Research in my group revolves around the chemical, biological, and physical cycling of trace elements in the environment. Many trace elements are biologically required while others serve as tracers of a variety of natural and anthropogenic processes. We study the supply of trace elements to the oceans from rivers and coastal sediments as well as from the atmosphere. The supply of trace elements to the open ocean, far from rivers and shallow sediments, is dominated by atmospheric transport of mineral dust and other aerosols. When the supply of iron from dust is too low, the phytoplankton cannot photosynthesize efficiently and it is estimated that primary productivity in 30-40% of the open ocean is limited by the lack of iron. There is additional evidence that some areas are co-limited by low supply of Mn, Co and Zn. We also study the atmospheric cycling and deposition of mercury because its incorporation into aquatic food webs leads to mercury concentrations in fish that are toxic to humans. It is essential to use ultra-clean sampling and analytical techniques to obtain reliable field data for trace elements, and we focus a lot of time on improving old techniques and developing new ones.

The data we collect is interpreted within a framework that includes chemical and biological processes overlain upon physical mixing in the atmosphere and oceans, and we collaborate with scientists who expertise in all of those areas. This relatively young field of research is referred to as “biogeochemistry”. By understanding and quantifying the mechanisms of trace element biogeochemistry, we help inform studies of paleo-climate and paleo-oceanography as well as the future of our environment.