Membrane Interface Probe Protocol for Contaminants in Low‐Permeability Zones

Abstract

Accurate characterization of contaminant mass in zones of low hydraulic conductivity (low k) is essential for site management because this difficult-to-treat mass can be a long-term secondary source. This study developed a protocol for the membrane interface probe (MIP) as a low-cost, rapid data-acquisition tool for qualitatively evaluating the location and relative distribution of mass in low-k zones. MIP operating parameters were varied systematically at high and low concentration locations at a contaminated site to evaluate the impact of the parameters on data quality relative to a detailed adjacent profile of soil concentrations. Evaluation of the relative location of maximum concentrations and the shape of the MIP vs. soil profiles led to a standard operating procedure (SOP) for the MIP to delineate contamination in low-k zones. This includes recommendations for: (1) preferred detector (ECD for low concentration zones, PID or ECD for higher concentration zones); (2) combining downlogged and uplogged data to reduce carryover; and (3) higher carrier gas flow rate in high concentration zones. Linear regression indicated scatter in all MIP-to-soil comparisons, including R(2) values using the SOP of 0.32 in the low concentration boring and 0.49 in the high concentration boring. In contrast, a control dataset with soil-to-soil correlations from borings 1-m apart exhibited an R(2) of ≥ 0.88, highlighting the uncertainty in predicting soil concentrations using MIP data. This study demonstrates that the MIP provides lower-precision contaminant distribution and heterogeneity data compared to more intensive high-resolution characterization methods. This is consistent with its use as a complementary screening tool.

Integrity of Clay Till Aquitards to DNAPL Migration: Assessment Using Current and Emerging Characterization Tools

“…Thereby, the ECD was too sensitive to be used at the DNAPL source zone. This is consistent with findings by Adamson et al (), where overload and carry‐over/drag‐down for the ECD is observed at their “high concentration” area (<40 mg/kg CVOC).…”

“…Adamson et al () also used the less sensitive PID and FID for contaminant characterization in the saturated low permeable zones. However, the FID data were not evaluated beyond initial screening as the response was negligible.…”

Fluorescent Dyes: A New Weapon for Conquering DNAPL Characterization

“…Various authors (Adamson et al 2014 ;Geoprobe 2017 ) have suggested modifications to MIP operating procedures and data interpretation to improve on the ability to screen for DNAPL or resolve high-concentration zones. This technique effectively provides qualitative to semi-quantitative screening of the magnitude of total VOC impacts in the subsurface, but is not designed for quantitative mapping of DNAPL or LNAPL (light nonaqueous phase liquid).…”

Enhanced Amendment Delivery to Low Permeability Zones for Chlorinated Solvent Source Area Bioremediation

“…The only recommended addition to conventional characterization efforts would be the use of one or more high-resolution methods to provide more detailed spatial information (particularly in the vertical direction) on contaminant distribution and permeability within the treatment area (Adamson et al, 2013, Sale et al, 2013. Depending on the site, there are a number of methods that may be appropriate, including (but not limited to) CPT, MIP, GeoProbe HPT or MiHPT, Waterloo APS , passive flux meters, and various geophysical approaches.…”