Characteristics of carbonaceous aerosol at a near-highway-traffic sampling site during spring 2006

The concentrations for mass, organic carbon (OC), and elemental carbon (EC) of fine (PM2.5) and inhalable (PM10) particulates were studied at a near-highway-traffic sampling site during March 6 to April 1, 2006, around central Taiwan. The primary OC/EC ratio approach is applied to assess the contribution of secondary organic aerosol (SOA) to the PM2.5 and PM10 mass at the near-highway-traffic sampling site. The mass average concentrations of PM2.5 and inhalable () PM10 particulates were found to be 67.5 μ g m-3 and 107.9 μ g m-3, respectively, during sampling period. Furthermore, analytical results indicated that the average OC and EC concentrations were 10.22 and 3.88 mg m-3, respectively, in PM2.5 particulates. The average OC and EC concentrations were 11.57 and 4.56 mg m-3, respectively, in PM10 particulates. The average mass concentration ratio of PM2.5to PM10 particulates was 1.6 during sampling period. The results also reflected that PM2.5 particulate concentrations were the primary species (average approximately 61%). Additionally, the OC/EC ratio of both PM10 and PM2.5 particulates was at all times greater than 1.7, indicating that OC constituted 66%-79% of total carbon (TC). Experimental results demonstrated that direct emissions of primary organic aerosol (POA) are greater than emissions of carbonaceous material (EC aerosol) for either PM10 or PM2.5 particles. In addition, the results also reflected that OC concentration was the major species at this sampling site.