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WP8 Assessment and Remediation of Mercury Contaminated Sites
() Impact of Remediation Activities on Atmospheric Emissions of Mercury.
Turner, R1, 1 RT Geosciences Inc, Squamish, BC, USA
ABSTRACT- Virtually every mining or industrial activity where mercury was a major constituent has left a footprint of elevated mercury concentrations in the terrestrial landscape surrounding these facilities. The footprint is especially evident in soils and tree rings, both of which record and preserve these activities including their cessation. Where Hg-contaminated sites are subsequently remediated atmospheric mercury emissions may again increase depending on both the nature of the remediation and the form(s) of mercury that must be dealt with. Remediation of a former chlor-alkali plant in British Columbia required four years (2000-2003) and involved excavation, stockpiling, washing, stabilization and/or offsite shipment of thousands of tons of soil and sludge. Mercury occurred in most of these materials principally in the elemental form. Offsite ambient air concentrations of mercury vapor increased from near background prior to commencement of remediation to levels during remediation that approached those observed during earlier plant operations, and then decreased again during the year following completion of remediation. Mercury concentrations in forest litter and tree rings followed a similar pattern although the incremental increase in stored mass due to remediation was small. In contrast to these observations remediation of another large Hg-contaminated site in Tennessee that involved excavation and relocation of contaminated soils with mercury mainly in the sulfide form had undetectable offsite impact on ambient air concentrations. For other contaminated sites where mercury occurs significantly in volatile form(s) one may expect detectable offsite impacts of remediation and monitoring programs should be established to provide assurance that no unacceptable risk is occurring.
Key words: emissions, mercury, remediation
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