title: Water soluble organic aerosols in the Colorado Rocky Mountains, USA: composition, sources and optical properties.
abstract: Atmospheric aerosols have been shown to be an important input of organic carbon and nutrients to alpine watersheds and influence biogeochemical processes in these remote settings. For many remote, high elevation watersheds, direct evidence of the sources of water soluble organic aerosols and their chemical and optical characteristics is lacking. Here, we show that the concentration of water soluble organic carbon (WSOC) in the total suspended particulate (TSP) load at a high elevation site in the Colorado Rocky Mountains was strongly correlated with UV absorbance at 254 nm (Abs254, r = 0.88 p < 0.01) and organic carbon (OC, r = 0.95 p < 0.01), accounting for >90% of OC on average. According to source apportionment analysis, biomass burning had the highest contribution (50.3%) to average WSOC concentration; SOA formation and motor vehicle emissions dominated the contribution to WSOC in the summer. The source apportionment and backward trajectory analysis results supported the notion that both wildfire and Colorado Front Range pollution sources contribute to the summertime OC peaks observed in wet deposition at high elevation sites in the Colorado Rocky Mountains. These findings have important implications for water quality in remote, high-elevation, mountain catchments considered to be our pristine reference sites.
authors.affiliation: Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309, United States.
authors.forename: Mingjie
authors.initials: M
authors.lastname: Xie
authors.affiliation: Department of Civil, Construction, and Environmental Engineering, San Diego State University, San Diego, California 92182, United States.
authors.forename: Natalie
authors.initials: N
authors.lastname: Mladenov
authors.affiliation: Institute for Arctic and Alpine Research and Department of Geography, University of Colorado, Boulder, CO 80309, United States.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Williams
authors.affiliation: Department of Geology, University of Colorado, Boulder, CO 80309, United States.
authors.forename: Jason C
authors.initials: JC
authors.lastname: Neff
authors.affiliation: Department of Civil, Construction, and Environmental Engineering, San Diego State University, San Diego, California 92182, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Wasswa
authors.affiliation: Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309, United States.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hannigan