Abstract

All pollutant contamination problems have both short and long term impacts on ambient air, water, and soil environments. Previous environmental pollution control programmes mainly focused on a single environmental medium (e.g., groundwater). Traditional environmental multimedia models (EMM) usually simulate pollutants' fate and transport in separate zones, based on one-dimensional, first-order mechanisms. This may lead to biased results and simulation errors. In this study, firstly, a new extended environmental multimedia model system (EEMMS) was set up, which includes four sub-modules (sources, air quality, unsaturated zone, groundwater) on a regional spatial-temporal scale. Three different approaches were evaluated for solving multi-dimensional coupled pollutants equations using experimental data from the literature: a) EEMMS/FEM (numerical finite element method); b) EEMMS /FDM (numerical finite difference method); and, c) EEMMS /analytical method. Furthermore, three validations related to the three approaches are conducted. First, experimental results from a pilot scale landfill were used to verify the spatial temporal accuracy of predicted emission fluxes and concentrations in both numerical spatial and temporal scale. Further systematic model validations were implemented and tested comparing with the dual domain mass transfer model and 2-D analytical model. Complicated 3-D real site validation was conducted through the Trail Road Sanitary Landfill site. 3-D reasonable results have been obtained through the comparisons of analytical and numerical solutions (FDM and FEM) in non-uniform and unsteady conditions. Implementing the EEMMS/FEM solution in the above three validations was found to be better than that of EEMMS/FDM, and EEMMS /analytical solutions. EEMMS/FEM solution also provided more stabilization technique, a better mesh that minimizes the error or even a faster solution. In addition, given a large amount of uncertainties associated with EMMS practices, sensitivity analyses approach such as retardation factor, Peclet number (Pe), hydraulic conductivity, bulk density, porosity, were embedded into the developed EEMMS. Lastly, the new EEMMS model containing both new environmental multimedia system (EMS) and Monte Carlo Method (MCM) was developed to an integrated tool for the risk assessment of contaminants. The new EEMMS would serve as a risk assessment tool to address the fate and transport of the pollutants in complex, multimedia environments and subsequently to help in the management of the resulting environmental impacts.