The current levels of aliphatic (20 μ g/L, IR method) and polycyclic aromatic (90 ng/L, fluorescence method) hydrocarbons in suspended particulate matter of surface water and in bottom sediments have been determined in the coastal areas of the Caucasian sector of the Black Sea within the boundaries of the Russian Federation (in September 2021, May and September 2022). Despite the decrease in hydrocarbon concentrations in surface water over recent years, the Kerch Strait belongs to the most polluted area, as before. Accumulation of hydrocarbons occurs in bottom sediments, which leads to an increase in their content in C _org (for aliphatic hydrocarbons, up to 14.2

В работе представлены результаты исследования изменчивости биооптических характеристик вод средней Волги на участке протяженностью 500 км от г. Нижний Новгород до пгт. Камское устье 9-17 сентября 2023 года. Измерения проводились непрерывно с борта движущегося катера с помощью флуоресцентного морского лидара УФЛ-9. По лидарным данным построены карты хлорофилла “а”, показателя поглощения а(440), как индикатора, окрашенного растворенного органического вещества, и минеральной взвеси для прямого и обратного маршрутов. Указаны диапазоны вариаций, рассмотрено проявление притоков и влияние метеоусловий. The paper presents the results of a study of the variability of the bio-optical characteristics of the waters of the Middle Volga in a 500 km section from Nizhny Novgorod to the village. Kama estuary September 9-17, 2023. Measurements were carried out continuously from the side of a moving boat using the fluorescent marine lidar UFL-9. Based on lidar data, maps of chlorophyll “a”, the absorption index a(440), as an indicator, colored dissolved organic matter, and mineral suspension for direct and reverse routes were constructed. The ranges of variations are indicated, the manifestation of inflows and the influence of weather conditions are considered.

Приведены результаты исследования состояния акватории Керченского пролива по данным портативного трехканального гиперспектрометра ЭММА, работающего с борта движущегося судна в течение светового дня с разрешением по направлению движения в несколько метров. По измеренным спектрам коэффициента спектральной яркости моря рассчитаны спектры показателя поглощения света водой в акватории Керченского пролива. Верификация этих данных проведена по результатам измерений глубины видимости диска Секки на станциях. Рассчитанные далее по спектрам суммарного поглощения света водой концентрации трех основных природных компонентов, средние по глубине проникновения света в толщу воды, были сопоставлены с измерениями в пробах, отобранных с поверхности воды по маршруту. Расхождение в этих оценках в некоторых районах говорит о неравномерном по глубине распределении компонентов, что было подтверждено при вертикальном зондировании на станциях; при калибровке результатов дистанционного зондирования данные из этих районов не использовались. Полученные по измерениям трехканальным гиперспектрометром данные дали осредненное по глубине распределение природных компонентов в акватории Керченского пролива, а также позволили получить некоторые характеристики антропогенного воздействия, зафиксированного со спутников. Study of the state of the Kerch Strait water area was carried out using data from a portable three-channel hyperspectrometer EMMA (Ecological Monitoring of Marine Areas), operating from board a moving vessel during daylight hours with a resolution of several meters along the route. Based on the measured spectra of the sea spectral radiance coefficient, the spectra of the light absorption index by water in the Kerch Strait were calculated. Verification of these data was carried out at the stations by measurements of Secchi disk visibility depth. The concentrations of the three main natural components averaged over the depth of light penetration into the water column were calculated from the spectra of total light absorption by water. They were compared with measurements in surface water samples taken along the route. The discrepancy in these estimates in some areas indicates a nonuniform depth distribution of the components, which was confirmed by vertical sounding at the stations; these areas are not used for calibration of remote sensing results. The EMMA data showed the distribution of the natural components in the water area of the Kerch Strait averaged over the depth of light penetration. It also made it possible to estimate some characteristics of the anthropogenic impact recorded by satellites.

The interaction of a spherical solid particle and a gas bubble in a liquid subjected to ultrasonic action is numerically studied. The ultrasonic parameters are chosen in such a way that the acoustic wavelength will be much larger than the sizes of both the bubble and the particle. The acoustic pressure field at a distance to the bubble is assumed to be uniform. In the absence of a particle, the flow is a spherically symmetric flow, and the velocity of the liquid–gas interface is found from the Rayleigh–Plesset equation. The problem considered in this paper is a generalization of the classical problem without a particle. The control of the movement of solid particles around the gas bubble is important for the flotation process, which is widely used in the mineral ore beneficiation technology. The problem is considered for high frequency and small or finite vibration velocity amplitude. In the leading order of smallness and taking into the viscosity of a liquid, a pulsating flow is found for the case of a heavy particle that remains its immobility. In the following order, the mechanisms of generation of an averaged flow in the liquid volume and near its boundaries are considered. Using the obtained averaged flow, the averaged vibrational force acting on the particle and its dependence on the distance to the bubble surface are determined. It is shown that this force is an attractive force. A comparison is made with the calculation data in the inviscid approximation. It has been found that, at small distances from the bubble, there is a deviation of the calculated value of vibrational force from the value known from the analytical expression, according to which this force is proportional to the square velocity gradient of pulsations. The results obtained demonstrate that, taking into account the viscosity of a liquid leads to a larger value of the averaged vibrational force near the bubble than the inviscid approach.

The current level and origin of hydrocarbons (HCs) was determined: aliphatic – AHCs and polycyclic aromatic – PAHs (September 2021, May and September 2022) in suspended particulate of surface waters (for AHCs – 20 µg/l; PAHs – 130 ng/l, fluorescent method) and in the bottom sediments of the coastal areas of the Caucasian sector of the Black Sea of the Russian Federation. Despite the decrease in HC concentrations in surface waters in recent years, the most polluted areas include, as before, the Kerch Strait. HC accumulate in bottom sediments, which leads to an increase in their content in the composition of Corg (up to 14.2% in the Tuapse region and 13.1% in the Novorossiysk region). It has been established that, along with pollution, HC levels are greatly influenced by natural processes (the productivity of the area, fluid flows from the sedimentary mass).

Based on the materials of 20 expeditions of the IO RAS conducted in various areas of the coastal zone of the Russian sector of the Black Sea in the period from 1999 to 2021, empirical equations the relationship between the relative transparency (depth of visibility of the white disk Zd) and the mass concentrations of the total suspended matter-SM and its mineral – SMM and organic – POM fractions (Csm, Csmm and Csom, respectively) were obtained. The values of Zd were recorded in the range from 0.1 to 21 m, the concentrations of SMM – from 0.11 to 104 mg/L, POM – from 0.09 to 2.0 mg/l and chlorophyll a (Ca) – from 0.03 to 4.4 mcg/l. The relative abundance of the POM in the suspension ranged from 1.1 to 48.7%. The estimation of the error in the calculations according to these equations is carried out. The coefficients of determination r2 = 0.85 (for lgCsm and lgCsmm ) and 0.72 ( for lg Csom). The influence of the concentration of POM – on the accuracy of the calculation of Csmm and the concentration of chlorophyll a on the accuracy of the calculation of Csom was revealed. It is concluded that it is possible to use empirical formulas related to the entire array to calculate the concentrations of these fractions of suspension in the entire studied water area. It is proposed to consider the method of estimating the content of suspension fractions based on the obtained empirical equations as a regional variant of the method of passive sounding of the upper layer of the sea using a white disk.

We present the results of optical studies of organic matter in the surface water layer of Gelendzhik Bay and adjacent areas of the Black Sea. The efficiency of remote laser sensing for determining the relevant grid of sampling stations is shown. A weak contribution of terrigenous dissolved organic matter (DOM) has been established. A slight increase in the concentration of humic substances was demonstrated near the mouth of the Su-Aran River. The maximal content of biolabile DOM is typical for coastal regions in Gelendzhik Bay. In the eastern part of the bay high levels of DOM, particulate organic matter (POM), as well as the maximum content of DOM and POM together, were observed on the basis of fluorescent lidar data.

Оперативный мониторинг прибрежных морских акваторий требует использования дистанционных средств наблюдения со спутников или воздушных носителей (самолетов, вертолетов, дронов), а также с борта движущихся судов. В работе рассмотрены возможности калибровки таких пассивных оптических измерений по спектрам коэффициента спектральной яркости, характеризующих водную толщу. Этот первый этап калибровки основан на разности спектров поглощения света атмосферными газами и водной средой. Вторым этапом калибровки дистанционно измеренных данных является сравнение их с данными, полученными в отобранных пробах воды. В работе дан метод отбора для этих целей тех проб воды, концентрации природных компонент в которых соответствуют концентрации, средней по глубине просвечиваемого светом слоя. Все выводы подтверждаются результатами комплексных измерений в восточной части Каспийского моря.

The paper presents the results of an analysis of the main pollutants (heavy metals, pesticides, detergents, hydrocarbons) in water, suspended particulate matter, and bottom sediments, as well as the hydrophysical fields in the Kerch Strait and adjacent Black Sea water area (2019–2020 ). In all seasons, the concentrations exceeded the maximum permissible values, often significantly, for a number of pollutants, such as hydrocarbons, certain metals, and pesticides. The highest pesticide concentrations were documented in summer, while those of other pollutants peaked in spring. It was observed that the maximum concentrations of most pollutants, as well as dissolved methane and mineral suspended matter, were generally confined to the plume of Sea of Azov waters entering the Black Sea; therefore, their distributions were largely controlled by currents and stratification in the strait.

Based on data of the three-channel hyperspectrometer designed for remote passive optical observations from a moving vessel at a frequency of 1 Hz, a distribution of areas of increased turbidity in the Kerch Strait was obtained. Comparison of these results with the analysis of temperature, salinity, and direction of water flow in depth measured at the stations, as well as with the flow system data made it possible to attribute various areas of the strait to the Azov Sea or the Black Sea water masses. It is shown that the penetration of the Azov Sea waters into the Black Sea at a relatively weak northeast wind proceeds in jets, in some places, the width of the jets themselves and the transition areas between them does not exceed several hundred meters. The different types of waters in the strait differ most strongly in the concentration of suspended matter which might be the result of the anthropogenic influence. Obtaining express information on the composition of waters based on complex measurements during vessel movement and at stations is important if it is necessary to assess the possible spread of polluting factors in the water area of the Kerch Strait and off the Black Sea coast.

The results of studying the concentration and composition of hydrocarbons in the suspension of surface water and in the surface layer of bottom sediments in the Kerch Strait in July 2020 in comparison with 2019 and with earlier studies in other regions of the Black Sea are presented. Despite the high concentrations of aliphatic hydrocarbons (especially in the water of the strait (on average 78 μ g/L) and in coarse-grained sediments (47 μ g/g), the composition of alkanes did not correspond to the oil composition due to the rapid transformation of petroleum aliphatic hydrocarbons. The factor analysis revealed that the pollution has two sources: the main, pyrogenic (from transport) and, to a lesser extent, the oil one.

Remote passive optical measurements of the state of waters in water basins studied from ships, airborne platforms, or satellites are most informative because they cover a large territory and are performed at a high frequency. At the same time, for correct estimation of the remotely obtained data some in situ measurements of the state of waters in water samples, taken at a limited number of points, should be performed. Studies carried out in the coastal regions of the Middle Caspian Sea were used as an example to identify the conditions when such point-like measurements are suitable for calibrating the remote hydro-optical measurements by the Ecological Monitoring of Marine Waters (EMMA) complex onboard a cruising vessel. The limitations identified were explained through analysis of the structure of coastal waters; this structure was measured through vertical sensing of water at stations and by operating a flow-through system for determining the temperature and salinity of surface waters. An algorithm is proposed for selecting water samples suitable for calibration of remote measurement by correlating them with Secchi disk depth, and the efficiency of this method is demonstrated. We showed what hydrophysical conditions should be taken into consideration for the preliminary selection of water sampling sites for calibrating remote measurements.

—It is known that linearly polarized translational vibrations can multiply the capture cross section of deposited solid particles by a single gas bubble suspended in a liquid. This fact is of great theoretical and practical importance for using vibrations to intensify the flotation process, which, however, involves multiple rising bubbles. The present work studied the capture of solid particles by a gas bubble ensemble in liquid exposed to high-frequency small amplitude vibrations in two-dimensional formulation numerically. The numerical solution was obtained using ANSYS Fluent software. The obtained fields of the averaged and pulsating components of the flow velocity were then processed by our own code in order to calculate the trajectories of small particles from a “cloud” located in the computational domain. The description of forces acting on the particle took the added mass of the fluid, gravity, the Archimedean force, Stokes force, Basset force, and the vibrational force due to the inhomogeneity of the pulsating field into account. The calculations were performed for millimeter air bubbles in water with particle characteristics significant for the flotation process. The influence of vibrations is shown to be significantly attenuated within the bubble ensemble due to the “screening” effect, which peaks at the highest vibration frequency and depends weakly on the distance between the bubbles. However, vibrations of a lesser frequency, at which the gas in bubbles is compressible, are still able to penetrate deep into the liquid volume at a sufficient excitation intensity, and thereby increase the particle capture region.

The possibilities of using satellite imagery of modern remote sensing satellites, both optical and radar, to study anthropogenic pollution and the state of the marine environment of the Kerch Strait are discussed. It is shown that satellite data and images allow one to quickly obtain practically complete information about a particular phenomenon and emergency situation in the strait.

The results of studying the content and composition of aliphatic hydrocarbons (AHCs) and polycyclic aromatic hydrocarbons (PAHs) in the suspended particulate matter of the surface water layer and in the surface layer of bottom sediments in Kerch Strait in April and September 2019 are given in comparison with other areas of the Black Sea. In spite of the high concentrations of AHCs, in waters of the strait (110–160 μg/L) and in sandy sediments (16–63 μg/g) in particular, the composition of alkanes does not correspond to oil because of the rapid transformation of oil AHCs. The contamination of water and sediments in the strait by oil HCs results in the presence of naphthenic-aromatic compounds in alkanes, the domination of phytane over pristine, and the domination of pyrogenic and to a smaller rate of oil HCs in the composition of PAHs.

Ship-based measurements of the biooptical characteristics of Lake Issyk-Kul waters with the passive remote sensing complex Ecological Monitoring of Marine Areas (EMMA), as well as measurements in water samples, were used to develop and test a new technique for estimating the composition of oligotrophic waters. It is the third part of the method for remote estimation of the concentrations of the main natural constituents in sea or lake waters using the spectrum of light absorption by pure sea water which we developed earlier for mesotrophic and eutrophic waters. This technique was used to estimate the concentrations of pigments of phytoplankton, colored organic matter, and suspension and their distribution over the lake water basin during three-day experiment in July 2018.

The results of studies of hydrophysical and bio-optical structure of the outflow of the Shakhe River, conducted during the IO RAS expedition “Black Sea-2018” at the marine site near Golovinka on the RV “Ashamba” on 1–2 June 2018, are presented. Information synchronously obtained, both with the help of remote sensing satellites (radar and optical sensors), infrared portable pyrometer, and onboard the RV (CTD probe as part of a shipboard flow system), was used. At the same time, seawater samples were taken from the sea surface layer, followed by laboratory analysis of their bio-optic and geochemical characteristics. Hydrophysical characteristics and submesoscale structure of the Shakhe River outflow at the test site studied both remotely and contactly, gave identical results. This makes it possible to further efficiently use these instruments on board of RVs to study the river outflows in the Black Sea. At the same time, portable infrared pyrometers make it possible to obtain significantly better spatial resolution in terms of temperature compared with satellite instruments, while satellite images can detect river outflows in the sea, their boundaries and structure.