An experimental program was designed to empirically relate acidic deposition to precursor emissions. Preliminary estimates of uncertainty were made in order to assess confidence in the experimental design. The five general areas studied include uncertainties in measurements, local scale data analyses, regional scale data analyses, model simulations, and data analyses for regional experiments. Measurement uncertainties are large compared to deposition losses for gases on the local scale. On a regional scale, the existing ambient sulfate measurements network has a resolution of order 500 km, which is adequate, but characteristic spacing of SO2 patterns requires resolution of less than 100 km. Model simulations indicated the frequency of tracer detectability at a receptor from a specific source is small and limited by meteorology. Also, the frequency of detectability is dependent on source strength. Local source modulations were modeled, and attainable modulation signals were found to be of insufficient magnitude to be detected over background concentrations when measurement uncertainties were considered. Results from these analyses of the effects of uncertainty were considered in the final experimental design.

Caption title. "December 1986." "EPA/600/3-86/069." Microfiche.