Ambient Aerosol Organic Carbon Concentrations

TABLE 13.4 Concentration of Aerosol Organic Carbon from Remote Marine Areas 

FIGURE 13.6 Annual mean OC concentration distribution in the United States based on samples from remote stations, (a) /xg m (b) percent of total aerosol mass. The influence of the urban centers has been eliminated to a large extent and the results depict the regional distributions (U.S. EPA, 1996). 

FIGURE 14.5 Ambient EC size distributions in southern California. A second mode is present with a mean of roughly 1 pm. (Reprinted with permission from Venkataraman, C., and Friedlander, S. K. Size distributions of polycyclic hydrocarbons and elemental carbon. 2. Ambient measurements and effects of atmospheric processes. Environ. Sci. Technol. 28. Copyright 1994 American Chemical Society.) 

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CMB Application to Central California PM Chow et al. (1992) apportioned source contributions to aerosol concentrations in the San Joaquin Valley of California. The source profiles used for CMB application are shown in Table 26.1. The standard deviations oa.. of the profiles (three or more samples were taken) are also included. To account for secondary aerosol components in the CMB calculations, ammonium sulfate, ammonium nitrate, sodium nitrate, and organic carbon were expressed as secondary source profiles using the stoichiometry of each compound. The average elemental concentrations observed at one of the receptors—Fresno, California, in 1988-1989— are shown in Table 26.2. The ambient concentrations of some species (c.g., Ga, As, Y, Mo, Ag) included in the source profiles were below the detection limits. These species... 

Comparisons among the results of these methods show that they agree within 5 to 15% on the total measured carbon from ambient aerosol and source samples (Kusko et al., 1989 Countess, 1990). However, the individual EC and OC values are often quite different (Countess, 1990 Hering et al., 1990). Finally, we should note that because these methods oxidize the organic compounds they measure organic carbon (OC) concentration (in... 

Values of Henry s law constant k =plc, where p is the partial pressure of the solute in the gas above the solution and c is the concentration of the solute) is a quantity frequently apphed in the thermodynamic description of dilute aqueous solutions, which is used in environmental chemistry and atmospheric physics as a major criterion for describing air-water partitioning of solutes at near ambient conditions. It plays amajor role in evaluating the transport of pollutants between atmosphere and aquatic systems, rainwater and aerosols. The octanol-water partition coefficient is a dimensionless number defined as the ratio of the compound s concentration in a known volume of octan-l-ol (Cq) to its concentration in a known volume of water (c ) after the octan-l-ol and water have reached equihbrium. It has been found to be related to water solubility, soil/sediment absorption coefficients and bioconcentration factors of pollutants for aquatic life. The adsorption coefficient normalised to the organic carbon content of the soil (sediment) is a useful indicator of the binding capacity of... 

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