Assessment of Carbonaceous Aerosols at Mount Tai, North China: Secondary Formation and Regional Source Analysis

To understand the concentrations, secondary organic aerosols (SOA) formation and source characteristics of carbonaceous aerosols in the regional environment of North China, a total of 48 fine particulate matter (PM_(2.5)) samples were collected at the top of Mount Tai in the summer of 2015. Organic carbon (OC) and element carbon (EC) were analyzed and resolved into eight carbonaceous species using an Organic/Elemental Carbon Analyzer following the IMPROVE thermal-optical reflectance (TOR) protocol. OC and EC mass concentrations were 4.42 ± 3.04 and 1.58 ± 0.92 μg m^(-3), respectively, which were much higher than that of other domestic or abroad observation sites. Carbonaceous aerosols showed weekday-high trend during sampling period, which can be partly explained by anthropogenic effects. Higher concentrations of secondary organic carbon (SOC) were estimated by EC-tracer method during cloud/fog processing, indicating the fact that aqueous-phase reaction in droplets was an important pathway for SOC formation. Two source analysis approaches, consisting of Potential Source Contribution Function (PSCF) and Positive Matrix Factorization (PMF) were adopted to identify the regional sources and emission sources of carbonaceous species, and the apportion contributed by these sources. PSCF result demonstrated that the potential regional sources in the northwest, southwest and east coastal areas of Mount Tai contributed significantly to carbonaceous species loading in PM_(2.5). Additionally, three main emission sources were identified according to PMF result: diesel vehicle exhaust, biomass burning and mixed sources of gasoline vehicle exhaust and coal combustion, and each of sources had an average contribution of 26.4%, 19.0% and 54.5% to carbonaceous aerosols, respectively.