Phosphorus characteristics, distribution, and relationship with environmental factors in surface sediments of river systems in Eastern China

Abstract

Phosphorus (P) is an essential nutrient for aquatic organisms. However, too much P discharged into limnetic ecosystems can induce eutrophication. The concentration of P in freshwater ecosystems has escalated in Eastern China due to overuse of fertilizer and excess emission of sewage, which is the result of the development of industry and agriculture in this area. However, little is known about the P characteristics and its environmental factors in river systems. Here, we present the results of P characterization and its relationships with environmental factors in Eastern China by applying SMT and 31 P-NMR methods. The results showed that the concentrations of P in surface sediments varied with the river system, and more than 50 % of the samples had P concentrations exceeding 500 mg kg −1. HCl-Pi was the dominant Pi in surface sediments, with the highest percentage (96.5 %) in the Yellow River System. Mono-P was the dominant Po in river sediments, followed by DNA-P. The PCA approach indicated that NaOH-Pi and ortho-P clustered in one group, with a second group including mono-P, diesters-P, and HCl-Pi. Phon-P and pyro-P belonged to different groups. On a regional scale, NaOH-Pi and Po showed a negative relationship with pH in sediments. Continuous eutrophication was induced by the presence of dams, and oxygen-consuming pollutants, such as NH 3 -N and CODcr, even when external P input was cut in heavily polluted rivers. The research revealed the characteristics of P in different river systems and proposed a conceptual model of P biogeochemical cycles in heavily polluted rivers. Results from this study may provide insight into P characteristics in Eastern China and would set a scientific basis for effective P management in developing countries.

Spatial Distribution and Environmental Significance of Phosphorus Fractions in River Sediments and Its Influencing Factor from Hongze and Tiaoxi Watersheds, Eastern China

“…Song et al [13] focused on the spatial distribution of P fractions in the Meiliang Bay sediment using the SMT sequential process. Zhang et al [3] explored phosphorus properties of surface water in the different river systems and its relationship to environmental impact in Eastern China by SMT fractionation.…”

Phosphorus Fractions in the Sediments of Yuecheng Reservoir, China

“…For five sampling sites, the rank order of P fractions concentrations was Ca-Pi > Po > Fe/Al-Pi. Po showed the P fraction bound to organic matters and its stability were relative to the different Po structures [12]. Po contents in the surface sediments varied from 188.6 to 358.8 mg kg −1 , and this contributed 12.1%-19.2% to the TP (Figure 2), which mainly resulted from the difference of TP contents.…”

“…Compared with other studies (Table 3), the TP concentration in the sediments was much smaller than that of almost all typical eutrophic lakes. Compared to Dianchi and Taihu, a greater proportion (more than 70%, Figure 2) of TP in the sediments was made up of Ca-Pi, which was considered to have little mobilization under physical-chemical conditions compared to Fe/Al-Pi [12,22]. Moreover, it is speculated that the behavior of the microbial degradation of Ca-Pi is driven by the microorganism to absorb reactive P nutrients from the environment for its own use.…”

“…This inorganic fraction was a subject of debate because it had long been considered to have little mobilization. However, much research has shown that this fraction could be mobilized with decreased pH and specific biochemical effects [12,22]. Figure 3 showed the typical distribution profiles of PO4 3− -P concentrations in the overlying water and sediments of five sampling sites.…”

“…This method, however, achieves limited effects because bottom sediments can also release phosphorus to the overlying water, especially when the P input is reduced [9,10]. Therefore, systematic studies of internal P loading are indispensable to understand the process of P circulation and support effective policies to manage eutrophication [11,12].…”