In the current study, the heterogeneous reaction of NO2 with soot and biosoot surfaces was investigated in the dark and under illumination relevant to atmospheric conditions (J(NO2) = 0.012 s(-1)). A flat-flame burner was used for preparation and collection of soot samples from premixed flames of liquid fuels. The biofuels were prepared by mixing 20% v/v of (i) 1-butanol (CH3(CH2)(3)OH), (ii) methyl octanoate (CH3(CH2)(6)COOCH3), (iii) anhydrous diethyl carbonate (C2H5O)(2)CO and (iv) 2,5 dimethyl furan (CH3)(2)C4H2O additive compounds in conventional kerosene fuel (JetA-1). Experiments were performed at 293 K using a low-pressure flow tube reactor (P = 9 Torr) coupled to a quadrupole mass spectrometer. The initial and steady-state uptake coefficients, gamma(0) and gamma(ss), respectively, as well as the surface coverage, N-s, were measured under dry and humid conditions. Furthermore, the branching ratios of the gas-phase products NO (similar to 80100%) and HONO (<20%) were determined. Soot from JetA-1/2,5-dimethyl furan was the most reactive [gamma(0) = (29.1 +/- 5.8) x 10(-6), gamma(ss)(dry) = (9.09 +/- 1.82) x 10-7 and gamma(ss)(5.5%RH) = (14.0 +/- 2.8)(-7)] while soot from JetA-1/1-butanol [gamma(0) = (2.72 +/- 0.544) x 10(-6), gamma(ss)(dry) = (4.57 +/- 0.914) x 10(-7), and gamma(ss)(5.5%RH) = (3.64 +/- 0.728) x 10(-7)] and JetA-1/diethyl carbonate [gamma(0) = (2.99 +/- 0.598) x 10(-6), gamma(ss)(dry) = (3.99 +/- 0.798) x 107, and gamma(ss)(5.5%RH) = (4.80 +/- 0.960) x 10(-7)] were less reactive. To correlate the chemical reactivity with the physicochemical properties of the soot samples, their chemical composition was analyzed employing Raman spectroscopy, NMR, and high-performance liquid chromatography. In addition, the BrunauerEmmettTeller adsorption isotherms and the particle size distributions were determined employing a Quantachrome Nova 2200e gas sorption analyzer. The analysis of the results showed that factors such as (i) soot mass collection rate, (ii) porosity of the particles formed, (iii) aromatic fraction, and (iv) pre-existence of nitro-containing species in soot samples (formed during the combustion process) can be used as indicators of soot reactivity with NO2.
