Quantification and molecular characterization of dissolved organic carbon released from leaf fragments, crop straw,...

Dissolved organic matter (DOM) is ubiquitous in the environment and plays an important role in global ecosystems. However, our understanding of the evolution and molecular diversity of DOM from different biomass materials and biochar is not enough. Herein, we investigated the changes in DOM from seven biomass and biochar samples over a bio-incubation of 28 days, and explored their contents, and optical, chemical, and molecular characteristics. The results indicated that dissolved organic carbon (DOC) from different sources all exhibited a gradually decreasing trends during the incubation, while the absorbance and aromaticity gradually increased. Biomass DOM was characterized by higher DOC concentrations and a higher degradation rate, whereas biochar DOM had high aromaticity and little variability. Parallel factor analysis results showed that the protein-like fluorescent groups were as only detected in biomass DOM, while the dominant humic-like components were identified in biochar DOM. Additionally, the molecular composition of DOM from different sources was different, and biomass DOM contained more carbohydrate-like and saturated compounds. More sulfur-containing compounds were detected in Ceratophyllum demersum (CD) DOM, which may indicate that the leaching of CD litter was an important source of sulfur-containing species in aquatic environments. Furthermore, biochar DOM had greater aromaticity and a higher degree of oxidation than the corresponding biomass DOM. This study provided a detailed understanding of the molecular diversity of DOM by considering its various sources, and the results are helpful for further understanding their chemical properties and structures.