|
1L - Exposure Modelling (WEP/85) Development of an unsteady-state lake model and application to several scenarios. Di Guardo, Antonio1, Ferrari, Claudia1, Paola, Gramatica2, 1 Environmental Research group, DBSF, University of Insubria, Varese, VA, ITALY2 QSAR and Environ. Chem. Res. Unit, University of Insubria, Varese, VA, ITALY ABSTRACT- The fate of chemicals in surface waters has been historically investigated with the help of modelling tools, which were employed to simulate typical situations such as the continuous discharge of a contaminant. This type of input can often be treated as a steady-state one and has lead to the development of a variety of models capable of calculating the mass balance of the contaminant in the lake. Some of the models developed can also simulate dynamic (unsteady-state) situations in which the fate of a chemical is studied starting with a "clean" system and adding the contaminant at a constant input until steady state is reached. Such type of model can be very useful to depict the main characteristics and time response of a lake but cannot be generally applied when the chemical input changes with time. An example of the latter is a single spill of a chemical in a lake or a specific application, such as that of a pesticide on a rice field. An unsteady state model for the simulation of the fate of organic chemicals in lakes and ponds was developed. It is based on a modification of the QWASI-fugacity model initially developed by Mackay and coworkers. The model can be used to simulate single application of chemicals, variable or continuous inputs. Some examples of the application of the model to a variety of environmental scenarios are shown to illustrate its usefulness in specific circumstances. Key words: QWASI, Lake model, Unsteady-state, fugacity |
