Biogeochemical assessment of changes in water composition after a large landslide in winter

Впервые в декабре 2018 г. при температуре –32 оС произошел оползень с крутого берега Бурейского водохранилища (Дальний Восток России), на водосборе которого встречаются островная, прерывистая и сплошная многолетняя мерзлота. Оползень общим объемом 24.5 млн. м3 полностью перекрыл бывшее русло реки Бурея, создав угрозу работе Бурейской ГЭС и затопления населенных пунктов. Для решения проблемы восстановления проточности были проведены крупномасштабные взрывные работы с использованием тротила, а также кумулятивных зарядов с гексогеном. Взрывные работы повлияли на спектр органических веществ и миграционную способность многих элементов в воде вокруг оползня. Методом газовой хроматографии в воде обнаружены метанол и метилированные производные бензола, их концентрация увеличивалась после дренажа воды сквозь тело оползня. Среди летучих органических веществ значительную долю составляли продукты трансформации высокомолекулярных природных соединений, которые принимают участие в процессах метаногенеза и метанотрофии (метанол, ацетаты, ксилолы) и толуол, основной продукт деструкции тротила. Исследования элементного состава воды в зоне влияния оползня до и после проведения взрывных работ были проведены методом масс-спектрометрии с индуктивно связанной плазмой на ICP-MS ELAN-9000 (Perkin Elmer). Ниже тела оползня отмечено увеличение содержания Al, Fe, W, Cr и Pb. Наиболее существенные изменения качества воды произошли после проведения взрывных работ. В воде искусственного канала отмечено резкое снижение содержания элементов (Fe, Cu, Zn и Pb) и увеличение концентрации ртути. For the first time in December 2018, at a temperature of 32°C below zero, on the steep bank of the Bureiskoe Reservoir (Far East, Russia) a landslide occurred. Insular, discontinuous, and continuous permafrost on the catchment basin of the reservoir is recorded. A landslide with a total volume of 24.5 million m3 completely blocked the former channel of the Bureya River. It created a threat to the operation of the Bureya Hydro-electric Power Station and flooding of settlements. Blasting operations with use of trinitrotoluene and shaped charges with hexogen were carried out for restoring the flow. Methanol and methylated benzene derivatives were detected in water by gas chromatography; its concentration increased after the water was drained through the landslide body. In the water of the artificial channel, decrease in the lithogenic elements (Fe, Cu, Zn, and Pb) content and an increase in the mercury concentration were recorded. Among the volatile organic substances, a significant portion belonged to the products of transformation of high molecular natural compounds that take part in the processes of methanogenesis and methanotrophy (methanol, acetates, and xylenes) and toluene, the main intermediate of trinitrotoluene. The studies of the elemental composition of water in the zone of influence of the landslide before and after the blasting operations were carried out by inductively coupled plasma mass spectrometry on an ICP-MS ELAN-9000 (Perkin Elmer). Below the landslide body, an increase in the content of Al, Fe, W, Cr and Pb is noted. The most significant changes in water quality occurred after the blasting operations. In the water of the artificial channel, a sharp decrease in the content of elements (Fe, Cu, Zn and Pb) and an increase in the concentration of mercury have been recorded.

Change in Abundance and Activity of Microbocenoses in the Area of Influence of a Large Landslide at the Bureya Reservoir

The results of field and experimental microbiological studies of water, soil, and rock samples in the influence zone of large landslide are presented. The landslide occurred in December 2018 and blocked the Bureya Reservoir from coast to coast. An artificial channel was created to restore the hydrological regime with the use of TNT (trinitrotoluene) and RDX (hexogen). A comparative analysis of the abundance of cultivated heterotrophic bacteria around the landslide body and in the artificial channel is carried out. The activity of microbial communities in relation to easily available (peptone, lactate, and starch) and difficult-to-mineralize humic compounds is also determined. With the use of spectrometry and gas chromatography, it is shown that an increase in the diversity of aromatic compounds in water is accompanied by an increase in the abundance of heterotrophic bacteria. A number of toxic substances, including methanol and methylated benzene derivatives, are found among the dominant components in the water. Its concentrations increased after the water drained through the landslide body and after imploding works. Many of the volatile organic compounds may have been products of microbial metabolism when water interacts with rocks. A hypothesis on the role of methanotrophic and methylotrophic bacteria in the genesis of methanol and toluene is discussed.

Extreme-flood-related peat blocks: An Anthropocene analogue to ancient coal-forming environments

Coal clasts associated with extreme floods are prone to survive and maintain their large size, contrary to the general belief that distance from the parent peat layer reduces the size of transported clasts. Contrary to apparent logic, moreover, a second flood event favors the preservation potential of such soft organic clasts, this being the minimal fragmentation. An Anthropocene example from an urban park in Spain demonstrates that peat clasts up to 1 m long can survive due to flotation for a distance of almost a hundred meters and are well preserved and stabilized thanks to a second flood. These peat blocks were generated by catastrophic flooding of urban peatlands along the Ebro River (city of Zaragoza) during exceptional rainfalls in Iberia. The water flow from the Ebro River flooded the peatland at the surface of the meander, ripping up peat clasts from a shear or detachment level formed by an indurated level characterized by rounded quartzite pebbles, which acted as a hydrological discontinuity surface. Extensive evidence of the paleoflow direction is provided by oriented crushed reeds and the widespread occurrence of imbricated and thrusted peat blocks on the eroded and exposed peatland and in the main urban accumulation areas. To be specific, peat blocks and minor clasts accumulated in four areas associated with different modes of transport and topographic steps. From proximal to distal these are as follows: i) a proximal rim including thrusted peat blocks on the eroded peatland, ii) two intermediate accumulation zones associated with topographic steps in the park, characterized by peat-clast imbrication, iii) gravity-fall peat clasts deposited in an artificial channel in the park, and iv) peat rafts of more than 1 m in diameter scattered over the surface of the park (at a distance of 90 m from the eroded peatland).

Influence of interaction between surface-modified magnetic nanoparticles with infectious biofilm components in artificial channel digging and biofilm eradication by antibiotics in vitro and in vivo

Artificial channels dug by non-interacting nanoparticles in infectious biofilms enhance antibiotic penetration and bacterial killing in vitro and in vivo.

Modelling the variability of hydrological parameters of the Sasyk reservoir impoundment under various options of its operation

This paper highlights the results of adaptation and verification of the Delft3D Flexible Mesh numerical model under the conditions of the Sasyk reservoir. The objective of this work is to evaluate the expected spatio-temporal variability of water salinity in the Sasyk reservoir after completion of the Sasyk renaturalization project by means of establishing a constant water exchange with the sea through the artificial channel. The Sasyk Lagoon was separated from the sea and transformed into a freshwater reservoir in the late 1970s. However, due to the poor water quality in the Sasyk reservoir in the modern period, the solution of the problem of transforming the reservoir to its original coastal conditions, i.e. the renaturalization, has acquired particular importance. Model results, obtained under conditions of 2019, indicate the possibility of using a hydrodynamic model to evaluate the effectiveness and possible consequences of various scenario-based decisions to be implemented for the management of the hydrological regime of the reservoir under various options of its operation. The model runs were used to evaluate the flushing time of the Sasyk Lagoon and the pattern of the salinity fluctuations in the reservoir after the restoration of the artificial channel in the sand bar with a width of 100 m and a depth of 1.5 m and the establishment of the constant “sea-lagoon” interconnection. Applying the hydrometeorological conditions of 2019, a scenario-based modelling for two consecutive years was performed. For the first year of the simulation, a variant of water management under the absence of freshwater inflow from the Danube and the presence of sea water inflow throughout the year was considered. The model results at the end of the first year of the simulation were set as the initial conditions for the second year, and the rest of the external forcing remained unchanged. Additionally, the variant considering the Danube discharge into the lagoon during May-July for the second year of simulation was investigated. Based on the simulation results, it was found that in the case of a constant water exchange with the sea through the connecting “sea-lagoon” channel (with the abovementioned morphometric characteristics) and under the absence of the Danube freshwater inflow throughout the year: 1) the flushing time of the lagoon will be 1 year and 5 months; 2) stabilization of water salinity in the lagoon will not occur, i.e. the salinization of the lagoon water takes place in the long-term perspective; 3) the time period from the moment of initiating the water exchange with the sea, during which the lagoon reaches the water salinity limit of 7-8 ‰, that is critical for the existence of freshwater species of flora and fauna, is expected to amount to 4 months for the southern part and to 5.5 months for the northern part of the lagoon; after which the formation of the marine ecosystem of the reservoir will begin. It is shown that the stabilization of water salinity in the lagoon in the second year of the simulation can be achieved under conditions of ensuring the Danubian freshwater discharge in the period of significantly higher water level in the Danube River, compared to the lagoon water level (May-July 2019).

Climate change overtakes coastal engineering as the dominant driver of hydrological change in a large shallow lagoon

Ecosystems in shallow micro-tidal lagoons are particularly sensitive to hydrologic changes. Lagoons are complex transitional ecosystems between land and sea, and the signals of direct human disturbance can be confounded by variability of the climate system, but from an effective estuary management perspective, the effects of climate versus direct human engineering interventions need to be identified separately. This study developed a 3D finite-volume hydrodynamic model to assess changes in hydrodynamics of the Peel–Harvey Estuary, a large shallow lagoon with restricted connection with ocean; this was done by considering how attributes such as water retention time, salinity and stratification have responded to a range of factors, focusing on the drying climate trend and the opening of a large artificial channel over the period from 1970 to 2016, and how they will evolve under current climate projections. The results show that the introduction of the artificial channel has fundamentally modified the flushing and mixing within the lagoon, and the drying climate has changed the hydrology by comparable magnitudes to that of the opening of the artificial channel. The results also highlight the complexity of their interacting impacts. Firstly, the artificial channel successfully improved the estuary flushing by reducing average water ages by 20–110 d, while in contrast the reduced precipitation and catchment inflow had a gradual opposite effect on the water ages; during the wet season this has almost counteracted the reduction brought about by the channel. Secondly, the drying climate caused an increase in the salinity of the lagoon by 10–30 PSU (Practical Salinity Unit); whilst the artificial channel increased the salinity during the wet season, it has reduced the likelihood of hypersalinity (>40 PSU) during the dry season in some areas. The opening of the artificial channel was also shown to increase the seawater fluxes and salinity stratification, while the drying climate acted to reduce the salinity stratification in the main body of the estuary. The impacts also varied spatially in this large lagoon. The southern estuary, which has the least connection with the ocean through the natural channel, is the most sensitive to climate change and the opening of the artificial channel. The projected future drying climate is shown to slightly increase the retention time and salinity in the lagoon and increase the hypersalinity risk in the rivers. The significance of these changes for nutrient retention and estuary ecology are discussed, highlighting the importance of these factors when setting up monitoring programmes, environmental flow strategies and nutrient load reduction targets.