Ammonia Nitrogen Migration Experiment And Simulation Studies Of Soil In The Wind And Sand Area

With the rapid development of economy, the growth of population and the accelerationof urbanization process, the human demand for water is significantly increasing. As the basiccondition of human survival and development, the sharp shortage of water resources hasbecome a global problem. As a kind of water resources, groundwater is a precious freshwaterresource, the water quality is directly related to the whole social production, living problemsand human health. In recent years, water pollution is increasingly serious in our country. Asthe first industry in our country, agriculture plays an important role in using water. A largenumber of survey statistics show that the use of agricultural fertilizer is one of the main causeof water pollution.Considered of the real fertigation situation in the study area, this paper is divided intotwo parts that include indoor test and software simulation to study the migration process ofammonia nitrogen in the vadose zone. Two soil column were filled to simulate saturated andunsaturated flows of vadose zone in the study area during the indoor test. According to theon-the-spot soil bulk density, we fill the column with the soil from the study area. In thelaboratory the parameters of vadose soil in the study area is tested include dry density,moisture content, soil water characteristic curve and soil organic matter, etc. Several watersupply conditions of ammonia nitrogen migration experiment were conducted in the soilcolumn1and soil column2. Finally we got the BTC (breakthrough curve) of each apertureabout ammonia nitrogen penetration in the soil column1and soil column2.The experiment shows:(1) With the same water supply intensity, the soil adsorptionquantity increases and the equilibrium time delays with the increase of initial concentration ofwater.(2) The water supply intensity plays an important role in the ammonia nitrogenmigration process with the same initial concentration of water. The lower rate of water supplyintensity, the less soil adsorption of ammonia nitrogen is, and the longer time is needed for thebalance in each aperture.In the software simulation part, the Hydrus-1D software developed by the United Statessoil laboratory is used to simulate the ammonia nitrogen migration process under the same conditions of experiment in laboratory, and the inverse solution function of Hydrus-1D is alsoused to calculate parameters like soil-water distribution coefficient Kd, organic carbondistribution coefficient Kocand retardation factor R according to the results of the laboratory.Compared the measured value in laboratory with the Hydrus-1D simulation of ammonianitrogen in the soil column, it is found that the simulation results has good consistency on thetrend with lab measured values, and the fitting effect is better in the soil column1than2dueto the good stability and uniformity of saturated flow. Through sensitivity analysis of the threemain parameters: retardation factor, groundwater flow rate and vertical dispersion degree, wefound the influence on the water ammonia nitrogen concentration at the bottom of the soilcolumn is: retardation factor> groundwater flow rate> vertical dispersion degree. The soiladsorption quantity is increased and a more gentle BTC is got by develop retardation factorand vertical dispersion degree, or reduce the groundwater flow velocity.