The Fluorescence Ocean Return and Observations (FLORO) Experiment: An investigation of marine plastic debris using fluorescence spectra and lifetime

Plastics are the most common marine debris; they can travel long distances and accumulate in convergence zones, eddies, and gyres. Passive imaging spectrometer data exploit unique plastic reflectance features in the NIR and SWIR, but this approach is limited to surface observations and is further impacted by foam, sun glint, clouds, atmospheric aerosol, and illumination/observation geometries. Building upon near/below surface studies of phytoplankton and oil spills using laser induced fluorescence (LIF), we investigate the capability of LIF to identify and characterize near surface and submerged marine plastic debris through our project the FLORO Experiment. Beyond marine plastic debris, we will include targets (e.g., phytoplankton and chromophoric dissolved organic matter or CDOM) to demonstrate sufficient differentiation in aquatic scenes. In addition to spectral measurements, we use time-correlated single photon counting (TCSPC) to measure fluorescence lifetime. The laboratory experiment consists of a tunable pulsed laser as the excitation source, a photon-sensitive fast detector, and spectral filters tuned to the targets peak emission wavelength. The proposed fluorescence lidar measurements would operate diurnally and at depth, filling existing observational gaps. The results from FLORO will inform a multi-instrument mission architecture to achieve global coverage for marine debris identification, characterization, and monitoring.