Sulfate concentration airborne

FIGURE 4-28 An example of output from ACID, a regional-scale model that simulates transport of S02 and sulfate, oxidation of S02 to sulfate, and sulfate deposition. Each contour represents the average airborne sulfate concentration in micrograms per cubic meter that would result in the Adirondacks region of New York per 1014 g of sulfur emitted annually anywhere along the contour line. For example, if a 1014 g/year source of S02 were sited in Tennessee, the resultant average addition to the airborne sulfate concentration in the Adirondacks would be 20 /cg/m3. 

Consideration of the chemical and physical properties of these accumulated substances permits some further conclusions. The volatility of surface reaction products is likely to be important, as are the ambient concentrations of ammonia, carbon dioxide, and other gases that could influence the surface acidity. Indeed, the ratio of ammonium to sulfate that has been found on zinc and aluminum surfaces after extended exposures is much lower than typical ratios for ammonium to sulfate in airborne particles (4). Clearly, ammonium is able to volatilize from these surfaces through a hydrolysis reaction or, after redistribution of anions and cations on the surface such as... 

There has been great interest in airborne particulate matter recently due to the results of a number of epidemiological studies showing a correlation between increased mortality and levels of airborne particles. Figure 2.14 shows one such correlation reported by Dockery et al. (1993). A clear relationship between mortality rates and the concentration of fine particles PM25, as well as with particle sulfate, is seen. Since sulfate is found primarily in fine particles, these observations are not independent. Schwartz et al. (1996) report a 1.5% increase in total daily mortality with an increase of 10 pg m-3 in PM25. Deaths due to chronic obstructive pulmonary disease increased by 3.3% and those to ischemic heart disease by 2.1%. 

Dimethyl sulfate forms V7-mcthylguannie in DNA when administered to rats in vivo. Urine collected from rats up to 48 h after exposure to airborne concentrations of - H-... 

The predictions of such models often can be expressed graphically an example is Fig. 4-28, which predicts the concentration of airborne sulfate... 

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