Laser-induced fluorescence (LIF)
As reported in Groundwater Monitoring and Remediation (38(3):28-42), DyeLIF™ is a new version of laser-induced fluorescence (LIF) for high-resolution 3D mapping of NAPLs in the subsurface. DyeLIF eliminates the requirement that the NAPL contains native fluorophores (such as those that occur in compounds like PAHs) and therefore can be used to detect chlorinated solvents and other nonfluorescing compounds.
NAPLs were previously 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. This paper describes a detailed field evaluation of the novel DyeLIF technology performed at a contaminated industrial site in Lowell, Mass., where chlorinated solvent DNAPL persists below the water table in sandy sediments..
The DyeLIF system was field tested at a Formerly Used Defense (FUD) facility in Massachusetts in Fall 2013 (Geoprobe® delivery) and again in March 2014 (CPT delivery). The primary field demonstration completed in 2013 included two components: one week of DyeLIF probing and a second week of follow-on soil coring using research-quality direct push (DP) soil coring methods in order to compare DyeLIF results to colorimetric dye shake tests and laboratory analysis.
Several performance objectives were established in the project demonstration work plan and all were met or exceeded. The performance objective for chemical analysis was 70% consistency between positive DyeLIF responses and samples when DNAPL saturations were greater than 5%. The demonstration results showed 100% consistency between chemical analysis and DyeLIF for saturations greater than 1.9% (35 of 35 samples), and 95% consistency for estimated saturations greater than 0.5% (40 of 42 samples).
ESTCP funded Project ER-201121 to demonstrate the DyeLIF technology. Additional details on the technology can be found at the U.S. Department of Defence Strategic Environmental Research and Development Program (SERDP) and the U.S. Department of Defence Environmental Security Technology Certification Program (ESTCP) link at SERDP-ESTCP.
2D and 3D Conceptual Site Models of a Contaminated Property
