北京平原包气带典型沉积物对NH_4^+-N吸附特性研究

Adsorption characteristics of typical sediments from unsaturated zone of Beijing Plain,China

采用批实验方法,研究了北京平原典型沉积物对NH4+-N的吸附规律。结果表明颗粒越细的沉积物,达到吸附反应平衡所需的时间越长,对NH4+-N的吸附量也越大;NH4+-N初始浓度在0～50 mg/L范围内,Henry、Langmuir、Freundlich吸附等温模式均能较好地描述北京平原典型沉积物对NH4+-N的吸附特性。沉积物对NH4+-N的吸附量随初始浓度的增加而增加;沉积物的颗粒越细,Henry吸附系数K越大,单位质量沉积物的饱和吸附量也越大;沉积物中TOC含量对沉积物的NH4+-N吸附行为有一定的控制作用,永定河、潮白河沉积物TOC值与Henry吸附系数K的相关系数R2分别为0.50,0.76;沉积物对NH4+-N的饱和吸附量随着土水比的增加而减少,通过乘幂的方式拟合不同土水比下的饱和吸附量,得出了北京平原包气带沉积物对NH4+-N的饱和吸附量;相同岩性条件下,特别是细颗粒沉积物中,潮白河沉积物对NH4+-N的吸附能力较永定河沉积物强,而同一流域内,中、下游沉积物的吸附能力较上游强。

Adsorption of ammonia on representative sediments obtained from the Beijing plain was investigated in this study by means of batch experiment.It was found that the equilibrium time and the adsorption capacity increased with the decrease in the grain size of sediments.With the initial concentration of ammonia between 0 to 50 mg/L,the adsorption isotherm can be described by Henry,Langmuir and Freundlich models.The adsorption capacity elevated with the increase in the initial concentration of ammonia.The Henry coefficient and the adsorption capacity increased with the decrease of the grain size of the sediments.Adsorption of ammonia was affected by the total organic carbon（TOC） in the sediments.The correlations of TOC and Henry absorption coefficient were 0.50,0.76 for sediments from Yongding River catchment and Chaobai River catchment,respectively.The adsorption capacity of ammonia decreased with the increase in the ratio of solid to liquid.Sediments from Chaobai River catchment,especially the fine-grained sediments,had a higher capacity for ammonia adsorption than those from Yongding River catchment with the same lithology.The ammonia adsorption capacities of sediments from middle and lower reaches were higher than those from upper reaches in the same catchment.