Abstract
Abstract. A large oil spill in Iloilo Straight that occurred on July 3, 2020, as well as a possible deliberate, small but frequent oil spill and surfactant contamination in Manila Bay, were mapped. The method employs the Sentinel 2-1C image, which is transformed into principal components to reveal the presence of oil spills and possibly surfactants. Additionally, a gradient boosting algorithm was trained to discriminate between pixels that were contaminated with oil and those that were not. The multi-band image with three principal components with a 99% cumulative explained variance ratio highlights the occurrence of an oil spill in Iloilo Straight. Further, the classified image produced by pixel-based classification clearly distinguishes between water and oil pixels in the said area. The methodology was applied to a Sentinel 2-1C image of Manila Bay, with pixels observed/identified as oil and classified as well. The highest density of supposedly oil-contaminated pixels (large or small but frequent) was observed on the eastern side of Manila Bay (Bataan). While there were no documented oil spills concurrent to the satellite image used, historical reports on the area indicate that the likelihood of an oil spill is extremely high due to the massive amount of shipping activity. Pixels supposedly contaminated by oil spills also occur in areas near ports where oil spills could occur as a result of ship operations. Pixels with the same properties as oil contamination are also visible in areas adjacent to fishponds and aquaculture, where phytoplankton and fish contribute to surfactant contamination.
Highlights
An oil spill accident results in the rapid leakage of a large amount of oil
Biosurfactants are amphiphilic compounds produced by bacteria that can help break down oil
The aforementioned Principal component analysis (PCA) multiband was classified using the CatBoost algorithm to distinguish between pixels contaminated with oil/surfactants and uncontaminated pixels
Summary
An oil spill accident results in the rapid leakage of a large amount of oil. Oil slicks caused by accidents float to the surface of the sea, wreaking havoc on the marine environment (Zhao et al, 2018). Biosurfactants are amphiphilic compounds produced by bacteria that can help break down oil These surfactants form slicks on the sea surface, altering the physical properties of the near-surface layer of the ocean by damping short gravity-capillary waves and suppressing turbulence structures (Parks et al, 2020). They are monolayers, with a thickness of only one molecular layer (typically 2.4–2.7 nm) They are made up of surface-active material (or surfactants) secreted by biota in the water column, such as phytoplankton and fish, and are typically located below the wave-stirred water layer (Wurl et al, 2016; Kurata et al, 2016 as cited by Alpers et al, 2017)
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