Fumigant methyl iodide can methylate inorganic mercury species in natural waters

Abstract

Methyl iodide or iodomethane (CH 3 I) has recently been registered as a fumigant in many countries, although its environmental impacts are not well understood. Here we report the results of a study on the methylation of mercury by CH 3 I in natural water by incubation experiments using both Hg (199 HgCl 2 and)- and hydrogen (CD 3 I)-stable isotope addition techniques. We find that methylation of Hg 0, and Hg 2+ by CH 3 I can occur in natural water under sunlight, while only Hg 0 and can be methylated in deionized water. We propose that the methylation of Hg by CH 3 I in natural waters is mediated by sunlight and involves two steps, the reduction of Hg 2+ to Hg 0 / and the subsequent methylation of Hg 0 / by CH 3 I. Further quantitative assessment suggests that CH 3 I-involved methylation of inorganic Hg could be an important source of CH 3 Hg + in an environment where CH 3 I has been used in large amounts as a fumigant. © 2014 Macmillan Publishers Limited. All rights reserved.