Molecular-level exploration of properties of dissolved organic matter in natural and engineered water systems: A critical review of FTICR-MS application

Dissolved organic matter (DOM) contains complex molecular compounds that dominate its heterogeneous dynamics and behaviors in aquatic environments. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) with ultra-high resolution has proven to be effective in characterizing aquatic DOM. However, a systematic summary of molecular-level compositions and behaviors of DOM in natural and engineered water systems remains insufficient. This study provides a critical review of DOM characterization by FTICR-MS, with emphasis on composition diversity, chemical properties, transformation, and dynamics in the natural and engineered water systems. First, FTICR-MS strategies for DOM characterization are introduced on data interpretation and collaborative analysis of complementary datasets (e.g. spectroscopic data). Second, DOM characteristics, including spatiotemporal distribution, photochemical activity, microbial modification, and interface adsorption in natural water environments were comprehensively summarized based on current FTICR-MS findings. Third, DOM molecular changes caused by different engineered treatment methods were reviewed to highlight the molecular variation, reaction, and transformation by focusing on the FTICR-MS results. Finally, we summarized current limitations, biases, and future directions of FTICR-MS, and future extended studies of natural/engineered-derived DOM behavior. This FTICR-MS application review provides favorable strategies for understanding the molecular chemistry and behaviors of aquatic DOM.