Since industrialization, the amount of mercury circulating in the atmosphere has roughly tripled. But the physical and chemical processes involved in the Hg cycle are poorly understood. Without knowing where Hg goes once it’s emitted into the atmosphere—from a coal-burning power plant, say—or how long it remains actively cycling, it’s difficult to make informed decisions about Hg pollution.
One piece of information that can be used to track Hg through the cycle is its isotopic composition. The seven stable isotopes of Hg don’t behave identically in chemical reactions and physical processes. As a result, naturally occurring samples can have measurably different isotope ratios. In most observed isotope fractionation, deviations in reactivity depend on the mass difference between isotopes, due either to kinetic effects or to differences in the zero-point energy of chemical bonds.
In 2007 Bridget Bergquist and Joel Blum of the University of Michigan in Ann Arbor discovered...
