Abstract

Environmental multimedia models (EMMs) have been used in environmental risk assessment since they reflect the interactive transport and fate processes of chemicals within multi-compartmental environmental systems. However, these existing models are limited in their abilities to predict contaminant concentrations in the multimedia environment at a better temporal-spatial resolution, especially for regional scale site contamination problems.
A novel regional numerical multimedia environmental modeling (RNEMM) approach is developed in this thesis for the multimedia environment. RNEMM consists of a water quality simulation module for river network system, a gaseous phase simulation module, a mass balance analysis module for soil, a food web module and a health risk assessment module. Two key developments are achieved to integrate these modules into the entire system: integrating different modules with non-uniform boundary conditions and inter-media flux, and coupling the modules based on practical considerations of regional scale multimedia contamination problems. Importantly, four validations related to the RNEMM development are conducted. First, a new model in 1D and 2D are established through considering the non-uniform boundary conditions and inter-media flux. Numerical algorithms, including the finite element method (FEM) and finite volume method (FVM), are used to solve the governing equations. The measured results in two landfill cases are used to validate the spatial and temporal accuracy of predicted concentrations obtained from these models. Second, a regional spatial environmental multimedia model (RSEMM) is developed by coupling the modules based on a different concept (i.e., a water quality model for the river network and a fugacity model) to provide predicted concentration profiles of contaminants at a regional scale. A third regional site validation is conducted through a case in the urban area of Tianjin City and reasonable results have been obtained through the comparison of simulated and measured results.
Subsequently, based on the two key developments, a regional numerical multimedia environmental modeling (RNEMM) approach is developed and tested by assessing spatial eco-environmental exposure risk of perfluorooctane sulfonate (PFOS) in the pearl river basin. The exposure risk assessment for children and adults is further conducted based on the integrated risk assessment model. In conclusion, the RNEMM can serve as a comprehensive management tool to assess and control the exposure risks associated with emerging contaminants on regional water, soil, and ecosystem at an adequate spatial-temporal resolution.