Simone Moos PhD '18 rejoins the Boyle Group as a postdoc having successfully defended her doctoral thesis ‘The Marine Biogeochemistry of Chromium Isotopes’ in September 2017. Moos developed one of the first reliable methods to measure Cr isotope ratios in seawater, which she now employs to study the relatively unexplored marine cycling of Cr. In seawater, Cr occurs at nano-molar concentrations and in two oxidation states (particle-reactive Cr(III) and soluble Cr(VI)). Moos’s research has direct implications for the interpretation of Cr isotope signatures in the geologic record, which are used to study the oxidation history of the atmosphere. In 2015, Moos traveled from Alaska to the North Pole aboard the icebreaker USCGC Healy. This expedition was part of the international research program GEOTRACES, which studies the biogeochemical cycling of trace elements and their isotopes in the ocean. During the 10-week Arctic mission, Moos collected seawater samples for her own novel Cr isotope research, the Boyle lab’s long-standing lead isotope research, and the wider US trace metal community.