Gaseous deposition described with the Industrial Source Complex model

The Industrial Source Complex (ISC) model is a steady-state Gaussian plume model that recently was updated with improved algorithms for estimating the amount of gaseous matter that is deposited on ground surfaces, including soils, plants, and water. Such estimates are especially useful for meeting emerging needs to assess the impacts of toxic air pollutants. Complex processes are involved in the transfer and deposition of gaseous pollutants at the surface. Describing these processes requires model inputs on properties of the depositing material (e.g., gas diffusivity, solubility, and reactivity), characteristics of the surface (e.g., surface roughness and vegetation type, amount, and physiological state), and atmospheric variables (e.g., wind speed, temperature, stability, and solar radiation). Obtaining all of the required information for model inputs on the properties of the substances is difficult for the wide variety of hazardous chemicals needing attention. A model sensitivity analysis has been performed to evaluate the relative importance of the various input parameters. Model-derived estimates are compared with observed values for some limited data sets available. These results will be useful to model users, as well as for designing future data collection programs for model assessment studies.