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 chamber. 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 occurred in a shallow layer of surface soil (<0.5 cm), where light penetration was possible. Sludge application increased soil Hg-0 emission by 1-2 orders of magnitude, to a daily average emission rate of similar to 100 ng m(-2) h(-1) greater than background. In the United States and Europe, municipal sewage sludge application to land may be responsible for 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 amendment worldwide, the land application of sewage sludge warrants further study as a global source of atmospheric Hg. This research calls into question the stability of any land application of Hg-contaminated materials; all surface application of Hg waste represents a potential source of atmospheric Hg-0.