Influence of Hydrochemical Ions on Three-Dimensional Fluorescence Spectrum of Dissolved Organic Matter in the Water Environment and the Proposed Classification Pretreatment Method

Three-dimensional fluorescence spectroscopy has broad application prospects in the in-situ water environment monitoring. However, due to its simple pretreatment method, the interference of hydrochemical ions in the water environment cannot be completely excluded, which could reduce the accuracy of water quality identification results. Currently, no relevant studies have classified this interference. In this study, we set nine kinds of hydrochemical ions (Na+, Cl-, NO3, CO32-, Ca2+, Mg2+, K2+, HCO3, SO42-) at the level of three ion concentrations (1 similar to 100 mg . L-1) and explored the changes of fluorescence characteristic by fluorescence parameters. Based on the fluorescence characteristic, the interference was divided into three different degrees using systematic clustering analysis: the first type (10 similar to 100 mg . L-1 CO32-), significant increase; the second type (10 similar to 100 mg . L-1 SO42- and 100 mg . L-1 NO3), significant reduction; the third type (1 similar to 10 mg . L-1 NO3, no added ions, 1 mg . L-1 CO32-, SO42- and 1 similar to 100 mg . L-1 Ca2+, Mg2+, K2+, HCO3, Na+, Cl-) mild interference. In other cases, priority should be given to methods that can remove the interference of hydrochemical ions, such as ion cyclotron resonance mass spectrometry. In addition, the combination of three-dimensional fluorescence spectroscopy and other technologies is strengthened to obtain more comprehensive information while reducing the limitations of a single technology. This study provides a data basis for restoring the real fluorescence spectra and a scientific basis for the selection and combined application of three-dimensional fluorescence and other techniques.