AN EXPERIMENTAL-STUDY OF 2 POTENTIAL METHYLATION AGENTS OF MERCURY IN THE ATMOSPHERE - CH3I AND DMS

Experimental results from a study of the gas and aqueous phase reactions of elemental mercury (Hg-o) with methyl iodide (CH3I) and dimethyl sulfide (DMS) are presented. In aqueous phase experiments with CH3I we found no observable increase in methyl mercury (MeHg). A small formation of MeHg, however, was observed in some (but not all) gas phase experiments in sunlight. A loss of Hg-o and a simultaneous formation of oxidized mercury (Hg(II)) was also observed in these experiments. No reaction, neither methylation or oxidation, was found between Hg-o and DMS under any conditions investigated. These experiments suggest that a simple homogeneous gas or aqueous phase methylation of Hg-o by DMS or CH3I in the atmosphere cannot account for the significant levels of MeHg observed in precipitation.