A field test of the exams model in the Monongahela River

Although there are many aquatic fate and transport models that predict environmental concentrations of pollutants over time or distance, the science of model validation is in its infancy. It has been recommended that high priority be given to future experimental work to field-validate existing models. This article presents a comparison of model predictions of phenol concentration downstream from a steel mill effluent derived from the Exposure Analysis Modeling System (EXAMS) with ambient phenol concentration data collected from the Monongahela River in Pennsylvania. The model predicted oxidation and biolysis as the most significant fate pathways for phenol degradation in the Monongahela River. Bacterial numbers were very low in river water, however, reducing the importance of the biolysis pathway. Agreement between observed levels of phenol and predicted model output was best achieved when a first-order decay of total molar oxidants in the water column was simulated by altering EXAMS molar oxidant input values.