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May 30, 2026

Transport and Transformation of Phosphorus in Different Forms in River-Lake Systems: A Case Study of Lake Caohai, Guizhou Province

PFPeixian FU XHXia HuangXi’an Jiaotong-Liverpool University WYWei YuZhejiang Normal University

Key Points

This study aims to understand the migration and transformation of different phosphorus forms in river-lake systems to address eutrophication.
Selected Zhonghe River, Dongshan River, and Lake Caohai as study sites.
Conducted multi-stage filtration and ultrafiltration techniques to analyze phosphorus forms.
Examined phosphorus composition including DOP, DIP, COP, CIP, POP, and PIP.
DIP predominated in river sections, while PIP became dominant in the lake.
POP transformed mainly to DOP in the lake, indicating endogenous biological production.
COP was primarily exogenous in rivers but endogenous and smaller in the lake.

Abstract

The issue of phosphorus-driven eutrophication has long been a central focus in lake research. Elucidating the migration, transformation, and biogeochemical cycling of different phosphorus forms in river–lake systems is essential for understanding the mechanisms of aquatic eutrophication and for developing strategies to control phosphorus pollution. In this study, the Zhonghe River and Dongshan River, together with Lake Caohai, were selected as the study sites. Using multi-stage filtration and ultrafiltration techniques, we systematically analyzed the compositional characteristics and migration–transformation processes of various phosphorus forms, including dissolved organic phosphorus (DOP), dissolved inorganic phosphorus (DIP), colloidal organic phosphorus (COP), colloidal inorganic phosphorus (CIP), particulate organic phosphorus (POP), and particulate inorganic phosphorus (PIP). The results showed that in the river–lake system, DIP predominated in the river section, whereas PIP became dominant upon entering the lake. This finding reveals a critical transition in phosphorus dynamics, shifting from the dominance of terrestrial inputs to that of bioavailable endogenous forms within the lake. In the river segments, POP was the main form; in contrast, in the lake area, it was primarily converted to DOP, indicating an enhanced transformation of POP to DOP and an increasing contribution from endogenous biological production. COP originated from two sources: in the inflowing rivers, COP was predominantly exogenous, largely consisting of large colloidal particles such as soil organic matter. In the lake, however, COP was mainly derived from endogenous sources and was characterized by smaller colloidal particles. The size of colloidal particles was influenced not only by environmental conditions such as pH and EC but also by the combined regulation of biological and physicochemical processes. Overall, research on the migration and transformation of different phosphorus forms in river–lake systems is of great significance for understanding phosphorus cycling mechanisms in lakes and can provide a theoretical basis for the protection and management of shallow lakes such as Lake Caohai.

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