A case study on the Po Delta in Italy on advancing the synergy of monitoring strategies for leakage litter from source-to-sink

There is a continuous societal interest in integrated monitoring strategies with a source-to-sink perspective about plastic waste for improved and targeted mitigation approaches. We present an exploratory investigation towards harmonising and having synergy of multi-scale approaches (i.e., low-cost camera, drone, model, satellite) for floating matter with a focus on plastic litter around the Po Delta region in Italy. Very fine to moderate pixel resolution imaging of the locations with suspected or known plastic litter presence was achieved using camera technologies on ground-fixed, airborne and satellite platforms. Very fine pixel remotely sensed images were used to detect and identify litter objects directly through visual inspection, anomaly detection and machine learning algorithms. Numerical model input parameters were obtained via visual and image analyses from the field surveys. Indirect observations of litter dynamics were assessed using numerical solutions, Sentinel-2/3 total suspended matter end-products. In-situ water sampling complemented the monitoring and net trawl harvested samples revealed a large portion of the plastics were containing polyethylene, polypropylene and polystyrene polymers. The assessment of our proof-of-concept modular observation approach showcased the possible harmony of monitoring technologies relevant for an improved holistic understanding of source-to-sink dynamics of litter. With further scientific evidence-based exploration our proposed monitoring concept could lead to an operational observing system dedicated to gathering information crucial for stakeholders involved in the mitigation and removal of plastics in the environment.