Reactive oxygen species (ROS) play a crucial role in aquatic biogeochemical processes. Dissolved organic matter (DOM), a photosensitive substance in natural waters, is a key source of ROS. For now, the specific characteristics of DOM in shallow lakes with varying trophic states, and their net photo-generation capacity for ROS remain largely unexplored. 

Researchers at the Wuhan Botanical Garden of the Chinese Academy of Sciences have characterized the composition of DOM in seven shallow lakes with varying tropic gradients using optical and mass spectrometry methods.

The study revealed that the DOM exhibited both endogenous and exogenous traits, with the endogenous characteristics increased with the trophic state of lakes. 

Compared to lakes with moderate-eutrophic and hyper-eutrophic states, the DOM in light-eutrophic states exhibited a higher capacity for photo-generated ROS. Further analysis identified specific DOM compounds, including those with phenolic and polyphenolic properties, such as lignin/CRAMs-like, aromatic compounds, tannins, and fulvic- and humic-like compounds, as positively correlated with the ROS photo-generation capacity. Moreover, the unique molecular composition of DOM, particularly the presence of lignin/CRAMs-like and aromatic compounds, showed a positive correlation with the  photo-generation capacity for ROS.

The results of this study deepen the understanding of DOM storage and photochemical transformation processes in lakes with different trophic states and further guide the ecological and environmental risks caused by this process.

The study was published in Water Research, titled "Insight into the characterization of dissolved organic matter in shallow lakes with different trophic states and their net photo-generation capacity of reactive oxygen species". LI Xiaolu is the first author, and Prof. XING Wei, Prof. LIU Guanglong and GAO Jiong are the corresponding authors. 

This research was supported by the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, the Postdoctoral Fellowship Program (Grade B) of China Postdoctoral Science Foundation, Wuhan Natural Science Foundation Exploration Program (Chenguang Program), Youth Science Fund of Hubei Academy of Agricultural Sciences, Hubei Province Postdoctoral Innovation Research Position Foundation.

Source and characterization of dissolved organic matter in shallow lakes with different trophic states and their net photo-generation capacity of reactive oxygen species (Image by WBG)