Characteristics and oxidative potential of atmospheric PM2.5 in Beijing: Source apportionment and seasonal variation

Abstract PM 2.5 (particulate matter with the aerodynamic diameter D p 2.5 concentrations, water-soluble ions and elements, carbonaceous components and ROS activity characterized by the dithiothreitol (DTT) assay were determined for the PM 2.5 samples collected in Beijing, China, over a whole year. Source apportionments of PM 2.5 and DTT activity were also performed. The mean ± standard deviation of PM 2.5 , DTT m (mass-normalized DTT activity) and DTT v (volume-normalized DTT activity) were 113.8 ± 62.7 μg·m −3 , 0.13 ± 0.10 nmol·μg −1 ·min −1 and 12.26 ± 6.82 nmol·m −3 ·min −1 , respectively. The seasonal averages of DTT m and DTT v exhibited peak values during the local summer. Organic carbon (OC), NO 3 − , SO 4 2− , NH 4 + and elemental carbon (EC) were the dominant components in the constituents tested. Higher concentrations of carbonaceous components occurred in autumn and winter compared with spring and summer. Based on the positive matrix factorization model (PMF), the simulation results of source apportionment for PM 2.5 in Beijing, obtained using the annual data, identified the main categories as follows: dust, coal combustion, secondary sulfate and industrial emissions, vehicle emissions and secondary nitrates. Most detected constituents exhibited significantly positive correlations with DTT v ( p v activity and source contribution to PM 2.5 manifested the sensitivity sequence of DTT v activity for the resolved sources as vehicle emissions > secondary sulfate and industrial emissions > coal combustion > dust. Capsule Based on a descending sequence of relative contribution, the diagnostic sources of DTT v activity in PM 2.5 from Beijing included primarily vehicle emissions, secondary sulfates and industrial emissions, coal combustion, and dust.