title: In-situ determination of field-scale NAPL mass transfer coefficients: Performance, simulation and analysis.
abstract: Better estimates of non-aqueous phase liquid (NAPL) mass, its persistence into the future, and the potential impact of source reduction are critical needs for determining the optimal path to clean up sites impacted by NAPLs. One impediment to constraining time estimates of source depletion is the uncertainty in the rate of mass transfer between NAPLs and groundwater. In this study, an innovative field test is demonstrated for the purpose of quantifying field-scale NAPL mass transfer coefficients (kl(N)) within a source zone of a fuel-contaminated site. Initial evaluation of the test concept using a numerical model revealed that the aqueous phase concentration response to the injection of clean groundwater within a source zone was a function of NAPL mass transfer. Under rate limited conditions, NAPL dissolution together with the injection flow rate and the radial distance to monitoring points directly controlled time of travel. Concentration responses observed in the field test were consistent with the hypothetical model results allowing field-scale NAPL mass transfer coefficients to be quantified. Site models for groundwater flow and solute transport were systematically calibrated and utilized for data analysis. Results show kl(N) for benzene varied from 0.022 to 0.60d(-1). Variability in results was attributed to a highly heterogeneous horizon consisting of layered media of varying physical properties.
authors: The Charles E. Via, Jr. Department of Civil & Environmental Engineering, 750 Drillfield, Virginia Tech, Blacksburg, VA 24061-0105, USA; GZA, GeoEnvironmental, Inc., Bedford, NH, USA.
authors: Michael
authors: M
authors: Mobile
authors: The Charles E. Via, Jr. Department of Civil & Environmental Engineering, 750 Drillfield, Virginia Tech, Blacksburg, VA 24061-0105, USA.
authors: Mark
authors: M
authors: Widdowson
authors: Praxis Environmental Technologies, Inc., Burlingame, CA, USA.
authors: Lloyd
authors: L
authors: Stewart
authors: Geosyntec Consultants, Oakland, CA, USA.
authors: Jennifer
authors: J
authors: Nyman
authors: Geosyntec Consultants, Oakland, CA, USA.
authors: Rula
authors: R
authors: Deeb
authors: Geosyntec Consultants, Oakland, CA, USA.
authors: Michael
authors: M
authors: Kavanaugh
authors: Tetra Tech, Sterling, VA, USA.
authors: James
authors: J
authors: Mercer
authors: The Charles E. Via, Jr. Department of Civil & Environmental Engineering, 750 Drillfield, Virginia Tech, Blacksburg, VA 24061-0105, USA.
authors: Daniel
authors: D
authors: Gallagher
mesh_terms: D001130:Arizona; D001554:Benzene / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D060587:Groundwater / Q000737:chemistry; D062070:Hydrology / Q000379:methods*; D008962:Models, Theoretical; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis* / Q000737:chemistry
chemical_list: D014873:Water Pollutants; D001554:Benzene
keywords: Benzene; Groundwater; Mass transfer; Non-aqueous phase liquid (NAPL); Petroleum hydrocarbons; Remediation