Dual‐Isotope Constraints on Seasonally Resolved Source Fingerprinting of Black Carbon Aerosols in Sites of the Four Emission Hot Spot Regions of China

Abstract

Despite much recent efforts, the emission sources of black carbon (BC) aerosols-central input to understanding and predicting environmental and climate impact-remain highly uncertain. Here we present observational δ 13 C/Δ 14 C-based constraints on the sources of BC aerosols over the four seasons in each of the four key hot spot emission regions of China: Beijing-Tianjin-Hebei (BTH-Wuqing; where Wuqing is the sampling location), Yangtze River Delta (YRD-Haining), Pearl River Delta (PRD-Zhongshan), and Sichuan Basin (SC-Deyang). Overall, BC loadings were highest in winter, yet elevated loadings were also observed in other seasons, for example, spring at SC-Deyang and fall at PRD-Zhongshan. Annually, the dominant BC sources were coal (50 ± 20%) for BTH-Wuqing, liquid fossil for YRD-Haining (46 ± 8%) and PRD-Zhongshan (48 ± 18%), whereas liquid fossil (42 ± 17%) and biomass burning (41 ± 14%) equally affected SC-Deyang. There is also different but distinct seasonalities in BC sources for the different sites. As an example, for BTH-Wuqing coal burning increased from summer to winter, while summer and spring BTH-Wuqing were more influenced by liquid fossil. In contrast, for YRD-Haining, the relative importance of emission sources was more constant over the year. These quantitative observational constraints on source-seasonality of BC aerosols in receptor sites located in China's four key economic zones highlight that regulatory control on BC aerosol emissions from different fuels should consider both seasonal and regional variations. Our results also suggest that models on estimates of BC-induced climate and air quality should consider variations over both regional and seasonal scales.Rapid industrial and economic development in China over the recent decades is accompanied by an increasing air pollution problem (e.g., Lu et al., 2011; World Economic Outlook Database, 2017;Zhang, He, et al., 2012;Zhang, Wang, et al., 2012). The large and sharply increasing emissions from industry, construction, traffic, residential cooking, heating, and cooling all contribute to high concentrations of aerosol particles. Frequent severe haze episodes in megacities in China have become a central and acute concern in recent FANG ET AL. 11,735Key Points:• Our observation-based results show a strong source seasonality of black carbon aerosol for BTH, PRD, and SC, while little variation for YRD • Annually, the dominant BC sources are coal for BTH, liquid fossil for YRD and PRD, whereas SC is dominated by biomass and liquid fossil fuels • Our results suggest that regionally seasonally tailored mitigation strategies are crucial to effectively reducing aerosol pollution in China Supporting Information:• Supporting Information S1

Variation in Concentration and Sources of Black Carbon in a Megacity of China During the COVID‐19 Pandemic

“…Based on the data analysis, we conclude that vehicles and industrial activities are the major sources of BC in Hangzhou, but BC from biomass burning in the suburban and rural areas should be given more attention. The result is consistent with the previous study that applied radiocarbon Δ 14 C and stable carbon δ 13 C to estimate the BC source apportionments in 2013: 24% for coal (industrial sector), 44% for liquid fossils (transportation sector) and 32% for biomass (residential sector) in the YRD (Fang et al, 2018).…”

Measurement report: Dual-carbon isotopic characterization of carbonaceous aerosol in Beijing and Xi'an: distinctions in primary versus secondary sources

“…The dual carbon isotope signatures of EC were used in a Bayesian Markov chain Monte Carlo (MCMC) scheme (Andersson, 2011), to conduct the mass-balance three source apportionment of EC (e.g., Andersson et al, 2015;Winiger et al, 2016Winiger et al, , 2017Fang et al, 2017Fang et al, , 2018. That is, the F 14 C and δ 13 C of ambient EC (F 14 C(EC) and δ 13 CEC) can be explained by burning of biomass (bb), coal (coal) and liquid fossil fuel (liq.fossil; i.e., vehicle emissions):…”

“…In addition, the analysis of the 13 C/ 12 C ratio can refine 14 C source apportionment, because coal combustion and vehicle emissions have different 13 C source signatures although they both completely depleted in 14 C (e.g., Andersson et al, 2015;Winiger et al, 2016Winiger et al, , 2017Fang et al, 2017Fang et al, , 2018Ni et al, 2018).…”

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

“…2.6 Source apportionment of EC using Bayesian statistics Using F 14 C and δ 13 C signatures of EC (F 14 C(EC), δ 13 CEC) and assuming isotope mass balance in combination with a Bayesian Markov chain Monte Carlo (MCMC) scheme, it is possible to differentiate the 3 main sources of EC: biomass burning, 5 liquid fossil fuel combustion (i.e., vehicle emissions) and coal combustion (Andersson et al, 2015;Li et al, 2016;Winiger et al, 2016;Fang et al, 2018):…”

“…In addition, analysis of the stable carbon isotopic composition (namely the 13 C/ 12 C ratio, expressed as δ 13 C in Eq. 1) of EC can be used to separate fossil sources into coal and liquid fossil fuel combustion (i.e., vehicle emissions), because EC from coal combustion is on 10 average more enriched in the stable carbon isotope 13 C compared to liquid fossil fuel combustion (Andersson et al, 2015;Winiger et al, 2015Winiger et al, , 2016Fang et al, 2018). The interpretation of the stable carbon isotope signature for OC source apportionment is more difficult, because OC is chemically reactive and δ 13 C signatures of OC are not only determined by the source signatures but also influenced by chemical reactions of the organic compounds in the atmosphere (Irei et al, 2011;Pavuluri and Kawamura, 2016).…”