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A Sensitivity Analysis of the Standard Deviation of the Copolarized Phase Difference for Sea Oil Slick Observation
摘要： In this paper, a time series of 33 TerraSAR-X copolarized synthetic aperture radar (SAR) imagery collected in Stripmap mode over the Gulf of Mexico in a wide range of incidence angles and sea-state condition is exploited, together with a theoretical framework based on the X-Bragg scattering model, to analyze the effects of noise, angle of incidence, (AOI) and wind speed on the standard deviation of the copolarized phase difference (στc ) evaluated over sea surface with and without oil slicks. This large data set represents an unprecedented opportunity to analyze, for the ?rst time, the in?uence of both SAR acquisition and surface parameters on the broadening of the copolarized phase difference probability density function (pdf), (τc). Experimental results show that the X-Bragg scattering model, here adopted to predict the sea surface pτc (τc), gives an understanding of the increasing trend of στc with respect to AOI. It is shown that the noise signi?cantly contributes to broaden pτc (τc) over both slick-free and slick-covered sea surface, while the effects of low-to-moderate wind regimes are negligible. In addition, στc exhibits a larger sensitivity to the scene variability, if compared to single-polarization intensity channels, over both slick-free and oil-covered sea surface. This sensitivity is more pronounced at lower AOIs due to the higher noise equivalent sigma zero (NESZ) that affects larger AOIs.
关键词： Oceans,oil pollution,synthetic aperture radar,radar polarimetry
更新于2025-09-23 15:22:29
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Comparative laser-induced fluorescence evolution analysis of different oil pollution on the terrestrial surface
摘要： We have studied the time evolution of the laser-induced fluorescence spectra of oil pollution on the terrestrial surface at a fluorescence excitation wavelength of 355 nm. The paper presents a block-diagram of the experimental laboratory setup and data processing results of the laser-induced fluorescence spectra for the oil-polluted soil and sand and conducts a comparative analysis of the fluorescence spectra evolution of pollution due to spilling crude oil and heavy and light petroleum products.
关键词： petroleum products,laser-induced fluorescence,terrestrial surface,oil pollution
更新于2025-09-12 10:27:22
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Spectral signatures of fluorescence and light absorption to identify crude oils found in the marine environment
摘要： To protect the natural marine ecosystem, it is necessary to continuously enhance knowledge of environmental contamination, including oil pollution. Therefore, to properly track the qualitative and quantitative changes in the natural components of seawater, a description of the essential spectral features describing petroleum products is necessary. This study characterises two optically-different types of crude oils (Petrobaltic and Romashkino) – substances belonging to multi-fluorophoric systems. To obtain the spectral features of crude oils, the excitation-emission spectroscopy technique was applied. The fluorescence and light absorption properties for various concentrations of oils at a stabilised temperature are described. Both excitation-emission spectra (EEMs) and absorption spectra of crude oils are discussed. Based on the EEM spectra, both excitation end emission peaks for the wavelength-independent fluorescence maximum (Exmax/Emmax) – characteristic points for each type of oil – were identified and compared with the literature data concerning typical marine chemical structures.
关键词： seawater,Excitation-emission spectra,fluorescence spectroscopy,oil pollution,absorption spectra
更新于2025-09-09 09:28:46
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Light penetration in seawater polluted by dispersed oil: results of radiative transfer modelling
摘要： The downwelling light in seawater is shaped by natural seawater constituents as well as by some external substances which can occur locally and temporally. In this study we focused on dispersed oil droplets which can be found in seawater after an oil spill or in the consequence of intensive shipping, oil extraction and transportation. We applied our modi?ed radiative transfer model based on Monte Carlo code to evaluate the magnitude of potential in?uence of dispersed oil droplets on the downwelling irradiance and the depth of the euphotic zone. Our model was validated on the basis of in situ measurements for natural (unpolluted) seawater in the Southern Baltic Sea, resulting in less than 5% uncertainty. The optical properties of dispersed Petrobaltic crude oil were calculated on the basis of Mie theory and involved into radiative transfer model. We found that the changes in downwelling light caused by dispersed oil depend on several factors such as oil droplet concentration, size distribution, and the penetration depth (i.e. vertical range of oil droplets occurrence below sea surface). Petrobaltic oil droplets of submicron sizes and penetration depth of 5 m showed a potentially detectable reduction in the depth of the euphotic zone of 5.5% at the concentration of only 10 ppb. Micrometer-sized droplets needed 10 times higher concentration to give a similar effect. Our radiative transfer model provided data to analyse and discuss the in?uence of each factor separately. This study contributes to the understanding of the change in visible light penetration in seawater affected by dispersed oil.
关键词： radiative transfer,droplet size distribution,dispersed oil,Oil pollution,downwelling irradiance
更新于2025-09-04 15:30:14