Fraction analysis of soil phosphorus and dissolved organic matter reveals the release potential of phosphorus and its influencing factors in the submerged area of the Sanhekou Reservoir, China

Abstract

Different forms of inorganic phosphorus in surface soils can be released into water or adsorbed into sediment in response to various environmental factors. Although the Sanhekou Reservoir is still under construction, the periodic wetting-drying events may result in the release of inorganic phosphorus from the soil into the water once it is completed. Therefore, this study aimed to investigate the background soil values and estimate the phosphorus release fluxes of the Puhe River, Wenshuihe River, and Jiaoxihe River of the reservoir. We would like to provide a theoretical basis for the subsequent management and ecological protection of the reservoir based on this study. The Chang–Jackson chemical continuous extraction method was used to determine the forms of inorganic phosphorus in the soil, and fluorescence data were obtained by excitation–emission matrix combined with parallel factor (EEM-PARAFAC). The results showed that there were four types of phosphorus in the soil of the reservoir, including calcium-bound phosphate, aluminium-bound phosphate, iron-bound phosphate, and occluded phosphate. The total quantities of these phosphorus types were measured to be 6.71 × 104, 1.14 × 104, 0.91 × 104, and 0.49 × 104t, respectively. Additionally, it was observed that there was 2.12 × 104 t of bioavailable phosphorus present in the soil.