Transport and Fate of 137Cs Released From Multiple Sources in the North Atlantic and Arctic Oceans

The North Atlantic and Arctic oceans, along with the North Pacific, are the main reservoirs of anthropogenic radionuclides introduced in the past 75 years. The POSEIDON-R compartment model was applied to the North Atlantic and Arctic oceans to reconstruct 137Cs contamination in 1945–2020 due to multiple sources: global fallout, exchange flows with other oceans, point-source inputs in the ocean from reprocessing plants and other nuclear facilities, the impact of the Chernobyl accident and secondary contamination resulting from river runoff and redissolution from bottom sediments. The model simulated the marine environment as a system of 3D compartments comprising the water column, bottom sediment, and biota. The dynamic model described the transfer of 137Cs through the pelagic and benthic food chains. The simulation results were validated using the marine database MARIS. The calculated concentrations of 137Cs in the seaweed and non-piscivorous and piscivorous pelagic fish mostly followed the concentration of 137Cs in water. The concentration in coastal predator fish lagged behind the concentration in water as a result of a diet that includes both pelagic and benthic organisms. The impact of each considered source on the total concentration of 137Cs in non-piscivorous fish in the regions of interest was analyzed. Whereas the contribution from global fallout dominated in 1960–1970, in 1970–1990, the contribution of 137Cs released from reprocessing plants exceeded the contributions from other sources in almost all considered regions. Secondary contamination due to river runoff was less than 4% of ocean influx. The maximum total inventory of 137Cs in the Arctic Ocean (31,122 TBq) was reached in 1988, whereas the corresponding inventory in the bottom sediment was approximately 6% of the total. The general agreement between simulated and observed 137Cs concentrations in water and bottom sediment was confirmed by the estimates of geometric mean and geometric standard deviation, which varied from 0.89 to 1.29 and from 1.22 to 1.87, respectively. The approach used is useful to synthesize measurement and simulation data in areas with observational gaps. For this purpose, 13 representative regions in the North Atlantic and Arctic oceans were selected for monitoring by using the “etalon” method for classification.

The arsenic spreading over thallus of Saccharina latissima of different habitats of the Barents Sea

The algae Saccharina latissima (Phaeophyceae) and bottom sediment were studied in two places of its habitat in the Zelenetskaya Bay of the Barents Sea: 1) in the zone of shipping traffic and ship parking (ZST&SP) and 2) algae plantations (AP) - the background part of the bay. According to the results of scanning electron microscopy and micro-X-ray spectral analysis, an active new formation of framboidal pyrite, iron oxides-hydroxides, and salt crystals were founded in the bottom sediment in the ZCST&SP of the bay. In the structure of the rhizoids of the thallom algae, inclusions of bottom sediment particles were revealed. The ICP MS method showed that the arsenic content in the S. latissima thallom significantly exceeds its level of presence in the bottom sediment. The maximum content of arsenic in algae from both habitats is determined in the rhizoids, and the lowest in the young part of the plate (meristem). The bottom sediment and thallom of S. latissima from the ZCST&SP contain two to three times more arsenic than the algae on the plantation.

Determination of optimal conditions for processing oil bottom sediments using electrohydraulic effect

Currently, there is an interest in effective technologies that cause minimal environmental harm, have low financial costs and allow you to obtain products with high added value. One of the ways to increase the yield of light and medium fractions from oil bottom sediments is to use the electrohydraulic effect. The electrohydraulic phenomenon is a new industrial method of converting electrical energy into mechanical energy, which occurs without the influence of intermediate mechanical links, with high efficiency. Statistical processing of experimental data was carried out with the identification of the optimal mode of the electrohydraulic effect on the destruction of the oil bottom sediment. The influence of various factors is shown (duration of contact, distance between electrodes, amount of added catalyst, capacitance of capacitor and value of applied voltage). The use of the generalized equation made it possible to determine the following optimal conditions for the destruction of the oil bottom sediment using electrohydraulic treatment: duration 7 min, distance 8 mm, amount of added catalyst 1.5 %, capacitance 0.3 μF, applied voltage 14 kV. In terms of the significance of the coefficient (tr), it should be noted that the dominant factors are the distance between the electrodes and the amount of added catalyst. The individual chemical composition of the light and medium fractions of the original oil residue and the processed oil residue was determined. Comparison of the individual chemical composition of fractions up to 200 °С and 200–300 °С, obtained from the oil bottom sediment and from the hydrogenated product, allows to conclude that the electrohydraulic effect has an effective effect on the destruction of the organic mass of the oil bottom sediment. The optimal conditions for electrohydraulic treatment of the oil residue aere established and it is shown that it is possible to utilize the oil bottom sediments

Features of designing underwater crossings of main pipelines under the conditions of riverbed and floodplain multi-branchness

Многолетняя практика применения регламентных норм учета русловых процессов и механизма транспорта донных руслоформирующих наносов подтверждает надежность принятых расчетов для проектирования и строительства подводных переходов магистральных трубопроводов (ППМТ) через большинство средних и крупных рек России. Но для рек, «перегруженных» донными наносами, традиционные расчетные методики параметров подводной траншеи трубопровода с учетом заносимости оказываются недостаточными и требуют дополнительных решений. Данная проблема была выявлена при строительстве основной и резервной ниток ППМТ ВСТО-2 через реку Амур и обусловлена гидроморфологическими особенностями, спецификой водного режима и значительным расходом донных наносов, характерными для этого водного объекта. В настоящей статье представлена усовершенствованная технология разработки траншеи ППМТ путем создания так называемых ложных траншей на участках с максимальными удельными расходами донных наносов. На примере строительства ППМТ ВСТО-2 (резервная нитка через реку Амур) рассмотрены сложности проектирования и строительства трубопровода при значительных объемах транспорта донных наносов, проанализированы риски строительства в данных условиях, описаны планирование и реализация технического решения по созданию ложных траншей для перехвата донных наносов. The long-term practice of regulatory standards for recoding of river bed evolutions and the transport mechanism of bottom riverbed-building sediments proves reliability of the adopted calculations for design and construction of underwater crossings of main pipelines through majority of medium and large rivers of Russia. However, in respect of the rivers which are «overloaded» with bottom sediments, the conventional calculation methods of parameters of the underwater pipeline trench, considering sediment accumulation, are insufficient and require additional solutions. This problem was identified during construction of the underwater crossing of the ESPO-II pipeline system across the Amur River and is associated with hydromorphological features, specifics of the water regime and significant flow rate of bottom sediments typical for this water body. This article presents an improved technology for developing an underwater trench by establishment of so-called false trenches in the areas with maximum specific flowrate of bottom sediment. Based on the example of construction of the underwater crossing of the reserve pipeline leg, the difficulties related to design and construction of a pipeline with significant amount of bottom sediment transport are considered, risks of construction under these conditions are analyzed, planning and implementation of a technical solution for establishment of false trenches for intercepting bottom sediment are described.

Concentration of organochlorine pesticides in water and bottom sediments of the Dniester River ecosystem

The main goal of this study is assessing the degree of water and bottom sediment pollution in the lower Dniester by organochlorine pesticides. During the study period, the waters of the lower Dniester were in satisfactory state, an excess of EQS was registered only for the γ-isomer of HCH (Lindane), for other pollutants, an excess of EQS was not noted. The main pollutants were accumulated in bottom sediments, which is associated with the input of organic matter, bio-sedimentation. The concentration of γ-isomer HCH (lindane) in bottom sediments exceeded EQS by 5 and 20 times in spring and summer, respectively, DDT exceeded EQS by more than 4 times in summer, POPs (dieldrin and heptachlor) in summer exceeded EQS by 10.8 and 2.5 times, respectively.

Contamination of Urban Watersheds: the Case of Arroio Moinho, Porto Alegre, Rio Grande do Sul, Brazil

This article aims to analyze the contamination of water and bottom sediment at Arroio Moinho (Mill Stream), in Porto Alegre (Rio Grande do Sul, Brazil). From two sample collections, a series of diagnostic measurements were carried out, such as: a) physical-chemical and biological analysis of the water; b) water quality index (WQI); c) metal contamination, granulometric and mineralogical analyses of the bottom sediment; d) total organic carbon (TOC); e) categorization into water quality classes; f) contamination factor (CF) and geoaccumulation index (Igeo) geoindicators; g) analysis of per capita income and population density. The analytical results of the water at the two sample locations exceeded the limits established by Class 4 (restricted use). The WQI revealed the worst level (very bad in 2012 and bad in 2018) at all sampling points. The bottom sediment analysis showed that the spring has a low fine-grained fraction content (3%) and TOC levels between 8 and 17%. However, the sediments revealed high levels of metals such as Zn and Cu and low to moderate Pb levels. These results allowed the stream to be classified as Class 3 in terms of soil quality, requiring identification of the source of the pollution and ongoing inspection to monitor contamination.

An Integrated Horizon Picking Method for Obtaining the Main and Detailed Reflectors on Sub-bottom Profiler Sonar Image

A sub-bottom profiler (SBP) can capture the sediment interfaces and properties of different types of sediment. Horizon picking from SBP images is one of the most crucial steps in marine sub-bottom sediment interpretation. However, traditional horizon picking methods are good at obtaining the main horizons representing the main reflectors while ignoring the detailed horizons. While detailed horizons are the prime objective, many tiny structures caused by interference echoes will also be picked. To overcome this limitation, an integrated horizon picking method for obtaining the main and detailed horizons simultaneously is proposed in this paper. A total of three main process steps: the diffusion filtering method, the enhancement filtering method as well as the local phase calculation method, are used to help obtain the main and detailed horizons. The diffusion filtering method smooths the SBP images and preserves reflectors. Enhancement filtering can eliminate outliers and enhance reflectors. The local phase can be used to highlight all of the reflections and help in the choosing of detailed horizons. A series of experiments were then performed to validate the effectiveness of the proposed method, and good performances were achieved.

Relationship Between Mercury Concentration in Water, Bottom Sediment And Two Mollusc Species (Crassostrea Gasar and Tympanotonus Fuscatus) From a Lagos Creek in Nigeria

Concentration of mercury was investigated in the flesh and shell of two species of benthic mollusc, Crassostrea gasar and Tympanotonus fuscatus and in water and sediment from Makoko Creek, adjacent to the Lagos Lagoon between January to September 2019. Values obtained for physicochemical parameters in Makoko Creek (water temperature- 28.92±0.1°C; pH- 7.73±0.02; salinity- 14.23±0.05 ppt; dissolved oxygen- 5.34±0.02 mg/l; biological oxygen demand- 7.780±0.1 mg/l and chemical oxygen demand- 12.34±0.02 mg/l) were within the acceptable levels for survival, metabolism and physiology of aquatic organism. The concentration of mercury followed decreasing order as sediment >water >flesh >shell across locations for both species. For all the tested samples of C. gasar and T. fuscatus, biowater accumulation factor in flesh and shell were higher than those of bio-sediment accumulation factor. The coefficients of variance (CV %) in shells were lower than those of the flesh for both investigated mollusc species. It was shown that mercury contents of flesh or shells of C. gasar and T. fuscatu are directly affected by those of water and bottom sediment. J. Bio-Sci. 29(1): 143-151, 2021 (June)