Influence on Shallow Groundwater by NH-4-N in Polluted River

NH₄-N pollution in surface water and groundwater is currently very severe. Experiment simulation of NH₄-N migration was carried out in a column filled with three kinds of natural sand under the reflux of domestic sewage. Adsorption saturation of NH₄-N in the column was reached within 17 days for the coarse sand and 130-140 days for the medium sand, suggesting the easiness of NH₄-N migration to groundwater. However, the field test in Liangshui River and its groundwater is incompatible with the experimental observation. When the concentration of NH₄-N reached 46.86 and 26.95 mg/L in Liangshui River, the groundwater has a NH₄-N concentration of less than 1.10 mg/L. The little influence of Liangshui River on the groundwater NH₄-N was attributed to the bottom mud, the thickness and character of the infiltration media underlying the river bed as well as the seepage quantity of the river. Importantly, the NH₄-N absorbed by the penetration media underlying the sewage-received river would be transported into the groundwater after addition of clean water and cleanup of the mud, causing a secondary pollution of groundwater.