Spectral diversities of chromophoric dissolved organic matter in paddy field water adjacent to black soil regions of Northeast China

Abstract

Dissolved organic matter (DOM) plays a crucial role in the aquatic ecosystem of rice paddies, and its content reveals the transport relationship of soil nutrients absorbed by rice seedlings, but there are few reports on this in the black soil. This paper analyzed the concentration of chromophoric dissolved organic matter (CDOM) in irrigation water of black soil in Wanchang Town, Jilin Province, China, using combination detection technology of excitation–emission matrix (EEM) spectroscopy and UV-vis absorption spectroscopy and correlational analysis. Four results demonstrated the CDOM characteristics of the black soil. The UV-vis absorption coefficient a375 is correlated positively with CDOM concentration and molecular weight, indicating the presence of macromolecular organics. E₄/E₆ is negatively correlated with the spectral slope S_R, with DOM dominated by humic acid and protein-like substances. The peak of the EEM spectrum has an average frequency shift difference of about 20 nm compared to non black soil areas. CDOM content is higher in rice paddy water than in irrigation channels and natural paddy water, influenced by microbial degradation, soil processes, and human inputs. These research results are conducive to optimizing irrigation management, improving water quality and enhancing the level of rice cultivation in the black soil. This combined detection and correlational analysis method effectively identified CDOM sources, offering valuable insights into DOM dynamics in agricultural irrigation systems.