Organomercury compounds hazard

This element is a chalcophile, and in unweathered rocks is most commonly found as the mineral cinnabar (HgS). In soil environments, the cationic form, is most common, as the reduced oxidation state (+1) has a limited stability range. Reduction to the metallic elemental form, H, is easily achieved in soils by both biological and chemical reactions. Elemental mercury is somewhat volatile, and the vapor is extremely toxic to organisms. Under anaerobic conditions at least, soil microbes methylate mercury, forming volatile organomercury compounds that are bioavail-able and present a health hazard. At the same time, however, anaerobic conditions can convert Hg into the exceedingly insoluble sulhde, HgS. Some of the more important transformations possible for mercury in soil are summarized in Figure 9.9. 

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