ABSTRACT

A flight campaign over sites in India using the National Aeronautics and Space Administration (NASA) Airborne Visible Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) was undertaken in 2016. Among the sites overflown were abandoned and active mining sites, Ambaji and Zawar, in northwestern India in the states of Gujarat and Rajasthan. AVIRIS-NG data was examined for signs of acid-generating minerals that could contribute to acid mine drainage and for distinct minerals or changes in spectral absorption features that could be signs of contamination by trace metals released by mining activities. Processing approaches used included an expert system/spectral feature fitting programme, MICA (Material Identification and Classification Algorithm), that matches absorption features in image spectra to those in user-defined library spectra. Also used were low abundance material detection approaches. Over the Ambaji site, the acid-generating mineral jarosite was mapped with the MICA approach and relative abundance was mapped with a low probability detection algorithm. The Zawar mine has a better-defined drainage which was mapped with MICA. A larger number of phyllosilicate minerals were mapped in the Tiri River drainage from the Zawar mine than were observed in similar sized rivers in other Ambaji and Zawar AVIRIS-NG flightlines. The 2.2 μm absorption feature associated with the minerals mapped in these drainages was examined to determine band parameters associated with the absorption. It was determined that minerals mapped, including montmorillonite, muscovite, and illite had a wider scatter in band parameters, principally asymmetry, but to a lesser extent bandwidth, than similar exposures of these mineral classes in the other riverbeds in the AVIRIS-NG scenes. Also mapped in the Tiri River, using a spectral matched filter, were gypsum precipitates. Field samples of this precipitate had high trace metal abundances. The combination of mapping the precipitates, such as gypsum, and an association with distorted absorption features (due to trace metal adsorption) holds the prospect for using imaging spectrometer data to assess the spread of trace metals from mining sites.

摘要

2016年，印度国家航空航天局（NASA）下一代机载可见红外成像光谱仪（AVIRIS-NG）在印度各地进行了飞行运动。溢出的地点被遗弃，活跃的采矿地点Ambaji和Zawar，在印度西北部的古吉拉特邦和拉贾斯坦邦。检查了AVIRIS-NG数据中是否有可能导致酸性矿山排水的产酸矿物迹象，以及可能是采矿活动释放的痕量金属污染迹象的独特矿物或光谱吸收特征变化。使用的处理方法包括专家系统/光谱特征拟合程序MICA（材料识别和分类算法），该程序将图像光谱中的吸收特征与用户定义的库光谱中的吸收特征相匹配。还使用了低丰度物质检测方法。在Ambaji站点上，使用MICA方法绘制了产酸矿物黄钾铁矾，并通过低概率检测算法绘制了相对丰度。Zawar矿山的排水条件更加清晰，并用MICA进行了映射。与其他Ambaji和Zawar AVIRIS-NG飞行路线的类似大小的河流相比，在Zawar矿的提里河排水道中测绘的页硅酸盐矿物数量更多。检查了与在这些排水渠中测绘的矿物相关的2.2μm吸收特征，以确定与吸收相关的能带参数。已确定所测矿物（包括蒙脱石，白云母和伊利石）在能带参数（主要是非对称性）方面具有较宽的散射，但带宽较小，比AVIRIS-NG场景中其他河床中这些矿物质类别的类似暴露要高。使用光谱匹配滤镜在提里河上还绘制了石膏沉淀物。该沉淀物的现场样品具有较高的痕量金属丰度。映射沉积物（例如石膏）以及与变形的吸收特征（由于痕量金属吸附）相关联的组合，为使用成像光谱仪数据评估痕量金属从采矿场的扩散提供了前景。