Chemical composition, concentration and source apportionment of atmospheric submicron aerosol particles at urban and background sites

Abstract

A quadrupole aerosol mass spectrometer (Q-AMS) was consecutively deployed for 6 months (March–August 2011) at an urban site (vicinity of Vilnius city) and two background sites (Rūgšteliškis, forested area; Preila, seaside area) in Lithuania. Analysis of semi-volatile non-refractory submicron aerosol particles (PM1) was based on measurements of chemical component mass concentration, assessment of long-range air masses and impact of local pollution sources on component concentration and source apportionment. A method for the quantification of nitrate and sulfate contributions to aerosol ammonium compounds was suggested, and results indicated a greater formation of ammonium nitrate than that of ammonium sulfate. The highest average mass concentration of PM1 (7.69 ± 6.83 µg m–3) was found at the Vilnius site, while at the Preila site concentration was 2-fold lower (3.44 ± 2.65 µg m–3). Analysis of chemical compound mass concentrations in the PM1 aerosol volume indicated organics fraction as the dominant at 68.8%, 77.1% and 77.0% for the Preila, Rūgšteliškis and Vilnius sites, respectively. The concentration of nitrate fraction at the Vilnius site was 4-fold higher than at the Preila site (1.84% and 7.68%, respectively) and was attributed to transport-related emissions. Results of Positive Matrix Factorization (PMF) indicated biomass burning organic aerosols (BBOA), hydrocarbon-like organic aerosols (HOA) and semi-volatile oxygenated organic aerosols (SV-OOA) at the urban site; BBOA, lowvolatility oxygenated organic aerosols (LV-OOA), SV-OOA at the background forested site, and LV-OOA and SV-OOA at the background seaside site. This study examines PM1 at urban and background sites in Lithuania and suggests a quantification method of ammonium-nitrate and ammonium-sulfate present in ammonium compounds from aerosol particles.