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| A fuzzy-stochastic integrated model of contaminated site risk assessment model and case study |
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Abstract Risk assessment is associated with uncertainties in nature, and neglect of those uncertain elements in evaluating risk will inevitably lead to difficulty for decision-makers in the stage of risk management and decision-making. Fuzzy theory was used to describe the fuzzy uncertainties, and probability theory was employed to describe the random uncertainties. A coupled fuzzy-stochastic model was built to resolve the problem of complex computation of fuzzy numbers in which fuzzy number are represented with the function of uniform random variables. Monte Carlo method was also used to simulate the computation between fuzzy numbers. One mercury contaminated site located in Qinghai Province was selected as a case to demonstrate the effectiveness and reasonability of this coupled model. The reasonability of this model was verified by comparing simulated results of the widely used RBCA model. The case study indicated that: 1) the main exposure pathway was oral intake with a contribution rate of 80%; 2) the health risk of this contaminated site was acceptable with non-carcinogenic Hazard Quotient (HQ) of 0.28 under normal exposure condition; under the most unfavorable exposure condition which appearance probability was less than 1%, the health risk was unacceptable with HQ equals to 1.28; 3) the health risk would decline in time and reach to an acceptable level after about six years. Therefore, it was suggested that the related responsibility should provide other drinking water resources to eliminate the exposure routine in the period of the first 6 years or the 6-8 years rather than take engineering measurements to remediate this contaminated site.
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Received: 08 November 2013
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