| Visibility, which is reduced by atmospheric aerosols, is protected in Class I areas by the Clean Air Act, Sec. 169A. (a)(1). Class I areas adjacent to large urban areas are particularly difficult to protect due to transport of primary aerosols and precursor gases. Characterization of aerosol and its source regions in Class I areas assists regulators in reducing visibility degradation.; In order to characterize and determine sources of the aerosol at a Class I area near Phoenix, Arizona, two novel techniques were developed; an Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) method to measure organic and inorganic functional groups and a back trajectory clustering method to determine source regions. The first part of this study utilized speciated PM2.5 data from the IMPROVE (Interagency Monitoring of Protected Visual Environments) network together with back trajectory cluster analysis to establish meteorological conditions that transport particulate matter to Tonto National Monument (TNM). This analysis showed that sulfate concentrations were typically high when back trajectories displayed a path over nearby copper smelters. Nitrate and total PM2.5 concentrations were often higher when air traveled over the Phoenix area, and soil concentrations were higher when air traveled over the desert region south and west of the sampling site. High total organic carbon concentrations, however, could not be attributed to one source region with this type of analysis.; To more fully characterize and provide source information for organic carbon at TNM, an ATR-FTIR spectroscopic technique and a multivariate calibration method were developed to quantify ambient organic aerosol functional groups. Size resolved particulate matter sampling was carried out in winter and summer of 2004 at three sites: a downtown Phoenix location, an urban fringe site (Goldfield) and TNM. Common aerosol compound classes such as aliphatic and aromatic CH, methylene, methyl, alkene, aldehydes and ketones, carboxylic acids, ammonium sulfate and nitrate as well as difficult to measure functional groups such as esters, anhydrides, carbohydrate hydroxyl and ethers, amino acids, and amines were quantified. Biogenic, urban and background sources were identified. |
