Emission Factors and Light Absorption Properties of Brown Carbon from Household Coal Combustion in China

Atmos. Chem. Phys., 17, 4769–4780, 2017 www.atmos-chem-phys.net/17/4769/2017/ doi:10.5194/acp-17-4769-2017 © Author(s) 2017. CC Attribution 3.0 License. Emission factors and light absorption properties of brown carbon from household coal combustion in China Jianzhong Sun1,2,5, Guorui Zhi2, Regina Hitzenberger4, Yingjun Chen1,3, Chongguo Tian1, Yayun Zhang2,6, Yanli Feng7, Miaomiao Cheng2, Yuzhe Zhang2,6, Jing Cai8, Feng Chen7, Yiqin Qiu7, Zhiming Jiang7, Jun Li8, Gan Zhang8, and Yangzhi Mo8 1Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China 2State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China 3State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Cities’ Mitigation and Adaptation to Climate Change, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China 4University of Vienna, Faculty of Physics, Boltzmanngasse 5, 1090 Vienna, Austria 5University of Chinese Academy of Sciences, Beijing, 100049, China 6College of Chemical Engineering, China University of Petroleum, Beijing 102249, China 7Institute of Environmental Pollution and Health, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China 8State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China Correspondence to: Guorui Zhi ([email protected]) and Yingjun Chen ([email protected]) Received: 13 December 2016 – Discussion started: 13 January 2017 Revised: 14 March 2017 – Accepted: 21 March 2017 – Published: 12 April 2017 Abstract. Brown carbon (BrC) draws increasing attention nificant decline in BrC EFs for bituminous coals than for an- due to its effects on climate and other environmental fac- thracites due to briquetting. (ii) The BrC EF peaks at the mid- tors. In China, household coal burned for heating and cook- dle of coal’s geological maturity, displaying a bell-shaped ing purposes releases huge amounts of carbonaceous parti- curve between EF and volatile matter (Vdaf/. (iii) The cal- cles every year; however, BrC emissions have rarely been es- culated BrC emissions from China’s residential coal burn- timated in a persuasive manner due to the unavailable emis- ing amounted to 592 Gg (1 Gg D 109 g) in 2013, which is sion characteristics. Here, seven coals jointly covering geo- nearly half of China’s total BC emissions. (iv) The absorp- logical maturity from low to high were burned in four typ- tion Ångström exponents (AAEs) of all coal briquettes are ical stoves as both chunk and briquette styles. The optical higher than those of coal chunks, indicating that the measure integrating sphere (IS) method was applied to measure the of coal briquetting increases the BrC = BC emission ratio and emission factors (EFs) of BrC and black carbon (BC) via thus offsets some of the climate cooling effect of briquet- an iterative process using the different spectral dependence ting. (v) In the scenario of current household coal burning of light absorption for BrC and BC and using humic acid in China, solar light absorption by BrC (350–850 nm in this sodium salt (HASS) and carbon black (CarB) as reference study) accounts for more than a quarter (0.265) of the total materials. The following results have been found: (i) the aver- absorption. This implies the significance of BrC to climate age EFs of BrC for anthracite coal chunks and briquettes are modeling. 1.08 ± 0.80 and 1.52 ± 0.16 g kg−1, respectively, and those for bituminous coal chunks and briquettes are 8.59 ± 2.70 and 4.01 ± 2.19 g kg−1, respectively, reflecting a more sig- Published by Copernicus Publications on behalf of the European Geosciences Union. 4770 J. Sun et al.: Emission factors and light absorption properties of brown carbon 1 Introduction the two BrC source categories are relatively rare, which is un- favorable for the accurate understanding of BrC in terms of The past decade saw increased interest in brown carbon sources and effects (Laskin et al., 2015; Zhi et al., 2015). In (BrC) due to its effects on atmospheric chemistry, air qual- addition, there is a more pressing need to characterize BrC ity, health, and particularly climate (Andreae and Gelenc- emissions from sources related to human activities so as to sér, 2006; Saleh et al., 2014; Forrister et al., 2015; Laskin et gain direct insight into the influence of anthropogenic emis- al., 2015). BrC refers to the fraction of organic carbon (OC) sions on global change. that can absorb light (Yan et al., 2014; Zhi et al., 2015; Jo In China, coal plays a dominant role in the energy et al., 2016; Wang et al., 2016). Compared with black car- structure. In 2013, coal consumption reached 4300 Tg bon (BC), which has usually been considered the strongest (1 Tg D 1012 g), accounting for approximately 70 % of light-absorbing aerosol carbon, with an absorption Ångström China’s total primary energy, 93 Tg of which was burned for exponent (AAE) of around 1.0, light absorption by BrC is household heating and cooking purposes (NBSC, 2014). Be- weaker, but more strongly wavelength dependent (Kirchstet- cause burning raw coal in residential cooking and heating ter and Novakov, 2004; Hoffer et al., 2006; Cai et al., 2014). stoves has the potential to release pollutants that consist of In other words, the light absorption efficiency of BrC in- up to 10 % of the fuel mass due to poor combustion condi- creases more than that of BC toward short wavelengths. Re- tions and control facilities (Zhang and Smith, 2007), huge cent advances in BrC research revealed its abundances and emissions of carbonaceous particles including OC, BrC, and properties in a number of regions and highlighted the impor- BC are expected in this sector. Our previous studies have tance of including BrC in the accurate modeling of aerosol shown that the emission factors (EFs) of BC for residen- radiative forcing (RF) (Mohr et al., 2013; X. Zhang et al., tial coal burning are closely related to coal rank (bitumi- 2013; Chakrabarty et al., 2014; Du et al., 2014; Kirillova et nous or anthracite) and processing style (raw coal chunk al., 2014; Forrister et al., 2015; Liu et al., 2015; Washen- or coal briquette), but they never addressed BrC that is re- felder et al., 2015; Cheng et al., 2016). For example, Feng leased concurrently with BC (Chen et al., 2006, 2009a; Zhi et al. (2013) used a global chemical transport model and a et al., 2008, 2009). Meanwhile, the optical properties of BrC radiative transfer model, finding that the strongly absorbing from coal combustion have almost never been addressed by BrC contributes up to C0.25 W m−2 or 19 % of the absorp- researchers, possibly because studies regarding BrC emis- tion by anthropogenic aerosols; meanwhile, the RF at the top sions have focused preferentially on the observed physical of the troposphere may change from −0.08 W m−2 (cooling) or chemical properties, particularly optical absorption (e.g., to 0.025 W m−2 (warming) in some areas when BrC data are AAE) of ambient aerosols for an overall characterization of considered in the RF model. Park et al. (2010) combined a 3- radiative impacts of BrC in the atmosphere, in a certain re- D global chemical transport model (GEOS-Chem) with air- gion, or from specific burning activities (Chakrabarty et al., craft and ground-based observations, finding that the aver- 2013; Feng et al., 2013; Lack and Langridge, 2013; Wu et aged RFs of BrC aerosol were 0.43 W m−2 at the surface and al., 2013; X. Zhang et al., 2013; Zheng et al., 2013; Du et 0.05 W m−2 at the top of the atmosphere (TOA), respectively, al., 2014; Washenfelder et al., 2015; Yan et al., 2015; Zhao et both of which accounted for more than 15 % of their respec- al., 2015; Cheng et al., 2016). This is not conducive to the un- tive total RFs (2.2 and 0.33 W m−2/ for absorbing aerosols. derstanding of China’s primary BrC emission characteristics, The sources of BrC can be defined in two categories: pri- especially BrC from the residential sector, the largest con- mary emission and secondary formation. The former relates tributor of primary carbonaceous particles in China (Streets to the incomplete (even smoldering) combustion of either et al., 2013; Cai et al., 2014; Zhi et al., 2015). fossil fuels (coal, petroleum, natural gas, etc.) or biomass– The general motivation of this study is to investigate biofuels (wood, agricultural residues, bioethanol, etc.), dur- the emissions and optical characteristics of BrC emitted by ing which BrC is generated and released into the atmo- China’s household coal burning. A group of coals jointly sphere as pollutants (Liu et al., 2014; Oris et al., 2014; covering geological maturity from low to high were burned Washenfelder et al., 2015; Zhi et al., 2015). The latter in- in various stoves as both chunk and briquette styles, accom- volves complex chemical reactions taking place in the atmo- panied by collecting particulate emissions on quartz fiber fil- sphere between various precursors, forming secondary or- ters (QFFs). The optical integrating sphere (IS) approach was ganic aerosols (SOAs), some of which are light-absorbing used to distinguish BrC from BC on the filters (Hitzenberger (Laskin et al., 2014; Lee et al., 2014; Smith et al., 2014; et al., 1996; Wonaschütz et al., 2009; Montilla et al., 2011), Tóth et al., 2014; Martinsson et al., 2015; Yan et al., 2015; followed by the calculation of EFs of BrC and other partic- Zhao et al., 2015).

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