An integrated stochastic environmental risk assessment method and its application to a petroleum-contaminated Site

Spills, leaks and other releases of gasoline, diesel fuel, heating oil, and other petroleum products often result in the contamination of soil and water. This is posing a serious threat to public health and the environment and is acquiring more and more attention by the public, federal and local government, and petroleum industries. This paper presented an integrated stochastic risk assessment method and its application to a petroleum-contaminated site. The integrated method incorporated an analytical groundwaler sohite transport model within the general risk assessment framework. The analytical solute transport model is used for predicting the benzene concentration at a downgradient water supply well through addressing advection, dispersion, adsorption, and chemical/biological degradation of the contaminant in the saturated zone. The stochastic risk assessment model is used for the integrated assessment of risks caused through different exposure pathways. Due to the extensive variability and uncertainty existed in the system, the parameters are represented as PDFs (probability distribution functions) with a variety of forms. Both models were solved using Monte Carlo simulation technique for approaching the theoretical output distributions. Results for a case study showed that the total cancer risk has approximately a lognormal distribution, regardless of the fact that a variety of distributions were used to define the related parameters. The results could provide local managers with the degree of safety for a given decision for specific site management.