Sample handling and data processing for fluorescent excitation-emission matrix (EEM) of dissolved organic matter...

In environmental engineering and science, fluorescent excitation-emission matrix (EEM) has increasingly been utilized to characterize chromophoric dissolved organic matter (CDOM). This study aims to delineate EEM data processing, including calculation of total fluorescence (TF) which is an emerging water quality parameter often used as a surrogate for micropollutant removal by advanced water treatment processes. In addition, sample handling procedures such as storage, use of preservatives, and oxidant quenching agents were evaluated. In this study, three antimicrobial preservatives were tested: sodium azide, sodium omadine, and thymol. All the tested preservatives altered optical properties of samples, and were therefore not suitable for the preservation of EEM samples. Without preservative, storage of samples at 4 °C maintained TF within 7.5% of its original value for 21 days, while TF of samples stored at the room temperature more drastically changed (up to 15%). The impacts of three oxidant quenching agents including ascorbic acid, sodium bisulfite, and sodium thiosulfate on EEM were also tested. Among the quenching agents, sodium bisulfite was found to be suitable since it little influenced optical properties of samples while the other two were not favorable due to interference. We also scrutinized the use of TF as surrogate to monitor micropollutant rejection by nanofiltration membrane.