Multimedia Environmental Distribution of Toxics (Mend-Tox). II: Software Implementation and Case Studies

Abstract

An integrated hybrid spatial-compartmental simulator is presented for analyzing the dynamic distribution of chemicals in the multimedia environment. Information obtained from such analysis, which includes temporal chemical-concentration profiles in various media, mass distribution, and intermedia chemical mass fluxes, can be used for subsequent exposure and risk analyses. The software architecture of the environmental simulator for multimedia environmental distribution of toxics (Mend-Tox) system is presented with emphasis on features that allow for rapid scenario design and analysis of dynamic chemical partitioning in the environment. Mend-Tox is a hybrid model that consists of both uniform (air, water, suspended solids, vegetation, biota, suspended solids, and atmospheric aerosols) and nonuniform (soil and sediment) environmental compartments. The model structure is described in a companion paper (Part I). The modular structure of the system provides for flexibility of model design, implementation of a variety of simulation scenarios, maintenance and reusability of model components, and ease of future improvements. The applicability of Mend-Tox is illustrated for the distribution of polycyclic aromatic hydrocarbons (PAHs) and their nitro-PAH daughter products in the Los Angeles Basin, a retrospective analysis of polychlorinated biphenyls in Lake Michigan, and the partitioning behavior of selected volatile organic compounds. The level of predictive multimedia analysis represented by these examples yields very reasonable agreement with reported measurements.