Abstract
A deep understanding of the loss and migration of various sizes of phosphorus (P) is crucial for the effective management of nutrients in agricultural watersheds. In this study, three P species including large-particle phosphorus (LPP, >1 μm), colloidal phosphorus (CP, 1 nm–1 μm), and dissolved phosphorus (DP, <1 nm), were observed and simulated. Then the size-dependent of nonpoint source P (NPS-P) process was discussed at both field and watershed scales. Finally, a stochastic rainfall algorithm was developed to investigate different P species driven by rainfall. The results indicated the losses of LPP, CP, and DP under different land use patterns differ markedly, whereas paddy fields are hotspots of CP loss. Sloping farmlands typically exhibit greater losses of DP and LPP, while CP account for 13 %–38 % of total P losses. At the watershed scale, the contribution of CP riverine inputs ranged from 13 % to 40 % due to its mobility and special feature. Compared with LPP, CP has an extended half-decay distance and is more capable of being transported to water bodies. Heavy rainfall significantly increases the contribution of CP to NPS-P. At rainfall levels of 300 mm, the contribution of CP riverine inputs from paddy fields can be up to 47.4 %. The findings provide novel insights into future agricultural nutrient management and NPS-P control from the perspective of the size effect.
Published Version
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