Articles | Volume 17, issue 23
Research article
06 Dec 2017
Research article |  | 06 Dec 2017

Field characterization of the PM2.5 Aerosol Chemical Speciation Monitor: insights into the composition, sources, and processes of fine particles in eastern China

Yunjiang Zhang, Lili Tang, Philip L. Croteau, Olivier Favez, Yele Sun, Manjula R. Canagaratna, Zhuang Wang, Florian Couvidat, Alexandre Albinet, Hongliang Zhang, Jean Sciare, André S. H. Prévôt, John T. Jayne, and Douglas R. Worsnop

Abstract. A PM2.5-capable aerosol chemical speciation monitor (Q-ACSM) was deployed in urban Nanjing, China, for the first time to measure in situ non-refractory fine particle (NR-PM2.5) composition from 20 October to 19 November 2015, along with parallel measurements of submicron aerosol (PM1) species by a standard Q-ACSM. Our results show that the NR-PM2.5 species (organics, sulfate, nitrate, and ammonium) measured by the PM2.5-Q-ACSM are highly correlated (r2 > 0.9) with those measured by a Sunset Lab OC  /  EC analyzer and a Monitor for AeRosols and GAses (MARGA). The comparisons between the two Q-ACSMs illustrated similar temporal variations in all NR species between PM1 and PM2.5, yet substantial mass fractions of aerosol species were observed in the size range of 1–2.5 µm. On average, NR-PM1−2.5 contributed 53 % of the total NR-PM2.5, with sulfate and secondary organic aerosols (SOAs) being the two largest contributors (26 and 27 %, respectively). Positive matrix factorization of organic aerosol showed similar temporal variations in both primary and secondary OAs between PM1 and PM2.5, although the mass spectra were slightly different due to more thermal decomposition on the capture vaporizer of the PM2.5-Q-ACSM. We observed an enhancement of SOA under high relative humidity conditions, which is associated with simultaneous increases in aerosol pH, gas-phase species (NO2, SO2, and NH3) concentrations and aerosol water content driven by secondary inorganic aerosols. These results likely indicate an enhanced reactive uptake of SOA precursors upon aqueous particles. Therefore, reducing anthropogenic NOx, SO2, and NH3 emissions might not only reduce secondary inorganic aerosols but also the SOA burden during haze episodes in China.

Short summary
We conducted the first field measurements of non-refractory fine aerosols (NR-PM2.5) in a megacity of eastern China using a PM2.5-ACSM along with a PM1-ACSM measurement. Inter-comparisons demonstrated that the NR-PM2.5 components can be characterized. Substantial mass fractions of aerosol species were observed in the size range of 1–2.5 μm, with sulfate and SOA being the two largest contributors. The impacts of aerosol water driven by secondary inorganic aerosols on SOA formation were explored.
Final-revised paper