Sorption dynamics, geochemical fraction and driving factors in phosphorus transport at large basin scale

Abstract

The transport and deposition of phosphorus (P) in large-scale basin are closely associated with the spatial distribution characteristics and nutritional status of river sediments. Samples of surface water (SW), suspended sediment (SS), bed sediment (BS), and sediment cores from the Yellow River (YR) were collected. The different fractions including total phosphorus (TP), organic P (OP), inorganic P (IP), HCl–P and NaOH–P were determined by standard measurement and testing method. The results showed that upper, middle, and downstream sedimentary texture exhibit spatial heterogeneity. Pearson correlation analysis and redundancy analysis revealed that medium grain size (Mz) is the most negative factor that influence P and fractions, indicating the importance of silt content. Additionally, TP and HCl–P content were positively and significantly correlated, and the calculated correlation coefficient was 0.96 (p < 0.05). Fe oxides had the greatest positive effect on the absorption of NaOH–P in sediments, followed by Al and Mn oxides. From the sediment cores perspective, the rose figure and logistic regression curve showed that significant growth trend, which indicates that vertical pollution status becomes more severe with increasing silt content. Overall, due to the strong adsorption ability of finer particle as silt that driving the P distribution, this study suggests a greater focus on the effects of fine sediment particles transport for the diffuse pollution control towards the whole basin.