Predicting DNAPL mass discharge and contaminated site longevity probabilities: Conceptual model and high‐resolution stochastic simulation. Issue 2 (2nd February 2015)

• Record Type: Journal Article
• Authors: Koch, J.; Nowak, W.
• Is Part Of: Water resources research. Volume 51:Issue 2(2015:Feb.)
• Page Start: 806
• Page End: 831
• Publication Date: 2015-02-02
• Subjects: contaminant source architecture -- stochastic model concepts -- mass discharge variability -- source longevity -- effects of simplifications -- uncertainty quantification; Hydrology -- Periodicals; 333.91
• DOI: 10.1002/2014WR015478
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Improper storage and disposal of nonaqueous‐phase liquids (NAPLs) has resulted in widespread contamination of the subsurface, threatening the quality of groundwater as a freshwater resource. The high frequency of contaminated sites and the difficulties of remediation efforts demand rational decisions based on a sound risk assessment. Due to sparse data and natural heterogeneities, this risk assessment needs to be supported by appropriate predictive models with quantified uncertainty. This study proposes a physically and stochastically coherent model concept to simulate and predict crucial impact metrics for DNAPL contaminated sites, such as contaminant mass discharge and DNAPL source longevity. To this end, aquifer parameters and the contaminant source architecture are conceptualized as random space functions. The governing processes are simulated in a three‐dimensional, highly resolved, stochastic, and coupled model that can predict probability density functions of mass discharge and source depletion times. While it is not possible to determine whether the presented model framework is sufficiently complex or not, we can investigate whether and to which degree the desired model predictions are sensitive to simplifications often found in the literature. By testing four commonly made simplifications, we identified aquifer heterogeneity, groundwater flow irregularity, uncertain and physically based contaminant source zones, and their mutual interlinkages as indispensable components of a sound model framework. Key Points: Conceptual model framework for mass discharge and depletion time predictions Physics and uncertainty need to be considered jointly Stochastic simulation of physical‐based source zone architectures