Transient water table influence upon Light Non-Aqueous Phase Liquids (LNAPLs) redistribution : laboratory and modelling studies

• Main Author: Sun, Simiao
• Published: University of Birmingham 2017
• Subjects: 628; GE Environmental Sciences
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.704858

Fluctuating water table conditions influence capillary-held LNAPL(Light Non-Aqueous Phase Liquids) mass above and below the water table. Risks posed by such dynamic source zones vary over time as water tables oscillate from tidal effects, seasonality or anthropogenic interferences. In this study, the first automated multiphase flow dynamic water table experimental system comprising both hardware and software, was developed to: i) automatically implement programmable cyclic water table fluctuations via Raspberry Pi\(^T\)\(^M\) based inexpensive electronics; ii) dynamically monitor the real-time saturation distributions of all fluids (red-dyed-LNAPL, blue-dyed-water and air) in 2-D sand tank, using high-temporal-and-spatial resolution automated multi-spectral photography; and iii) accurately interpret large detailed datasets via advanced multi-spectral imaging. Such automated data acquisition and processing permit LNAPL releases and their redistributions under oscillating water table to be demonstrated in videos of photographic records, interpreted 2-D saturation contours and 1-D profiles. Eight experimental scenarios were undertaken to discern the influencing mechanisms of cyclic fluctuations incorporating with other influential factors including aquifer media and heterogeneities, volume and timing of releases, etc. Applicability of standard modelling by NAPL simulator was exercised, which provided a good general match of overall features of the release and oscillation dynamics. The high-resolution-and-frequency detailed quantitative dataset harvested was expected to supplement and expand the theories of multiphase flow distribution in porous media, where owing to the realization of the automated system, unprecedented processes were captured; and serve as a robust validation source of numerical and conceptual models which are essential tools in contamination site characterization, prediction, and remediation.