Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv Thermo-optical properties of residential coals and combustion aerosols Máté Pintér a , Tibor Ajtai a,b,c,* , Gergely Kiss-Albert a,d , Noémi Utry b , Diána Kiss a , Tomi Smausz a,b , Attila Kohut a , Béla Hopp a , Gábor Galbács e , Ákos Kukovecz f,g , Zoltán Kónya f,g , Gábor Szabó a,b , Zoltán Bozóki a,b a Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Hungary b MTA-SZTE Research Group on Photoacoustic Spectroscopy, H-6720 Szeged, Hungary c ELI-HU Non-Profit Ltd., H-6720 Szeged, Hungary d Hilase Development, Production, Service and Trading Limited, Székesfehérvár H-8000, Hungary e Department of Inorganic and Analytical Chemistry, University of Szeged, Dom Square 7, 6720 Szeged, Hungary f Department of Applied and Environmental Chemistry, University of Szeged, Szeged, Rerrich Béla tér 1, 6720, Hungary g MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Szeged, Rerrich Béla tér 1, 6720, Hungary ARTICLE INFO Keywords: PhotoAcoustic Spectroscopy Household coal Laser ablation Aerosol Angström Exponent Calorific value ABSTRACT In this study, we present the inherent optical properties of carbonaceous aerosols generated from various coals (hard through bituminous to lignite) and their correlation with the thermochemical and energetic properties of the bulk coal samples. The nanoablation method provided a unique opportunity for the comprehensive in- vestigation of the generated particles under well controlled laboratory circumstances. First, the wavelength dependent radiative features (optical absorption and scattering) and the size distribution (SD) of the generated particulate matter were measured in-situ in aerosol phase using in-house developed and customised state-of-the- art instrumentation. We also investigated the morphology and microstructure of the generated particles using Transmission Electron Microscopy (TEM) and Electron Diffraction (ED). The absorption spectra of the measured samples (quantified by Absorption Angström Exponent (AAE)) were observed to be distinctive. The correlation between the thermochemical features of bulk coal samples (fixed carbon (FC) to volatile matter (VM) ratio and calorific value (CV)) and the AAE of aerosol assembly were found to be (r 2 = 0.97 and r 2 = 0.97) respectively. Lignite was off the fitted curves in both cases most probably due to its high optically inactive volatile material content. Although more samples are necessary to be investigated to draw statistically relevant conclusion, the revealed correlation between CV and Single Scattering Albedo (SSA) implies that climatic impact of coal com- busted aerosol could depend on the thermal and energetic properties of the bulk material. 1. Introduction Atmospheric carbonaceous particulate matter (CPM) is in the focus of scientific interest due its adverse climatic and human health effects (; Andreae and Ramanathan, 2013; Stocker et al., 2013; Penner et al., 1992; Yu et al., 2006; Pope and Dockery, 1996). Ambient aerosol particles emitted from fossil fuel combustion alter the energy budget of the Earth-atmosphere system through scattering and absorbing solar radiation (Bond et al., 2013). Particles that do not absorb, only scatter solar light (e.g. sulfates) produce a cooling effect (Charlson et al., 1991). However, aerosol particles with significant optical absorption in the solar wavelength range cause a remarkable heating effect (Haywood and Shine, 1995). Black Carbon (BC) is the most dominant component of atmospheric light absorbing carbonaceous particulate matter (LAC) (Bond et al., 2013; Rosen et al., 1981). Today, the radiative forcing of BC is one of the biggest uncertainties in climatic models (Bond et al., 2013; Lack et al., 2006). The most important reasons for that are found in the lack of proper knowledge regarding CPM emission rates, lifetimes and optical properties (Bond et al., 2002). Climatic models require the precise and reliable determination of size distribution and the complex optical properties of CPM as input para- meters (Bond et al., 2002; Twomey, 1977). Due to their availability and low price, coal alongside with biofuels have gained new popularity in developing and developed countries as well (Khodaei et al., 2017; Weldu et al., 2017). Carbonaceous particles emitted from domestic coal combustion for both cooking and heating make a significant contribution to the atmospheric concentration of particulate matter (PM) a global and a regional scale as well (Cooke et al., 1999; Bond et al., 2002). According to the most recent estima- tions, coal burning contributes to almost 50% of CPM emitted from https://doi.org/10.1016/j.atmosenv.2018.01.036 Received 24 August 2017; Received in revised form 20 December 2017; Accepted 23 January 2018 * Corresponding author. Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Hungary. E-mail address: ajtai@titan.physx.u-szeged.hu (T. Ajtai). Atmospheric Environment 178 (2018) 118–128 1352-2310/ © 2018 Published by Elsevier Ltd. T