9:30 AM - 9:45 AM
[MIS17-03] Eliminating the interference of water for direct sensing of submerged plastics using hyperspectral near-infrared imager
Keywords:Aquatic plastic pollution, Hyperspectral imaging, Spectral band optimization
Interference from water in the reflectance spectra of plastics is a major obstacle to optical sensing of plastics in aquatic environments. Here we present evidence of the feasibility of sensing plastics in water using hyperspectral near-infrared to shortwave-infrared imaging techniques. We captured hyperspectral images of nine polymers submerged to four depths (2.5–15 mm) in water using an improved imaging system (wavelength range: 900–1700 nm) that combines near-infrared to shortwave-infrared light sources (400–2500 nm coverage). We also developed algorithms to predict the reflectance spectra of each polymer in water using the spectra of the dry plastics and water as independent variables in a multiple linear regression model after a logarithmic transformation. We then successfully predicted reflectance spectra for the four most widely used polymers in water: polyethylene, polypropylene, polystyrene, and polyvinyl chloride. A narrow 1100–1300 nm wavelength range, in which the optical depth of water was smaller than at longer wavelengths, was advantageous for detection of polyethylene, polystyrene, and polyvinyl chloride in water down to the 160–320 µm size range, while a wider 970–1670 nm wavelength range was beneficial for polypropylene reflectance spectrum prediction in water. Furthermore, we found that the spectra of the other five polymers, comprising polycarbonate, acrylonitrile butadiene styrene, phenol formaldehyde, polyacetal, and polymethyl methacrylate, could also be predicted within their respective optimized wavelength ranges, despite being relatively less abundant in the environment. Our findings provide fundamental information for direct sensing of plastics in water on both benchtop and airborne platforms.