Hyperspectral longwave infrared reflectance spectra of naturally dried algae, anthropogenic plastics, sands and shells

Abstract

Abstract. Remote sensing of litter is foreseen to become an important source of additional information relevant to scientific awareness about plastic pollution. Here, we document directional hemispherical reflectance measurements of anthropogenic and natural materials gathered along the shorelines of the Chiloé Archipelago, Chile. These spectral observations were completed in a Chilean laboratory using a state-of-the-art hyperspectral HyLogger-3™ thermal infrared (TIR) spectrometer starting from the medium-wave infrared spectrum (6 µm) and going to the longwave infrared (14.5 µm) spectrum at 0.025 µm intervals. The samples we investigated included sands, shells, algae, nautical ropes, Styrofoam®, gunny sacks and several fragments of plastic-based items. The apparent visible colours of these samples included shades of black, blue, brown, green, orange, white and yellow. We grouped the samples using robust statistical approaches (derivatives, peak-seeking technique) and visual analyses of the derived hyperspectral reflectances. In each group we derived an average or TIR end-member signal and determined diagnostic wavebands. Most of the diagnostic wavebands picked were found to be inside the atmospheric window of the TIR spectrum region. Furthermore, this laboratory reference dataset and findings might become useful in related field observations using similar thermal infrared technologies, especially in identifying anomalies resulting from environmental and meteorological perturbations. Validation and verification of proposed diagnostic wavebands would be part of a continuing effort to advance TIR remote sensing knowledge as well as support robust detection algorithm development to potentially distinguish plastics in litter throughout the natural environments. Data are available in open-access form via the online repository PANGAEA, database of the World Data Center for Marine Environmental Sciences: https://doi.org/10.1594/PANGAEA.919536 (Acuña-Ruz and Mattar, 2020).

Towards Robust River Plastic Detection: Combining Lab and Field-based Hyperspectral Imagery

“…Based on the knowledge that macroplastics reflect light in a unique way compared to other floating litter and natural or anthropogenic background materials [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], this study addressed two objectives. First, an understanding of the difference between lab-based and field-based hyperspectral imaging was made by comparing the associated hyperspectral signatures.…”

“…Developed by NASA, this library is widely used in estimating vegetation abundance and classifying mineral surfaces [49,50]. Including hyperspectral signatures of plastics as found in [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and this study in such reference libraries is essential. This can either be done as an addition to existing libraries, or by the establishment of a completely new open-access library specifically designed for plastics.…”

“…An approach gaining rapid attention in the remote sensing community is multispectral or hyperspectral imaging of plastics. Hyperspectral imaging of plastics is key to better understand plasticspecific detection features and the subsequent design of new monitoring instruments [5,6]. Subsequently, these techniques offer potential for upscaling and harmonization plastic monitoring across aquatic ecosystems.…”

MARIDA: A benchmark for Marine Debris detection from Sentinel-2 remote sensing data

“…Furthermore, to better understand the spectral behaviour of Marine Debris, hyperspectral measurements have been conducted, exploring sensors' capabilities in distinguishing plastics from other features such as vegetation, natural material, and water types [24][25][26][27][28]. Investigating Marine Debris characteristics (including its spectral behavior) has been also attempted via multispectral satellite observations [10,12,13,29], highlighting that spectral discrimination of Marine Debris from other sea surface features (e.g., ships, foam) is not straightforward.…”

High-Resolution Aerial Detection of Marine Plastic Litter by Hyperspectral Sensing

“…The plastics floating on the sea and ingested by marine organisms are responsible for choking, starvation, internal injuries and digestive tract blockage [1]. For this reason, there is the need for innovative, affordable, and sustainable approaches to monitor the presence of plastics in the marine environment [2][3][4].…”