Estimate of heavy metals in soil and streams using combined geochemistry and field spectroscopy in Wan-sheng mining area, Chongqing, China

Abstract

Heavy metals contaminated soils and water will become a major environmental issue in the mining areas. This paper intends to use field hyper-spectra to estimate the heavy metals in the soil and water in Wan-sheng mining area in Chongqing. With analyzing the spectra of soil and water, the spectral features deriving from the spectral of the soils and water can be found to build the models between these features and the contents of Al, Cu and Cr in the soil and water by using the Stepwise Multiple Linear Regression (SMLR). The spectral features of Al are: 480nm, 500nm, 565nm, 610nm, 680nm, 750nm, 1000nm, 1430nm, 1755nm, 1887nm, 1920nm, 1950nm, 2210nm, 2260nm; The spectral features of Cu are: 480nm, 500nm, 610nm, 750nm, 860nm, 1300nm, 1430nm, 1920nm, 2150nm, 2260nm; And the spectral features of Cr are: 480nm, 500nm, 610nm, 715nm, 750nm, 860nm, 1300nm, 1430nm, 1755nm, 1920nm, 1950nm. With these features, the best models to estimate the heavy metals in the study area were built according to the maximal R2. The R2 of the models of estimating Al, Cu and Cr in the soil and water are 0.813, 0.638, 0.604 and 0.742, 0.584, 0.513 respectively. And the gradient maps of these three types of heavy metals’ concentrations can be created by using the Inverse distance weighted (IDW).The gradient maps indicate that the heavy metals in the soil have similar patterns, but in the North-west of the streams in the study area, the contents are of great differences. These results show that it is feasible to predict contaminated heavy metals in the soils and streams due to mining activities by using the rapid and cost-effective field spectroscopy.