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Re-emission of legacy mercury from soil adjacent to closed point sources of Hg emission
Journal article   Peer reviewed

Re-emission of legacy mercury from soil adjacent to closed point sources of Hg emission

Wei Zhu, Zhonggen Li, Ping Li, Ben Yu, Che-Jen Lin, Jonas Sommar and Xinbin Feng
Environmental pollution (1987), Vol.242(Pt A), pp.718-727
11/2018
DOI: https://doi.org/10.1016/j.envpol.2018.07.002
PMID: 30029171
Web of Science ID: WOS:000446150300077

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Abstract

Chlor-alkali plant Polyvinyl chloride production Legacy mercury Mercury isotope signatures Air-soil mercury flux Mercury reemission Environmental Chemistry Isotope Geochemistry
Mercury (Hg) emissions from point sources to air may disperse over long distance depending on Hg speciation in the plume. A significant fraction of Hg, particularly in its divalent forms, deposits locally and causes pollution to surrounding biomes. The objective of this study was to investigate (1) the historic Hg deposition to the immediate vicinity of an industrial complex that had intentional use of Hg (i.e., chlor-alkali and polyvinyl chloride production) for 5 decades until 2011, and (2) the Hg-0 re-emission from soil to air soon after the closure of the facility. The spatial distribution of near-ground Hg-0 vapor in air, soil Hg concentration and stable isotope ratio, air-soil Hg-0 flux and Hg-0 concentration in soil pore-gas were measured. It was found that the surrounding soils are severely contaminated with Hg due to the Hg release of the industrial complex, displaying soil Hg content up to 4.8 mu g g(-1). A spatial trend of Hg mass dependent isotope fractionation signature (delta Hg-202 = -2.11 parts per thousand to 0.72 parts per thousand) with respect to the distance from the closed facility was identified, representing a mixing between regional background and industrial Hg sources. Hg release from the industrial operation enhanced surface soil Hg content within a 6.5-km radius from the facility. Inside the facility, residual Hg wastes (i.e., electrolysis sludge and consumed HgCl2 catalyst) represent a strong localized emission source of atmospheric Hg-0. Near-ground atmospheric Hg-0 concentration and soil Hg-0 efflux progressively elevated toward the facility with an increase by 2-3 orders of magnitude compared to the values observed in the off-site background. These results suggest that the natural soil surfaces surrounding the closed industrial facility act as a large nonpoint source emitting legacy deposited Hg as much as the release from naturally enriched mines.

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