Towards spectral-based detection of plastic litter in freshwater environments

Advances in sensor technology have enabled the development of spectral-based remote sensing approaches to detect plastic litter in the environment. This study modelled mixed-pixel conditions for freshwater environments and proposes a new spectral index for detecting plastic litter in these complex environments. Based on the freshwater zone framework, synthetic spectra for mixed-pixel environmental conditions were generated by linearly mixing plastic spectra with those of selected background surfaces. Using the spectral absorption feature of plastics at 1729 nm, several candidate indices were formulated. Index E was selected as the optimal index for plastic detection across all freshwater zones, as it demonstrated the highest separability across all freshwater zones. However, the separability of this optimal index remains constrained to the non-plastic materials assessed in this study. Therefore, extending the separability assessment to a wide range of material substrates in natural freshwater environments is necessary to determine its robustness and improve its transferability to other heterogeneous environments.