Modeling the transport and fate of chromium and copper in the Mahoning River

Abstract

The transport and fate of heavy metals in the aquatic environment has been of grave concern to the public, environmental engineers and regulatory agencies. To assess the physical quantities of heavy metals in various forms in an aquatic environment, water quality modeling is very useful. One model develop for this purpose by the USEPA scientists is MICHRIV (Michigan River Model). MICHRIV is a computer program which facilitates modeling and transport and fate of chemicals in rivers and streams. MICHRIV is a one dimensional steady state model. It calculates the suspended solids concentration in the water column given estimates of settling and resuspension rates, solids concentration in the bed, and depth of water and active bed. Chemical concentrations are calculated along the length of the river in both the water column and sediment bed. Modeling with MICHRIV was performed for chromium and copper in the Mahoning River. Estimates of heavy metals loadings into the river were based on the Ohio EPS's permissible limits of Waste Load Allocation. The initial model inputs for the various kinetic parameters in the model were based on literature values. The calibrated model results show good agreement with the available field data for 1989. Sensitivity analysis were performed for the heavy metals loadings, settling and resusupension velocities, and partition coefficient. The predictions of the model show that heavy metal concentrations in the water column would drop dramatically if the current loadings were reduced by half. Further studies are recommended to identify the historical flows and loadings to the river during and prior to the industrial era in the Mahoning Valley.