受污染城市河道沉积物磷吸附特征及其影响因素

Characteristics and influencing factors of phosphorus adsorption in pollutedurban river sediments

采集了典型受污染城市河道——陕西省新河不同季节的沉积物,研究其磷吸附特征及影响因素,并考察其缓冲外源污染的能力,评估其磷释放风险。结果显示,沉积物平均粒径在秋季小于夏季和春季,pH为7.64~8.88;沉积物总磷(TP)为870~2173 mg·kg^(-1);计算了沉积物磷富集系数,明确了新河部分点位为重度污染类型。吸附动力学研究结果表明:0~2 h沉积物对磷的吸附量在正负之间波动;2~4 h吸附量迅速增加,吸附速率也达到了峰值;之后吸附量增加趋势变缓,并在48 h达到平衡。绘制吸附等温线,可知沉积物的磷吸附-解吸平衡质量浓度(EPC0)为0.39~2.21 mg·L^(-1),高于同时段上覆水中磷的质量浓度,具有释放风险;磷最大缓冲容量MBC和Freundlich常数KF呈现秋季>>夏季>春季的规律;经D-R模型拟合,绝大多数样品的吸附能为8.45~11.18 kJ·mol^(-1),说明吸附机制为离子交换。相关性分析结果表明,沉积物的磷吸附速率常数与钙的相对含量呈显著相关(P<0.05)。EPC0与沉积物的总磷和易释放态磷含量呈显著相关(P<0.01),与沉积物平均粒径和有机质显著相关(P<0.05),与pH显著相关(P<0.05)。本研究结果可为受污染城市河道治理提供参考。

The sediment samples of Xinhe River were collected,which was a typical polluted urban river in Shaanxi Province.The phosphate immobilization capacities of the sediment samples were studied through adsorption experiments,and the influencing factors were also analyzed though a statistical method.The results showed that the pH of sediments was between 7.64 and 8.88,and their average particle size in autumn was smaller than that in summer and spring.The total phosphorus contents of the sediment were between 870.00 and 2173.00 mg·kg^(-1).The sediment phosphorus enrichment coefficient was calculated,and some sites of Xinhe River were identified as the type of heavy pollution.The adsorption kinetics showed that the phosphate adsorption amount of the sediment fluctuated between positive and negative in the first 2 hours,and then increased rapidly in 2 to 4 h,and the adsorption rate reached the peak.Subsequently,the adsorption amount increased slowly and reached equilibrium at 48 h.The adsorption isotherms showed that the phosphate adsorption-desorption equilibrium concentration(EPC0)of the sediment ranged from 0.39 to 2.21 mg·L^(-1),which was higher than the phosphate concentration in the overlying water,and had the risk of release.The maximum phosphorus buffer capacity(MBC)and Freundlich constant KF showed the tendency of autumn>summer>spring.For most of the samples,adsorption energy was between 8.45 and 11.18 KJ·mol^(-1),indicating that the adsorption mechanism was ion exchange.The correlation analysis showed that the phosphate adsorption rate constant was significantly positively correlated with the calcium content of the sediment(P<0.05).The EPC0 value was highly significantly positively correlated with the total phosphorus and easily released phosphorus content(P<0.01),and was significantly positively correlated with the average particle size and organic matter(P<0.05).Nevertheless,EPC0 was negatively correlated with pH(P<0.05).This study could offer reference for the remediation of polluted urban river.