Unraveling the links between molecular weight and multidimensional dynamics of dissolved organic matter in the runoff from gentle sloping land under rainfall

Guo Chen; Hao Wang; Qiang Zhang; Chao Chang; Fei Wang; Qingwei Zhang; Jian Wang; Yu Pang; Ming Li; Biao Zhu; Ding He

doi:10.1016/j.watres.2025.124061

Unraveling the links between molecular weight and multidimensional dynamics of dissolved organic matter in the runoff from gentle sloping land under rainfall

Water Res. 2025 Jun 20:285:124061. doi: 10.1016/j.watres.2025.124061. Online ahead of print.

Authors

Guo Chen¹, Hao Wang², Qiang Zhang¹, Chao Chang³, Fei Wang¹, Qingwei Zhang¹, Jian Wang¹, Yu Pang⁴, Ming Li³, Biao Zhu⁵, Ding He⁴

Affiliations

¹ State Key Laboratory of Soil and Water Conservation and Desertification Control, College of Soil and Water Conservation Science and Engineering (Institute of Soil and Water Conservation), Northwest A&F University, Yangling, Shaanxi, China.
² State Key Laboratory of Soil and Water Conservation and Desertification Control, College of Soil and Water Conservation Science and Engineering (Institute of Soil and Water Conservation), Northwest A&F University, Yangling, Shaanxi, China. Electronic address: wang.hao@nwafu.edu.cn.
³ College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi, China.
⁴ Department of Ocean Science and Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
⁵ State Key Laboratory for Vegetation Structure, Function and Construction (VegLab), Ministry of Education Key Laboratory for Earth Surface Processes, and College of Urban and Environmental Sciences, Peking University, Beijing, China; Ministry of Education Key Laboratory for Ecology and Resource Use of the Mongolian Plateau, Inner Mongolia Key Laboratory for Grassland Ecology, and School of Ecology and Environment, Inner Mongolia University, Huhhot, China.

PMID: 40561624
DOI: 10.1016/j.watres.2025.124061

Abstract

Molecular weight is a fundamental intrinsic property of dissolved organic matter (DOM), playing a crucial role in its bio-stability, microbial transformation, and contributions to regional carbon cycling. However, the complex relationships between the molecular weight and multidimensional dynamics of DOM in the runoff remain insufficiently understood. In this study, fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to elucidate the associations between molecular weight and multidimensional dynamics of DOM in surface runoff and subsurface runoff from gentle sloping land (i.e. bare land and farmland). Overall, DOM-bacteria bipartite network analysis revealed a more complex co-occurrence network in subsurface runoff from farmland, with interaction strength rising alongside molecular weight. Furthermore, null modeling from different perspectives, including molecular characteristics, biochemical transformations, and a comprehensive perspective, revealed that the DOM compositional assembly processes in runoff was dominated by deterministic processes, particularly variable selection, with variation also linked to molecular weight. Notably, variable selection always dominated the assembly process of DOM potential transformation despite the scale-dependent effects affecting the assembly process of DOM molecular characteristics. Therefore, the relationship between DOM molecular weight and its dynamics may vary across microbial communities and geographic scales. Overall, these findings not only help to deepen the understanding of the role of DOM in natural ecosystems, but also provide an important reference for the study of soil carbon cycling, biogeochemical cycling and microbial ecological processes.

Keywords: Assembly process; Dissolved organic matter; Molecular weight; Potential transformation; Runoff.