Articles | Volume 11, issue 22
Research article
27 Nov 2014
Research article |  | 27 Nov 2014

Large methyl halide emissions from south Texas salt marshes

R. C. Rhew, M. E. Whelan, and D.-H. Min

Abstract. Coastal salt marshes are natural sources of methyl chloride (CH3Cl) and methyl bromide (CH3Br) to the atmosphere, but measured emission rates vary widely by geography. Here we report large methyl halide fluxes from subtropical salt marshes of south Texas. Sites with the halophytic plant, Batis maritima, emitted methyl halides at rates that are orders of magnitude greater than sites containing other vascular plants or macroalgae. B. maritima emissions were generally highest at midday; however, diurnal variability was more pronounced for CH3Br than CH3Cl, and surprisingly high nighttime CH3Cl fluxes were observed in July. Seasonal and intra-site variability were large, even taking into account biomass differences. Overall, these subtropical salt marsh sites show much higher emission rates than temperate salt marshes at similar times of the year, supporting the contention that low-latitude salt marshes are significant sources of CH3Cl and CH3Br.

Short summary
Methyl halides, compounds that contribute to stratospheric ozone destruction, have both anthropogenic and natural sources, but their natural sources are poorly characterized. The manuscript reports large emissions of methyl chloride and methyl bromide from subtropical salt marshes on the Gulf Coast of Texas, USA. The emission rates, including some of the largest observed from a natural source, contrast the much lower emission rates reported from higher-latitude salt marshes.
Final-revised paper