Site-specific risk assessment and management of point and diffuse sources - Environmental Deterioration and Contamination: Problems and their Management - page 346

4.2.4 Combined approach for watershed-scale transport
and fate modeling of diffuse pollution
The combined approach of contaminant transport and fate modeling at watershed scale
merges known transport and fate input parameters of a numerical model (i.e., environ-
mental conditions, transport medium, contaminant characteristics) with a black box
model to predict the environmental concentration in the compliance point of the water-
shed (Figure 10.8). Data on environmental conditions along the transport pathway
include but are not limited to geochemistry, hydrogeology, microbiology, temperature,
pH, redox potential. Input data related to the contaminant transport medium comprise
soil type, infiltration rate, capillarity, water conductivity, ion binding capacity, etc. In
reference to the contaminant characteristics, the input data for a numerical model
include information on the chemical form, partition, chemical transformation, micro-
biological transformation, etc. The black box model considers the environment and its
interactions with the contaminant along the transport pathway as a homogenous black
box, characterized by an average RRR rate ( RRR watershed ). The RRR watershed represents
Figure 10.8 Combined approach for watershed-scale transport and fate modeling of diffuse pollution.