Perry Canyon, Nevada. Acid Mine Drainage and UAS remote sensing

Weathering and transport of potentially acid generating material (PAGM) at abandoned
mines can degrade downstream environments and contaminate water resources. Monitoring the
thousands of abandoned mine lands (AMLs) for exposed PAGM using field surveys is time intensive.
Here, we explore the use of Remotely Piloted Aerial Systems (RPASs) as a complementary remote
sensing platform to map the spatial and temporal changes of PAGM across a mine waste rock pile on
an AML. We focus on testing the ability of established supervised and unsupervised classification
algorithms to map PAGM on imagery with very high spatial resolution, but low spectral sampling.
At the Perry Canyon, NV, USA AML, we carried out six flights over a 29-month period, using
a RPAS equipped with a 5-band multispectral sensor measuring in the visible to near infrared
(400–1000 nm). We built six different 3 cm resolution orthorectified reflectance maps, and our tests
using supervised and unsupervised classifications revealed benefits to each approach. Supervised
classification schemes allowed accurate mapping of classes that lacked published spectral libraries,
such as acid mine drainage (AMD) and efflorescent mineral salts (EMS). The unsupervised method
produced similar maps of PAGM, as compared to supervised schemes, but with little user input.
Our classified multi-temporal maps, validated with multiple field and lab-based methods, revealed
persistent and slowly growing ‘hotspots’ of jarosite on the mine waste rock pile, whereas EMS
exhibit more rapid fluctuations in extent. The mapping methods we detail for a RPAS carrying a
broadband multispectral sensor can be applied extensively to AMLs. Our methods show promise to
increase the spatial and temporal coverage of accurate maps critical for environmental monitoring
and reclamation efforts over AMLs.

废弃矿山中可能产生酸性的物质（PAGM）的侵蚀与迁移，会损害下游环境并污染水资源。利用现场调查对成千上万的废弃矿山土地（AMLs）中暴露的PAGM进行监测是一项耗时的工作。在本研究中，我们探讨了利用遥控飞行器系统（RPASs）作为一种补充的遥感平台，以绘制AML上矿山废石堆中PAGM的空间和时间变化。我们专注于测试现有监督和无监督分类算法在具有极高空间分辨率但低光谱采样率的影像上绘制PAGM的能力。在美国内华达州佩里峡谷的AML，我们在29个月的时间内进行了六次飞行，使用装备有5波段多光谱传感器的RPAS进行测量，该传感器的工作波长范围为可见光至近红外（400–1000 nm）。我们构建了六幅不同分辨率的3厘米正射校正反射率地图，并使用监督和无监督分类进行了测试，揭示了两种方法的优势。监督分类方案允许准确绘制缺乏已发布光谱库的类别，例如酸性矿山排水（AMD）和析出矿物盐（EMS）。无监督方法与监督方案相比，产生了类似的PAGM地图，但用户输入较少。我们使用多时相分类地图，通过多种现场和实验室方法进行验证，揭示了矿山废石堆上持久且缓慢增长的明矾石“热点”，而EMS在范围上表现出更快的波动。我们详细描述的携带宽带多光谱传感器的RPAS的绘图方法，可以广泛应用于AMLs。我们的方法显示出提高AMLs环境监测和复垦工作中精确地图的空间和时间覆盖范围的潜力。