Chemical characterization of fine particulate matter in Changzhou, China, and source apportionment with offline aerosol mass spectrometry

• Published in: Atmospheric chemistry and physics 2017-02, Vol.17 (4), p.2573-2592
• Main Authors: Ye, Zhaolian, Liu, Jiashu, Gu, Aijun, Feng, Feifei, Liu, Yuhai, Bi, Chenglu, Xu, Jianzhong, Li, Ling, Chen, Hui, Chen, Yanfang, Dai, Liang, Zhou, Quanfa, Ge, Xinlei
• Format: Article
• Language: English
• Subjects: Aerosol chemistry; Aerosols; Air pollution; Air pollution control; Aluminum; Analytical methods; Anthropogenic factors; Apportionment; Aromatic compounds; Aromatic hydrocarbons; Atmospheric aerosols; Atomic oxygen; Atomic properties; Carbon; Chemical properties; Chemicophysical properties; Chromium; Coal combustion; Cooking; Copper; Emissions; Humidity; Hydrocarbons; Hydrogen; Identification; Ions; Iron; Manganese; Mass spectrometry; Mass spectroscopy; Molecular weight; Nitrates; Nitrogen; Nitrogen enrichment; Organic carbon; Organic matter; Organic nitrogen; Outdoor air quality; Oxygen; Oxygen enrichment; Particulate emissions; Particulate matter; Particulate matter sources; Polycyclic aromatic hydrocarbons; Population density; Ratios; Scientific imaging; Soot; Species; Stationary sources; Sulfates; Suspended particulate matter; Trace elements; Vehicle emissions; Water; Water analysis; Water chemistry; Water pollution; Winter; Zinc
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-17-2573-2017

Knowledge of aerosol chemistry in densely populated regions is critical for effective reduction of air pollution, while such studies have not been conducted in Changzhou, an important manufacturing base and populated city in the Yangtze River Delta (YRD), China. This work, for the first time, performed a thorough chemical characterization on the fine particulate matter (PM2.5) samples, collected during July 2015 to April 2016 across four seasons in this city. A suite of analytical techniques was employed to measure the organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-soluble inorganic ions (WSIIs), trace elements, and polycyclic aromatic hydrocarbons (PAHs) in PM2.5; in particular, an Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was deployed to probe the chemical properties of water-soluble organic aerosol (WSOA). The average PM2.5 concentration was found to be 108.3 µg m−3, and all identified species were able to reconstruct ∼ 80 % of the PM2.5 mass. The WSIIs occupied about half of the PM2.5 mass (∼ 52.1 %), with SO42−, NO3−, and NH4+ as the major ions. On average, nitrate concentrations dominated over sulfate (mass ratio of 1.21), indicating that traffic emissions were more important than stationary sources. OC and EC correlated well with each other and the highest OC ∕ EC ratio (5.16) occurred in winter, suggesting complex OC sources likely including both secondary and primary ones. Concentrations of eight trace elements (Mn, Zn, Al, B, Cr, Cu, Fe, Pb) can contribute up to ∼ 5.0 % of PM2.5 during winter. PAH concentrations were also high in winter (140.25 ng m−3), which were predominated by median/high molecular weight PAHs with five and six rings. The organic matter including both water-soluble and water-insoluble species occupied ∼ 21.5 % of the PM2.5 mass. SP-AMS determined that the WSOA had average atomic oxygen-to-carbon (O ∕ C), hydrogen-to-carbon (H ∕ C), nitrogen-to-carbon (N ∕ C), and organic matter-to-organic carbon (OM ∕ OC) ratios of 0.54, 1.69, 0.11, and 1.99, respectively. Source apportionment of WSOA further identified two secondary OA (SOA) factors (a less oxidized and a more oxidized oxygenated OA) and two primary OA (POA) factors (a nitrogen-enriched hydrocarbon-like traffic OA and a local primary OA likely including species from cooking, coal combustion, etc.). On average, the POA contribution outweighed SOA (55 % vs. 45 %), indicating the important role of local anthropogenic emissi