PM_2.5 characterization and source-receptor relations in South Carolina

Ambient PM_2.5 aerosol samples were collected at three sites at Clemson University during January and June of 2001. The PM_2.5 mass concentrations averaged 12.2 μg/m³ in January and 21.2 μg/m³ in June. Chemical characterization of the samples identified an average of 99% of the fine particulate matter collected in January and 96% in June. The primary ingredients of the PM_2.5 aerosol were organic carbon compounds (49% in January and 44% in June) and sulfates (21% in January and 33% in June). Total heavy metals on average contributed 0.3% of the fine aerosol mass. Source-receptor reconciliation was completed for the fine aerosol using a chemical mass balance model, Chemical Mass Balance v. 8 (CMB8). In January, approximately 105% of the measured mass was accounted for, and the major sources were soil dust, ammonium sulfate, and ammonium nitrate. In June, an average of 80% of the measured mass was accounted for, and the major sources were the same as in January, except that the contribution of ammonium nitrate was negligible. A composite source of organic compounds that includes gasoline vehicle exhaust, meat cooking, cigarette smoke, and wood burning, was one of the major sources for both June and January seasons. Key words: PM_2.5, CMB8, source receptor modeling.