Stochastic multimedia risk assessment for a site with contaminated groundwater |
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| Authors: | H-W Ma |
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| Institution: | (1) Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Road, Taipei, Taiwan 106 e-mail: hwma@ccms.ntu.edu.tw, TW |
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| Abstract: | There exist many sites with contaminated groundwater because of inappropriate handling or disposal of hazardous materials
or wastes. Health risk assessment is an important tool to evaluate the potential environmental and health impacts of these
contaminated sites. It is also becoming an important basis for determining whether risk reduction is needed and what actions
should be initiated. However, in research related to groundwater risk assessment and management, consideration of multimedia
risk assessment and the separation of the uncertainty due to lack of knowledge and the variability due to natural heterogeneity
are rare. This study presents a multimedia risk assessment framework with the integration of multimedia transfer and multi-pathway
exposure of groundwater contaminants, and investigates whether multimedia risk assessment and the separation of uncertainty
and variability can provide a better basis for risk management decisions. The results of the case study show that a decision
based on multimedia risk assessment may differ from one based on risk resulting from groundwater only. In particular, the
transfer from groundwater to air imposes a health threat to some degree. By using a methodology that combines Monte Carlo
simulation, a rank correlation coefficient, and an explicit decision criterion to identify information important to the decision,
the results obtained when uncertainty and variability are separate differ from the ones without such separation. In particular,
when higher percentiles of uncertainty and variability distributions are considered, the method separating uncertainty and
variability identifies TCE concentration as the single most important input parameter, while the method that does not distinguish
the two identifies four input parameters as the important information that would influence a decision on risk reduction. |
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| Keywords: | : Multimedia risk assessment Risk management Sensitivity Uncertainty Monte Carlo methods |
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