More sensitive signatures of DOM are stimulated by socioeconomic-related anthropogenic influences in a typical loess watershed

Abstract

Dissolved organic matter (DOM) plays a critical role in carbon cycling within aquatic systems, and its dynamics are influenced by both natural and human-induced factors. How and to what extent these factors stimulate DOM dynamics, particularly socioeconomic-driven impacts on carbon cycling in aquatic systems, urgently need to be quantified. This study employed partial least squares structural equation modelling (PLS-SEM) to reveal that socioeconomic conditions were the dominant factors shaping the DOM components. Rapid socioeconomic development has led to higher concentrations of protein-like DOM (λ = 0.95) and lower concentrations of terrestrially-derived humic-like components (λ = -0.78), suggesting anthropogenic inputs have become the primary source of protein-like DOM in urban river systems. In contrast, climatic conditions had a strong positive effect on the relative abundance of terrestrial humic-like DOM, while exhibiting a significant negative impact on the protein-like components. Additionally, changes in hydrological conditions may have indirect impacts on DOM components by stimulating or inhibiting the transformation of DOM. Using protein-like components as anthropogenic tracers, the study identified non-point source pollution inputs as the main anthropogenic source of DOM in the Weihe River basin (48.3 %). This suggests that controlling the overflow of industrial wastewater and domestic sewage, as well as optimizing agricultural irrigation practices, are effective strategies to improve water quality and reduce the accumulation of protein-like DOM. Altogether, these results can help deepen the scientific understanding of how river DOM dynamics respond to global change, and provide a robust scientific basis to inform watershed water resource and ecohydrology issues management.