Combining unmanned aerial vehicle-based remote sensing and stable water isotope analysis to monitor treatment peatlands of mining areas

Abstract

Treatment peatlands are water purification systems located on existing mires. They are commonly used to treat different types of waters, ranging from municipal wastewaters to mine effluent. This study evaluated the capacity of unmanned aerial vehicle (UAV)-based thermal infrared (TIR) imaging, color infrared imaging, and stable water isotopes as a combined method for monitoring the functioning of a treatment peatland purifying mine process effluent water under boreal conditions in northern Finland. The results showed that TIR was an efficient tool for pinpointing cold groundwater seepage points in the peatland area that were not otherwise visible. Color infrared imaging was used to define Normalized Difference Vegetation Index (NDVI), as an indicator of plant health in the treatment area. A NDVI map of the area, measured on a day representing the main growing season (summer, +12 °C day temperature), revealed areas with stressed coniferous trees. This was probably due to excess water in these areas, resulting from successful spread of the process effluent water to the treatment peatland. Stable water isotopes were able to spatially differentiate the treated process effluent water, surface waters, and groundwater in different parts of the treatment peatland. This first attempt at combining these methods in monitoring of treatment peatlands was promising, as the results obtained with different methods complemented each other. While they produce only a snapshot of prevailing conditions, all three methods, singly and in combination, could be valuable tools in treatment peatland management.

Mapping the Groundwater Level and Soil Moisture of a Montane Peat Bog Using UAV Monitoring and Machine Learning

“…Therefore, vegetation is responsive to water regime (i.e., dry surfaces cause changes in the surface temperature), and we also extracted the relative surface temperature from thermal scenes. TIR imaging is also used to estimate the temperature of various surfaces, which allows mapping of temperature patterns providing information on hydrological processes [24].…”

“…Further, [24] used UAV-based thermal infrared (TIR) imaging and color infrared imaging, combining stable water isotope studies to identify treatments along a mining area in Finland. Most studies practiced one or two sensors in studying peatland environments.…”

Evaluation of Stream and Wetland Restoration Using UAS-Based Thermal Infrared Mapping

“…Lightweight TIR sensors provide another remotely sensed data type that can be used to generate high-resolution (<1 m) TIR orthophotos (e.g., [5]). However, the use of TIR-equipped UAS is relatively novel, only recently finding environmental and hydrological applications [1,[5][6][7][8][9][10]. Examples include environmental monitoring of natural geothermal systems [5] and distinguishing sewer and stormflow discharges from groundwater based on characteristic temperatures [9].…”

“…Examples include environmental monitoring of natural geothermal systems [5] and distinguishing sewer and stormflow discharges from groundwater based on characteristic temperatures [9]. In engineered peatlands, UAS TIR was used to guide water isotopic sampling for a similar goal of parsing groundwater discharge endmembers [10].Recently, there has been a movement to better incorporate ecological services and functions into stream and wetland restoration projects [11]. Hydrological process-based wetland restoration requires understanding of site-wide hydrodynamics, which often involves scaling-up measurements from discrete physical sampling points to the square-kilometer scale [12].…”

“…Examples include environmental monitoring of natural geothermal systems [5] and distinguishing sewer and stormflow discharges from groundwater based on characteristic temperatures [9]. In engineered peatlands, UAS TIR was used to guide water isotopic sampling for a similar goal of parsing groundwater discharge endmembers [10].…”