DyeLIF™: A New Direct‐Push Laser‐Induced Fluorescence Sensor System for Chlorinated Solvent DNAPL and Other Non‐Naturally Fluorescing NAPLs

Abstract

DyeLIF™ is a new version of laser‐induced fluorescence (LIF) for high‐resolution three‐dimensional subsurface mapping of nonaqueous phase liquids (NAPLs) in the subsurface. DyeLIF eliminates the requirement that the NAPL contains native fluorophores (such as those that occur in compounds like polynuclear aromatic hydrocarbons [PAHs]) and can therefore be used to detect chlorinated solvents and other nonfluorescing NAPLs that had previously been undetectable with conventional LIF tools. With DyeLIF, an aqueous solution of water and nontoxic hydrophobic dye is continuously injected ahead of the sapphire detection window while the LIF probe is being advanced in the subsurface. If soil containing NAPL is penetrated, the injected dye solvates into the NAPL within a few milliseconds, creating strong fluorescence that is transmitted via fiber‐optic filaments to aboveground optical sensors. A detailed field evaluation of the novel DyeLIF technology was performed at a contaminated industrial site in Lowell, Massachusetts, USA where chlorinated solvent dense nonaqueous phase liquid (DNAPL) persists below the water table in sandy sediments. Continuously cored boreholes were drilled adjacent to 5 of 30 DyeLIF probes that were advanced at that site. The cores were subsampled in high resolution to generate discrete‐depth soil samples as splits at the same depths where DNAPL was detected in the colocated DyeLIF probes. The cores were analyzed above ground using (1) colorimetric screening using hydrophobic dye tests, (2) laboratory extraction and quantitative chemical analysis, (3) “Benchtop” DyeLIF, and (4) volumetric moisture content. Correlation between DyeLIF and aboveground analyses of the soil cores was excellent: 98% agreement with positive DNAPL detections in samples where DNAPL pore saturations were >0.7% (based on quantitative soil analyses) and the ex situ tests. DyeLIF produced the equivalent of one aboveground colorimetric dye test every 0.2 inch (0.5 cm) of probing. With average daily probing of 395 linear feet (120.4 m), this was the equivalent of 12,039 discrete‐depth colorimetric dye tests/day. Because DyeLIF is an in situ measurement, there are no issues with soil core recovery like there would be for conventional ex situ colorimetric dye tests and 100% characterization of the probed intervals is achieved. Tracking the injection rate and pressure of the dye solution provides simultaneous data regarding relative soil permeability, similar to other direct push (DP) hydraulic profiling tools. Conventional LIF is considered the premier DP tool to identify and map NAPL containing PAHs in the subsurface or confirm its absence. While chlorinated solvent DNAPLs at some field sites contain impurities (e.g., solvated greases or oils) that make them detectable with conventional LIF techniques, at other sites, the DNAPL cannot be detected with conventional LIF. At such sites, the injection of a hydrophobic dye ahead of the sapphire window with the DyeLIF system now makes the LIF technology applicable to the many t...

In Situ Thermal Remediation for Source Areas: Technology Advances and a Review of the Market From 1988–2020

“…As a result, pre‐design investments that further refine the spatial distribution of NAPL will attain a higher level of certainty that ISTR will achieve remedial objectives. High‐resolution site characterization (HRSC) tools, including direct‐push hydraulic profiling tools (HPTs), optical screening tools such as the traditional or dye‐enhanced laser induced fluorescence (LIF) systems (e.g., Einarson et al 2018), membrane interface probe (MIP) systems, and other geophysical tools are now widely available for improving source zone delineation. These systems allow for 3D modeling and visualization of the geology and NAPL distribution, which provides increased confidence that the ISTR footprint encompasses the entire NAPL source zone and will not leave behind areas with significant mass that may continue to diffuse to the surrounding plume.…”

Direct‐Push Color Logging Images Spatial Heterogeneity of Organic Carbon in Floodplain Sediments

“…Dalan et al (2011), Hausmann et al (2018), and Rabiger‐Völlmer et al (2020) used multiple vertical color logs along profiles to detect and map the geometry of archeological features based on spatial and vertical color contrasts. Similar probes have been used to detect and map contaminants and dye tracers in the subsurface (Einarson et al, 2018; Kram et al, 2001; McCall et al, 2018; Reischer et al, 2020). The vertical resolution is in the centimeter range.…”

“…These requirements are met by direct‐push in situ color logging, in which a rod with an outward oriented sapphire glass window is continuously advanced into the ground by standard direct‐push machines. A sensor in the probe or in a surface processing unit records a defined wavelength or the entire visual spectrum of light reflected from the sediments upon illumination by a white light or a laser (Ackerson et al, 2017; Bujewski & Rutherford, 1997; Einarson et al, 2018; Hausmann et al, 2016; Kram et al, 2001; McCall et al, 2018). Sounding locations can be spaced in the low decimeter range for high horizontal resolution and executed along transects or grids with more than 100 m of probing per day (Einarson et al, 2018; Hausmann et al, 2016; McCall et al, 2018).…”

High‐Resolution Characterization of a Chlorinated Solvent Impacted Aquifer Using a Passive Profiler

“…Some of the common existing technologies for subsurface site characterization in unconsolidated media include monitoring and multilevel wells, sediment cores, borehole logging, membrane interface probe (MIP), hydraulic profiling tool (HPT), the Waterloo Groundwater Profiler (Pitkin et al 1999) and advanced profiler system (APS), Geoprobe Screen Point (SP) sampler, and laser-induced fluorescence (Dye-LIF; Einarson et al 2018). Monitoring wells allow for diverse data sets to be gathered through the use of different tools, but typically over broad intervals and characteristic of the most permeable regions.…”

“…1999) and advanced profiler system (APS), Geoprobe Screen Point (SP) sampler, and laser‐induced fluorescence (Dye‐LIF; Einarson et al. 2018). Monitoring wells allow for diverse data sets to be gathered through the use of different tools, but typically over broad intervals and characteristic of the most permeable regions.…”