Priscilla Z. Viana, Ph.D., Arcadis U.S., Inc.
Karl J. Rockne, Ph.D., PE, BCEE, University of Illinois at Chicago

Gas ebullition can be a significant mechanism for mass transport of NAPL and other contaminants from sediments to the surface water column. Accurate evaluation of the presence and potential of gas ebullition to facilitate NAPL and contaminant migration from sediment to the water column is a critical step in contaminated sediment site characterization, conceptual site model development, assessment of remedial alternatives, and remediation design.

The migration of gas bubbles through sediment and surface water is called gas ebullition. In many organic-rich sediment environments, microorganisms can produce gas comprised of methane with a typical range from 40 to 90%, and lesser amounts of carbon dioxide and other gaseous end products (Casper 2000, Huttunen et al. 2001, Rockne et al. 2011, and Viana et al. 2012). Gas ebullition requires that the gas production rate must be sufficiently rapid to cause gas bubbles to grow, fracture the sediment, and subsequently migrate upward (Boudreau 2012, Zamanpour et al. 2020). Gas ebullition can represent an important mass transport mechanism of NAPL and/or other contaminants to the water column (Fendinger et al. 1992, Viana et al. 2012, Viana et al. 2018, Yuan et al. 2009, Zamanpour et al. 2020). Viana and Rockne (2021) summarize the mechanisms of biogenic gas production in sediment, ebullition processes, and NAPL transport via ebullition. They also provide a summary of site-specific conditions and characteristics that affect gas production, gas ebullition, and associated NAPL and contaminant transport.

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