Mercury contamination in Pavlodar and Borovoe, Kazakhstan: Evaluation of atmospheric emissions and cycle systems, site assessment, and human health risk characterization

Faculty Development Competitive Research Grant Program 2018-2020

The first objective of the proposed project is to assess the temporal and spatial distributions of atmospheric mercury (Hg) total concentrations in two different locations in Kazakhstan: a heavily Hg-contaminated region (in Pavlodar), and a remote/clean location (Borovoe National Nature Park) which may or may not be significantly affected by Hg atmospheric transport from remote Hg-contaminated sites including Pavlodar. The main intent of the Pavlodar campaign is to conduct seasonal field flux measurements and to develop dispersion models investigating the kinetics of Hg emission flux (MEF) from contaminated land around a former chlor-alkali plant. The main intent of the Borovoe campaign is to improve the understanding of various mechanisms influencing the dynamics of atmospheric Hg in Kazakhstan including atmospheric transport and deposition to water and terrestrial receptors with changing meteorological conditions. A special weight is given to the atmospheric fluxes and the subsequent transportation of Hg as the preliminary investigations from the site revealed that elemental form of Hg, which is highly volatile, is widespread present on the site (see Methodology below for the details).
The second objective of the present project is to complete a contaminated site assessment by collecting and analyzing environmental samples (water and soil samples on top of atmospheric Hg measurements taken to reach the first objective) and a subsequent human health risk assessment for the Hg-contaminated region. The main intent in performing the site assessment is to quantify and better evaluate the extent of Hg contamination in the region. The main intent of the human health risk characterization is to address specific populations and scenarios and then to quantify potential risk for human health based on the most up to date information and tools available. The additional site assessment and risk characterization is a part of the study as the preliminary investigations on and around the site indicated that some populations in the region would be exposed to Hg via different pathways.
The proposed work also aims to develop a pilot system for the Kazakhstan Atmospheric Hg Cycle System (KAMCS) that will be a combination of state-of-the-art meteorological, dispersion, and environmental fate models. The data to be collected from several sampling and monitoring campaigns from two sampling locations (e.g., ambient concentrations of atmospheric Hg, soil and water emission fluxes, meteorological parameters) will be used to test, improve, and validate the performance of KAMCS.
Specific objectives to be achieved by the proposed project are:
1. to describe and possibly explain the temporal, seasonal, and spatial patterns in the ambient concentrations (i.e., source-receptor relationship) of Hg in the sampling regions
2. to evaluate the local and regional distribution and evasion (or volatilization) rates from a heavily contaminated site and the atmospheric transport and deposition fluxes in a rural/clean site in Kazakhstan
3. to develop an atmospheric Hg database by providing information on past, current, and future depositions in Borovoe and emissions of Pavlodar sites
4. to develop a state-of-the-art distribution (Co-kriging) and transportation modeling (Hysplit) system - the Kazakhstan Atmospheric Hg Cycle System (KAMCS).
5. to assess the relative importance and magnitude of the contributions of the regional transport to the total budget of atmospheric Hg entering to and leaving Kazakhstan
6. to run an environmental fate model based on fugacity (mathematical mass-balance chemical model simulating specific processes involved in contaminant cycles across different environmental compartments) to predict Hg distribution across different compartments of earth
7. to perform a contaminated site assessment addressing atmospheric, soil, and water contamination which may also provide a future example to be used for other similar sites in Kazakhstan
8. further classify the Hg contamination data to subgroups (atmospheric, water, volatile soil, residual soil) such that it would be used in a detailed exposure assessment
9. based on the results of site contamination assessment and site information, identify susceptible populations and possible exposure scenarios taking into consideration oral, inhalation, and dermal pathways of exposure
10. to assess human exposure and characterize the risk on previously identified populations for their possible exposure to Hg in that environment, address site management recommendations
Scientific significance and novelty:
Significance: Hg is a non-essential element which is highly toxic to humans. It is on the list of priority pollutants of the US EPA (2014) and is one of the most toxic and preoccupying metals concerning human exposure (Tchouwnou et al. 2014). Hg chemistry and transport is complex as it has multiple species (elemental, inorganic, and organic) with different physio-chemical properties. Furthermore, the toxicity and the bioavailability of these species change based on the specific exposure pathway (ingestion, inhalation, and/or dermal) (Guney et al. 2013). As a result, site characterization and health assessment for Hg contaminated sites is a challenging task. Therefore, developing and improving research methods for a proper characterization of Hg-contaminated sites followed by an appropriate characterization of human health risks is a research priority.
Novelty: Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, and following emission, elemental Hg can be transported long distances before oxidation and removal by particle and gas-phase dry deposition or scavenging by precipitation (Driscoll et al. 2013). The anthropogenic sources include industry such as chlor-alkali plants, as in the case of Pavlodar. In the literature, Hg monitoring research reporting is not generally accompanied by detailed urban and contaminated zone measurements. An integrated approach to characterization taking into account different environmental media and Hg species is required to significantly improve the understanding of partition, transport, and potential risks of Hg. Furthermore, the atmosphere is the foremost transport pathway of Hg emissions (Driscoll et al. 2013) and the atmospheric transport of Hg is possible over long distances. Remote region measurements as included in the present study may allow the elimination of locally influenced data, and may bring an important contribution to the current state of knowledge on the atmospheric modeling of Hg transport and transformation.
Although Pavlodar is an important hotspot of Hg contamination with a potential to adversely affect nearby areas as well as remote locations, published research is limited regarding Hg contamination in Pavlodar (few studies) or Hg atmospheric cycle dynamics in general in Kazakhstan (no peer-reviewed studies could be located). For Pavlodar, a detailed literature research revealed only three scientific articles on the impact of Hg contamination, distribution, and transport on nearby water, sediment, aquatic biota, and food chain (Ulrich et al. 2007a, 2007b, 2007c). Apart from research in the area, the other only available resources of significant importance included a book chapter on Hg bioremediation (Ilyuschenko et al. 2013) and three online technical reports (Ilyuschenko and Daukeyev 2011, Ilyuschenko et al. 2010, Khrapunov et al. 2004) addressing soil treatment, site management, and environmental risk assessment issues on the contaminated site. For the area, additional research is highly needed on atmospheric impacts of the pollution on nearby and remote locations as well as on an up-to-date site assessment followed by a human health risk characterization using most up to date modern tools.