Towards the development of new, rapid, high-frequency indicators for monitoring Escherichia coli by fluorescence spectrometry as part of active bathing area management

Over the past two decades, there has been a notable advancement in the development of novel high-frequency metrology devices for the monitoring of biophysical and chemical parameters in surface waters. Optical probes, in particular fluorescence probes, have emerged as a central technology in this transition towards the integration of high-frequency measurement techniques into environmental monitoring. One of the emerging applications associated with fluorescence measurements is the continuous estimation of the concentration of fecal indicator bacteria (FIB). A sampling and analysis campaign was conducted in central Paris at the end of the summer season 2023. A total of 135 samples of Seine River water were collected, enabling a comparison of fluorescence spectrometry measurements with bacteriological results obtained using standard reference methods (NF EN ISO 9308-3 and NF-EN ISO 7899-1). By extracting 325 explanatory variables from the fluorescence spectra, a series of predictive models were constructed using machine learning algorithms. The most effective of these (R²=0.77) demonstrated the potential of fluorescence spectrometry for estimating the concentration of Escherichia coli observed in the Seine within Paris. The methodology employed in this project could subsequently be applied as a reference for the development of new models specifically adapted to other bathing sites. Fluorescence spectrometry, in utilizing the Fluocopée® fluorescence probe, may then be employed as an in situ, high-frequency monitoring tool to ensure the health of bathers on an ongoing basis.