This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This project applies a multifaceted approach focused to address the following questions: What is reactive gaseous mercury (RGM)? Does the chemical form of RGM vary over space and time? What are the processes responsible for RGM formation? How does dry deposition of RGM vary across environmental settings? All of these questions address significant uncertainties in the global biogeochemical cycle of Hg. A working hypothesis is that the form of RGM in the air at a site will be a function of the atmospheric oxidants in the air masses interacting with that location. RGM is hypothesized to be formed by reactions with ozone, hydroxyl radical and halogen containing compounds. RGM associated with marine air masses may be predominantly HgCl2, while HgBr2 may be the dominant form in air masses derived from the free troposphere and in the air at high elevation sites, and HgO the form associated with urban areas where ozone and hydroxyl radical will be abundant. Field sites for this project have been chosen to include all of the above areas with 2 coastal sites, 3 high elevation sites, 1 urban site and 3 continental sites. RGM concentrations and deposition will be quantified using a standard automated analytical method and a dry deposition model, as well as using newly developed passive samplers and surrogate surfaces, respectively. The form of RGM will be identified using a method designed to identify specific compounds based on the temperature at which they are released from surrogate surfaces. Back trajectory analyses will be applied to understand the source of the air associated with specific forms of RGM collected at each site; and the Community Multiscale Air Quality model with the mercury module will be used to understand the atmospheric chemistry responsible for the observed air Hg concentrations and deposition.
Students from five high schools, as well as four undergraduate students from several institutions will help collect, analyze and interpret data each year of this project making them an integral component of the research team.
