Sources of humic-like substances (HULIS) in PM2.5 in Beijing: Receptor modeling approach.

Recent work has identified the presence of humic-like substances (HULIS) in ambient fine particulate matter (PM 2.5) in Beijing, China and that residential coal combustion as well as biomass burning are significant contributors to its presence. These results were based on the characterization of emissions from representative stoves and modeling of the aerosol with the Community Multiscale Air Quality (CMAQ) chemical transport model. The CMAQ source apportionment estimated that residential coal and biofuel burning and secondary aerosol formation were important annual sources of ambient HULIS, contributing 47.1%, 15.1%, and 38.9%, respectively. In this study, chemical composition data including concentrations of water-soluble organic carbon and HULIS across four seasons during 2012–2013 were analyzed with positive matrix factorization (PMF) to provide a complementary source apportionment. The PMF results indicate that the identified sources were Traffic, Biomass Burning, Nitrate/Sulfate, Incineration, Sulfate, Coal Combustion/Ammonium Chloride, Residential Coal/Biofuel Combustion, and Road Dust/Soil with mass contributions (fractions) to PM 2.5 of 12.35 (10.4%), 8.70 (8.9%), 24.51 (22.4%), 5.64 (7.2%), 25.14 (24.5%), 7.10 (6.2%), 14.18 (15.4%), and 5.33 μg/m3 (5.0%), respectively. The contributions to the observed HULIS concentrations were 0.63 (10.9%), 0.38 (6.4%), 0.07 (1.7%), 0.00 (0%), 1.12 (28.8%), 0.00 (0%), 1.50 (52.2%), and 0.01 μg/m3 (0.3%), respectively. These PMF modeling results were in reasonable agreement with the CMAQ values supporting the attribution of significant amounts of primary HULIS to residential coal and biofuel combustion. Currently, efforts are underway in China to replace solid fuel combustion for heating and cooking with natural gas and electricity by 2020. Thus, future studies should be able to see substantial reductions in both PM 2.5 and HULIS in the near term future. Unlabelled Image • Sources of PM2.5 and HULIS were apportioned for 2012–2013 using additional variables. • Eight sources were resolved including residential coal/wood and incinerator emissions. • Adding gaseous pollutants provided better agreement between PMF and CMAQ results. • Residential combustion was a major source of PM2.5 and HULIS in Beijing. [ABSTRACT FROM AUTHOR]