Progress in the Study of Stable Hg Isotope Geochemistry

During recent decades,remarkable progress has been made in the study of Hg stable isotope geochemistry.Previous studies have reported both mass-dependent fractionation(MDF) and mass-independent fractionation(MIF) of Hg isotopes,especially MIF of odd Hg isotopes.Up to now,Hg is thus the only metal element that displays significant MIF of isotopes in the nature.This paper introduced the background of Hg isotope studies,and gave a summary of Hg isotope analysis methods(pre-concentration and isotope measurement),processes of Hg isotope fractionating and the isotopic compositions of Hg in different reservoirs on the Earth.Moreover,recent studies also have reported significant MIF of even Hg isotopes in precipitation.Neither laboratory experiment nor fieldwork has identified the mechanisms and processes inducing MIF of even Hg isotopes.Further study is thus needed to verify this observation and to get the best understanding of the mechanisms.The possible three-dimension of the Hg isotope system may provide new insight into all aspects of global bio-geochemical Hg cycle.