Processes controlling aqueous concentrations for riverine spills

The aqueous concentrations of sparingly soluble compounds resulting from oil, fuel, or chemical spills onto rivers predicted by numerical spill models contain an inherent degree of uncertainty due to the inaccuracies, or bias, of the user supplied rate coefficients. Methods for estimating the values of spreading, evaporation, dissolution, volatilization, and longitudinal dispersion coefficients for a small sheltered river are reviewed, and the uncertainties associated with each coefficient are estimated. The uncertainties in the predicted aqueous concentrations are then computed using a concurrently developed riverine spill model for a simulated spill of 10,000 kg of jet fuel. The resulting aqueous concentrations were found to be most sensitive to the saturation concentrations and the dissolution rates, moderately sensitive to the evaporation rates and longitudinal dispersion coefficient, and nearly completely insensitive to the volatilization coefficient.