Quantitative Approach to Studying Film Pollution of the Sea Surface Using Satellite Imagery

Abstract

Purpose. Numerous studies of various film pollutions (oil spills, surfactants etc.) are performed by means of satellite monitoring of seas and oceans. However, the problem of formal ranking the water areas of the regions under study by frequency and intensity of pollution is still unsolved. The conditions and periodicity of satellite survey can differ greatly depending on the monitoring region that determines both spatial variability of the probability of film pollution detection and the need to take this feature into consideration. Here we attempt to develop a quantitative approach to studying the sea surface film pollutions based on processing of large volumes of satellite optical and radar imagery. Methods and Results. The concept “index of sea surface exposure to film pollutions”, dfpMON, and the method for calculating its quantitative value on a regular spatial grid are proposed. The value of dfpMON is defined as a ratio of the pollution area observed at the site to the area of the analyzed resolution elements (where detection of film pollution is theoretically possible). Within the framework of this approach, the already existing methods for analyzing the results of long-term satellite seawater pollution monitoring were improved due to taking into account the meteorological conditions and the spatial distribution of the observation amount. Having been applied, the proposed approach permitted to study spatial distribution of the non-biogenic film pollutions in the northern part of the Black Sea; they were detected resulting from interpretation of 4428 satellite images obtained in 2019 by the Landsat-8, Sentinel-2A/B and Sentinel-1A/B satellites (2499 cases of pollution processed). The average value of the dfpMON index was 0.012%. Three regions, where the dfpMON values exceeded the average one by more than 30 times were identified. Conclusions. The example of a site in the northern Black Sea has shown the possibility of obtaining representative information products of satellite oceanography, which quantitatively characterize spatial variability of the sea surface film pollution recorded during the long-term episodes of satellite monitoring.