A Multi-Tracer Push-Pull Diagnostic Test for In Situ Air Sparging Systems

Abstract

This document describes the development and initial application of a multi-tracer push-pull test designed to provide near real-time point-specific measures of contaminant volatilization and aerobic biodegradation rates during in situ air sparging (IAS) operation. Measured biodegradation and volatilization rates are specific to the tracers used, so the results provide relative measures useful for identifying spatial differences in treatment performance and changes in performance with changes in system operation and design. The diagnostic test involves injecting a solution containing multiple tracer compounds into the target treatment zone through a monitoring well, piezometer, or drive point. The injected solution is initially deoxygenated and can contain: (a) a nondegradable, non-volatile conservative tracer, (b) one or more nondegradable, volatile chemicals, (c) an aerobically biodegradable, nonvolatile compound, and (d) a visible dye. After some predetermined hold time, an excess quantity of groundwater is extracted from the same injection point and the change in the concentrations of the tracer compounds is measured. Volatilization and oxygen utilization rates are then estimated from mass balances on the tracer components. The development of this diagnostic tool was conducted in a controlled physical model study and then initial field tests were conducted at the U.S. Navy Hydrocarbon National Test Site (HNTS) in Port Hueneme, California. Spatial variations in oxygenation and volatilization rates were observed, with oxygenation rates varying from 0 to 51 mg-O 2 /L-water/d, and tracer volatilization rates varying from 0 to 47%/d. Acetate and sulfur hexafluoride (SF 6 ) were used as tracers in the initial testing, and it was discovered that these are not ideal choices due to the potential for anaerobic acetate biodegradation and SF 6 partitioning into trapped gas in the aquifer.

What Does Syria Want? A Presentation by Raymond Hinnebusch for the Center for Naval Analyses and the Forum du Futur (France)

“…This project was conducted by the authors of this document, with input and review from an expert panel comprised of practitioners, program managers, and members of academia. Under this project, both laboratory-and field-scale experiments were conducted, and the results of the individual studies have been, and continue to be reported elsewhere (Amerson, 1997;Amerson et al, 2001;Bruce et al, 1998;Johnson et al, 1999;Rutherford and Johnson, 1996). The ultimate goal of this project, however, has been the development of a technically defensible and practicable air sparging Design Paradigm.…”

“…The stainless steel tubing was bent so that the Swagelock fitting terminated at a 100-mesh stainless steel screen that was PVC-welded to the PVC riser. Sampling intervals were installed at each multi-level sampler with the Swagelock fitting at the following depths bgs: 2,4,6,8,10,11,12,13,14,15,16,17,18, and 19 ft. A silica sand and filter pack was installed across the screened interval and bentonite pellets were used to fill the remaining annular space to grade. The bentonite pellets were frozen prior to use for installation below the water table.…”

“…At that point it is difficult to assess real-time system performance via traditional measurements (e.g., groundwater monitoring, SVE off-gas sampling, etc.). In those cases, if real-time assessment is important, users should consider the tracer-based tests utilized by Amerson et al (2001) and Bruce et al (2001).…”

Multi-Site Air Sparging

“…This project was conducted by the authors of this document, with input and review from an expert panel comprised of practitioners, program managers, and members of academia. Under this project, both laboratory-and field-scale experiments were conducted, and the results of the individual studies have been, and continue to be reported elsewhere (Amerson, 1997;Amerson et al, 2001;Bruce et al, 1998;2001;Johnson et al, 1999;Rutherford and Johnson, 1996). The ultimate goal of this project, however, has been the development of a technically defensible and practicable air sparging Design Paradigm.…”

A Push–Pull Test To Measure Root Uptake of Volatile Chemicals from Wetland Soils

“…A volatilization PPT has been proposed previously, 26 but the utility of this earlier approach was limited by the partitioning of the volatile tracer sulfur hexafluoride (SF 6 ) into subsurface gas bubbles and by the lack of a quantitative framework to scale tracer-derived mass transfer rates to other chemicals. In this contribution, we resolve these problems by developing a dual volatile tracer method that minimizes errors from bubble partitioning and by demonstrating an empirical relationship between uptake rate constants and a chemical's molecular diameter.…”