Abstract
Plastic pollution in the world’s natural waters is of growing concern and currently receiving significant attention. However, remote sensing of marine plastic litter is still in the developmental stage. Most progress has been made in spectral remote sensing using visible to short-wave infrared wavelengths where optical physics applies. Thermal infrared (TIR) sensing could potentially monitor plastic water pollution but has not been studied in detail. We applied radiative transfer theory to predict TIR sensitivity to changes in the surface fraction of water covered by plastic litter and found that the temperature difference between the water surface and the surroundings controls the TIR signal. Hence, we mapped this difference for various months and times of the day using global SST (sea surface temperature) and t2m (temperature at 2 m height) hourly estimates from the European Centre for Medium-Range Weather Forecasts (ECMWF), ERA5. The maps show how SST-t2m difference varied, altering the anticipated effectivity of TIR floating plastic litter remote sensing. We selected several locations of interest to predict the effectivity of TIR sensing of the plastic surface fraction. TIR remote sensing has promising potential and is expected to be more effective in areas with a high air–sea temperature difference.
Highlights
Plastic pollution in the world’s oceans rivers and lakes is of growing concern and currently receiving significant attention, but there are still many unknowns
Most progress has been made in the field of spectral remote sensing in visible (VIS), near-infrared (NIR) and short-wave infrared (SWIR) spectra where optical physics applies
Spectral light reflectance measurements of floating plastic litter have been made in situ [4], from unmanned aerial vehicles (UAV) [5], airplanes [6] and very recently, the Sentinel-2 satellite [5]
Summary
Plastic pollution in the world’s oceans rivers and lakes is of growing concern and currently receiving significant attention, but there are still many unknowns. Most progress has been made in the field of spectral remote sensing in visible (VIS), near-infrared (NIR) and short-wave infrared (SWIR) spectra where optical physics applies. Over these wavelengths, spectral light reflectance measurements of floating plastic litter have been made in situ [4], from unmanned aerial vehicles (UAV) [5], airplanes [6] and very recently, the Sentinel-2 satellite [5]. It has become clear that spectral remote sensing would be improved by using complementary measurements using different sensing technologies [7]. At the longer end of the TIR spectrum, it does not need clear weather, and solar rays are diffusely reflected from the water surface, which reduces the sensitivity to solar glint
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