Study On Detecting LNAPL Contaminated Soils By GPR And Imaging Method

With the increase of gas station and oil storage facilities in the city,due to various factors part of the oil products penetrate into the situation of the underground environment always happened.These substances will be accumulated cluster in the deep underground,to become a threat to the environment and pollution of water resources.So the detection in these oil pollution place will be enormous significance to environmental.Due to the infiltration of oil pollution in the underground has fluidity,the traditional physical detection methods can cause the changes in the pollution area of underground structure,and lead to the oil pollution moved again and cause secondary pollution,therefore,condition of electromagnetic detection methods,such as ground penetrating radar(GPR)is more suitable for detection of these pollutants.Traditional ground penetrating radar(GPR)for this kind of small dielectric constant which mixed with the surrounding environment of oil pollutants resolving power is limited,and the imaging result is worse.For the better information of underground oil pollution,and high resolution imaging,this paper introduces the full polarimetric ground penetrating radar and polarization migration algorithm.Full polarimetric ground penetrating radar(GPR)get polarimetric scattering matrices of subsurface objects by different combinations of transmitters and receivers.Different basis matrices contains information from different types of subsurface objects,which provides a possibility to improve the ability of GPR detection.Polarimetric migration is a new method which is developed by merging the Pauli polarimetric decomposition technique with the Krichhoff migration equation.In this paper,we apply the polarimetric migration method to image LNAPLs contamination in soil.We set up a model of LNAPL contaminated soil using quartz and diesel in the laboratory and conduct the detection by a full polarimetric GPR system.The range of the LNAPL contamination can be imaged clearly after polarimetric migration is applied to the pre-processed data.By reconstructing and imaging the data containing the polarimetric information,the detection ability of GPR can be improved.