Methyl Mercury Contamination and Emission to the Atmosphere from Soil Amended with Municipal Sewage Sludge

Abstract

AbstractIn an effort to identify the effect of municipal sewage sludge application on mercury (Hg) concentrations in soil, we studied the contamination of sludge‐amended soil with inorganic and methyl Hg and the emission of these contaminants to the atmosphere using a Teflon dynamic flux chamber. The routine application of municipal sewage sludge to cropland significantly increased both total and methyl Hg in surface soil from 80 to 6100 µg kg−1 and 0.3 to 8.3 µg kg−1, respectively. Both inorganic and methyl Hg were transported from the sludge/soil matrix to the environment by emission to the atmosphere, however, there was no indication of Hg transport in limited soil water lysimeter experiments. Our data from soil amended with municipal sewage sludge represent the first quantitatively measured terrestrial source of methyl mercury (MeHg) to the atmosphere. Sludge‐amended soil emitted an average of 12 to 24 pg m−2 h−1 of monomethyl Hg and ∼100 ng m−2 h−1 of inorganic Hg to the atmosphere. A simple dispersion model suggests that sludge‐amended soil may increase regional atmospheric MeHg concentrations by ∼5%. These data highlight the need for further research to quantify the transport of Hg from sludge‐amended soil and identify the sources of MeHg in the atmosphere.