The effects of native adsorptive substances in sediment on the P adsorption capacity of the Yangtze River were investigated.Sediments sampled from Cuntan and Wuhan were washed with HCl of different concentrations,and the native adsorptive P,Fe,Al,Ca and organic matter(OM)on sediment released by different degrees was studied.The washed sediments were then used to investigate the P adsorption capacity by batch equilibrium adsorption experiments.The results showed that:(1) after being washed by diluted HCl,the contents of Fe and Al on sediment had little change,while the contents of Ca,OM,as well as P decreased significantly,which caused a reduction of P equilibrium adsorption capacity.A significant positive correlation (P ＜ 0.05) was observed between the equilibrium adsorption capacity of P and the content of TP and Ca,OM.Therefore,the native adsorptive OM and Ca on sediment were of great impact on the P adsorption capacity.(2)The contents of OM and Ca of sediment from Cuntan (OM:72.64 mg/g,Ca:63.52 mg/g)were significantly higher than those from Wuhan(O M:52.20 mg/g,Ca:45.03 mg/g),which indicated that the P adsorption capacity of sediment in the upstream of the Three Gorges Dam was much higher than that in the downstream.Namely,during the early operation of the Three Gorges reservoir,the sediment here can be a'sink'for external P,and the adsorption on sediment increases gradually.However,along with the running time extension,the sediment will be a potential internal P load.%分别选取三峡大坝上游寸滩河段和下游武汉河段沉积物,用不同浓度(0 ～3 mol/L)的HCl对沉积物进行清洗,降低本底吸附w(P)、w(Fe)、w(Al)、w(Ca)及w(OM)(OM为有机质),通过测定沉积物的P平衡吸附量,研究长江沉积物上本底吸附物对P吸附容量的影响.结果表明:①经稀HCI清洗后,两种沉积物的w(Ca)、w(OM)、w(P)均显著减少,沉积物的P平衡吸附量随之减少,而w(Fe)、w(Al)则没有明显变化,同时,沉积物对P的平衡吸附量、沉积物中w(TP)均与本底w(Ca)、w(OM)呈显著正相关(P＜0.05),因此长江沉积物对P的吸附容量的主要影响因素为本底吸附OM和Ca;②三峡库区内沉积物中w(OM)及w(Ca)较高,二者分别为72.64、63.52 mg/g,三峡大坝下游武汉段沉积物中则相对偏低,二者分别为52.20、45.03 mg/g,说明库区沉积物的P吸附容量明显大于大坝下游沉积物,在三峡水库运行前期,沉积物的P吸附量将逐渐增加,成为三峡水库运行后期富营养化的潜在内源.
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