Investigating the anthropogenic impact and potential nutrient release from sediments is essential for both ecological and economic reasons. However, the absence of effective and affordable tracking techniques presents a major challenge. In this study, we analyze the optical properties and molecular composition of dissolved organic matter (DOM) from surface sediments (n=41) collected along the land-sea continuum of an industrialized bay in China. We employ optical techniques, including UV–visible spectroscopy and Excitation–emission matrix fluorescence spectroscopy, alongside Fourier-transform ion cyclotron resonance mass spectrometry for characterizing sedimentary DOM. Through Parallel Factor analysis (PARAFAC), we identify five fluorescent components, which reflect various sources and types of sedimentary DOM, such as aromatic/terrestrial, microbial, anthropogenic, and protein-like substances. Our molecular analysis uncovers 14,052 unique compounds, revealing distinct characteristics for sedimentary dissolved organic nitrogen (DON), phosphorus (DOP), and sulfur (DOS). Notably, sedimentary DOP displays the highest saturation, DON has the greatest aromaticity, and DOS shows the highest molecular weight. We find significant correlations between optical parameters and specific molecular formulas of sedimentary DON, DOP, and DOS, indicating that optical signatures can serve as diagnostic tools for assessing internal nutrient release and point source pollution in aquatic ecosystems. This linkage will facilitate efficient large-scale monitoring of sedimentary heteroatomic compound cycling using optical techniques with reliable interpretations, which is important for sustainable watershed management.
 

FT-ICR MS,DON,DOS,DOP,DOM