Environmental\nFingerprints of Nonoxygen Heteroatomic\nMolecules in Aquatic Dissolved Organic Matter Elucidated by Ultra-High-Resolution\nMass Spectrometry

The\nquality and chemodiversity of aquatic dissolved organic matter\n(DOM), crucial to global carbon cycling and aquatic ecological functions,\nare affected by microbial and anthropogenic activities. In this study,\nmolecular characteristics of DOM collected from 14 field water samples\nwere compared with three standard samples from the International Humic\nSubstances Society using Fourier transform ion cyclotron resonance\nmass spectrometry (FT-ICR MS). Results indicated that microbially\nand terrestrially derived DOM contributed to the surface water and\ngroundwater DOM pool, with higher DOM molecular lability (higher H/C<sub><i>iw</i></sub>) in field water than IHSS standards, which\nwas related to the overall impact of diverse biogeochemical processes\nand anthropogenic factors. The microbial and anthropogenic perturbations\ncontribute more nonoxygen heteroatomic (N, S, and Cl atoms) molecules\nin the field water, and organic pollutants (surfactants and sucralose)\nhad significant DOM signatures in waters affected by intensive anthropogenic\nemissions. A strong correlation among microbial indicators, nutrients,\nand DOM molecular characteristics indicated that the synthetic results\nof microbial and anthropogenic activities within the basin contributed\nmore nonoxygen heteroatoms and increased the DOM molecular diversity.\nThis study has highlighted the environmental molecular signatures\nof nonoxygen heteroatoms in reflecting the microbial and anthropogenic\nfactors, shedding new insights into freshwater health.