Applications of Mercury Stable Isotopes in Environmental Forensics

Mercury is a globally distributed toxic trace metal, which can travel long distances in the atmosphere and bioaccumulate to elevated levels in ecosystem food webs. Since 2013, various parts of the mercury life cycle, including the production, use, emissions, releases, as well as the environmental and ecosystem fate, have been governed via the global treaty on mercury, the Minamata Convention of Mercury. The convention also calls attention to the application of mercury stable isotopes for distinguishing between various mercury sources in environmental media and for identifying sources, which require targeted risk management. Here, we introduce ways in which mercury stable isotopes can be applied in the field of environmental forensics to identify sources responsible for local contamination and global cycling that require international governance. This review is divided into: 1) the general overview on the mercury speciation and cycling, 2) the nomenclature of mercury stable isotope systems, and 3) the introduction of case studies that have successfully utilized mercury isotopes to interpret legacy and recent mercury sources in atmospheric and freshwater environments. We conclude the review by making specific recommendations as to how mercury stable isotopes can be better utilized in the field of local and global environmental forensics. These recommendations include the development of comprehensive anthropogenic mercury source inventories and isotopic-based evidence on the transboundary transport of mercury.