title: Surface and Airborne Measurements of Organosulfur and Methanesulfonate Over the Western United States and Coastal Areas.
abstract: This study reports on ambient measurements of organosulfur (OS) and methanesulfonate (MSA) over the western United States and coastal areas. Particulate OS levels are highest in summertime, and generally increase as a function of sulfate (a precursor) and sodium (a marine tracer) with peak levels at coastal sites. The ratio of OS to total sulfur (TS) is also highest at coastal sites, with increasing values as a function of Normalized Difference Vegetation Index (NDVI) and the ratio of organic carbon to elemental carbon. Correlative analysis points to significant relationships between OS and biogenic emissions from marine and continental sources, factors that coincide with secondary production, and vanadium due to a suspected catalytic role. A major OS species, methanesulfonate (MSA), was examined with intensive field measurements and the resulting data support the case for vanadium's catalytic influence. Mass size distributions reveal a dominant MSA peak between aerodynamic diameters of 0.32-0.56 μm at a desert and coastal site with nearly all MSA mass (≥ 84%) in sub-micrometer sizes; MSA:non-sea salt sulfate ratios vary widely as a function of particle size and proximity to the ocean. Airborne data indicate that relative to the marine boundary layer, particulate MSA levels are enhanced in urban and agricultural areas, and also the free troposphere when impacted by biomass burning. Some combination of fires and marine-derived emissions leads to higher MSA levels than either source alone. Finally, MSA differences in cloud water and out-of-cloud aerosol are discussed.
authors.affiliation: Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, United States ; Atmospheric Sciences, University of Arizona, Tucson, AZ, United States ; Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ, United States.
authors.forename: Armin
authors.initials: A
authors.lastname: Sorooshian
authors.affiliation: Atmospheric Sciences, University of Arizona, Tucson, AZ, United States.
authors.forename: Ewan
authors.initials: E
authors.lastname: Crosbie
authors.affiliation: Atmospheric Sciences, University of Arizona, Tucson, AZ, United States.
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Maudlin
authors.affiliation: Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ, United States.
authors.forename: Jong-Sang
authors.initials: JS
authors.lastname: Youn
authors.affiliation: Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, United States.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, United States.
authors.forename: Taylor
authors.initials: T
authors.lastname: Shingler
authors.affiliation: Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, United States.
authors.forename: Amber M
authors.initials: AM
authors.lastname: Ortega
authors.affiliation: Olin College of Engineering, Needham, MA, United States.
authors.forename: Scott
authors.initials: S
authors.lastname: Hersey
authors.affiliation: Center for Interdisciplinary Remotely Piloted Aircraft Studies, Naval Postgraduate School, Monterey, CA, United States.
authors.forename: Roy K
authors.initials: RK
authors.lastname: Woods