Environmental significance of phosphorus existing forms in the sediments of Yuqiao Reservoir in Tianjin

Abstract

It is of great significance to study the status of eutrophication and its process in water source reservoirs by analyzing the spatial and vertical distribution characteristics of phosphorus forms in the sediment of Yuqiao Reservoir in Tianjin. The samples of surface sediments and sediment cores were collected by grab-type sampler and column-type sampler, respectively, and the phosphorus forms of sediments were analyzed by continuous extraction method proposed by Psenner, in order to reveal the spatial distribution of various forms of phosphorus in the reservoir, as well as the distribution in the vertical direction of different regions. The results showed: The contents of total phosphorus in the surface sediments of Yuqiao Reservoir were 303.7-997.8 mg/kg, and the order of the mass fraction of phosphorus forms was: Ca-P>Fe-P>Res-P>Al-P>Org-P>Ex-P. The Fe-P, Al-P, Ca-P and TP in the surface sediments gradually decreased from east to west, mainly affected by the input of exogenous phosphorus entrained by the Lihe River. The Res-P is gradually increasing from east to west, contrary to the distribution of active phosphorus, indicating that the water quality in the downstream of the reservoir is better than that in the upstream. For the vertical distribution, there is little difference between the bottom sediments and the surface sediments in the southern region, which indicates that the deposition amount of phosphorus is relatively large since the 1960s; and the Fe-P and Org-P contents in the western sediments are higher, and the trend is significantly reduced as the depth increases. The various forms of phosphorus and TP contents in the central area are almost the lowest, and gradually decrease with the depth, phosphorus in the sediments at this stage is mainly retained with small release potential.