“…In an earlier study by Pierson, et al at the Allegheny Mountain site in southwestern Pennsylvania (see Figure 1), the dominant chemical feature of the aerosol was the stoichiometric balance of the SO4 anion with NHj and H+ cations; H + was the more abundant cation when sulfate levels were high. 16 Moreover, sulfate and its associated NH^, H + , and water constituted nearly all of the aerosol fine mass. 16 Data from rural areas in the Ohio River Valley showed that during extreme events in August 1980, sulfur expressed as ammonium sulfate accounted for 80 percent of fine particle mass (<2.5-MHI aerodynamic diameter).…”