Oxygen Input Research Articles

Porous Transport Layers with Laser Micropatterning for Enhanced Mass Transport in PEM Water Electrolyzers.

Efficient electrochemical energy conversion technologies, such as fuel cells and water electrolyzers, require high current densities to lower the capital cost for large-scale commercialization but are often limited by mass transport. In this study, we demonstrated exceptional electrochemical performances in proton electrolyte membrane water electrolyzers (PEMWEs) creating micropatterned pore channels in the porous transport layer (MPC PTL) using a picosecond laser. This approach yielded an impressive performance of 1.82 V @ 2 A·cm-2, which is better than commercial PTL of 1.90 V @ 2 A cm-2. The significant performance enhancement is attributed to the micropatterned porous channel structure, facilitating the efficient expulsion of oxygen bubbles and input of reactant water. This work provides valuable insights for the design of PTL responsible for biphasic transport in electrochemical energy conversion technologies.

Simulated plant-mediated oxygen input has strong impacts on fine-scale porewater biogeochemistry and weak impacts on integrated methane fluxes in coastal wetlands

Methane (CH4) emissions from wetland ecosystems are controlled by redox conditions in the soil, which are currently underrepresented in Earth system models. Plant-mediated radial oxygen loss (ROL) can increase soil O2 availability, affect local redox conditions, and cause heterogeneous distribution of redox-sensitive chemical species at the root scale, which would affect CH4 emissions integrated over larger scales. In this study, we used a subsurface geochemical simulator (PFLOTRAN) to quantify the effects of incorporating either spatially homogeneous ROL or more complex heterogeneous ROL on model predictions of porewater solute concentration depth profiles (dissolved organic carbon, methane, sulfate, sulfide) and column integrated CH4 fluxes for a tidal coastal wetland. From the heterogeneous ROL simulation, we obtained 18% higher column averaged CH4 concentration at the rooting zone but 5% lower total CH4 flux compared to simulations of the homogeneous ROL or without ROL. This difference is because lower CH4 concentrations occurred in the same rhizosphere volume that was directly connected with plant-mediated transport of CH4 from the rooting zone to the atmosphere. Sensitivity analysis indicated that the impacts of heterogeneous ROL on model predictions of porewater oxygen and sulfide concentrations will be more important under conditions of higher ROL fluxes or more heterogeneous root distribution (lower root densities). Despite the small impact on predicted CH4 emissions, the simulated ROL drastically reduced porewater concentrations of sulfide, an effective phytotoxin, indicating that incorporating ROL combined with sulfur cycling into ecosystem models could potentially improve predictions of plant productivity in coastal wetland ecosystems.

An Innovative Approach to Alleviate Zinc Oxide Nanoparticle Stress on Wheat through Nanobubble Irrigation.

The extensive utilization of zinc oxide nanoparticles in consumer products and the industry has led to their substantial entry into the soil through air and surface runoff transportation, which causes ecotoxicity in agro-ecosystems and detrimental effects on crop production. Nanobubbles (diameter size < 1 µm) have many advantages, such as a high surface area, rapid mass transfer, and long retention time. In this study, wheat seedlings were irrigated with a 500 mg L-1 zinc oxide nanoparticle solution delivered in the form of nanobubble watering (nanobubble-ZnO-NPs). We found that nanobubble watering improved the growth and nutrient status of wheat exposed to zinc oxide nanoparticles, as evidenced by increased total foliar nitrogen and phosphorus, along with enhanced leaf dry mass per area. This effect can be attributed to nanobubbles disassembling zinc oxide aggregates formed due to soil organic carbon, thereby mitigating nutrient absorption limitations in plants. Furthermore, nanobubbles improved the capability of soil oxygen input, leading to increased root activity and glycolysis efficiency in wheat roots. This work provides valuable insights into the influence of nanobubble watering on soil quality and crop production and offers an innovative approach for agricultural irrigation that enhances the effectiveness and efficiency of water application.

Microbial community function and methylmercury production in oxygen-limited paddy soil

Methylmercury is a neurotoxic compound that can enter rice fields through rainfall or irrigation with contaminated wastewater, and then contaminate the human food chain through the consumption of rice. Flooded paddy soil has a porous structure that facilitates air exchange with the atmosphere, but the presence of trace amounts of oxygen in flooded rice field soil and its impact on microbial-mediated formation of methylmercury is still unclear. We compared the microbial communities and their functions in oxygen-depleted and oxygen-limited paddy soil. We discovered that oxygen-limited paddy soil had higher methylmercury concentration, which was strongly correlated with soil properties and methylation potential. Compared with oxygen-depleted soil, oxygen-limited soil altered the microbial composition based on 16 S rRNA sequences, but not based on hgcA sequences. Moreover, oxygen-limited soil enhanced microbial activity significantly, increasing the abundance of more than half of the KEGG pathways, especially the metabolic pathways that might be involved in methylation. Our study unveils how microbial communities influence methylmercury formation in oxygen-limited paddy soil. Environmental implicationsThis study examined how low oxygen input affects microbial-induced MeHg formation in anaerobic paddy soil. We found that oxygen-limited soil produced more MeHg than oxygen-depleted soil. Oxygen input altered the microbial community structure of 16 S rRNA sequencing in anaerobic paddy soil, but had little impact on the hgcA sequencing community structure. Microbial activity and metabolic functions related to MeHg formation were also higher in oxygen-limited paddy soil. We suggest that oxygen may not be a limiting factor for Hg methylators, and that insufficient oxygen input in flooded paddy soil increases the risk of human exposure to MeHg from rice consumption.

A Control Method for Output Voltage Stability of Proton Exchange Membrane Fuel Cells

The widely used PEMFC (Proton Exchange Membrane Fuel Cell) analysis found that when the REMFC load is changed, its instantaneous output voltage fluctuates, and it causes voltage loss. The main reason is that it is activated by activation. The characteristics of the three-proton exchange membrane fuel battery characteristics of Ohm overvoltage and thickness cause voltage loss. By using the corresponding empirical formula in the Matlab / Simulink environment, the study designs the PID and the Fuzzy PID Controllers. After the established dynamic model of PEMFC, it controls the hydrogen supply module, changes the ratio of hydrogen and oxygen input, and indirectly controls the output voltage. Through experiments, it was found that Fuzzy PID Controller can achieve faster and smoother voltage stability than an ordinary PID Controller and less overshoot when load change, The controller can control the system voltage to reach a set point and to stabilize the supply voltage for the load.

Sediment geochemical records of water quality deterioration in lake Jiren, a remote alpine lake on the southeastern margin of the Tibetan Plateau

Limited human activities in catchments make remote alpine lakes valuable sites for studying the evolution of lake environments in response to climate change and atmospheric deposition; however, this issue remains rarely studied owing to the scarcity of monitoring data. In this study, water quality evolution in Lake Jiren, a remote alpine lake on the southeastern margin of the Tibetan Plateau, over the past two centuries was reconstructed through geochemical analyses of aliphatic hydrocarbons, major and trace elements, and organic matter (OM) pyrolysis products in a dated sediment core, and the associated drivers were identified by temporally comparing the geochemical results with document records. All geochemical data demonstrated that the lake water remained relatively pure until 1947, after which the n-alkane and αβ-hopane proxies indicated eutrophication and petroleum contamination. The OM pyrolysis proxy hydrocarbon index indicated more eutrophic conditions after 1957. Concurrently, hypolimnetic deoxygenation increased, as indicated by redox-sensitive proxies, such as the enrichment factors (EFs) of molybdenum (Mo). These proxies recorded further intensification of deoxygenation after 1976. The EFs for other trace elements indicated cadmium contamination after 1967. The greater anthropogenic emissions of reactive nitrogen, petroleum products, and heavy metals in East and South Asia since approximately 1950 and the subsequent atmospheric transport of these materials to the lake might be the basic driver of water quality deterioration. Eutrophication induced by nitrogen deposition was responsible for increased hypolimnetic deoxygenation by enhancing phytoplankton productivity and OM input. The further intensification of deoxygenation was attributed to climate warming since the 1970s, as prolonged water column stratification under this condition decreased oxygen input from the epilimnion to the lake bottom. These findings may be beneficial for understanding the natural and anthropogenic effects on the water quality of alpine lakes and help in the environmental management of Lake Jiren and other alpine lakes.

Bivalves from the Changhsingian (upper Permian) Bellerophon Formation of the Dolomites (Italy): ancestors of Lower Triassic post‐extinction benthic communities

AbstractDiverse shallow marine fossil assemblages from the Changhsingian Bellerophon Formation (Dolomites) record late Palaeozoic marine life immediately before the end‐Permian mass extinction. We classified c. 6500 bivalves from western Dolomites localities, identifying 26 species including one new family (Ladinomyidae), three new genera (Ladinomya, Lovaralucina, Gardenapecten) and 10 new species: Acharax frenademezi, Bakevellia (Bakevellia) preromangica, Edmondia hautmanni, Etheripecten stuflesseri, Ladinomya fosteri, Lovaralucina covidi, Palaeolima badiotica, Promytilus merlai, Tambanella? stetteneckensis and Volsellina carinata. The occurrence of three Eumorphotis species with different stratigraphic distributions, leads us to propose an upper Permian ‘Lower Eumorphotis Zone’, divided into E. praecurrens, E. striatocostata and E. lorigae subzones, and distinct from the existing Lower Triassic Eumorphotis Zone (here renamed ‘Upper Eumorphotis Zone’). Palaeoecological analysis produced six biofacies and four ecofacies, based on richness, dominance and ecological lifestyle. The bivalves inhabited lagoonal to nearshore environments affected by stressed conditions: high temperatures, high salinity, shallow water depths, low oxygen and high terrigenous input. The upper Bellerophon Fm is characterized by increasingly fully marine conditions, although eurytopic taxa still suggest stressed conditions. Bivalve richness of the upper Permian Bellerophon and Lower Triassic Werfen formations was compared to estimate the genus‐level extinction rate. The disappearance of almost half (47%) of Bellerophon Fm genera is remarkably low compared with other, coeval bivalve faunas. Pre‐extinction bivalve faunas were dominated by stress‐adapted taxa (Unionites, Eumorphotis, Bakevellia, Towapteria) able to thrive in extreme environmental conditions, survive the end‐Permian mass extinction, and become the dominant biotic component of Lower Triassic benthic communities globally.

The Effect of Power on Nitrate Synthesis and The Emission Intensities of Reactive Species Using Anodic Plasma Electrolysis

Nitrates are used as fertilizer to fulfill nutrients for plants. Anodic plasma electrolysis technology can be an effective and environmentally friendly solution in nitrogen fixation into nitrate compounds. This research aimed to determine the effect of controlling voltage and power in nitrate synthesis using plasma electrolysis with air as the raw material injected at the anode. The material used is an electrolyte solution of 0.02 M K2SO4, the electrodes used are in the form of tungsten and stainless steel, and a nitrate reagent is used for the nitrate test. The results of the study showed that at 400 W, the optimal rate was 0.8 L men-1 with 1889 mg L-1 of nitrate formed. While at 500 W and 600 W, the optimal rate of 1 L men-1 with nitrate formed was 2213 mg L-1 and 2453 mg L-1. The emission intensities of reactive species N, N2*, N2+,•OH, •H, and •O at an optimal rate of 0.8 L men-1 400 W 700 V in 20139 au, 28540 au, 18023 au, 30863 au, 12547 au, 49800 au. The addition of air injection will increase the oxygen input into the plasma zone, which can produce reactive species •O and nitrogen produces reactive species N, N2*, N2+ forms NO. The formed NO compounds can be oxidized to NO2, and the reaction between NO2 and reactive species •OH forms nitrates.

Controlling anammox speciation and biofilm attachment strategy using N-biotransformation intermediates and organic carbon levels

Conventional nitrogen removal in wastewater treatment requires a high oxygen and energy input. Anaerobic ammonium oxidation (anammox), the single-step conversion of ammonium and nitrite to nitrogen gas, is a more energy and cost effective alternative applied extensively to sidestream wastewater treatment. It would also be a mainstream treatment option if species diversity and physiology were better understood. Anammox bacteria were enriched up to 80%, 90% and 50% relative abundance, from a single inoculum, under standard enrichment conditions with either stepwise-nitrite and ammonia concentration increases (R1), nitric oxide supplementation (R2), or complex organic carbon from mainstream wastewater (R3), respectively. Candidatus Brocadia caroliniensis predominated in all reactors, but a shift towards Ca. Brocadia sinica occurred at ammonium and nitrite concentrations > 270 mg NH4–N L−1 and 340 mg NO2–N L−1 respectively. With NO present, heterotrophic growth was inhibited, and Ca. Jettenia coexisted with Ca. B. caroliniensis before diminishing as nitrite increased to 160 mg NO2–N L−1. Organic carbon supplementation led to the emergence of heterotrophic communities that coevolved with Ca. B. caroliniensis. Ca. B. caroliniensis and Ca. Jettenia preferentially formed biofilms on surfaces, whereas Ca. Brocadia sinica formed granules in suspension. Our results indicate that multiple anammox bacteria species co-exist and occupy sub-niches in anammox reactors, and that the dominant population can be reversibly shifted by, for example, changing nitrogen load (i.e. high nitrite concentration favors Ca. Brocadia caroliniensis). Speciation has implications for wastewater process design, where the optimum cell immobilization strategy (i.e. carriers vs granules) depends on which species dominates.

Self-supported ultrathin Co3O4 nanoarray enabling efficient paired electrolysis of 5-hydroxymethylfurfural for simultaneous dihydroxymethylfuran (DHMF) and furandicarboxylic acid (FDCA) production

Production of value-added chemicals and fuels from biomass via electrochemical methods has been of emerging interest in light of the increasing environmental, economic, and political challenges. Paired electrolysis, with anodic oxidation and cathodic reduction reactions pairing in a single electrochemical cell, offers an effective way to produce desired products in both electrodes, thus achieving complete electron economy. In this work, an efficient 5-hydroxymethylfurfural (HMF) paired electrolysis system is developed over a self-supported ultrathin Co3O4 nanoarray electrocatalyst for simultaneous production of value-added 2,5-dihydroxymethylfuran (DHMF) and 2,5-furandicarboxylic acid (FDCA). The as-designed paired electrolysis cell achieves a high HMF conversion and DHMF/FDCA selectivity at both anode and cathode without external hydrogen and oxygen input. A near-quantitative yield (95.7%) of FDCA and 78.8% yield of DHMF can be achieved in the paired electrolysis system, with a total Faradaic efficiency of 127%. This work will open up new opportunities in designing efficient electrochemical devices to simultaneously produce building-block chemicals from biomass-derived molecules in both anode and cathode.

The dissolved oxygen budget of a small Canadian Shield lake during winter

AbstractDeep‐water hypoxia is an environmental concern in temperate lakes. Seasonal turnover events provide a mechanism for deep‐water oxygenation; however, the lake oxygen budget and mixing dynamics during turnovers are poorly understood. In the present study, the oxygen cycle in a small dimictic lake was investigated from long‐term field measurements supplemented with output from a three‐dimensional numerical model. Photosynthetic production and atmospheric exchange were modeled to predominate during spring and fall turnovers, respectively, contributing 92% (surprisingly) and 8% of the net dissolved oxygen (DO) input to the lake. Of the DO production, 41% occurred under‐ice, with a potential to supply 17% ± 11% of the hypolimnetic DO saturation deficit at spring turnover. The corresponding DO sinks were sediment oxygen demand (− 54%), mineralization (− 33%), and nitrification (− 13%). The watercolumn circulation and stratification during pre‐winter and spring turnover controlled the inter‐annual variability in hypoxia during the following summer. Warm winters (~ 4°C watercolumn leading to rapid summer stratification) and severely cold winters (strong winter stratification with shallow convective mixing in spring) were followed by incomplete spring turnover, whereas, following cold winters (moderate winter stratification and extended convection) turnover was complete. This underscores the connection between winter hydrodynamics and summer water quality in dimictic lakes.

Influence Factor Analysis and Prediction Model of End-Point Carbon Content Based on Artificial Neural Network in Electric Arc Furnace Steelmaking Process

In this manuscript, we consider the accuracy of end-point carbon content prediction affected by oxygen injection in multiple stages of electric arc furnace (EAF) melting process. Such a prediction would help to further evaluate process control strategies and optimize overall operation of the electric arc furnace. Principal component analysis (PCA) was used to normalize the 13 input variables affecting the endpoint carbon content. log-sigmoid and tan-sigmoid functions were used to verify the same sample, and it was found that the Mean squared error(MSE) of the model under logsig + logsig function was smaller, indicating that the model was more stable. At the same time, different hidden layer nodes were tried, and finally the structure of the model was determined as 13 × 10 × 8 × 1, and the activation function was logsig + logsig. Using historical smelting data to train and test the neural network model, the correlation coefficient (R) of the verified model is 0.7632, the model prediction is in the range of ±0.03%, the hit rate of the model is 64.5%, and the hit rate of the model is 42% in the range of ±0.02%. Combining the verification basis of the model with the metallurgical reaction principle of the EAF steelmaking process, a pretreatment method of phased input of total oxygen is proposed. The oxygen is divided into three stages, which are the oxygen consumption volume of 0–5 min, 5–30 min and more than 30 min and other variables are kept unchanged. The same neural network is used to train and verify the same data. After verification, the R of the oxygen staged model is 0.8274. The model prediction is in the range of ±0.03%, the hit rate of the model is 78.5%, and the hit rate of the model is 58% in the range of ±0.02%. Finally, an on-line carbon content prediction system based on artificial neural network model is developed and applied to actual production. Running results illustrated that the hit rate of end-point carbon content is 96.67%, 93.33% and 86.67%, respectively when the prediction errors are within ±0.05%, ±0.03% and ±0.01%, the improved neural network model can effectively predict the end-point carbon content, which provides a good basis for the carbon content at the end point of EAF steelmaking process.

Oxygenation of a karst subterranean estuary during a tropical cyclone: mechanisms and implications for the carbon cycle

AbstractSeasonal precipitation affects carbon turnover and methane accumulation in karst subterranean estuaries, the region of coastal carbonate aquifers where hydrologic and biogeochemical processes regulate material exchange between the land and ocean. However, the impact that tropical cyclones exert on subsurface carbon cycling within karst landscapes is poorly understood. Here, we present 5‐month‐long hydrologic and chemical records from 1 and 2 km inland from the coastline within the Ox Bel Ha Cave System in the northeastern Yucatan Peninsula. The record encompasses wet and dry seasons and includes the impact of rainfall during the development of Tropical Storm Hanna in October 2014. Methane accumulated in highest concentrations at the inland site, especially during the wet season preceding the storm. Intense rainfall led to episodic increases in water level and salinity shifts at both sites, indicating a spatially widespread hydrologic response. The most profound storm effect was a ~ 0.8 mg L−1 pulse of dissolved oxygen that declined to zero within 2 weeks and corresponded with a reduction of methane. A positive shift in methane's stable carbon isotope content from −62.6‰ ± 0.6‰ before the storm to −44.0‰ ± 2.4‰ after the storm indicates microbial methane oxidation was a mechanism for the loss of groundwater methane. Post‐storm methane concentrations did not recover to pre‐storm levels during the observation period, suggesting tropical cyclones have long‐lasting (months) effects on the carbon cycle. Compared to seasonal effects, mixing and oxygen inputs during storm‐induced hydrologic forcing have an outsized biogeochemical influence within stratified coastal aquifers.

Microbial iron reduction compensates for phosphorus limitation in paddy soils.

Limitation of rice growth by low phosphorus (P) availability is a widespread problem in tropical and subtropical soils because of the high content of iron (Fe) (oxyhydr)oxides. Ferric iron-bound P (Fe(III)-P) can serve as a P source in paddies after Fe(III) reduction to Fe(II) and corresponding H2PO4- release. However, the relevance of reductive dissolution of Fe(III)-P for plant and microbial P uptake is still an open question. To quantify this, 32P-labeled ferrihydrite (30.8 mg P kg-1) was added to paddy soil mesocosms with rice to trace the P uptake by microorganisms and plants after Fe(III) reduction. Nearly 2% of 32P was recovered in rice plants, contributing 12% of the total P content in rice shoots and roots after 33 days. In contrast, 32P recovery in microbial biomass decreased from 0.5% to 0.08% of 32P between 10 and 33 days after rice transplantation. Microbial biomass carbon (MBC) and dissolved organic C content decreased from day 10 to 33 by 8-54% and 68-77%, respectively, suggesting that the microbial-mediated Fe(III) reduction was C-limited. The much faster decrease of MBC in rooted (by 54%) vs. bulk soil (8-36%) reflects very fast microbial turnover in the rice rhizosphere (high C and oxygen inputs) resulting in the mineralization of the microbial necromass. In conclusion, Fe(III)-P can serve as small but a relevant P source for rice production and could partly compensate plant P demand. Therefore, the P fertilization strategies should consider the P mobilization from Fe (oxyhydr)oxides in flooded paddy soils during rice growth. An increase in C availability for microorganisms in the rhizosphere intensifies P mobilization, which is especially critical at early stages of rice growth.

Secular variation in seawater redox state during the Marinoan Snowball Earth event and implications for eukaryotic evolution

Abstract The ocean is hypothesized to have been anoxic throughout the Marinoan “Snowball Earth” event, from ca. 649 to 635 Ma, with potentially catastrophic implications for the survival of eukaryotic life. However, the precise nature of ocean redox chemistry across this critical interval, and hence the factors that governed the persistence of eukaryotes, remains unknown. We report records of pyrite iron and sulfur isotopes, combined with Fe speciation, for glaciogenic diamictites from the Nantuo Formation of South China. These data provide constraints on seawater redox state across the Marinoan glaciation, and they reveal that the redox state of the ocean fluctuated in concert with waxing and waning extents of glaciation, to include intervals of expanded oxygenation. The input of meltwater-derived oxygen provides a potential explanation for the persistence of eukaryotes through the Cryogenian “Snowball Earth” events, which ultimately paved the way for subsequent intervals of rapid biological innovation.

PEMYH için COMSOL'da Üç Boyutlu Çoklu Akış Modeliyle Altın Oran Yöntemi ile Oksijen ve Hidrojen Giriş Hızlarının Optimizasyonu

A three dimensional (3D), gas-liquid multi-phase flow and transport model in COMSOL Multiphysics has been developed to simulate flow and transport phenomena in a proton exchange membrane fuel cell (PEMFC) with several operational parameters. The effects of changes in oxygen and hydrogen input velocities on concentration change at electrodes, current density in polymeric membrane and cell performance have been investigated in PEMFC. The simulations, made in COMSOL for numerical method, were presented with an emphasis on the physical and fundamental insight afforded by distributions of velocity vector, local current density, overpotential, oxygen and water concentrations. Using Golden Section Method, optimization of the change in the speed vector was made based on the numerical models for velocity values. Results showed that computational and numerical methods are in great harmony. The polarization curve, which is used as a measure of efficiency in cell performance, were supportive with results. The data show that the power density obtained for the optimum model is higher, with such a model performance of 92.87%. Compared to the currently used PEMFC, while hydrogen saving achieved between 4.2% and 7.1%, electrical efficiency increase were between 1% and 2.4%.

Causes of the extensive hypoxia in the Gulf of Riga in 2018

Abstract. The Gulf of Riga is a relatively shallow bay connected to the deeper central Baltic Sea (Baltic Proper) via straits with sills. The decrease in the near-bottom oxygen levels from spring to autumn is a common feature in the gulf, but in 2018, extensive hypoxia was observed. We analyzed temperature, salinity, oxygen, and nutrient data collected in 2018, along with historical data available from environmental databases. Meteorological and hydrological data from the study year were compared with their long-term means and variability. We suggest that pronounced oxygen depletion occurred in 2018 due to a distinct development of vertical stratification. Seasonal stratification developed early and was stronger in spring–summer 2018 than on average due to high heat flux and weak winds. Dominating northeasterly winds in early spring and summer supported the inflow of saltier waters from the Baltic Proper that created an additional deep pycnocline restricting vertical transport between the near-bottom layer (NBL) and the water column above. The estimated oxygen consumption rate in the NBL in spring–summer 2018 was about 1.7 mmolO2m-2h-1, which exceeded the oxygen input to the NBL due to advection and vertical mixing. Such a consumption rate leads to near-bottom hypoxia in all years when vertical mixing in autumn reaches the seabed later than on average according to the long-term (1979–2018) meteorological conditions. The observed increase in phosphate concentrations in the NBL in summer 2018 suggests a significant sediment phosphorus release in hypoxic conditions counteracting the mitigation measures to combat eutrophication. Since climate change projections predict that meteorological conditions comparable to those in 2018 will occur more frequently, extensive hypoxia would be more common in the Gulf of Riga and other coastal basins with similar morphology and human-induced elevated input of nutrients.

The Benefits of Swimming on the Lungs Vital Capacity

Sport is an activity that is useful to nourish the individual body physically and spiritually. Health is an important need and has a major role in survival. Physical health or also called physical fitness has a vital contribution in indicators of a person's overall health status. Through descriptive-qualitative research method by collecting secondary and primary data from several journals. Swimming is a sport that is a form of water sports. Swimming is also a water aerobics sport, where this sport requires a lot of oxygen input. The benefits of this swimming sport are on the respiratory system. The respiratory system is one of the systems found in the individual's body that plays an important role in the process of life. In swimming, which is an aerobic exercise that requires a lot of oxygen, this affects the vital capacity of the lungs. The vital capacity of the lungs is the maximum amount of oxygen that enters the lungs. So that by doing swimming regularly, the vital capacity of the lungs will be better.

Impacts of The Wetland Sedge Carex aquatilis on Microbial Community and Methane Metabolisms

Microbial activity in the soil of wetlands is responsible for the emission of more methane to the atmosphere than all other natural sources combined. This microbial activity is heavily impacted by plant roots, which influence the microbial community by exuding organic compounds and by leaking oxygen into an otherwise anoxic environment. This study compared the microbial communities of planted and unplanted wetland soil from an Alaskan bog to elucidate how plant growth influences populations and metabolisms of methanogens and methanotrophs. A common boreal wetland sedge, Carex aquatilis, was grown in the laboratory and DNA samples were sequenced from the rhizosphere, unplanted bulk soil, and a simulated rhizosphere with oxygen input but no organic carbon. The abundance of both methanogens and methanotrophs were positively correlated with methane emissions. Among the methanotrophs, both aerobic and anaerobic methane oxidizing microbes were more common in the rhizosphere of mature plants than in unplanted soil, while facultative methanotrophs capable of utilizing either methane or other molecules became relatively less common. These trends indicate that the roots in this experiment created an environment which favored highly specialized microbial metabolisms over generalist approaches. One aspect of this specialized microbiome is the presence of both aerobic and anaerobic metabolisms, which indicates that oxygen is present but is a limiting resource controlling competition.

Redox conditions of bottom sediments and macrozoobenthos characteristics in the Kruglaya and Kazachya bays (Sevastopol)

A lack of systemic and environmentally efficient approach to exploitation of the Kruglaya and Kazachya bays (Sevastopol) resulted in their severe pollution. The conjunction of natural and anthropogenic factors led to deterioration of habitat conditions of benthic communities. The aim of this work was to carry out complex research of Kruglaya and Kazachya bays’ ecosystems to study peculiarities of formation of redox conditions in bottom sediments and bottom water layer, as well as their effect on macrozoobenthos characteristics. Bottom sediments were sampled by diver in plexiglass tubes hermetically sealed at the top and bottom; it helped in preserving a fine structure of bottom sediments and bottom water layer. To study benthic communities, samples were taken in the same spot with a manual sampler. To obtain chemical composition of pore waters with high vertical resolution, the voltammetry analysis was carried out. Calculation of an oxygen flux at the boundary and in the upper layer of bottom sediments was performed according to the vertical profile of oxygen concentration in pore waters and geochemical analysis with applying the equation for the Fick’s first law and considering concentration gradient and molecular diffusion of oxygen in pore waters. Standard hydrobiological methods were applied for the analysis of benthic material. When calculating the values of the Shannon diversity index (H’), the binary logarithm was used. The data analysis showed as follows: a high level of anthropogenic load and restricted water dynamics resulted in siltation of bottom sediments in the studied water areas, which obstructed oxygen penetration; the accumulation of organic carbon contributed to its active consumption. Stratification of a water column due to limited water exchange, high temperature of bottom water, accompanied by a decrease in oxygen solubility, and finely dispersed nature of bottom sediments contributed to the fact that the rate of oxygen input was lower than the rate of oxygen consumption for organic matter oxidation. This was followed by the development of oxygen deficiency zones and emergence of reduced compounds, in particular hydrogen sulfide. Importantly, suboxic conditions prevailed in the upper sediment layer, and anaerobic conditions prevailed below. Due to this, the main forms of macrozoobenthos were species tolerant to oxygen deficiency and organic pollution. Specifically, in some spots of the Kazachya Bay, polychaetes alone were recorded. At the same time, in the Kruglaya Bay mouth area, intense water dynamics and morphological peculiarities of bottom sediments contribute to saturation of the upper sediment layer with oxygen. Based on oxygen concentration data for the surface (0–5 mm) sediment layer (pore waters) and on geochemical peculiarities of bottom sediments (moisture and porosity), the oxygen flux at st. 4 (the Solenaya Bay) was calculated; the value was 0.73 M·m−2·year−1. Considering oxygen concentration in bottom water layer (259 μM), the time for complete depletion of oxygen or its renewal is about 5 months if taking into account biogeochemical processes alone. Hence, it can be assumed that the ecosystems of the Kruglaya and Kazachya bays are in the stage of degradation. Their further exploitation without a developed systemic and rational approach will result in a critical deterioration of the ecosystems – the emergence and spread of environmental risk zones. It will reduce the recreational and socioeconomic attractiveness of these areas.