Department of Physics
Portland State University

Current Research Areas

Isotopic atmospheric methane

Emissions from rice agriculture

Role of trees in the methane budget

Methyl halide emissions from estuaries

Carbon flux from cities

Method development

Methyl halide emissions from the Florida Everglades

Gobal budgets for methyl halides (CH3Cl and CH3Br) are poorly constrained. Sinks for methyl halides outweigh sources, and the oceanic flux, the largest natural source of methyl halides, cannot with present uncertainties contribute to a balanced budget. Studies point to terrestrial tropical and subtropical systems as sources that would balance the global budget but information on these potential sources are severely limited.

Coastal marine wetlands have biogeochemical properties that would enhance the production and emission of methyl halides. These wetlands are generally areas of high primary production that receive large quantities of halides from seawater inundation and atmospheric deposition.

The Florida Everglades and coastal waters are ideally situated to study the processes responsible for CH3Cl and CH3Br emission in coastal marine systems. The Florida Everglades and coastal waters are situated in a warm subtropical environment and consequently have an abundance of sunlight that can drive the generation of methyl halides through primary production and photochemical degradation of disolved organic matter (DOM).

Our research in the Florida Everglades is led by PI Dr. Norman Scully and focuses on methly halide formation rates from photochemical transformation of DOM and direct production from periphyton mats. Results from research on periphyton mats were published in Marine Ecology Progress Series:

Raffel., A, R. Jones, C. Butenhoff, A. Rice and N. Scully, Methyl chloride production by calcareous periphyton mats from the Florida Everglades, Mar Ecol Prog Ser, doi:10.3354/meps10956, 2014

Funding for this work was provided by the National Science Foundation Chemical Oceanography