不同扰动强度下城市重污染河道底泥对磷吸收和固定的影响

以重污染河道底泥和上覆水为材料,研究了周期性加入外源磷条件下,不同扰动强度下底泥吸附和固定磷的作用机制.结果表明,扰动可以增加底泥对外源磷的吸附,而且扰动强度越大,底泥对外源磷吸附效率越高.另外,尽管加入的磷以溶解性磷酸盐(DIP)形态存在,但扰动强化了DIP向颗粒态磷(PP)的转化,从而降低了水体中生物可利用磷含量.内源磷形态分析表明,弱吸附态磷(NH4Cl-P)呈降低趋势,而铁铝结合态磷(Fe/Al-P)、钙结合态磷(HCl-P)和残渣磷(Res-P)均呈增加趋势,但以Fe/Al-P增加幅度最大(占总磷的百分比超过80%,以3种扰动强度下平均值计).结合到非闭蓄态Fe/Al-P中的外源磷逐渐增加占Fe/Al-P净增加量的百分比分别为37.49%(100 r·min-1)、42.32%(200 r·min-1)、54.24%(300r·min-1),导致闭蓄态铁铝结合态磷净增加量占总磷净增加量的百分比随扰动强度增加有所降低,同样,钙结合态磷的变化趋势也基本一致.说明在较短的时间尺度上和较大的扰动强度下,连续加入的外源磷主要以易释放态磷形式存在,即底泥对外源磷的吸附以暂时性的持留为主.

Influence of Different Disturbance Intensity on the Phosphorus Adsorption and Immobilization by the Sediments from an Inner City Heavily Polluted Canal

The mechanism of phosphorus (P) adsorption and immobilization under different disturbance intensities was investigated in laboratory. The sediments and water used were taken from an inner-city heavily polluted canal. Addition of KH₂PO₄ into the experimental units were made similar to the external P input into the canal and carried out periodically. The results show that sediment disturbance could increase the P adsorption amount by suspended solids. The higher disturbance intensity is, the greater P adsorption amount is obtained. Dissolved inorganic P (DIP) is the main form of additional KH₂PO₄, but sediment disturbance enhances the transformation of P from DIP to PP (particulate P), indicating that sediment disturbance decreases the bioavailable P in the overlying water. Sequential fractionation indicated that the NH₄Cl-P decreased, but the Fe/Al-P, HCl-P and Res-P increased. More than 80% (the average value under three disturbance intensities) of the incorporated P accounts for Fe/Al-P in the sediments. The incorporated Fe/Al-P accounts for 37.49% (100 r·min^-1), 42.32% (200 r·min^-1) and 54.24% (300 r·min^-1) of non-occluded Fe/Al-P in the sediments respectively, indicating that the percentage of incorporated P to occluded Fe/Al-P decreases with the increase of disturbance intensity. The variation of HCl-P under the same disturbance intensity is the same as the occluded Fe/Al-P. It suggests that the continuous addition of external P is mainly incorporated into the mobile P forms under short-term and high-intensity disturbance, which means the adsorption of P by sediments is the short-term immobility.