| Phosphorus is the major restrictive factor for growth of algae and eutrophication of lake, and phosphorus in surface sediments is important impact for the eutrophication by its binding ways and specific release pattern. The surficial sediment samples were collected from the Dongping Lake to investigate the physicochemical parameters and binding ways of phosphorus, and the impacts of pH and disturbance on the release of TP from the surficial sediments. Phosphorus sorption capacity of the surface sediment was estimated by the phosphorus sorption index (PSI) and the degree of phosphorus saturation (DPS) of the sediments in the Dongping Lake. And the risk of potential phosphorus release was also investigated. The main conclusions drawn from present study were listed as follows.(1) The Dongping Lake was under the moderate eutrophic. The nitrogen: phosphorus ratios ranged from 10.3 to 78, 19 to 46, and 10.2 to 35 for spring, summer, and autumn, respectively. The nitrogen: phosphorus ratios were all higher than 7, indicating the phosphorus was the limited factors for the eutrophication of Dongping Lake.(2) The average contents of total phosphorus (TP) were 851.3 mg·kg-1 in the surficial sediments of Dongping Lake, which was a little higher than the other lakes in China. And the phosphorus mainly distributed in inorganic fractions (IP), ranging from 384.87 to 772.35 mg·kg-1, which accounted for 73.57 % of TP in the surficial sediments of Dongping Lake. The decease order of different inorganic fractions was Ca-P>Res-P>Al-P+Fe-P>Exp-P, accounting for 47.87 %, 29.78 %, 21.41 %, and 0.94 % of IP, respectively. The the average contents of bio-available phosphorus was 274.95 mg·kg-1, accounting for 32.30 % of TP in the surficial sediments of Dongping Lake.(3) The result of phosphorus release experiment showed that the release content of TP from the surficial sediments obvious distinction: alkaline condition>acidic condition>neutral condition. In neutral condition, the phosphorus in sediments was stable relatively, which didn't easily released into the water. Compared with the neutral conditions, the release content of TP from the surficial sediments increased due to the dissolution of Ca-P in acidic condition. And the release content of TP from the surficial sediments increased obviously due to the exchange behavior of Fe-P in alkaline condition.(4) Disturbance would enhance the release of TP from the surficial sediments significantly,and the release content of TP and the release rate significantly increased with increasing disturbance intensity. The results showed that no significant impacts could be found for the disturbance on the pH of lake water, while the soluble cations increased obviously under the disturbance.Under the disturbance intensity of 25,50,100 rpm, the accumulative releasing contents of total phosphorus (TP) increased by 0.185,0.263,0.320 mg·kg-1 compared to the static state, increased by 43.2 %,61.4 %,74.7 %, respectively. And the releasing velocity of TP increased by 36.2 %,41.7 %,127.6 % compared to the static state.(5) Phosphorus sorption capacity of the surface sediments and the risk of potential phosphorus release were investigated by the phosphorus sorption index (PSI) and the degree of phosphorus saturation (DPS) of the sediments in the Dongping Lake. The results showed that the phosphorus sorption index ranged from 30.3 to 45.2 (mg P·(100g)-1)·(μmol·L-1)-1, increasing gradually from the mid-lake and the east to the north and the south of the lake. However, the variation tendency of the degree of phosphorus saturation (DPS) was exactly opposite, ranging from 6.9 % to 24.7 %. The phosphorus sorption index was very significantly and positively correlated to iron (FeOX) and summation of iron and aluminum extracted from sediment by ammonium oxalate. The degree of phosphorus saturation was significantly and positively correlated to phosphorus (POX) extracted from sediment by ammonium oxalate. And iron extracted from sediment by ammonium oxalate might be played a major role in adsorbing phosphorus. Additionally, the results showed that the phosphorus release risk index (ERI) ranged from 15.9 % to 69.3 %. The results of the phosphorus release risk index indicated that the Dongping Lake might be in high potential eutrophication risk due to the release of phosphorus from the surfacial sediments.
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