The Studies Of Nitrate Contamination Processes To Groundwater System In The Laixi Area

If there is excessive NO3- - N content in groundwater, it can make people are cancer diseases, and if the crops absorb excessive NO3- - N from the irrigation water, it can induce many kinds of diseases and influence the quality of the crops. At the same time, the content of NO3- - N can directly influence the quality of groundwater.The content of the NO3- -N in groundwater in Laixi is mainly over the national standards. The contaminated area is over 150 km2 and the region has the increasing trend. According to recent monitoring data and the field survey, considering of the accumulation and transport of the nitrogen in the vadose zone, three typical profiles are selected which vertical to the DaGu River. With a number of outdoor and indoor experiments, the parameters of the dynamic reaction of the contaminants in the water-soil system and the hydro-geological parameters in the vadose zone are received. At the same time, the mass-flow coupling model of the typical profiles is established. Finally it studies the regulation of the migration and transform of the nitrogen in the soil-water system. In this dissertation, the numerical simulation is attempted to simulate these processes on different initial and boundary conditions, then some practical plans are provided to control the groundwater contamination.Because of the intensive adsorption of the. NHl -N by the soil and the nitrification process, a lot of NH4+ -N is transformed into NO3- - N. When raining or irrigating the NO3- - N can get into groundwater. Based on the simulation results, the contamination degree of the groundwater is mainly attributed by the NO3- - N content in the soil and the quantity of the irrigation. Considering the irrigation, fertilization conditions and different crops, three schemes are presented. That using the NH4- - N fertilizers on the spraying conditions can largely decrease the quantity of the nitrate in the groundwater and finally relieve the contamination of the groundwater. According to the research results, the reason why the content of the nitrate in groundwater exceed seriously the national standards is the infiltration of the N-fertilizers from the vadose zone.