Estimation of hazardous and noxious substance (toluene) thickness using hyperspectral remote sensing

According to the Protocol on Preparedness, Response and Co-operation to Pollution Incidents by Hazardous and Noxious Substances (OPRC-HNS Protocol), hazardous and noxious substances (HNS) is referred to as a chemical substance, except for oil, that impairs the ocean by destroying the environment or are harmful to humans and marine life [1]. The increase in maritime transport of HNSs from the larger and faster ships entails the potential risk of marine HNS spill accidents. Highly toxic HNSs, such as benzene, toluene, and xylene, have serious adverse effects on the human body and various organisms living in the marine ecosystems. Most colorless and transparent HNSs have limitations in visual identification and can cause secondary accidents due to explosions and fires, making human access difficult. So, HNS remote sensing based on satellites and aircraft is important for HNS detection at sea because it has the advantage of monitoring a wide area and observing it at a high resolution. To monitor this HNS spill, we designed and performed a ground HNS spill experiment using a hyperspectral sensor to detect HNS areas and estimate the spill volume. The experiment was conducted at the Centre of Documentation, Research and Experimentation on Accidental Water Pollution (CEDRE) marine pool in BREST, France. The HNS image was obtained by pouring 1 L of toluene into an outdoor marine pool and observing it with a hyperspectral sensor capable of measuring the short-wave infrared (SWIR) channel installed at a height of approximately 12 m (Figure 1). At a height of 12 m, the spatial resolution of the SWIR sensor is 10.3 mm and 5.3 mm in the horizontal and vertical directions, respectively. The pure endmember spectra of toluene and seawater were extracted using principal component analysis (PCA) and N-FINDR. This method has the advantage of not requiring input variables other than the number of pure substances. And a Gaussian mixture model (GMM) was applied to the toluene abundance fraction.