镧改性膨润土对长荡湖底泥磷的释放机制

Study on the inhibitory effect of lanthanum-modified bentonite on the release of phosphorus from the overlying water and sediment of Changdang Lake

在监测常州长荡湖水样和沉积物磷形态与含量的基础上,开展了在温度、pH、溶氧度等不同环境因子背景下镧改性膨润土对底泥磷释放的抑制效果研究.通过对比监测上覆水体磷的浓度、底泥磷的形态变化,考察了镧改性膨润土对水体磷的钝化效果以及底泥磷的固定作用.结果表明,镧改性膨润土可以很好地抑制底泥释磷,抑制底泥的释放率达到了55%—75%.温度和溶氧度的变化对镧改性膨润土的抑磷率无影响,而强酸碱(pH=4、pH=10)环境相较与中性环境(pH=7)抑磷效率减少15%;沉积物中Ex-P和Fe/Al-P等活性态磷含量下降了55%—60%,而Ca-P等稳定态磷含量上升1—1.1倍,说明镧改性膨润土可以改变沉积物磷的形态,由不稳定态转化为稳定态,提高了底泥对磷的滞留能力,降低了对上覆水释放的风险.利用镧改性膨润土控制长荡湖水体磷污染具有较好的应用前景.

Based on the monitoring of phosphorus forms and contents in water samples and sediments of Changdang Lake in Changzhou,the inhibition effect of lanthanum modified bentonite on phosphorus release from sediment under three different environmental factors,namely temperature,pH and dissolved oxygen,was studied.The passivation effect of lanthanum modified bentonite on phosphorus in water and the fixation of phosphorus in sediment were investigated by comparing and monitoring the phosphorus concentration in overlying water and the form changes of phosphorus in sediment.The results show that La-modified bentonite can inhibit phosphorus release from sediment very well,and the inhibition rate of phosphorus release from sediment reaches 60%—75%.The change of temperature and dissolved oxygen has no effect on the phosphorus inhibition rate of lanthanum modified bentonite,but the phosphorus inhibition efficiency of strong acid-base environment(pH=4,pH=10)is reduced by 15%compared with that of neutral environment(pH=7);The content of active phosphorus such as Ex-P and Fe/Al-P in sediment decreased by 55%—60%,while the content of stable phosphorus such as Ca-P increased by 1-1.1 times,which indicated that lanthanum modified bentonite could change the form of phosphorus in sediment from unstable state to stable state,improve the retention capacity of phosphorus in sediment and reduce the risk of releasing overlying water.Using lanthanum modified bentonite to control phosphorus pollution in Changdang Lake has a good application prospect.