| According to the physical difference between the target geologic body and the nearby surroundings,the location and distribution of the target geological body can be identified by the geophysical methods.In recent years,the geophysical methods are widely used to detect environmental pollutants because of theirs advantages of space comprehensiveness,in-situ nondestructive,low cost and fast speed.In the investigation of polluted site,the parameters such as the resistivity of the study areas are changed when the pollutants entering the strata,and then the anomaly zones are drawn out in the geophysical survey section.The electrical method is one of the most widely geophysical methods used in the environmental,in order to apply the electrical method better and more effectively to the site pollution detection,this paper studied the influence of different measuring factors on the measurement results.The electrical parameters of resistivity and chargeability of heavy metal-organic compound polluted medium were studied in laboratory for the first time.On the basis,the high-density resistivity method and the induced polarization method were applied to the field detection of different types of contaminated sites,the main contents and conclusions are as follows:(1)The influence of supply voltage,measuring instrument,grounding condition and measuring device on the measurement result were studied through the field experiment of high density resistivity method.The results showed that the supply voltage of 45V and 90V had little effects on the measured results under the condition in this paper.The two instruments studied in this paper can identify the underground anomaly,but there were differences in the sensitivity of low resistance and high resistance recognition.In the measured data of the plate electrodes(poor grounding condition),only the data near the surface differed greatly with the copper electrodes(good grounding condition).Compared with Wenner(WN)devices,the dipole-dipole(DP)device had higher resolution in the identification of horizontal low resistivity anomaly and longitudinal anomaly.(2)Electrical parameters are the prerequisite of electrical method,and the experimental research of heavy metal-organic compound pollution were carried out for the first time.The experimental results showed that,with the increasing of Pb2+concentration,the resistivity of Pb2+ polluted medium decreased,and the chargeability increased.With the increase of Pb2+ concentration and the organic matter volume fraction,the resistivity of Pb-organic compound polluted medium decreased,and the chargeability increased at first and then start to decreased.(3)Based on the above research,the high-density resistivity method and the induced polarization method were applied to the field pollution detection.The high-density resistivity method and the induces polarization method were used to detect the pollution of a heavy metal-organic compound polluted site in Hunan Province,and the results showed that the combination of high-density resistivity method and induced polarization method could effectively identify heavy metal-organic compound pollution.By using high-density resistivity method for pollution detection in a heavy metal pollution-chromium contaminated site in Hunan Province,the resistivity value 19.95 ?·m was determined as the limit for determining the pollution of the site,and the spatial distribution of pollutants in the site were ascertained by combining borehole data and groundwater sampling test results.On the basis of the factors affecting the measurement results of high-density resistivity method and induced polarization method,and research on resistivity and chargeability of heavy metal-organic compound polluted medium.This paper applied these two geophysical methods to field pollution detection,which enriches theory research and practical application of geophysical methods in pollution detection,especially the heavy metal-organic compound pollution detection. |
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