Abstract
Mercury (Hg) is one of the trace toxic and bioaccumulative global pollutants, and due to its long atmospheric lifetime, it presents a significant global challenge. The present study (1) utilizes total gaseous mercury (TGM) measurements made around a former Hg-cell chlor-alkali plant (CAP) located in Pavlodar, Kazakhstan, and predicts the spatial distribution of Hg over its premises and the nearby city. It then (2) estimates the environmental repartition of Hg deposited by the CAP using three fugacity models of varying complexity: Level I, QWASI, and HERMES. Finally, it (3) predicts long-range Hg transport via forward trajectory-based cluster analysis. The atmospheric Hg levels measured in Pavlodar and around Lake Balkyldak were elevated: in the range of 1–37 ng/m3 with an urban background level at 4.9 ng/m3. Specifically, concentrations up to 37 ng/m3 close to Lake Balkyldak and up to 22 ng/m3 nearby the city’s industrial zone (where the CAP was located) had been observed. Interpolation maps created using kriging also suggest these locations as the primary sources of atmospheric Hg in the city. The Level I fugacity model indicated that almost all of Hg is expected to end up in the atmosphere. The modeling results obtained using more complex QWASI and HERMES models showed that some significant quantity of Hg would still be associated with the sediments of Lake Balkyldak (a large wastewater discharge pond nearby the CAP). The forward trajectory-based cluster analysis method revealed the long-range atmospheric transportation routes and local, regional, and global impact zones. Furthermore, a source-receptor relationship using air transportation pathways to identify “areas of impact” was addressed. During both heating and non-heating seasons, the frequency-based analysis identified the distribution of Hg reaching the territories of Mongolia, northwest China, southwest Kazakhstan. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT-4) model forward trajectory analysis has confirmed similar patterns during heating and non-heating seasons, except with shorter impact distances during the non-heating period. Even though the CAP was closed more than 30 years ago and those past remediation efforts cleaned up the site, the residual Hg pollution seems significant and should be further investigated in different environmental media.
Highlights
Atmospheric mercury (Hg) is one of the most dangerous global pollutants due to its atmospheric lifetime and toxicity [1,2,3]
The urban background level of Hg was determined as 4.9 ng/m3, as an average value of Hg concentrations measured at least 5 km away from the source
Geospatial interpolation-based visualized atmospheric Hg levels recorded during the measurement campaigns in Pavlodar and around Lake Balkyldak and its surrounding area are given in Figures 3 and 4
Summary
Atmospheric mercury (Hg) is one of the most dangerous global pollutants due to its atmospheric lifetime and toxicity [1,2,3]. After being released to the atmosphere, elemental Hg can travel over long distances due to residence time up of to one year before its removal through oxidation on particle surfaces as well as gas-phase dry and wet deposition [8,9]. Once deposited in water or terrestrial bodies, it may be further oxidized into methylmercury (MeHg), which can bio-accumulate in the food chain and increase exposure to humans and wildlife [10]. Because of its long-range atmospheric transportation routes, Hg may be distributed globally and reach even remote areas [11]. Gaseous elemental Hg can be directly inhaled, and most dose exposures by inhalation are absorbed into the blood and quickly pass through the blood–brain barrier, crossing into the extracellular fluid of the central nervous system and as a result causing damage to the brain [12]
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