Fluorescence spectroscopy as an indicator tool for pharmaceutical contamination in groundwater and surface water

Knowledge of contaminant distribution and transport of contaminant plumes in groundwater is important for effective remediation. Tedious and expensive laboratory analyses could be supplemented with optical measurements such as fluorescence to offer a rapid alternative with the potential for on-site measurements. Here, we explore the applicability of fluorescence spectroscopy as an on-site alternative to identifying the extent of a groundwater contaminant plume in Grindsted, Denmark. We show that three abundant contaminants (sulfanilamide, sulfaguanidine, and sulfanilic acid) emit very strong, but highly similar fluorescence distinct from the naturally occurring organic matter. The limit of detection for the sum of these three contaminants was 14 and 142 μg/L using benchtop measurements and handheld sensors, respectively. We demonstrate that low-volume solid-phase extractions can be a tool to lower the detection limits through the selective enrichment of contaminants. However, the co-occurrence of natural and anthropogenic fluorescent organic matter presents a significant challenge for the reliable quantification of contaminants. The high similarity between investigated fluorescent contaminants poses a significant challenge for machine learning approaches that are commonly used to increase sensitivity and selectivity. Nonetheless, the results demonstrate how fluorescence spectroscopy can be applied as a viable indicator and classification tool to identify pharmaceutical contamination in groundwater, as well as surface waters.