Abstract
Nowadays, the contamination of groundwater and soils by highly hazardous and toxic chlorinated solvents is a global issue. Over the past years, different remediation strategies have been developed, involving injection of reactive solutions and/or particles. However, a major difficulty is the monitoring of injected particles during the injection and after secondary mobilisation by groundwater flow. This study is focussed on the development of directly traceable particles by combining fluorescein with Layered Double Hydroxides (LDHs). We present here the facile and easily tuneable synthesis of fluorescing LDHs (Fluo-LDH) via co-precipitation under supersaturation conditions. Their ability to mimic particle sizes of previously studied reactive LDHs, which proved to be able to adsorb or degrade chlorinated organic solvents from aqueous solutions, was investigated as well. Tests using a novel Optical Image Profiler (OIP) confirmed that the fluorescent LDHs can be easily detected with this tool. Even LDHs with the lowest amount of fluorescent dye were detectable. Together with the use of an OIP, which is capable of exciting the fluorescent material and collecting real-time pictures, this can provide a new, efficient, and cost-effective method for in situ tracing of injected particles in the subsurface.
Highlights
In recent years, the removal of chlorinated organic solvents, which can deeply penetrate aquifers, accumulating in the sub-surface as lenses of highly hazardous and toxic pollutants [1,2] from groundwater and soil, has become a major problem
This study is focussed on the development of directly traceable particles by combining fluorescein with Layered Double Hydroxides (LDHs)
We present here the facile and tuneable synthesis of fluorescing LDHs (Fluo-LDH) via co-precipitation under supersaturation conditions
Summary
The removal of chlorinated organic solvents, which can deeply penetrate aquifers, accumulating in the sub-surface as lenses of highly hazardous and toxic pollutants [1,2] from groundwater and soil, has become a major problem. Thereby, a major difficulty is the monitoring of reactants during the injection and after secondary mobilisation by groundwater flow. Their behaviour in the sub-surface is usually estimated based on data gathered about contaminant transport behaviour and source zone geometries [12,19]. One promising example was presented by Gillies et al [20] Detection of these novel particles can be achieved by using and/or adapting already existing systems to detect different kind of tracers, or tools to detect induced fluorescence of aquifer contamination by non-aqueous phase liquids; these are the Ultra-violet Optical Screening Tool (UVOST®) and Tar-Specific Green Optical Screening Tool (TarGOST®) from Dakota Technologies Inc. Detection of these novel particles can be achieved by using and/or adapting already existing systems to detect different kind of tracers, or tools to detect induced fluorescence of aquifer contamination by non-aqueous phase liquids; these are the Ultra-violet Optical Screening Tool (UVOST®) and Tar-Specific Green Optical Screening Tool (TarGOST®) from Dakota Technologies Inc. (Dargo, ND, USA) [21,22], the Rapid Optical Screening Tool (ROSTTM) from Fugro Geoscience Inc. (Houston, TX, USA) [23,24], and the Optical Image Profiler (OIP)-UV and OIP-G from Geoprobe Systems®; Kejr Inc. (Salina, KS, USA) [25,26]
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