Bromoform and Dibromomethane in Coastal Waters During the Gulf of Mexico and East Coast Carbon (GOMECC) Cruise

Brominated organic compounds are major contributors for reactive radical species BrOx (Br + BrO) in the atmosphere. Reactive radical bromine is one of the catalysts for stratospheric ozone depletion. It is fifty times more effective than chlorine in depleting stratospheric ozone. The very short live (VSL) polybrominated compounds, bromoform (CHBr3) and dibromomethane (CH2Br2), are potentially significant sources of the reactive radical species to the stratosphere. They are predominately from natural sources, but anthropogenic sources are also important for coastal waters with seawater cooled power plants and treated water outfalls. Bromoform, with the atmospheric lifetime of ~2-3 weeks, is the dominate by-product of chlorinated seawater. Many of the previous studies were focused on the biogenic portions of the bromoform and dibromomethane budgets. Relatively few studies have examined bromoform concentrations in chlorinated seawater from power plants located in Europe and Asia. The Gulf of Mexico and East Coast Carbon (GOMECC) Cruise in 2007 provided us with the opportunity to measure the air, surface seawater and depth profile concentrations of both CHBr3 and CH2Br2 in the U.S. coastal region that may be affected by both biogenic and anthropogenic sources. High levels of chlorophyll were observed along the coast, which may be used as an indicator of biogenic source. Elevated surface seawater concentrations of bromoform and dibromomethane were detected near three nuclear power plants outfalls along the Florida coast, and elevated levels were associated with the new treated water outfall located just outside Boston Bay. Fluxes, production rates and emissions from this region will be presented.