基于地面实测光谱的多金属矿区土壤重金属含量反演研究

多金属矿区土壤重金属元素调查是矿区成矿元素地球化学异常评价和找矿预测的依据,也是矿区可耕种土壤重金属污染调查和恢复的依据。在土壤中羟基官能团与重金属游离态阳离子吸附反应分析的基础上,结合地面实测光谱及其数据处理,提取了研究区土壤在500 nm、770 nm、1 340 nm和2 100~2 300 nm波段范围内的特征光谱。通过土壤重金属元素与实测光谱特征(吸收深度、吸收面积、反射率比值、对称度)的皮尔森相关分析,确定了参加不同金属元素回归分析的实测光谱特征,建立了基于地面实测光谱估算重金属元素含量的回归方程。由此,成功地提取碾子沟-洛金洼多金属矿区土壤中Cu、Pb、Cd、Zn等重金属元素含量。与检验样本比较,Cu的均方根误差为0.392 1ω(B)/10-6,平均绝对误差为0.300 6ω(B)/10-6。在试验矿区,根据土壤中金属元素含量分布,发现采矿场东北方向有一高值异常区,为该区进一步找矿提供依据。另外,采矿场西北农用地中Pb、Cd元素分布相对较高,应该引起重视。

Study on the inversion of soil heavy metal elements concentrations from field spectra in the polymetallic mining area

Soil heavy metal element investigation in metal mining area provides a tools for geochemical anomaly evaluation of ore-forming elements and prospecting and it is also foundation for metal heavy pollution investigation in arable soil and restoration. Based on adsorption mechanism of hydroxyl groups in the soil and free positive ions, the field spectral data are processed and the spectral features concentrating on 500nm, 770nm, 1340nm, and 2100nm-2300nm are extracted. By Pearson Correlation analysis between soil heavy metal elements and field spectral features (absorption depths, absorption area, reflectance ratio, and symmetry degree), the regression equations for the field spectral features and metal element concentrations are determined to estimate the heavy metal element contents. Therefore, the heavy metal contents, including Cu, Pb, Cd, and Zn, are retrieved successfully. Compared with testing samples, the root-mean-square error of Cu is 0.3921 and its mean absolute error is 0.3006. In testing mining area, there exists a high-value anomaly zone in the northeastern direction of mining area, which provides the basis for further prospecting. Besides, the Pb and Cd contents in northwestern farmland in the mining area deserve the attention for farming environment protection.