., exposure to other Hg sources not considered. Air inhalation and soil ingestion pathways contributed to the highest ⅀HI values (up to 99.9% and 92.0%, respectively). The residential exposure scenario (among four) presented the greatest human health risks, with ⅀HI values ranging from 1.23 × 10−2 to 0.125. Although the local urban and rural population is exposed to acceptable risks coming from exposure to Hg-contaminated environmental media, an assessment of contamination directly on the former CAP site on the industrial complex could not be performed due to access prohibition. Furthermore, the risks from ingesting contaminated fish were not covered as methyl-Hg was not targeted. An additional assessment may be needed for the scenarios of exposure of workers on the industrial complex and of the local population consuming fish from contaminated Lake Balkyldak. Studies on the fate and transport of Hg in the contaminated ecosystem are also recommended considering Hg methylation and subsequent bioaccumulation in the food chain.
Highlights
Consequences of rapid industrialization with far-reaching impacts include discharges of potentially toxic elements (PTEs) into the environment and their subsequent accumulation in various environmental sinks [1]
Hg concentrations of the environmental samples with their physicochemical characteristics have been previously analyzed by our research group, and the results are reported in detail in our recent publications [25,26]
The presence of organic matter in the soil was characterized by the contents of total carbon (TC) (2.21–12.82 g/kg), total organic carbon (TOC) (2.14–10.79 g/kg), and total nitrogen (TN) (0.033–0.167%) in the selected samples
Summary
Consequences of rapid industrialization with far-reaching impacts include discharges of potentially toxic elements (PTEs) into the environment and their subsequent accumulation in various environmental sinks [1]. Mercury (Hg), a ubiquitous element, is a PTE. Sustainability 2021, 13, 13816 classified as a priority hazardous substance according to the adopted Water Framework. Hg exists in the environment in three main forms: elemental (Hg0 ), organic (e.g., methyl Hg (Me-Hg)), and inorganic (e.g., Hg2+ ) [6,7]. Despite the ability of Hg to be transformed into its other more toxic forms, elemental Hg cannot be broken down or reduced into less harmful substances [6]. Inorganic Hg can enter water or soil through weathering of
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