PAC絮凝沉积藻量对水-底泥系统营养盐释放的影响

聚合氯化铝(PAC)絮凝除藻对降低水体藻密度效果显著,但絮凝形成的沉积藻量对水-底泥系统营养盐释放的影响鲜有报道。通过监测不同量的絮凝藻沉积于一定量的底泥表面时上覆水水质和底泥组成的变化,探究使用PAC絮凝除藻时沉积藻量对水体水质及底泥内源释放的影响。结果表明,沉积藻会显著增加底泥中的氮向上覆水释放,当泥与藻的干质量之比为167.2、83.6和41.8时,反应器上覆水中NH4^+-N浓度均值分别为控制反应器(CK)的2.86、2.42和1.43倍,对应TN浓度均值分别为CK的2.06、1.66和1.09倍。此外,沉积藻会促进泥水界面处的反硝化过程,促进效果与沉积藻量呈负相关。然而,沉积藻对于控制底泥磷释放具有积极作用,试验期间CK上覆水中TP和PO4^3--P浓度均值分别为0.35和0.22 mg/L,而覆有沉积藻的所有反应器中TP和PO4^3--P浓度均值分别都低于0.05和0.03 mg/L,且沉积藻量越大,对应的磷浓度越低。

Effect of Algae Deposition Formed by PAC Flocculation on Nutrient Release in Water-sediment System

Polyaluminium chloride(PAC)flocculation is an efficient approach to reduce algae density in water,but the effect of the algae deposition formed by PAC flocculation on nutrient release in the water-sediment system is rarely reported.By monitoring the changes of overlying water quality and sediment composition when different amounts of flocculated algae were deposited on a certain amount of sediment surface,the effects of algae deposition formed by PAC flocculation on water quality and sediment endogenous release were investigated.Algae deposition could significantly increase the nitrogen release from sediment to the overlying water.When the dry mass ratios of sediment to algae were 167.2,83.6 and 41.8,the mean concentrations of NH4^+-N in the overlying water of the reactor were 2.86 times,2.42 times and 1.43 times of the control reactor(CK),and the corresponding mean concentrations of TN were 2.06 times,1.66 times and 1.09 times of CK,respectively.Furthermore,the algae deposition could promote denitrification at the water-sediment interface,and the effect was negatively correlated with algae amount.However,the algae deposition played an active role in controlling the phosphorus release from the sediment.The mean concentrations of TP and PO4^3--P in the overlying water of CK were 0.35 mg/L and 0.22 mg/L during the experiment.However,all the corresponding values in the algae deposition reactors were lower than 0.05 mg/L and 0.03 mg/L,and the lower concentration of phosphorus would be achieved with the higher algae deposition amount.