ИСТИНА

Проект направлен на изучение процессов переноса и трансформации пластикового мусора (главным образом макро, то есть в диапазоне размеров от нескольких миллиметров до десятков сантиметров) в речных устьях и речных плюмах на основе натурных наблюдений и численного моделирования. Основная рабочая гипотеза, выдвигаемая авторами проекта, заключается в следующем: плавающий пластиковый мусор в прибрежном океане в основном сосредоточен в речных плюмах, связанных с материковым пресноводными стоком, и его динамика в значительной степени определяется динамикой этих плюмов. Исследование будет сосредоточено на репрезентативных регионах, представляющих различные условия речного стока и антропогенных нагрузок, а именно на участках, прилегающих к Керченскому проливу и устью реки Мзымта в Черном море, а также отдельных шельфовых районах арктических морей (Россия); район к северу от эстуария Ла Плата рек Парана и Уругвай (La Plata River) вблизи устья лагуны Патос (Patos Lagoon) на шельфе штата Рио Гранде до Сул в Южной Атлантике (Бразилия); и устьев двух рек в Китае, впадающих в Тайваньский пролив Южно-Китайского моря - реки Жиулонг (Jiulong River) в провинции Ксиамен и реки Жемчужной (Чжуцзян, Zhujiang или Pearl River) в районе г. Гонконг. Научную новизну проекта составит использование новых методов исследования морского мусора и пластиковых отходов, в том числе: - Автоматизированное обнаружение и картирование морского пластика с помощью лазерного зондирования с борта судна; - Использование лагранжевой гидродинамической модели речного плюма для воспроизведения траекторий движения макроскопических объектов пластикового мусора в океане; - Анализ таксономической структуры биообрастаний на объектах пластикового мусора в море для дифференциации объектов речного и иного происхождения; - Изучение влияния обрастаний на объектах морского и речного пластикового мусора на их гидродинамические характеристики.

Plastic pollution is known to have affected significantly ecosystems at the sea surface, seabed, water column, and shorelines [e.g., Woodall et al., 2014]. Plastic debris have been encountered in at least 693 marine biological species [Gall and Thompson, 2015]. The impact of plastic on marine life includes entanglement, ingestion, contamination by persistent pollutants, and introduction of invading species [Derraik, 2002]. Although many studies have investigated ocean plastic pollution, relatively few of them focused on its origins and pathways. While all principal sources and pathways have been identified [Van der Wal et al., 2015], their individual contributions to worldwide plastic pollution are still unknown [Bruge et al., 2018]. Rivers are recognized as a major source for plastic litter entering the ocean; however, only a few studies attempted to quantify it. For example, [Lechner et al., 2014] estimated the mean flux of litter into the Black Sea from the Danube River as 174 kg per hour. On a global scale, the total discharge of plastic waste from rivers into the ocean is estimated between 1.1 and 2.4 million metric tons per year [Lebreton et al., 2017]. Given that the overall annual land-based discharge of plastics into the ocean is believed to range between 4.8 and 12.7 million tons [Jambeck et al., 2015], this means that the World’s river estuaries, which occupy only a small fraction of the global coastline, are likely accountable for up to 50% of all plastic waste in the ocean. This is due to not only the fact that they accumulate waste from extensive watersheds, but also the ability of buoyant river plumes in the ocean propagate to large distances offshore. While floating litter locally washed away or blown by wind from the coast will in most cases return to the land soon because of the action of waves and near-shore currents, the plastic waste introduced with river discharges can be dragged far away from the shore by the inertial or wind-driven motion of the plume and remain afloat for indefinitely long time. Therefore, understanding the dynamics of river plumes and their inter-relations with buoyant or suspended plastic litter under various forcing conditions is a key to identifying the pathways of plastic pollution in different regions, specifying the areas of maximum exposure, and developing strategies for mitigation. The proposed project seeks to investigate the relations between the buoyant plumes formed by fluvial continental runoffs and plastic debris (mainly macro, but also micro) by means of in situ observations and numerical modeling. The study will be focused on specific model regions representing different conditions of river discharges and anthropogenic loads, namely, the areas adjacent to the Kerch Strait and the Mzymta River mouth in the Black Sea (Russia), the Patos Lagoon mouth in South Atlantic (Brazil), and … (China?). The principal working hypothesis to be tested is as follows: the floating plastic litter in the coastal ocean is mainly concentrated in the river plumes associated with continental freshwater discharges, and its dynamics is largely controlled by the dynamics of the plumes. The latter can be traced based on their reduced salinity and high content of suspended matter by means of in situ measurements, remote sensing, and hydrodynamic modeling. Firstly, we will conduct field investigations of marine plastics in all areas selected for this study. These measurements will be aimed at obtaining detailed spatial maps of the concentrations of floating plastic litter in the coastal ocean and evaluating to what extent the patterns seen in these maps are coincident with the buoyant river plumes as manifested in salinity, density and turbidity fields. We will also focus on details of the litter distributions inside the plumes. To this end, the observations of plastics will always be accompanied by detailed hydrographic mapping. In addition to the conventional observational methods such as visual registration and video recording, as well as sampling by towed nets, we intend to try a novel technique for automatic detecting floating macroplastics by means of a ship-borne ultraviolet fluorescent LiDAR. The instrument in possession of the Russian team was originally designed and extensively tested for measuring the concentrations of chlorophyll-“a” and dissolved organic matter based on their fluorescence induced by laser pulses [Pelevin et al., 2017, Zavialov et al., 2018]. If the laser ray accidentally hits a piece of floating marine plastic, this results in an isolated, abnormally high amplitude signal in the fluorescent response. In the previous applications of the LiDAR, such outliers have been filtered out from the data record. However, they may hold important information on plastic litter. If properly validated and methodologically substantiated, this approach may result in great advancement in detecting and mapping marine plastics, covering large areas at high spatial resolution. Secondly, we will apply numerical modeling to simulate the dynamics of the plumes carrying litter. The principal instrument to be used in this respect is STRiPE (Surface-Trapped River Plume Evolution) model recently developed by the Russian team with the specific purpose of simulating buoyant river plumes [Osadchiev and Zavialov, 2013]. This model is based on fully Lagrangian approach, therefore, it should be an ideal tool for investigating the fate of floating litter as Lagrangian particles travelling within the plumes. The questions to be addressed include the description of the pathways and dispersion patterns for marine plastics in all study areas under different conditions of wind forcing and ambient coastal circulation. We will also evaluate the longer-term fate of the floating litter and estimate how much of it (and where in the selected study regions) eventually settles at the coast while the rest remains in the sea for indefinitely long time. Model experiments will allow establishing links between the properties of the river discharge flow, such as the discharge rate and the Froude number, and the characteristics of the associated litter dispersal. Thirdly, we will conduct process-oriented studies of the transformaion of plastic litter in estuaries and river plumes, biological fouling of macroplastic debris, and their role in transporting potentially invasive species in planktonic and algal communities. The 3 national teams of the project consortium will complement each other with respect to the fields of their primary expertise, as well as the oceanographic and socio-economic conditions of the focal areas of their research.