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- Title
Spatial and seasonal variations of fine particle water-soluble organic carbon (WSOC) over the southeastern United States: implications for secondary organic aerosol formation.
- Authors
Zhang, X.; Liu, Z.; Hecobian, A.; Zheng, M.; Frank, N. H.; Edgerton, E. S.; Weber, R. J.
- Abstract
Secondary organic aerosol (SOA) in the south-eastern US is investigated by analyzing the spatial-temporal distribution of water-soluble organic carbon (WSOC) and other PM2.5 components from 900 archived 24-h Teflon filters collected at 15 urban or rural EPA Federal Reference Method (FRM) network sites throughout 2007. Online measurements of WSOC at an urban/rural-paired site in Georgia in the summer of 2008 are contrasted to the filter data. Based on FRM filters, excluding biomass-burning events (levoglucosan <50 ngm-3), WSOC and sulfate were highly correlated with PM2.5 mass (r² ∼ 0.7). Both components comprised a large mass fraction of PM2.5 (13% and 31%, respectively, or ∼25% and 50% for WSOM and ammonium sulfate). Sulfate and WSOC both tracked ambient temperature throughout the year, suggesting the temperature effects were mainly linked to faster photochemistry and/or synoptic meteorology and less due to enhanced biogenic hydrocarbon emissions. FRM WSOC, and to a lesser extent sulfate, were spatially homogeneous throughout the region, yet WSOC was moderately enhanced (27%) in locations of greater predicted isoprene emissions in summer. A Positive Matrix Factorization (PMF) analysis identified two major source types for the summer WSOC; 22% of the WSOC were associated with ammonium sulfate, and 56% of the WSOC were associated with brown carbon and oxalate. A small urban excess of FRM WSOC (10%) was observed in the summer of 2007, however, comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008 showed substantially greater difference in WSOC (31%) relative to the FRM data, suggesting a low bias for urban filters. The measured Atlanta urban excess, combined with the estimated boundary layer heights, gave an estimated Atlanta daily WSOC production rate in August of 0.55mgCm-2 h-1 between mid-morning and mid-afternoon. This study characterizes the regional nature of fine particles in the south-eastern US, confirming the importance of SOA and the roles of both biogenic and anthropogenic emissions.
- Subjects
UNITED States; CARBON &; the environment; ATMOSPHERIC aerosols; CLIMATE change; POLYTEF; SOLUBILITY; BIOMASS burning; PHOTOCHEMISTRY
- Publication
Atmospheric Chemistry & Physics, 2012, Vol 12, Issue 14, p6593
- ISSN
1680-7316
- Publication type
Article
- DOI
10.5194/acp-12-6593-2012