Effect of moisture content on spectral characteristics and attribute estimation of reclaimed soil

In order to explore the influence of different soil moisture content on reclaimed soil perspectra characteristics and inversion accuracy of soil properties, this paper takes the reclamation area of a coal mine in Huaibei, Anhui Province as the research object, soil physical and chemical properties and soil spectral information before and after air drying were measured. Analyze the differences between reclaimed and non-reclaimed soils, and clarify the spectral absorption characteristics under different moisture conditions. Paired sample ttest was used to explore the spectral influence bands under different moisture conditions. Radiation transfer model and direct standardization algorithm were used to remove soil moisture, and the removal effects of the two algorithms were compared with the change of absorbance . Taking soil total nitrogen as an example,different spectral screening methods (Successive Projections Algorithm, SPA、Pearson Correlation Coefficient, PCC、PCC-SPA) were used to establish soil properties prediction models for dry soil, wet soil and corrected spectral. The results show that:① the spectral reflectance of reclaimed soil was significantly higher than that of non-reclaimed soil after air drying, and the spectral difference between reclaimed soil and non-reclaimed soil in visible band was significantly higher than that in near-infrared band. The central bands of soil moisture were 1 000, 1 450,1 950 and 2 200 nm, and the difference of visible band was also caused when the water content was too high or too low. ② Compared with the direct standardized algorithm, the radiative transfer model can remove soil moisture more effectively, and the average absorbance of the obtained spectral curve almost coincides with that of dry soil.Under the influence of soil moisture, the prediction model of total nitrogen in reclaimed soil decreased by 45.38%. The accuracy of the prediction model established after removing soil moisture by radiative transfer model was significantly improved, and the validation set R2 was increased by more than 30%, and the difference with dry soil R2 was less than 10%. ③ Three band screening methods can effectively screen out important wavelength variables, among which no more than 7 bands are screened by PCC-SPA, which greatly optimizes the model structure and reduces the modeling time.The results of this study can be used as an important method to estimate the soil properties of wet soil in this region, and provide a new idea for further improving the in-situ monitoring of soil properties in coal mine reclamation.