Assessment on applicability of common source tracking tools for particulate organic matter in controlled end member mixing experiments.

In this study, ideal mixing behaviors of the three commonly-used source tracking tools, which include fluorescence spectroscopy, stable isotope ratios, and lipid biomarkers, were evaluated in controlled particular organic matter (POM) mixtures of two contrasting end members e.g., soil and algae. In parallel, three different extraction methods based on water (WEOM) and two alkaline solutions were compared to identify the preferential pre-treatment option that leads to a good performance of the spectroscopic source tracking indices on the dissolved organic matter (DOM) extracted from the POM. Based on three evaluation criteria concerning the linearity of the relationships, the discrimination sensitivity, and the conservative mixing behavior of fourteen tested indices, the fluorescence proxies such as the relative distribution of the fluorescence components and the modified fluorescence index YFI of the WEOM were found to be reliable and robust indices for POM source tracking. The carbon stable isotope ratios of the POM samples exhibited an ideal mixing behavior even after the DOM extraction, while the biomarkers of sterols/stanols did not present a good linear and conservative behavior at similar conditions. In addition, the WEOM was identified as the preferred extraction method for the application of spectroscopic indices for POM source discrimination. This study provides a guideline to select the optimum indices for the POM source discrimination via the end member mixing analysis.