Comparison of water quality models for pesticides

Water quality models have been applied increasingly to represent the interaction between pollutants and aquatic environment due to transport and transformation phenomena: These models can be used to better understand pollution phenomena and to choose between different, alternative management strategies. The paper compares the results of two different water quality models, which have been applied to a water column-sediments system of a lake with an inflow contaminant loading. In the former, the system is idealized as well-mixed surface-water underlain by a well-mixed active sediment layer, where the resulting concentrations are attained by direct analytical solutions at the steady-state and in time-variable conditions. The latter is TOXI5 model, which is part of WASP5 modeling framework developed by USEPA. The models were applied to an idealized case in order to predict steady-state and time-variable concentrations in the water-column and in the active sediment layer for 4 pesticides. Comparison between the results obtained through the two models shows a good agreement both for the steady-state concentrations and for the time-variable ones. The transients from no-concentrations to the steady-state and from steady-state to negligible concentrations were performed; the simulations have pointed out the very long time for attaining both steady-state conditions and the system recovery in the lake and in the active sediments layer especially.