Phosphorus transport in different soil types and the contribution of control factors to phosphorus retardation.

Iron (Fe) minerals, organic matter (OM), and pH can effectively regulate phosphorus (P) transport in the soil. However, their respective contributions in this regard are still unclear. In this study, P transport in soil columns was investigated by monitoring breakthrough curves and transport model fitting, and the contributions of Fe and total organic carbon (TOC) concentrations, as well as pH to P retention, were determined using multiple linear regression (MLR). The results showed that the rate of P transport in Fe-rich laterite soil was significantly lower (retardation factor R = 458.5) than that in the other soil types (R = 108.4-247.6). Additionally, it was observed that OM formed rate-limited adsorption sites, causing the rapid release of labile P, and owing to P release and readsorption. Even though more significant P releases were observed, chernozem soil had an obvious inhibiting effect on P transport owing to its relatively high Fe content, and the high P-Fe increment (48.9-90.4%) indicated the essential role of Fe minerals in P immobilization. Further, P was readily transported in natural or artificially modified fluvo-aquic soils with high calcium concentrations, and it was also observed that the convection-dispersion equation (CDE) and Thomas models were suitable for describing P retardation and adsorption, respectively. Furthermore, the contribution weights of Fe and TOC concentrations as well as pH to P retardation, based on MLR calculations, were approximately 1.0, -0.3, and -0.2, respectively. Our findings can support the control of eutrophication pollution caused by P leaching.

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