Dissolved organic matter data of Fuxi River

This research hypothesized that changes in hydrological regimes can result in variations in DOM characteristics among different seasons, and anthropogenic influence on the DOM characteristics could be enhanced in the rainy season due to strong flux conditions. This study thus conducted a comprehensive eco-hydrogeochemical investigation with the phytoplankton community composition, 16S rRNA gene high-throughput sequencing, stable carbon and nitrogen isotopic analysis, and DOM optical and molecular characteristics, aiming to (1) delineate the abundance, composition, and source of DOM among two different seasons; (2) quantitatively identify the relative contribution of natural and anthropogenic forces to riverine DOM in different seasons; (3) unravel the underlying mechanisms controlling DOM transformation in different seasons.
The research data showed the differences in water quality and organic matter composition of the Fuxi River basin in different seasons.
The following conclusions can be drawn from these data:
(1) The results revealed that seasonal variations in hydrological and nutrient conditions significantly controlled DOM characteristics in the Fuxi River. EEM-PARAFAC analysis identified one autochthonous tryptophan-like component (C2) and two allochthonous humic-like components (C1, C3). In March, the autochthonous production of algae-derived DOM increased due to higher water temperatures and N:P ratios than those in September, which could lead to high C2% (57.34 ± 8.72 %) and BIX values (1.05 ± 0.02). In September, enhanced rainfall and river fluxes facilitated the input of allochthonous terrestrial-derived DOM substances into river waters, resulting in high C3% (52.45 ± 14.94 %) and HIX values (0.65 ± 0.11).
(2) The results also revealed seasonal variations in the contributions of various potential sources to riverine DOM. EMMA results showed that hydrophyte (25.70%) and algae (21.10%) were the most dominant DOM sources in March, whereas livestock manure (21.50%) and soil (19.30%) as the most dominant DOM sources in September. Besides, the high relative abundance of heteroatom formulas (CHON, CHOS, and CHONS) (60.87 ± 2.58 %) in the Fuxi River also highlighted the intensive impact of rapid urbanization and agricultural activities on carbon and nutrient cycling in river ecosystems.