Approaching PM2.5 and PM2.5 − 10 source apportionment by mass balance analysis, principal component analysis and particle size distribution

A chemical characterization was carried out for PM2.5 and PM2.5–10 samples collected in a suburban area and the concentrations of 12 elements were determined in 8 size segregated fractions using a Berner Impactor. Two main objectives were proposed in this work: 1) to test for closure among chemical and gravimetric measurements of PM2.5 and PM2.5–10 and 2) evaluate the performance of Multilinear Regression Analysis (MLRA) and Mass Balance Analysis (MBA) in the determination of source contribution to Particulate Matter (PM) concentrations. The fraction unaccounted for by chemical analysis comprised on average 17% and 34% of gravimetric PM2.5 and PM2.5–10, respectively. The lack of closure in PM2.5 and PM2.5–10 mass (i.e., constituent concentrations not adding up to gravimetrically measured) could partly result from the presence of water associated with particles and errors in the estimation of unmeasured species. MLRA and MBA showed very similar results for the temporal variation of the source contributions. However, quantitatively important discrepancies could be observed, principally due to the lack of mass closure in PM2.5 and PM2.5–10. Both methods indicated that the major PM2.5 aerosol mass contributors included secondary aerosol and vehicle exhaust. In the coarse fraction, marine and mineral aerosol contributions were predominant.