Amy L. Corp, P. Chem, EP, Anchor QEA, LLC

Accurately quantifying gas ebullition and related mass transport of NAPL and other contaminants from sediment to the overlying water column is an important issue at some contaminated sediment sites. This article summarizes procedures for building and using flux chambers to collect technically defensible data.

Gas ebullition is gas bubble formation and growth in sediment, followed by sediment fracture and the subsequent upward migration of gas bubbles through sediment to the surface water column. Migration of gas bubbles through nonaqueous phase liquid (NAPL) or other organic contaminants in sediments may result in the transport of NAPL/contaminants from sediments to surface water (i.e., ebullition-facilitated transport [EFT]). This can be an important transport mechanism for contaminated sediment sites, moving isolated contaminants into the biologically active zone (Viana and Rockne 2021, 2022 ; Fendinger et al. 1992; Viana et al. 2012, 2018; Yuan et al. 2009). Also, at sites where sediment capping is planned as part of the remedy, ebullition should be evaluated to understand potential impacts to cap design such as contaminant transport and potential gas buildup (which could potentially destabilize a remedial cap).

read more