Stable carbon isotopic compositions and source apportionment of the carbonaceous components in PM2.5 in Taiyuan, China

Abstract

To determine the stable carbon isotopic compositions (δ13C) and source apportionment of carbonaceous components in Taiyuan, PM2.5 samples were collected using medium flow samplers (TH-150C) during 4 months in 2014. The δ13C values of organic carbon (OC) and elemental carbon (EC) in PM2.5 were determined using an MAT-251 gas mass spectrometer with a dual inlet system. Moreover, δ13CEC values from industrial and domestic coal combustion were synchronously measured. In March, May, August, and December, the mean δ13COC values were −23.9 ± 0.9‰, −25.2 ± 0.2‰, −25.3 ± 0.6‰, and −22.9 ± 1.0‰, respectively; the corresponding δ13CEC values were −23.8 ± 0.8‰, −24.2 ± 0.5‰, −25.3 ± 0.4‰, and −23.8 ± 0.3‰; and the corresponding δ13CTC values were −23.8 ± 0.7‰, −24.8 ± 0.2‰, −25.3 ± 0.4‰, and −23.2 ± 0.6‰. Notable differences were observed in temporal distributions of stable carbon isotopic compositions of OC, EC, and total carbon (TC). The heavier δ13CEC values in December and March was caused by increased coal combustion and C4 plant burning during the heating season. The δ13CEC value was heavier than the δ13COC value in May, whereas the opposite was true in December. The δ13COC value may have been changed in atmospheric reactions during secondary organic aerosols formation in May and photochemical aging in December. There was almost no difference between δ13COC and δ13CEC in March and August. Source apportionment suggest that the EC sources in Taiyuan during the 4 months were different. EC in March and December was mainly due to fossil fuels (93.8%) and C4 plant burning (6.2%), EC in May was mainly affected by industrial coal combustion (50.0%) and vehicle exhaust (50.0%), and EC in August was the comprehensive result of fossil fuels (63.6%) and charcoal burning (36.4%). These results may enhance understanding of the sources of carbonaceous components in fine particles and may provide valuable data for environmental management.