Indoor experiment and numerical simulation study of ammonia-nitrogen migration rules in soil column

• 作者: LI Wu-jin LI Zhi-ping ZHAN Jiang ZHAO Gui-zhang
• 来源期刊: 地下水科学与工程：英文版
• 学科: 工学
• 关键词: Soil COLUMN Ammonia-nitrogen MIGRATION RULE HYDRUS-1D Numerical simulation MINERALIZATION NITRIFICATION
• 年，卷（期）: 2018,（3）
• 页码范围: 205-219
• 页数: 15页
• 分类号: TV

摘要

The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration,RBF).This is of great importance to groundwater safety along the riverbank.This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column,and then makes comparison with the indoor experiment results in combination with the numerical simulation method.The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including“removal-water saturation-saturation”.As the contents of clay particles in soil sample increase,the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio.During the removal period,the removal ratio of Column 1,Column 2 and Column 3 averages 68.8%(1-12 d),74.6%(1-22 d)and 91.1%(1-26 d).The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies.But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm.It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil.HYDRUS-1D model is used to simulate this experiment process,analyze the change of the bottom observation holes by time and depth in three columns(the tenth day),and make comparison with the experiment result.The coefficients of determination for fitting curves of Column 1,Column 2 and Column 3 are 0.953,0.909,0.882 and 0.955,0.740,0.980 separately.Besides,this paper examines the contribution of absorption,mineralization and nitrification in the simulation process.In the early removal stage,mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%.As time goes by,absorption starts to function and gradually assumes a dominant position.In the middle and late removal stage,nitrification