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

Abstract

Abstract. 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 (PM 2.5 ) 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), watersoluble organic carbon (WSOC), water-soluble inorganic ions (WSIIs), trace elements, and polycyclic aromatic hydrocarbons (PAHs) in PM 2.5 ; 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 PM 2.5 concentration was found to be 108.3 µg m −3 , and all identified species were able to reconstruct ∼ 80 % of the PM 2.5 mass. The WSIIs occupied about half of the PM 2.5 mass (∼ 52.1 %), with SO 2− 4 , NO − 3 , and NH + 4 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 PM 2.5 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 watersoluble and water-insoluble species occupied ∼ 21.5 % of the PM 2.5 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-toorganic 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 emissions in the aerosol pollution in Changzhou. Our measurement also shows the abundance of organic nitrogen species in WSOA, and the source analyses suggest these species are likely associated with traffic emissions, which warrants more investigations on PM samples from other locations.

Summertime Day-Night Differences of PM2.5 Components (Inorganic Ions, OC, EC, WSOC, WSON, HULIS, and PAHs) in Changzhou, China

“…The major inorganic ions (SO 4 2− , NH 4 + , NO 3 − , NO 2 − , and K + ) of the extracts were analyzed by an ion chromatograph (Aquion, ThermoFisher Scientific, Waltham, MA, USA). Ion chromatograph equipped with a Dionex CS12A column was used for cation analysis (20 mM methanesulfonic acid as eluent), and a Dionex AS23 column was employed for the anions (4.5 mM NaHCO 3 and 0.8 mM Na 2 More details regarding the analytical methods can be found in our previous work [29]. The concentration of WSON was determined by subtracting the water soluble inorganic nitrogen (WSIN) from the WSTN as follows: OC and EC: OC and EC were measured using a thermal/optical carbon analyzer (DRI Model 2001A, Desert Research Institute, Las Vegas, NV, USA) following the temperature protocol described by Chow et al [32].…”

“…Polycyclic aromatic hydrocarbons (PAHs): The PAH compounds were analyzed with a gas chromatography-mass spectrometer (GC-MS) (Agilent 7890-7000B, City of Santa Clara, CA, USA) using a DB-5ms capillary column (30 m × 0.25 mm × 0.5 µm), following the standard procedure detailed in our previous work [29]. 18 PAH compounds including naphthalene (NaP), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Flu), phenanthrene (Phe), anthracene (Ant), fluoranthene (Flua), pyrene (Pyr), benzo(a)anthracene (BaA), chrysene (Chr), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene(BaP), Benzo(e)pyrene (BeP), benzo(j)fluoranthene (BjF), benzoperylene (BghiP), indeno(1,2,3-cd)pyrene (InP), and dibenz(a,h)anthracene (DBA) were measured.…”

Chemical and Light Extinction Characteristics of Atmospheric Aerosols in Suburban Nanjing, China

“…In this work, we chose 1.8 as the conversion factor by considering previous values, especially those from Nanjing [15,18,51]. Apart from the ocean source, coal combustion may emit a certain amount of Cl − as well, and the IMPROVE formula may overestimate the contribution of sea salt.…”

Field characterization of the PM<sub>2.5</sub> Aerosol Chemical Speciation Monitor: insights into the composition, sources, and processes of fine particles in eastern China

“…Although ambient organic carbon (OC) and elemental carbon (EC) can be measured semi-continuously, typically in hourly resolution, they can only be used to differentiate primary and secondary OC using the EC-tracer technique (Turpin and Huntzicker, 1995). In addition, size-segregated filter samples can provide detailed chemical information in different size ranges but are greatly limited by the sampling duration, which is typically days and even weeks (Huang et al, 2014;Xu et al, 2015;Ye et al, 2017). Therefore, real-time characterization of PM 2.5 is important to have a better understanding of aerosol chemistry and sources of fine particles in highly polluted environments in China.…”