Chemical characterization of submicron aerosol particles during wintertime in a northwest city of China using an Aerodyne aerosol mass spectrometry

- Characterizations of NR-PM1 were researched during wintertime in Lanzhou.
- Source apportionment of organic aerosols using PMF analysis with ME-2 algorithm.
- Primary emissions play important role in causing high aerosol pollution in winter.
- Westerly air masses are associated closely with the aerosol pollution in Lanzhou.

An Aerodyne quadrupole aerosol mass spectrometry (Q-AMS) was utilized to measure the size-resolved chemical composition of non-refractory submicron particles (NR-PM1) from October 27 to December 3, 2014 at an urban site in Lanzhou, northwest China. The average NR-PM1 mass concentration was 37.3 μg m−3 (ranging from 2.9 to 128.2 μg m−3) under an AMS collection efficiency of unity and was composed of organics (48.4%), sulfate (17.8%), nitrate (14.6%), ammonium (13.7%), and chloride (5.7%). Positive matrix factorization (PMF) with the multi-linear engine (ME-2) solver identified six organic aerosol (OA) factors, including hydrocarbon-like OA (HOA), coal combustion OA (CCOA), cooking-related OA (COA), biomass burning OA (BBOA) and two oxygenated OA (OOA1 and OOA2), which accounted for 8.5%, 20.2%, 18.6%, 12.4%, 17.8% and 22.5% of the total organics mass on average, respectively. Primary emissions were the major sources of fine particulate matter (PM) and played an important role in causing high chemically resolved PM pollution during wintertime in Lanzhou. Back trajectory analysis indicated that the long-range regional transport air mass from the westerly was the key factor that led to severe submicron aerosol pollution during wintertime in Lanzhou.

Various emission sources can contribute to the severe air pollution during wintertime in Lanzhou, including vehicle exhaust, coal combustion, industrial emission, dust, resident activity, etc. In order to provide insight into the possible contributions of various sources quantitatively, an aerodyne quadrupole aerosol mass spectrometer (Q-AMS) was deployed to measure the size-resolved chemical characterizations of non-refractory submicron aerosol (NR-PM1) during wintertime in Lanzhou.280