Abstract
At present, there is a lack of research on the soil environmental pollution caused by the mining gold mines in Mojiang, Yunnan Province, China. This study focuses on the polluted farmland soil in Mojiang Hani Autonomous County, Yunnan Province, and 61 soil samples from the region. Continuous Wavelet Transform (CWT) analysis was performed on raw soil hyperspectral reflectance (R) near infrared spectra and after first-order derivative transformation (R′) using seven decomposition scales. Four models (Ridge, Lasso, Elastic net, and partial least squares (PLS) regression) were used for quantitative prediction of soil arsenic (As) content. The simulation results show that: (1) appropriately increasing the CWT decomposition scale can effectively extract feature bands and amplify the differences between features. In most cases, the modeling accuracy of the model, initially increases and then decreases as the CWT decomposition scale increases, with scale five being the optimal decomposition scale. (2) The R′-CWT method, improves the correlation coefficient between hyperspectral data and arsenic content. The modeling results for predicting soil As content using R′-CWT are superior to those obtained with R-CWT. (3) Regularized modeling methods that incorporate a regular term in the loss function can improve the prediction accuracy and generalization ability of the model. (4) The performance of predicting soil As content based on R′-CWT transformation is ranked as follows: Ridge regression>Elastic net regression>Lasso regression>PLS regression. The ridge regression model based on first derivative spectra using continous wavelet transformation with a scale factor of 5 (R′-CWT-25) has the highest prediction accuracy, with validation sets of root mean square error (RMSE), coefficient of determination (r2), residual prediction deviation (RPD) and the ratio of performance to the interquartile range (RPIQ) of 0.07 g∙kg-1, 0.94, 3.9, and 3.7, respectively. This study can provide a certain scientific reference for the ecological environment management of polluted soil around the gold mining area in Mojiang County.
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