Mercury (Hg) Contaminated Sites in Kazakhstan: Review of Current Cases and Site Remediation Responses

Abstract

Mercury (Hg) emissions from anthropogenic sources pose a global problem. In Central Asia, Kazakhstan’s central and northern regions are among the most severely Hg-contaminated territories. This is due to two former acetaldehyde (in Temirtau) and chlor-alkali (in Pavlodar) plants, discharges from which during the second half of the 20th century were estimated over 2000 tons of elemental Hg. However, the exact quantities of Hg released through atmospheric emissions to the environment, controlled discharges to the nearby aquatic systems, leakages in the cell plant, and contaminated sludge are still unknown. The present review is the initiation of a comprehensive field investigation study on the current state of these contaminated sites. It aims to provide a critical review of published literature on Hg in soils, sediments, water, and biota of the impacted ecosystems (Nura and Irtysh rivers, and Lake Balkyldak and their surrounding areas). It furthermore compares these contamination episodes with selected similar international cases as well as reviews and recommends demercuration efforts. The findings indicate that the contamination around the acetaldehyde plant site was significant and mainly localized with the majority of Hg deposited in topsoils and riverbanks within 25 km from the discharge point. In the chlor-alkali plant site, Lake Balkyldak in North Kazakhstan is the most seriously contaminated receptor. The local population of both regions might still be exposed to Hg due to fish consumption illegally caught from local rivers and reservoirs. Since the present field data is limited mainly to investigations conducted before 2010 and given the persisting contamination and nature of Hg, a recent up-to-date environmental assessment for both sites is highly needed, particularly around formerly detected hotspots. Due to incomplete site remediation efforts, recommendations given by several researchers for the territories of the former chlor-alkali and acetaldehyde plant site include ex-situ soil washing, soil pulping with gravitational separation, ultrasound and transgenic algae for sediments, and electrokinetic recovery for the former and removal and/or confinement of contaminated silt deposits and soils for the latter. However, their efficiency first needs to be validated. Findings and lessons from these sites will be useful not only on the local scale but also are valuable resources for the assessment and management of similar contaminated sites around the globe.

Assessment of Distribution of Potentially Toxic Elements in Different Environmental Media Impacted by a Former Chlor-Alkali Plant

“…Over the last 60 years, the region's industrial facilities have significantly aggravated the environmental situation due to regular emissions including PTEs [17]. Around 1300 tons of Hg were estimated having been used during the operational period of the former CAP [18], with Hg loss estimated at 1000 t and large amounts of which still unaccounted for [19,20]. Lake Balkyldak, which is located to the north of the CAP, is considered as one of the primary pollution receivers used as a settling lagoon, where sludge and other industrial waste as well as a major part of Hg was discharged to [20,21] (Figure 1).…”

“…Around 1300 tons of Hg were estimated having been used during the operational period of the former CAP [18], with Hg loss estimated at 1000 t and large amounts of which still unaccounted for [19,20]. Lake Balkyldak, which is located to the north of the CAP, is considered as one of the primary pollution receivers used as a settling lagoon, where sludge and other industrial waste as well as a major part of Hg was discharged to [20,21] (Figure 1). Computer models showed the contaminant possibly migrating from the groundwater under the site to Irtysh River [22].…”

“…Furthermore, consumption of fish from Lake Balkyldak and Irtysh River was suggested to pose high risks to local population, along with studies indicating elevated concentrations of Hg in biota and in other environmental compartments (e.g., [19,22,23]). After the CAP was closed, a suggested remediation plan could not be fully executed and was limited to dismantling Hg electrolysis buildings and stabilizing its area, the removal of contaminated surface soils, covering pollution hotspots with clay, and the construction of a cut-off wall and a storage facility [20]. Table 1.…”

“…Table 1. Sources, toxicity, and adverse health effects of different forms of Hg [20,24,25]. For the Pavlodar urban zone as well as the CAP-affected zone, studies on the current situation of Hg contamination as well as the PTE contamination are needed [20].…”

A Questionnaire Survey on Contaminated Site Regulators’ View of Implementing Green and Sustainable Remediation in China

“…Green and sustainable remediation (GSR) aims to reduce negative impacts and maximize the long-term benefits of remediation projects, and ensure an overall net benefit among social, economic, and biophysical conditions [5]. GSR is an increasingly important part of the management of contaminated site and has attracted widespread attention [6,7].…”