Interaction and driving factors influencing microplastics and dissolved organic matter in the hyporheic ecosystem of the Jinghe River Basin under different land-use types

Microplastics (MPs) and dissolved organic matter (DOM) interact and participate in natural carbon cycling in hyporheic ecosystems. Existing research has mainly examined the effects of different land-use types on DOM; the interaction between MPs and DOM across land-use types remains unclear. This study investigated the interactions and driving factors influencing MPs and DOM in sediments under different land-use patterns. The results revealed that the Jinghe River Basin was dominated by weakly alkaline siliceous gravel and sand. DOM characteristics showed strong spatial heterogeneity between anthropogenic and natural land uses. The main MPs were fibrous, blue and ≤ 500 µm, and the abundance of MPs ≥ 2000 µm in anthropogenic land was higher than those in mixed and natural land. Statistical analyses showed that the land use type directly determined the differences in the fractions of DOM, and sand and MPs ≥ 2000 µm were the main factors influencing DOM concentration. Release and adsorption were the main interaction mechanisms between DOM and MPs, which were driven by surrounding environmental factors, different land-use types, and MP characteristics. These findings provide a reference for further research on the complex interactions between MPs and DOM in aquatic environments and theoretical support for carbon cycle modelling in hyporheic ecosystems.