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 0 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 ∼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 ∼5 × 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 .