Source assessment of atmospheric fine particulate matter in a Chinese megacity: Insights from long-term, high-time resolution chemical composition measurements from Shanghai flagship monitoring supersite

Abstract

Here we present a long-term, hourly resolution dataset (from January 2014 to April 2015) of secondary inorganic aerosol (SIA) matter, organic matter (OM) and black carbon (BC) as PM_2.5 chemical components in China. Seasonally differentiated weekly diurnal profiles of major particulate species were investigated in conjunction with potential source contribution function (PSCF) analysis. The average concentration of PM_2.5 was 48.3 ± 35.1 μg m^-3, in which OM was the major constituent (29.7 ± 13.9%), followed by sulfate (25.1 ± 8.1%), nitrate (18.5 ± 8.3%), ammonium (13.3 ± 3.8%), and other trace species (6.8 ± 4.0%). Interestingly, unlike other PM species, OM concentrations kept very similar level among different seasons, indicating on-road traffic is a stable source of PM_2.5. Besides, a persistently strong particulate OM pollution belt was found along the lower reaches of Yangtze River. Significant enhancement of SIA (mainly nitrate) was coincided with high PM_2.5 mass loading. Source apportionment were conducted and found the overwhelming dominance of long-range transport of the pollutants from north China. Using a case study, we further integrate Weather Research and Forecasting (WRF) meteorological modeling and lidar observation to better understand the evolution process of a typical pollution episode. Our assessment of the extremely large datasets derived from Shanghai supersite demonstrated the online instrumentation as a robust and credible alternative to filter-based sampling techniques for long-term PM_2.5 monitoring and characterization in heavily polluted areas.

Keywords: Black carbon and PM(2.5); Organic aerosol; Secondary inorganic aerosol.