Physiochemical properties of carbonaceous aerosol from agricultural residue burning: Density, volatility, and hygroscopicity

TitlePhysiochemical properties of carbonaceous aerosol from agricultural residue burning: Density, volatility, and hygroscopicity
Publication TypeJournal Article
Year of Publication2016
AuthorsLi, C, Hu, Y, Chen, J, Ma, Z, Ye, X, Yang, X, Wang, L, Wang, X, Mellouki, A

Size-resolved effective density, mixing state, and hygroscopicity of smoke particles from five kinds of agricultural residues burning were characterized using an aerosol chamber system, including a volatility/hygroscopic tandem differential mobility analyzer (V/H-TDMA) combined with an aerosol particle mass analyzer (APM). To profile relationship between the thermodynamic properties and chemical compositions, smoke PM1.0 and PM2,5 were also measured for the water soluble inorganics, mineral elements, and carbonaceous materials like organic carbon (OC) and elemental carbon (EC). Smoke particle has a density of 1.1-1.4 g cm(-3), and hygroscopicity parameter (K) derived from hygroscopic growth factor (GF) of the particles ranges from 0.20 to 0.35. Size- and fuel type-dependence of density and K are obvious. The integrated effective densities (rho) and hygroscopicity parameters (kappa) both scale with alkali species, which could be parameterized as a function of organic and inorganic mass fraction (f(org) & f(inorg)) in smoke PM1.0 and PM2.5: rho(-1) = f(inorg.)rho(inorg) (-1)+ f(org).rho(-1)(org)and K =f(inorg).kappa(inorg) + f(org).kappa(org). The extrapolated values of rho(inorg) and rho(org) are 2.13 and 1.14 g cm(-3) in smoke PM1.0 while the characteristic kappa values of organic and inorganic components are about 0.087 and 0.734, which are similar to the bulk density and kappa calculated from predefined chemical species and also consistent with those values observed in ambient air. Volatility of smoke particle was quantified as volume fraction remaining (VFR) and mass fraction remaining (MFR). The gradient temperature of V-TD1VIA was set to be consistent with the splitting temperature in the OC-EC measurement (OC1 and OC2 separated at 150 and 250 degrees C). Combing the thermogram data and chemical composition of smoke PM1.0, the densities of orgatiic matter (OM1 and OM2 correspond to OC1 and OC2) are estimated as 0.61-0.90 and 0.86-1.13 g cm(-3), and the ratios of OW/OC1 and OM2/OC2 are 1.07 and 1.29 on average, indicating more volatile organic materials have less density and lower OM/OC ratios in the external mixed smoke particles. (C) 2016 The Authors. Published by Elsevier Ltd.