Sources of non-fossil-fuel emissions in carbonaceous aerosols during early winter in Chinese cities

Abstract

Abstract. China experiences frequent and severe haze outbreaks from the beginning of winter. Carbonaceous aerosols are regarded as an essential factor in controlling the formation and evolution of haze episodes. To elucidate the carbon sources of air pollution, source apportionment was conducted using radiocarbon ( 14 C) and unique molecular organic tracers. Daily 24 h PM 2.5 samples were collected continuously from October 2013 to November 2013 in 10 Chinese cities. The 14 C results indicated that non-fossil-fuel (NF) emissions were predominant in total carbon (TC; average = 65 ± 7 %). Approximately half of the EC was derived primarily from biomass burning (BB) (average = 46±11 %), while over half of the organic carbon (OC) fraction comprised NF (average = 68 ± 7 %). On average, the largest contributor to TC was NF-derived secondary OC (SOC nf ), which accounted for 46 ± 7 % of TC, followed by SOC derived from fossil fuels (FF) (SOC f ; 16 ± 3 %), BB-derived primary OC (POC bb ; 13 ± 5 %), POC derived from FF (POC f ; 12 ± 3 %), EC derived from FF (EC f ; 7±2 %) and EC derived from BB (EC bb ; 6 ± 2 %). The regional background carbonaceous aerosol composition was characterized by NF sources; POCs played a major role in northern China, while SOCs contributed more in other regions. However, during haze episodes, there were no dramatic changes in the carbon source or composition in the cities under study, but the contribution of POC from both FF and NF increased significantly.

Intra-regional transport of black carbon between the south edge of the North China Plain and central China during winter haze episodes

“…eBC enhancement along with air qual-ity deterioration has also been reported elsewhere (Q. Liu et al, 2016;. At LH and HA, the enhancement of the eBC level from clean to polluted periods was due to both elevated BC emissions from biomass burning (BC bb ) and fossil fuel combustion (BC ff ) (Fig.…”

Sources and formation of carbonaceous aerosols in Xi'an, China: primary emissions and secondary formation constrained by radiocarbon

“…For example, Zhang et al (2015a) found that 48 ± 9 % total carbonaceous aerosols were contributed by non-fossil sources in urban areas of four large Chinese cities in the winter of 2013. 14 C measurements conducted in early winter in 10 Chinese cities show that, on average, 65 ± 7 % total carbonaceous aerosols were derived from non-fossil sources (Liu et al, 2017). When 14 C analysis is conducted for OC and EC separately, contributions from biomass burning and other non-fossil sources to carbonaceous aerosols can be separated for a more comprehensive source apportionment.…”

“…Fossil WSOC (WSOC fossil ) therefore is thought to be a good proxy of fossil SOC (SOC fossil ). 14 C analysis of WIOC and WSOC can thus provide new insights into sources and formation processes of primary and secondary OC, respectively, and has been applied in several source apportionment studies (e.g., Liu et al, 2016a, b;Dusek et al, 2017;Liu et al, 2017). For example, using this approach, Y. L. Zhang et al (2014) found that secondary fossil OC dominates total fossil OC in a background site in southern China.…”

Sources and formation of carbonaceous aerosols in Xi'an, China: primary emissions and secondary formation constrained by radiocarbon

“…For example, Zhang et al (2015b) found that 48 ± 9% total carbonaceous aerosols were contributed by non-fossil sources in urban areas of 4 large Chinese cities in winter of 2013. 14 C measurements conducted in early winter in 10 Chinese cities show that on average 65 ± 7% total carbonaceous aerosols were derived from non-fossil sources (Liu et al, 2017). When 14 C analysis is conducted for OC and EC separately, contributions from biomass burning and other non-fossil sources to carbonaceous aerosols can be separated 25 for a more comprehensive source apportionment.…”

“…(WSOCfossil) therefore is thought to be a good proxy of fossil SOC (SOCfossil). 14 C analysis of WIOC and WSOC can therefore provide new insights into sources and formation processes of primary and secondary OC, respectively, and has been applied in several source apportionment studies (e.g., Liu et al, 2016aLiu et al, , 2016bDusek et al, 2017;Liu et al, 2017). For example, using this approach, Y. L. found that secondary fossil OC dominates total fossil OC in a background site in southern China.…”