Chemical characterization and source identification of PM<sub>2.5</sub> at multiple sites in the Beijing–Tianjin–Hebei region, China

Abstract

Abstract. The simultaneous observation and analysis of atmospheric fine particles (PM 2.5 ) on a regional scale is an important approach to develop control strategies for haze pollution. In this study, samples of filtered PM 2.5 were collected simultaneously at three urban sites (Beijing, Tianjin, and Shijiazhuang) and at a regional background site (Xinglong) in the Beijing-Tianjin-Hebei (BTH) region from June 2014 to April 2015. The PM 2.5 at the four sites was mainly comprised of organic matter, secondary inorganic ions, and mineral dust. Positive matrix factorization (PMF) demonstrated that, on an annual basis, secondary inorganic aerosol was the largest PM 2.5 source in this region, accounting for 29.2-40.5 % of the PM 2.5 mass at the urban sites; the secondlargest PM 2.5 source was motor vehicle exhaust, particularly in Beijing (24.9 %), whereas coal combustion was also a large source in Tianjin (12.4 %) and Shijiazhuang (15.5 %), with particular dominance in winter. Secondary inorganic aerosol plays a vital role in the haze process, with the exception of the spring haze in Shijiazhuang and Tianjin, for which the dust source was crucial. In addition to secondary transformations, local direct emissions (coal combustion and motor vehicle exhaust) significantly contribute to the winter haze at the urban sites. Moreover, with the aggravation of haze pollution, the OC / EC mass ratio of PM 2.5 decreased considerably and the nitrate-rich secondary aerosol increased during all four seasons in Beijing, both of which indicate that local motor vehicle emissions significantly contribute to the severe haze episodes in Beijing. To assess the impacts of regional transport on haze pollution, the PMF results were further processed with backward-trajectory cluster analysis, revealing that haze pollution usually occurred when air masses originating from polluted industrial regions in the south prevailed and is characterized by high PM 2.5 loadings with considerable contributions from secondary aerosols. This study suggests that control strategies to mitigate haze pollution in the BTH region should focus on the reduction of gaseous precursor emissions from fossil fuel combustion (motor vehicle emissions in Beijing and coal combustion in Tianjin, Hebei, and nearby provinces).

Chemical Characteristics and Sources of Submicron Particles in a City with Heavy Pollution in China

“…The source profile could be explained by about five to six factors, including secondary source, industry, traffic (vehicle), coal combustion, biomass burning, and dust, primarily consistent with this study. As for the autumn source contributions, the results in this study were generally acceptable, compared with the results from Huang et al [83] and published data from the local government [84]. The higher proportion of secondary source than the annual average level [85] may result from intensive biomass burning during the study period.…”

“…C6 mainly represented the mid-BTH region, involving several heavily polluted cities such as Tangshan (TS), Tianjin (TJ), Langfang (LF), and Baoding (BD). Previous studies showed the component of OC in this area was mostly emitted from fuel (e.g., coal and oil) burning [83]. Among the cities, TJ had a substantial vehicle population of 2.74 million in 2016 [89] and TS is famous for its steel production, powered by great quantities of coal burning [90].…”

Non-polar organic compounds in autumn and winter aerosols in a typical city of eastern China: size distribution and impact of gas–particle partitioning on PM<sub>2.5</sub> source apportionment

“…5a), implying ambient PAHs underwent photochemical degradation and were influenced by vehicle emissions and coal combustion. It was reported that the free ends of C-C scission products of PAHs remain tethered together, which prevent fragmentation and help in forming more functional groups from the reactions with OH q radical (Hunter et al, 2014) -ultimately forming the lowvolatility species which can condense on the particle phase. There were several deviation points in the lower-left corner, and the values were smaller than the values of the tunnel and vehicle source profile, indicating mixed influence from traffic origins and degradation.…”

“…To develop strategies for controlling atmospheric pollution caused by particulate matter, receptor-based models (e.g., positive matrix factorization, PMF) have been widely applied to quantitatively apportion sources of particulate matter Li et al, 2016;Huang et al, 2017). However, the output factors of the receptor model are not necessarily emission sources, because there exist some atmospheric processes like photodegradation or gas-particle partitioning.…”

Impacts of short-term mitigation measures on PM<sub>2.5</sub> and radiative effects: a case study at a regional background site near Beijing, China

“…The second source factor was linked to traffic-related emissions, and it was characterized by strong loadings of EC (42.1 %) and Cu (40.7 %) and moderate contributions of OC (29.1 %), Zn (27.1 %), and Br (22.2 %). Previous studies have indicated that carbonaceous aerosols are components of gasoline and diesel engine exhaust (Cao et al, 2005), and therefore EC and OC have been used as indicators for motor vehicle emissions (Chalbot et al, 2013;Khan et al, 2016a), and Br may also be emitted from internal combustion engines (Bukowiecki et al, 2005). Aerosol Cu and Zn are derived from other types of vehicle emissions, including those associated with lubricant and oil, brake linings, metal brake wear, and tires (Lin et al, 2015).…”