Characterization of carbon fractions for atmospheric fine particles and nanoparticles in a highway tunnel

Abstract

Fine particles (PM(2.5)) and nanoparticles (PM(0),1)were sampled using Dichotomous sampler and MOUDI, respectively, in Xueshan Tunnel, Taiwan. Eight carbon fractions were analyzed using IMPROVE thermal-optical reflectance (TOR) method. The concentrations of different temperature carbon fractions (OC1-OC4, EC1-EC3) in both PM(2.5) and PM(0.1) were measured and the correlations between OC and EC were discussed. Results showed that the ratios of OC/EC were 1.26 and 0.67 for PM(2.5) and PM(0.1), respectively. The concentration of EC1 was found to be more abundant than other elemental carbon fractions in PM(2.5), while the most abundant EC fraction in PM(0.1) was found to be EC2. The variation of contributions for elemental carbon fractions was different among PM(2.5) and PM(0.1) samples, which was partly owing to the metal catalysts for soot oxidation. The correlations between char-EC and soot-EC showed that char-EC dominated EC in PM(2.5) while soot-EC dominated EC in PM(0.1). Using eight individual carbon fractions, the gasoline and diesel source profiles of PM(0.1) and PM(2.5) were extracted and analyzed with the positive matrix factorization (PMF) method. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.