Model Study On The Migration And Transformation Of Organic Pollutants In Vadose Zone

Groundwater resources is a valuable resource which human development and survivalcannot be missing and groundwater pollution have a profound impact on people’s lives.Vadose zone is connected to the channel surface and groundwater, and it plays an importantrole for the controlling of pollution of underground water. It is timely and economy for modelsimulating and predicting the behavior of contaminants in the vadose zone and waterenvironment. The modeling method is based on the principle of water movement andmigration and transformation of pollutants. Vadose zone model is the primary means to studythe migration of contaminants in the vadose zone, and it is a true characterization of thevadose zone contamination. Simulating of pollutants behavior in the model to the vadose zone,not only able to determine the amount of packet transport and transformation of pollutants inthe vadose zone, but also pave the way to the correct guidance of groundwater pollution riskassessment.This paper analyzes the adsorption, volatile diffusion, hydrolysis, biodegradation of organiccontaminants in the vadose zone, and according to the removal processes of organic pollutants,build transformation model of organic pollutants in the vadose zone. Then some resultsobtained by the mechanism of organic pollutants in the vadose zone, as well as indoor staticexperiments and column experiments:（1） The model needs to be built on the basis of numerous assumptions, and basedcomputing the medium permeability coefficient layered partition, which will simplify thecomplex vadose zone area. When organic pollutants into the vadose zone partition, accordingto the mass balance equation: the original pollutants quality of the vadose zone partition andinto the vadose zone contaminants quality equal pollutants migrated partition plustransformed quality and the remaining amount. And organic pollutants in a certain period oftime can be achieved gas-liquid-solid three-phase equilibrium in the vadose zone. We can getpollutants concentration and content in the vadose zone partition then through equation editor computing, and finally got the model by integrating formula.（2） Fine sand, silt, clay for the adsorption of diesel in line with the Freundlich adsorptionisotherm, obtained by experimental measurement of fine sand for the diesel adsorptionequation is S=11.98c^0.4902, silt for the diesel adsorption equation is S=16.89c^0.5179, clay forthe diesel adsorption equation is S=21.27c^0.5835.Diesel hydrolysis in acidic and alkalinesolutions, but in neutral solution, hydrolysis is very weak. Diesel hydrolyzed parameter underacidic conditions is K_H=0.0002825, under neutral conditions is K₀=0.0002166, under alkalineconditions is K_OH=0.0001306.（3） The model simulates the diesel pollutant transport and transformation in the vadosezone of different media, and conduct comparative experiments. Result can be drawn throughthe contrast of simulation calculation results with the experimental results. Fine sand and claylayer medium experimental test results of concentration change rate and simulation results ofconcentration change rate are similar. But the second layer and the third layer of theexperimental results with the simulation results are quite different. But this two layer resultscannot give a true reflection of the accuracy of modeling because of testing reason. So fromthe first layer simulation results, the effect of model simulation is closer to the real situation.