Dimethyl Sulfide Emissions from Dairies and Agriculture as a Potential Contributor to Sulfate Aerosols in the California Central Valley
Thursday, 18 December 2014
Whole air samples have been collected throughout Southern California during the previous five years of the NASA Student Airborne Research Program (SARP). During a flight over the Salton Sea in 2014, higher concentrations of dimethyl sulfide (DMS), a known marine emitted gas, were observed over neighboring agricultural land than over the sea itself. A comparison of DMS to methyl iodide, another known marine emitted gas, showed minimal correlation, revealing that DMS was being emitted from local sources. Ground samples at the Salton Sea verified that the DMS was not transported from the Pacific Ocean. Previous SARP studies have shown that DMS is emitted from dairies. The enhancements in ethanol (another dairy tracer) and DMS in several airborne samples collected south of the Salton Sea suggest dairy emissions of the observed DMS. DMS is a compound of interest because its oxidation can form cloud condensation nuclei. Based on data from all six SARP flights between 2009-2014, we propose that dairy and farming emissions of DMS in the San Joaquin Valley may be impacting aerosol loading in this region. A simple model that takes into account the particulate matter mass loadings was used to calculate the percent contribution of DMS to aerosol formation for the San Joaquin Valley.