SUNLIGHT-MEDIATED EMISSION OF ELEMENTAL MERCURY FROM SOIL AMENDED WITH MUNICIPAL SEWAGE-SLUDGE

We studied the fate and atmospheric emission of mercury (Hg) from soil amended with municipal sewage sludge using a Teflon dynamic flux cham ber. A sunlight-mediated, in situ reduction of oxidized Hg to volatile elemental mercury (Hg-0) resulted in the atmospheric transport of Hg from land-applied sludge. The reduction of oxidized Hg to Hg-O occurre d in a shallow layer of surface soil (<0.5 cm), where light penetratio n was possible. Sludge application increased soil Hg-0 emission by 1-2 orders of magnitude, to a daily average emission rate of similar to 1 00 ng m(-2) h(-1) greater than background. In the United States and Eu rope, municipal sewage sludge application to land may be responsible f or the flux of similar to 5 x 10(6) g yr(-1) of Hg-0 to the atmosphere . Considering that municipal sludge is used extensively as a soil amen dment worldwide, the land application of sewage sludge warrants furthe r study as a global source of atmospheric Hg. This research calls into question the stability of any land application of Hg-contaminated mat erials; all surface application of Hg waste represents a potential sou rce of atmospheric Hg-0.