Bioconcentration And Reflectance Spectra Of Crops Around Mining Area Under Cd Pollution

Long-term mining activities have brought huge economic benefits,but also brought serious ecological damage to the surrounding area,such as heavy metal pollution of soil around the mining areas,crop yield reduction and so on.According to study bioconcentration and spectra characteristics of Corn and Rape,which provide a theoretical basis for monitoring Cd pollution in farmland around the mining areas.A pot experiment was conducted under various concentrations of Cd with 25?50?75?100 and 125 mg/kg.(1)Plant height,root length and biomass of each part of Corn and Rape decreased with the increase of Cd pollution concentration.The highest Cd content was 531.72mg/kg at the Corn?s root,and the lowest was 108.6 mg/kg at the jointing stage leaves.At Cd 25 mg/kg,bioconcentration factor and transfer factor were greater than 1,showing the characteristics of Cd hyperaccumulated plants.The highest Cd content was 531.72 mg/kg in Rape?s root,and the lowest was 0.05 mg/kg in rapeseed.Bioconcentration factor(except rapeseed bioconcentration factor)is greater than 1,the transfer factor is less than 1,and Rape has a strong rhizosphere enrichment ability in 25-125 mg/kg Cd treatments.(2)The total chlorophyll content per unit area of Corn and Rape,the thickness of Corn?s leaves and the short diameter of vascular bundle sheath,and the average length of fence tissue of Rape,have decreased with the increase of Cd pollution concentration and growth period.The reflectivity of visible band increases while that of near-infrared band decreases.The red edge positions of Corn and Rape have showed different degrees of"blue shift".The displacements of Corn were 1.9 nm and 9.1 nm respectively at the jointing stage and mouth opening stage.The displacements were 1.5 nm,2.7 nm and 3.1 nm at Rape late seedling,bud stage and flowering stage.(3)Correlation significance analysis of Cd content in plant leaves with original spectrum and first-order derivative spectrum were conducted,and multiple regression model was established.The fitting R~2 of the first-order derivativeat at Corn jointing stage and the mouth opening stage were better,which were 0.95 and 0.94,F value were 507.25 and 935.856,RMSE were 0.08?1.267 mg/kg,respectively,which has strong Cd inversion ability.R~2 and RMSE of the Rape model were affected by the growth period of the plant.In the three growth periods of Rape,the model established by the original spectrum of the leaves in the flowering period had a better effect.R~2 and RMSE were 0.97 and 0.58mg/kg.(4)Correlation significance analysis were carried out on the original spectra and first-order derivative spectra of leaves with Cd content in plant soil,and a multiple regression model was established.The first-order derivative fitting R~2 at the jointing stage and mouth opening stage of Corn were 0.922 and 0.957,respectively,and RMSE were verified to be 1.375 and 0.948 mg/kg,respectively.The first-order derivative model of late seedling,bud stage and flowering stage were better than the original spectrum,and the fitting degree R~2 were 0.97,0.964 and 0.961,respectively,indicating that the value of soil Cd content predicted by the multivariate regression model established by the first-order derivative is the closest to the real value.