An integrated approach for marine litter hot spots identification

Abstract

Marine litter is defined as any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment, and it is among the most important environmental problems which are affecting the sea nowadays. In this work, we present an integrated approach to the marine litter hot spots identification. The results come from a coordinate activity of filed campaigns, satellite monitoring and numerical model simulations. A dynamical view of the marine litter is at the core of the approach, so numerical models for the simulation of the floating pollutants dispersion in the sea are one of the key tools involved in the hot spot identification. Among all the available codes, the class of Lagrangian models is considered the most suitable to simulate the journey of the marine litters; specifically, the NOAA PyGnome software is the tool implemented for the purpose. The ability to monitor wide and hardly accessible coastal areas, using remote sensing imagery, is the second source of independent information used to identify the marine litter accumulation prone area. The routinely and operationally available ESA Sentinel 2 mission data has been considered for the purpose. Due to the coarser spatial resolution of the remote sensing data, with respect the typical marine litter size, the identification of floating or beached debris requires the analyses of the spectral reflectance, for each pixel in an image, searching for spectral signatures of the marine litter presence. Both modelling and satellite results are combined to pick up the coastal areas to be likely candidates for marine litter hot spots. Results of the method are encouraging, since the simulated accumulation areas clearly emerge from the background and the link to the sources is straightforward because of each simulated trajectory allows to know the origin of each beached Lagrangian element. It is expected the presented approach will help in planning actions to remove beached debris and to identify the sources mostly contributing in input the floating waste material in the marine environment. The method currently is applied on the Adriatic basin as part of the MARLESS INTERREG IT-HR project.