Source Term Estimation from Persistent Measurement of Airborne Contaminants

Characterization and quantification of the source term of airborne contaminants is dependent upon measurement sensitivity and the sample integration period needed to provide sufficient signal to background resolution. Lower concentration emissions require sampling closer to the source in order to provide a sufficient signal to noise ratio for analysis, or longer sampling for longer periods in order to overcome variability in background concentrations. Decreasing distance from the source, and temporal variations in emissions complicate source term estimates obtained from downwind measurements. Environmental sampling using long duration samples, or averaging multiple short duration samples, reduces sensitivity to random model errors and unknown environmental conditions at distances where a plume has become well mixed within the environment. For near-field sampling, turbulent conditions often dictate that the plume is only present for a short period within the sample integration. In these cases, persistent sampling can be applied to characterize the source characteristics and the integrated contaminant emission. Sensitivity in source characterization will be analyzed using historical source and receptor measurements from persistent measurements at Savannah River Site at distances ranging from 2 to 150 km.