扰动强度对太湖沉积物中磷释放及其形态转化的影响

通过室内试验模拟了太湖沉积物在不同扰动强度下的悬浮过程,研究了沉积物扰动强度对磷释放及其形态转化的影响.结果表明,较高扰动强度下(相当于太湖风速12 m.s-1),水体中不同形态磷(总磷、颗粒态磷、溶解性总磷)含量均高于较低扰动强度(相当于太湖风速8 m.s-1).其中,两者分别扰动1h后,总磷和颗粒态磷分别达到0.950 mg.L-1、0.384 mg.L-1和0.882 mg.L-1、0.328 mg.L-1,该水平保持到试验结束.然而,溶解性总磷则呈逐渐降低的趋势.这主要归因于悬浮物的吸附和微生物的快速利用.较高和较低扰动强度下,悬浮物上总磷(Tot-P)分别增加了10 mg.kg-1(平均值)和60 mg.kg-1(平均值).较高扰动强度下铁铝结合态磷的变化恰好说明了形态磷间存在转化趋势.因为铁铝结合态磷增加了85.7 mg.kg-1(平均值),明显高于Tot-P的实测值(10 mg.kg-1,平均值)和理论值(27 mg.kg-1,平均值),说明有其它形态磷转化成铁铝结合态磷.弱吸附态磷和钙结合态磷含量的降低正说明这一点.这显示在扰动状态下,不同形态磷之间至少发生了以水为媒介的间接性转化.

Effect of Disturbance Intensity on Phosphorus Release and Its Transformation in the Sediment from Taihu Lake

Lab-scale experiments were conducted to investigate the effect of sediment disturbance under different intensity conditions on phosphorus (P) release and sedimentary P transformation. The sediments came from Taihu Lake. The results show that the concentrations of total P (TP), particulate P (PP) and dissolved total P (DTP) in the overlying water under high intensity conditions (equal to the force of 12 m ·s^-1 wave velocity on the bottom sediment in Taihu Lake) were higher than those under low intensity conditions (equal to the force of 8 m ·s^-1). The concentrations of TP and PP were up to 0.950 mg ·L^-1, 0.384 mg ·L^-1and 0.882 mg ·L^-1, 0.328 mg ·L^-1 for both intensities after 1 h and then the levels kept unchanged almost till the end of the experiments. However, the DTP decreased gradually. It is attributed to the adsorption by suspended sediments and quick uptake by microorganisms. Under both intensities conditions, the Tot-P of the suspended particulate matter (SPM) due to disturbance increased by 10 mg ·kg^-1(mean during 0-12 h) and 60 mg ·kg^-1(mean during 0-12 h). The changes of Fe/Al-P during the experiment (0-12 h) verified the transformation trend between sedimentary P forms in the SPM under high intensity. Because the net increase (85.7 mg ·kg^-1, mean during 0-12 h) was higher than the measured value (10 mg ·kg^-1, mean during 0-12 h) and the theoretically calculated value (27 mg ·kg^-1, mean during 0-12 h). It suggests that other sedimentary P forms were transformed into Fe/Al-P. Correspondingly, the decrease of NH₄Cl-P and HCl-P can verify this. It suggested that sediment disturbance might induce the indirect transformation between sedimentary P forms by the assistance of overlying water.