Source contributions and potential source regions of size-resolved water-soluble organic carbon measured at an urban site over one year

Abstract

In this study, 24 h size-segregated particulate matter (PM) samples were collected between September 2012 and August 2013 at an urban site in Korea to investigate seasonal mass size distributions of PM and its water-soluble components as well as to infer the possible sources of size-resolved water-soluble organic carbon (WSOC) using a positive matrix factorization (PMF) model. The potential source contribution function (PSCF) was also computed to identify the possible source regions of size-resolved WSOC. The seasonal average contribution of water-soluble organic matter to PM was in the range from 12.7 to 19.7%, but higher (21.0%) and lower contributions (8.9%) were observed during a severe haze event and an Asian dust event, respectively. The seasonal mass size distribution of WSOC had a dominant droplet mode peaking at 0.55 μm and a minor coarse mode peaking at 3.1 μm. The droplet mode WSOC was found to strongly correlate with oxalate, SO, NO, and K, suggesting that in-cloud processes and biomass burning emissions are important sources of droplet mode WSOC. This finding was verified by the results obtained using PMF models. Secondary organic aerosols (oxalate + SO + NO) and biomass burning were the most important contributors (70.3%) to condensation mode WSOC. In the droplet mode, in-cloud processes and secondary NO (+biomass burning) were important sources of WSOC, contributing on average 46.4 and 25.9% to the WSOC, respectively. In the coarse mode, soil dust and secondary processes contributed 52.5 and 42.5% to the WSOC, respectively. The PMF analyses and PSCF maps of WSOC, SO, and K indicate that condensation mode WSOC was mostly influenced by the secondary organic aerosols and biomass burning from both local and long-range transported pollutants, while droplet mode WSOC was primarily the result of atmospheric processing during the long range transport of biogenic and anthropogenic pollutants from the eastern regions of China.

Absorption properties and size distribution of aerosol particles during the fall season at an urban site of Gwangju, Korea

“…) under typical ambient conditions at an urban site showed dominant droplet modes peaking at 0.55 m [2,38,39]. Meanwhile particle size distributions at the urban site during the haze event with air stagnation, high RH, and regional transportation, in the fall season, exhibited dominant droplet modes at a particle size of 1.0 m [3].…”

“…Meanwhile particle size distributions at the urban site during the haze event with air stagnation, high RH, and regional transportation, in the fall season, exhibited dominant droplet modes at a particle size of 1.0 m [3]. Yu et al [2] also conducted a source apportionment of size-resolved WSOC for one year at an urban site. In their study, condensation mode WSOC was found to be strongly associated with secondary organic aerosols and biomass burning (BB) emissions, while heterogeneous reactions and long-range transports were found to be important contributors to the droplet mode WSOC formation.…”

“…In their study, condensation mode WSOC was found to be strongly associated with secondary organic aerosols and biomass burning (BB) emissions, while heterogeneous reactions and long-range transports were found to be important contributors to the droplet mode WSOC formation. Results from previous studies have indicated that the size distributions of major chemical components in ambient aerosol particles depend on season, location, concentration of precursor gases, meteorological conditions, and long-range transport [2,3,[38][39][40][41][42]. Therefore, to investigate the cause of haze formation during fall, size distributions of water-soluble chemical species in ambient aerosol particles need to be further explored.…”

“…The sampling site was on the rooftop of a three-story building at Chonnam National University, approximately 150 m away from a four-lane traffic road. The sampling location is described in detail in our previous publications [2][3][4][5]39]. Collection of size-segregated aerosol samples was conducted using a 10-stage Micro-Orifice Uniform Deposit Impactor (MOUDI, MSP 110; MSP Corp., MN), having cut-off diameters between 0.055 and 18.0 m (0.055, 0.095, 0.17, 0.32, 0.55, 1.00, 1.8, 3.1, 6.2, 9.9 and 18.0 m) at a flow rate of 30 L/min.…”

“…In recent years, the Korean peninsula has suffered from severe air pollution every fall due to stable weather conditions and regional transport of natural and anthropogenic sources from China [1][2][3]. Stable air conditions such as low wind speed, high surface pressure, and low boundary layer lead to the formation of a low-hanging layer and the poor dispersion of air pollutants.…”