Abstract
Hydroxymethanesulfonate (HMS), a product of the heterogeneous reaction between S(IV) and HCHO, was measured in atmospheric aerosol samples collected at two locations indicating it can exist outside of clouds. Sampling was performed through collection with filters and analysis using ion chromatography with a treatment step to distinguish between HMS and uncomplexed S(IV). Concentrations of HMS were found to range from below the detection limit to 6.5
ng
m
-3 for samples collected in central New Mexico in the summer and around 30
ng
m
-3 for two samples collected in Seattle, Washington in the spring. Higher concentrations were associated with greater occurrence of clouds, which is the presumed source of the HMS. In the samples collected in Seattle, about half of the HMS was found associated with fine particles. In the central New Mexico samples, molar ratios of HMS to sulfate in particulate matter were found to be less than 0.002 indicating that HMS was a minor contributor of aerosol sulfur under the conditions of the measurements.