Abstract: There is little information on deep reservoirs with phosphate mining and their management. Physical and chemical characteristics of sediment and its interactive water in Xuanmiaoguan Reservoir of Huangbai River basin, located in Yichang City, were studied. The results showed that (1) the total phosphorus (TP) contents ranged from 5 356.0-9 631.5 mg/kg. The Pfraction concentrations were ranked in the following order: P associated with calcium (CaP) ??Organic P (OP)??P bound to aluminum, ferrum oxides and hydroxides (Fe/AlP). CaP, accounting for 86.4%-93.0%, was the main component of TP. (2) Due to the input of phosphate ore from exogenous, TP and total carbon (TC) increased from the head to the end of the reservoir. The organic matter (TOC, TN, OP) are mainly derived from the deposition of endogenetic organisms, which is more similar to deep lakes. (3) A gradient of the orthophosphate (PO3-4P) occurred at the sedimentwater interface and its diffusion flux ranged from 0.41±0.09-0.86±0.14 mg/(m2·d), which indicated a great ecological risk of the reservoir. Statistical analysis showed that P diffusion flux was the first component of this basin, which was related to TP and CaP contents.
Key words：phosphorus fraction; PO3-4P diffusion flux; surface sediment; Xuanmiaoguan Reservoir; phosphate mining area