Hyperspectral inversion of heavy metal content in subsided waters of coal mines

In order to study a rapid and effective monitoring method for the heavy metal elements in the subsidence wa- ters of a mining area,the subsidence water area of Panyi Mine in Huainan,China,was taken as a research area. First- ly,the spectral data of sampling points were collected by ASD FieldSpec 4 spectrometer and some samples were col- lected. The contents of six heavy metals including Cu,Pb,Zn,As,Cd and Cr in water samples were determined using atomic absorption spectrometer and atomic fluorescence spectrometer. Then,the spectral data was subjected to differen- tial transformation and reciprocal logarithmic transformation. The correlation analysis was carried out with the water content of the metal and the characteristic spectrum was extracted. The significant correlation bands were selected ac- cording to the correlation analysis results. Single-band analysis,multiple stepwise regression ( SMLR) analysis and band depth and partial least squares regression (PLSR) were combined to establish a prediction model for estimating heavy metal content in water based on spectral reflectance,and the accuracy of the prediction model was evaluated.The best prediction model for each heavy metal content was selected. The results show that the correlation coefficient between the spectral band of the differential transformation and the heavy metal element content of the water body is significantly improved and a higher correlation is achieved. After differential transformation,the maximum correlation coefficients of six heavy metal elements including Cu,Pb,Zn,As,Cd and Cr are 0. 874,-0. 648,0. 824,0. 764,0. 636 and -0. 885,respectively. Based on the Cu,Cr content and second-order differential transformation spectrum,the es- tablished single-band regression model is their best predictive model,and the R2 is verified to be 0. 823 and 0. 806,re- spectively. The stepwise regression model established by the second-order differential of Pb,Zn,As and Cd content and spectral data is their best prediction model. The verification R2 is 0. 774,0. 724,0. 564,and 0. 767,respectively. The models can be used for the rapid monitoring of heavy metal content in the subsided waters at Panyi Mine.