岩溶地下河沉积物对氨氮的等温吸附特征

岩溶含水层是西南地区最重要的含水层之一.含水层的管道系统蕴藏着丰富的沉积物,这些沉积物可能成为污染物运移和转化的载体.以广西柳州市2个典型地下河系统为例,通过室内模拟的方法,研究地下河沉积物对氨氮的吸附特征.沉积物对氨氮的吸附平衡时间都小于2 h,最短的时间不足1 h,沉积物5 h平衡吸附量达到了最大吸附量的71%～9...

Characteristic of Ammonia Nitrogen Adsorption on Karst Underground River Sediments

Karst aquifers are one of the most important aquifers in Southwestern China. One of the characteristics of karst aquifers is the enhanced permeability permits high flow velocities are capable of transporting suspended and bedload sediments. Mobile sediment in karst may act as a vector for the transport of contaminates. 14 sediment samples were collected from two underground rivers in two typical karst areas in Liuzhou city, Guangxi Autonomous Region, China. According to simulated experiment methods, characteristic of adsorption of ammonia nitrogen on sediment was studied. The results of ammonia nitrogen adsorption dynamics on sediments showed that the maximum adsorption velocity was less than 2 h. The adsorption balance quantity in 5 h accounted for 71%-98% of the maximum adsorption quantity. The maximum adsorption quantity of ammonia nitrogen was 385.5 mg/kg, which was sediment from a cave in the middle areas of Guancun underground river system. The study of isotherm adsorption indicated adsorption quantity of NH⁺₄ increase followed by incremental balance concentration of NH⁺₄ in the aquatic phase. Adsorption quantity of ammonia nitrogen in sediments has a relative linear relationship with adsorption balance concentrations. Adsorption-desorption balance concentrations were all low, indicating sediments from underground rivers have great adsorption potential. Under the condition of low and high concentrations of ammonia nitrogen in overlying water, Langmuir and Tempkin couldn't simulate or simulate results couldn't reach remarkable level, whilst Linear and Freundlich models could simulate well. Research on different type sediments, sampling times and depths from two underground rivers shows characteristic of ammonia nitrogen adsorption on karst underground river sediments doesn't have good correspondence with the type of sediments. One of the reasons is there is no big difference between sediments in the development of climate, geology, hydrological conditions and pollution history. The other reason maybe the article is lack of research on pH, salinity and others factors which may affect adsorption and desorption.