Source apportionment of fine organic aerosol in Mexico City during the MILAGRO experiment 2006 E. A. Stone1, D. C. Snyder1, R. J. Sheesley1, A. P. Sullivan2, R. J. Weber2, and J. J. Schauer2 1Environmental Chemistry and Technology, University of Wisconsin-Madison, Madison, WI, USA, 53706 2School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA, 30332
Abstract. Organic carbon (OC) comprises a large fraction of fine particulate matter
(PM2.5) in Mexico City. Daily and select 12-h PM2.5 samples were
collected in urban and peripheral sites in Mexico City from 17–30 March
2006. Samples were analyzed for OC and elemental carbon (EC) using
thermal-optical filter-based methods. Real-time water-soluble organic carbon
(WSOC) was collected at the peripheral site. Organic compounds, particularly
molecular markers, were quantified by soxhlet extraction with methanol and
dichloromethane, derivitization, and gas chromatography with mass
spectrometric detection (GCMS). A chemical mass balance model (CMB) based on
molecular marker species was used to determine the relative contribution of
major sources to ambient OC. Motor vehicles, including diesel and gasoline,
consistently accounted for 49% of OC in the urban area and 32% on the
periphery. The daily contribution of biomass burning to OC was highly
variable, and ranged from 5–26% at the urban site and 7–39% at the
peripheral site. The remaining OC unapportioned to primary sources showed a
strong correlation with WSOC and was considered to be secondary in nature.
Comparison of temporally resolved OC showed that contributions from primary
aerosol sources during daylight hours were not significantly different from
nighttime. This study provides quantitative understanding of the important
sources of OC during the MILAGRO 2006 field campaign.
Citation: Stone, E. A., Snyder, D. C., Sheesley, R. J., Sullivan, A. P., Weber, R. J., and Schauer, J. J.: Source apportionment of fine organic aerosol in Mexico City during the MILAGRO experiment 2006, Atmos. Chem. Phys., 8, 1249-1259, doi:10.5194/acp-8-1249-2008, 2008.