Study On The Prediction Model Of Soil Cadmium Concentration Based On Dielectric Constant

The remediation and assessment of heavy metal-contaminated soils need to identify the pollution boundary of the soil,and the prediction of pollution concentration is the core of the identification.This paper took cadmium(Cd)polluted soil as the research object and studied the applicability of the acoustic wave method and the relative permittivity method in the prediction of soil pollution concentration.Moreover,the main factors affecting the relative permittivity of soil were analyzed.Importantly,we put forward a prediction model to measure the Cd mass fraction in soil by using high and low frequency relative permittivity,which provided a new idea for quickly determining the concentration of heavy metal pollution in soil.The research results were as follows:(1)The comparative experimental results of the wave velocity method and the dielectric constant method showed that the Cd mass fraction has a positive correlation between the soil relative dielectric constant and the Cd mass fraction in the range of 0-4096 mg/kg,while the soil wave velocity fluctuates around the mean.(2)The results of the study on relative dielectric constants and soil characteristics show that the main factors affecting the relative permittivity of soil were the frequency of electromagnetic waves and the volume water content,and both of them could amplify the effect of Cd mass fraction on the relative permittivity,the lower the frequency,the greater the volume water content,and the more obvious greater the amplification effect.(3)Based on the research results of soil properties and relative permittivity,the paper proposed the research idea of using high and low frequency soil relative permittivity to measure the Cd mass fraction and then used the same batch of soil samples to carry out experimental verification.According to the data of the test group(8 groups),two empirical relationships of high-frequency relative permittivity and volume water content,and low-frequency relative permittivity and Cd mass fraction have been established,which can well predict the Cd mass fraction of the verification group(2 groups).