Characterization and source apportionment of black carbon aerosol in the Nanjing Jiangbei New Area based on two years of measurements from Aethalometer

Abstract

Black carbon (BC) aerosols were measured using a seven channel Aethalometer at a suburban site of Nanjing, East China from January 2015 to December 2016 to study its temporal variations and quantify the magnitude of BC from fossil fuel (BCff) and biomass burning (BCbb) sources. The mean BC mass concentration was observed to be 2200 ± 1309 ng/m3 at the sampling site during the entire observation period, with the highest (lowest) concentrations found in the winter (summer and spring). A distinct diurnal variations in BC revealed with two maximum peaks occurred between 06:00 and 09:00 local time (LT) and 19:00 and 22:00 LT in all four seasons, was correlated with source emissions, meteorology, and dynamics of the atmospheric boundary layer. A significant seasonality was observed in the absorption Ångström exponent (α) with higher in spring and winter seasons, and lower during the summer. Further, it is evident that the contribution of BCff (BCff%) dominated during the observation period with the mean contributions of BCff % and BCbb% to the BC were found to be ~81% and 19%, respectively. Similar to α, BCbb% also exhibited high fractions in spring and winter suggests an enhanced contribution from biomass burning sources, and a low in summer. The results from both the potential source contribution function (PSCF) and concentration weighted trajectory (CWT) models indicated that the air masses originating from the northern Zhejiang and Anhui provinces were the potential source areas responsible for the high BC concentrations attributed from agricultural waste burning in Nanjing.