Oceanic dissolved oxygen(DO)concentration is crucial for assessing the status of marine ecosystems.Against the backdrop of global warming,DO shows a general decrease,posing a threat to the health of marine ecosystems....Oceanic dissolved oxygen(DO)concentration is crucial for assessing the status of marine ecosystems.Against the backdrop of global warming,DO shows a general decrease,posing a threat to the health of marine ecosystems.Therefore,there is an urgent need to develop advanced tools to characterize the spatio-temporal variations of three-dimensional(3D)DO.To address this challenge,this study introduces the Light Gradient Boosting Machine(Light-GBM),combining satellite remote sensing and reanalysis data with Biogeochemical Argo data to accurately reconstruct the 3D DO structure in the Mediterranean Sea from 2010 to 2022.Various environmental parameters are incorporated as inputs,including spatiotemporal features,meteorological characteristics,and ocean color properties.The LightGBM model demonstrates excellent performance on the testing dataset with R^(2) of 0.958.The modeled DO agrees better with in-situ measurements than products from numerical models.Using the Shapley Additive exPlanations method,the contributions of input features are assessed.Sea surface temperatures provide a correlation with DO at the sea surface,while spatial coordinates supplement the view of the ocean interior.Based on the reconstructed 3D DO structure,we identify an oxygen minimum zone in the western Mediterranean that expands continuously,reaching depths of approximately 300–800 m.The western Mediterranean exhibits a significant declining trend.This study enhances marine environmental evidence by proposing a precise and cost-effective approach for reconstructing 3D DO,thereby offering insights into the dynamics of DO variations under changing climatic conditions.展开更多
This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessme...This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessment Report,including CCP scenarios,projecting a significant temperature rise of 3.3–5.7℃in the case o very high GHG emission power,the research investigates how these shifts may influence dissolved oxygen levels in Lake Biwa.Through a one-dimensional model incorporat ing sediment redox reactions,various scenarios where ai temperature and wind speed are changed are simulated.I is revealed that a 5℃increase in air temperature leads to decreasing 1-2 mg/L of dissolved oxygen concentrations from the surface layer to the bottom layer,while a decrease in air temperature tends to elevate 1–3 mg/L of oxygen lev els.Moreover,doubling wind speed enhances surface laye oxygen but diminishes it in deeper layers due to increased mixing.Seasonal variations in wind effects are noted with significant surface layer oxygen increases from 0.4to 0.8 mg/L during summer to autumn,increases from 0.4 to 0.8 mg/L in autumn to winter due to intensified vertica mixing.This phenomenon impacts the lake’s oxygen cycle year-round.In contrast,precipitation changes show limited impact on oxygen levels,suggesting minor influence com pared to other meteorological factors.The study suggests the necessity of comprehensive three-dimensional models that account for lake-specific and geographical factors fo accurate predictions of future water conditions.A holistic approach integrating nutrient levels,water temperature,and river inflow is deemed essential for sustainable management of Lake Biwa’s water resources,particularly in addressing precipitation variations.展开更多
To investigate the influence of oxygen content in a physiological liquid environment on the corrosion behavior of biomedical zinc-based alloys,a simulated bodily fluid environment with varying dissolved oxygen was est...To investigate the influence of oxygen content in a physiological liquid environment on the corrosion behavior of biomedical zinc-based alloys,a simulated bodily fluid environment with varying dissolved oxygen was established in vitro using external oxygen supply equipment.The influence of dissolved oxygen concentration on the corrosion behavior of pure Zn and Zn−Cu alloys was studied with scanning electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectrometry,and electrochemical analysis.Due to oxygen absorption corrosion,the increase in dissolved oxygen concentration increases the pH value of the solution and promotes the accumulation of corrosion product layer.Compared with the environment without additional oxygen supply,the corrosion rate of the sample under the continuous oxygen supply condition is increased by one order of magnitude.Because the Zn−Cu alloy has micro-galvanic corrosion,its corrosion rate is about 1.5 times that of pure zinc under different dissolved oxygen conditions.展开更多
Oceanic dissolved oxygen(DO)in the ocean has an indispensable role on supporting biological respiration,maintaining ecological balance and promoting nutrient cycling.According to existing research,the total DO has dec...Oceanic dissolved oxygen(DO)in the ocean has an indispensable role on supporting biological respiration,maintaining ecological balance and promoting nutrient cycling.According to existing research,the total DO has declined by 2%of the total over the past 50 a,and the tropical Pacific Ocean occupied the largest oxygen minimum zone(OMZ)areas.However,the sparse observation data is limited to understanding the dynamic variation and trend of ocean using traditional interpolation methods.In this study,we applied different machine learning algorithms to fit regression models between measured DO,ocean reanalysis physical variables,and spatiotemporal variables.We demonstrate that extreme gradient boosting(XGBoost)model has the best performance,hereby reconstructing a four-dimensional DO dataset of the tropical Pacific Ocean from 1920 to 2023.The results reveal that XGBoost significantly improves the reconstruction performance in the tropical Pacific Ocean,with a 35.3%reduction in root mean-squared error and a 39.5%decrease in mean absolute error.Additionally,we compare the results with three Coupled Model Intercomparison Project Phase 6(CMIP6)models data to confirm the high accuracy of the 4-dimensional reconstruction.Overall,the OMZ mainly dominates the eastern tropical Pacific Ocean,with a slow expansion.This study used XGBoost to efficiently reconstructing 4-dimensional DO enhancing the understanding of the hypoxic expansion in the tropical Pacific Ocean and we foresee that this approach would be extended to reconstruct more ocean elements.展开更多
Dissolved oxygen(DO)usually refers to the amount of oxygen dissolved in water.In the environment,medicine,and fermentation industries,the DO level needs to be accurate and capable of online monitoring to guide the pre...Dissolved oxygen(DO)usually refers to the amount of oxygen dissolved in water.In the environment,medicine,and fermentation industries,the DO level needs to be accurate and capable of online monitoring to guide the precise control of water quality,clinical treatment,and microbial metabolism.Compared with other analytical methods,the electrochemical strategy is superior in its fast response,low cost,high sensitivity,and portable device.However,an electrochemical DO sensor faces a trade-off between sensitivity and long-term stability,which strongly limits its practical applications.To solve this problem,various advanced nanomaterials have been proposed to promote detection performance owing to their excellent electrocatalysis,conductivity,and chemical stability.Therefore,in this review,we focus on the recent progress of advanced nanomaterial-based electrochemical DO sensors.Through the comparison of the working principles on the main analysis techniques toward DO,the advantages of the electrochemical method are discussed.Emphasis is placed on recently developed nanomaterials that exhibit special characteristics,including nanostructures and preparation routes,to benefit DO determination.Specifically,we also introduce some interesting research on the configuration design of the electrode and device,which is rarely introduced.Then,the different requirements of the electrochemical DO sensors in different application fields are included to provide brief guidance on the selection of appropriate nanomaterials.Finally,the main challenges are evaluated to propose future development prospects and detection strategies for nanomaterial-based electrochemical sensors.展开更多
The structure of liquid water is primarily composed of three-dimensional networks of water clusters formed by hydrogen bonds,and dis-solved oxygen is one of the most important indicators for assessing water qual-ity.I...The structure of liquid water is primarily composed of three-dimensional networks of water clusters formed by hydrogen bonds,and dis-solved oxygen is one of the most important indicators for assessing water qual-ity.In this work,distilled water with different concentration of dissolved oxygen were prepared,and a clear negative correlation between the size of water clus-ters and dissolved oxygen concentration was observed.Besides,a phenomenon of rapid absorption and release of oxygen at the water interfaces was unveiled,suggesting that oxygen molecules predominantly exist at the interfaces of water clusters.Oxygen molecules can move rapidly through the interfaces among water clusters,allowing dissolved oxygen to quickly reach a saturation level at certain partial pressure of oxygen and temperature.Further exploration into the mechanism by molecular dynamics simulations of oxygen and water clusters found that oxygen molecules can only exist stably at the interfaces among water clusters.A semi-empirical formula relating the average number of water molecules in a cluster(n)to ^(17)O NMR half-peak width(W)was summarized:n=0.1 W+0.85.These findings provide a foundation for exploring the structure and properties of water.展开更多
Hypoxia off the Changjiang River Estuary has been the subject of much attention,yet systematic observations have been lacking,resulting in a lack of knowledge regarding its long-term change and drivers.By revisiting t...Hypoxia off the Changjiang River Estuary has been the subject of much attention,yet systematic observations have been lacking,resulting in a lack of knowledge regarding its long-term change and drivers.By revisiting the repeated surveys of dissolved oxygen(DO) and other relevant hydrographic parameters along the section from the Changjiang River Estuary to the Jeju-do in the summer from 1997 to 2014,rather different trends were revealed for the dual low-DO cores.The nearshore low-DO core,located close to the river mouth and relatively stable,shows that hypoxia has become more severe with the lowest DO descen ding at a rate of -0.07 mg/(L·a) and the thickness of low-DO zone rising at a rate of 0.43 m/a.The offshore core,centered around 40-m isobath but moving back and forth between 123.5°-125°E,shows large fluctuations in the minimum DO concentration,with the thickness of low-DO zone falling at a rate of -1.55 m/a.The probable factors affecting the minimum DO concentration in the two regions also vary.In the nearshore region,the decreasing minimum DO is driven by the increase in both stratification and primary productivity,with the enhanced extension of the Changjiang River Diluted Water(CDW) strengthening stratification.In the offshore region,the fluctuating trend of the minimum DO concentration indicates that both DO loss and DO supplement are distinct.The DO loss is primarily attributed to bottom apparent oxygen utilization caused by the organic matter decay and is also relevant to the advection of low-DO water from the nearshore region.The DO supplement is primarily due to weakened stratification.Our analysis also shows that the minimum DO concentration in the nearshore region was extremely low in 1998,2003,2007 and 2010,related to El Ni?o signal in these summers.展开更多
Oxygen facilitates the breakdown of the organic material to provide energy for life.The concentration of dissolved oxygen(DO) in the water must exceed a certain threshold to support the normal metabolism of marine org...Oxygen facilitates the breakdown of the organic material to provide energy for life.The concentration of dissolved oxygen(DO) in the water must exceed a certain threshold to support the normal metabolism of marine organisms.Located in the northern B eibu Gulf,Qinzhou B ay receives abundant freshwater and nutrients from several rivers which significantly influence the level of the dissolved oxygen.However,the spatial-temporal variations of DO as well as the associated driving mechanisms have been rarely studied through field observations.In this study,a three-dimension al coupled physical-biogeochemical model is used to investigate the spatial and seasonal variations of the DO and the associated driving mechanisms in Qinzhou B ay.The validation against observations indicates that the model can capture the seasonal and inter-annual variability of the DO concentration with the range of 5-10 mg/L.Sensitivity experiments show that the river discharges,winds and tides play crucial roles in the seasonal variability of the DO by changing the vertical mixing and stratification of the water column and the circulation pattern.In winter,the tide and wind forces have strong effects on the DO distribution by enhancing the vertical mixing,especially near the bay mouth.In summer,the river discharges play a dominant role in the DO distribution by inhibiting the vertical water exchange and delivering more nutrients to the Bay,which increases the DO depletion and results in lower DO on the bottom of the estuary salt wedge.These findings can contribute to the preservation and management of the coastal environment in the northern Beibu Gulf.展开更多
Dissolved oxygen(DO)and apparent oxygen utilization(AOU)are essential parameters for evaluating the impact of climate change on marine ecosystems.In this study,we utilized data on DO and AOU collected from the Amundse...Dissolved oxygen(DO)and apparent oxygen utilization(AOU)are essential parameters for evaluating the impact of climate change on marine ecosystems.In this study,we utilized data on DO and AOU collected from the Amundsen Sea(western Antarctic)and the Cosmonaut Sea(eastern Antarctic)during the 38th Chinese National Antarctic Research Expedition,along with chlorophyll a(Chl a)data,to analyze the impact of primary production and the spatial distribution and structural features of water masses in these regions.The findings show that the standard deviation range of parallel DO samples is between 0.1 and 3.9μmol·L^(-1),meeting the precision criteria of the survey method.AOU values lower than 0.0μmol·L^(-1) were commonly observed in the surface waters of both regions,with the highest incidence in the polynya of Amundsen Sea,indicating a strong influence of high primary production.The Cosmonaut Sea exhibited the highest AOU values(higher than 160.0μmol·L^(-1))in the 75-500 m layer,while AOU value in the Amundsen Sea did not exceed 160.0μmol·L^(-1),suggesting potential upwelling of Circumpolar Deep Water to 100 m in the Cosmonaut Sea with minimal changes in its properties,whereas significant changes were noted in the properties of upwelling modified Circumpolar Deep Water in the Amundsen Sea.AOU values lower than 125.0μmol·L^(-1)were detected in the near-bottom waters of the Cosmonaut Sea,indicating the presence of Antarctic Bottom Water.展开更多
A dissolved oxygen fuzzy system predicting model based on neural network was put forward in this study. 106 groups of data were used to confirm the fitness of the predicting model. The first 80 groups of data were act...A dissolved oxygen fuzzy system predicting model based on neural network was put forward in this study. 106 groups of data were used to confirm the fitness of the predicting model. The first 80 groups of data were acted as training input and the other 26 groups of data were acted as the confirmed data in the system. The result showed that the testing data was approximately the same as the predicted data. So it gave a new way to solve the problem that the status of the water quality couldn＇t be predicted in time and it＇s hard to watching and measuring the factors dynamic.展开更多
Influence of the combination of nutrient feed with dissolved oxygen control on taxol production in suspension cultures of Taxus chinensis (Pilg.) Rehd. was investigated in bioreactors. Addition of feeding medium with ...Influence of the combination of nutrient feed with dissolved oxygen control on taxol production in suspension cultures of Taxus chinensis (Pilg.) Rehd. was investigated in bioreactors. Addition of feeding medium with 20 g/L sucrose on day 16 enhanced both the biomass and taxol production in 5-L bioreactors. Further investigation of the fed-batch cultures in a 20-L bioreactor showed that cultivation under a low dissolved oxygen tension (DOT) of 20% for the entire culture resulted in the highest taxol content of 0.98 mg/g DW, while the taxol production was lower than that with 40% and 60% DOT. Moreover, taxol accumulation was remarkably improved by the cultivation of cells initially under DOT of 60% for 20 d followed by changing the DOT to 20% for another 12 d. By combining the use of these two strategies, a maximum taxol content of 18.7 mg/L was obtained in a 20-L bioreactor.展开更多
Dissolved oxygen(DO)concentration is regarded as one of the crucial factors to influence partial nitrification process.However,achieving and keeping stable partial nitrification under different DO concentrations were ...Dissolved oxygen(DO)concentration is regarded as one of the crucial factors to influence partial nitrification process.However,achieving and keeping stable partial nitrification under different DO concentrations were widely reported.The mechanism of DO concentration influencing partial nitrification is still unclear.Therefore,in this study two same sequencing batch reactors(SBRs)cultivated same seeding sludge were built up with realtime control strategy.Different DO concentrations were controlled in SBRs to explore the effect of DO concentration on the long-term stability of partial nitrification process at room temperature.It was discovered that ammonium oxidation rate(AOR)was inhibited when DO concentration decreased from 2.5 to 0.5 mg/L.The abundance of Nitrospira increased from 1011.5 to 1013.7 copies/g DNA,and its relative percentage increased from 0.056%to 3.2%during 190 operational cycles,causing partial nitrification gradually turning into complete nitrification process.However,when DO was 2.5 mg/L the abundance of Nitrospira was stable and AOB was always kept at 1010.7 copies/g DNA.High AOR was maintained,and stable partial nitrification process was kept.Ammonia oxidizing bacteria(AOB)activity was significantly higher than nitrite oxidizing bacteria(NOB)activity at DO of 2.5 mg/L,which was crucial to maintain excellent nitrite accumulation performance.展开更多
The Changjiang Estuary and its adjacent waters form one of the most important estuarine and coastal areas in China. Multi source and long-term data are assembled to examine the temporal-spatial distribution features o...The Changjiang Estuary and its adjacent waters form one of the most important estuarine and coastal areas in China. Multi source and long-term data are assembled to examine the temporal-spatial distribution features of dissolved oxygen （DO） in the Changjiang Estuary and its adjacent waters for the past SO a. The results show that the DO concentration in the surface of different seasons generally stays stable, while the DO concentration in winter displays a slight increase for the last 50 a. The DO average concentration in winter and spring varies from 7 to 11 rag/L, and in summer and autumn from 6 to 8 mg/L. Hypoxic values first appear in May, and low DO value plume can be observed on the bottom in spring along coastal areas of Zhejiang and Fujian Provinces, China. In summer, the plume advances northward, and the hypoxic intensity of northern transects is much higher than southern transects. Until autumn, hypoxia areas fade away little by little, and completely disappear in winter. Within last 50 a, hypoxia in the Changjiang Estuary and its adjacent waters starts to appear in the 1980s. Since 2000, the degree of hypoxia has increased seriously and the distribution depth has become smaller. It is performed based on a large amount of historical data, and the research results will be of great significance to further study on the dynamic development of hypoxia around the Changjiang Estuary.展开更多
The effect of residual dissolved oxygen （DO） on the corrosion behavior of carbon steel in 0.1 M NaHCO3 solution was investigated by electrochemical measurements, corrosion mass loss test, scanning electron microsco...The effect of residual dissolved oxygen （DO） on the corrosion behavior of carbon steel in 0.1 M NaHCO3 solution was investigated by electrochemical measurements, corrosion mass loss test, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. In the initial immersion stage, the increase of the dissolved oxygen concentration led to the change of from a reductive state of active dissolution to an oxidizing state of pseudo passivation in low carbon steel. While in the final stage, all the steels transformed into the steady state of pseudo passivation. In the anaerobic solution, the formation of c^-FeOOH was attributed to the chemical oxidization of the ferrous corrosion products and the final cathodic process only included the reduction of c^-FeOOH, while in the aerobic solution, it included the reduction of oxygen and （x-FeOOH simultaneously. As the main corrosion products, the content of （x-FeOOH was increased while that of Fe6（OH）12CO3 was decreased with increasing concentration of dissolved oxygen. The total corrosion mass loss of the steel was promoted with the increase of dissolved oxygen concentration.展开更多
The corrosion behavior of 2205 duplex stainless steel was investigated in hot concentrated seawater with different dissolved oxygen(DO) concentration by electrochemical measurement techniques and surface analysis meth...The corrosion behavior of 2205 duplex stainless steel was investigated in hot concentrated seawater with different dissolved oxygen(DO) concentration by electrochemical measurement techniques and surface analysis methods. DO obviously enhances the cathodic reaction process, the formation of passive film and polarization resistance. With increasing the DO concentration from 0.34 to 3.06 mg L^(-1), the relative contents of Fe_(2)O_(3) and Cr_(2)O_(3) and the Cr-enrichment gradually enlarge in the passive film. The higher DO concentrations result in lower defect densities and thicker of space charge layers in the passive films,whichmayeffectively inhibit the intrusion of aggressive chloride ions. The increment inDOconcentration clearly increases the pitting potential, but decreases the repassivation potential. It may weaken both the occurrence and repassviation tendencies of stable pitting corrosion.展开更多
Dissolved oxygen and nitrogen form have important effects on rice root growth and nitrogen availability.An indica hybrid rice,Guodao 1,and a conventional japonica rice,Xiushui 09,were cultured in hypoxic nutrient solu...Dissolved oxygen and nitrogen form have important effects on rice root growth and nitrogen availability.An indica hybrid rice,Guodao 1,and a conventional japonica rice,Xiushui 09,were cultured in hypoxic nutrient solution with NH4NO3 or(NH4)2SO4 as the nitrogen source for six weeks in pools.A portion of the Guodao 1 seedlings after treatment in the pools for four weeks were transferred to a split-root system at different dissolved oxygen contents and cultured for an additional two weeks.Biomass,root morphological traits and nitrogen accumulation were recorded.Under the low rhizosphere dissolved oxygen content(0-1.0 mg/L),plant biomass was significantly increased under NH4NO3-N supply by about 69% in Guodao 1 and 41% in Xiushui 09 compared with those under NH4+-N alone.Similar results were observed for root number,maximum root length,root dry weight and root activity.Nitrogen accumulations in roots and shoots were increased by 60% and 52% for Guodao 1,and by 41% and 33% for Xiushui 09,respectively,in the NH4NO3-N treatment.In the split-root system,the high rhizosphere dissolved oxygen content(8.0-9.0 mg/L) promoted root growth and development.Root biomass was increased by 21.6%,root number by 27%,maximum root length by 14%,and root volume by 10%.Moreover,nitrogen accumulation in roots was increased by 11% under high rhizosphere oxygen conditions.In conclusion,enhanced dissolved oxygen content and combined ammonium-nitrate nitrogen source have positive effects on root growth and nitrogen accumulation of rice plants.展开更多
In the Orbal oxidation ditch, denitrification is primarily accomplished in the outer channel. However, the detailed characteristics of the flow field and dissolved oxygen （DO） distribution in the outer channel are n...In the Orbal oxidation ditch, denitrification is primarily accomplished in the outer channel. However, the detailed characteristics of the flow field and dissolved oxygen （DO） distribution in the outer channel are not well understood. Therefore, in this study, the flow velocity and DO concentration in the outer channel of an Orbal oxidation ditch system in a wastewater treatment plant in Beijing （China） were monitored under actual operation conditions. The flow field and DO concentration distributions were analyzed by computed fluid dynamic modeling. In situ monitoring and modeling both showed that the flow velocity was heterogeneous in the outer channel. As a result, the DO was also heterogeneously distributed in the outer channel, with concentration gradients occurring along the flow direction as well as in the cross-section. This heterogeneous DO distribution created many anoxic and aerobic zones, which may have facilitated simultaneous nitrificafion-denitrification in the channel. These findings may provide supporting information for rational optimization of the performance of the Orbal oxidation ditch.展开更多
Deoxygenation has frequently appeared in coastal ecosystems over the past century due to the joint infl uence of increasing anthropogenically induced nutrient inputs and global warming.The semi-enclosed Bohai Sea is a...Deoxygenation has frequently appeared in coastal ecosystems over the past century due to the joint infl uence of increasing anthropogenically induced nutrient inputs and global warming.The semi-enclosed Bohai Sea is a typical system that is prone to deoxygenation,with regular hypoxia events consistently recorded in recent decades.Based on in-situ observation data collected in large-scale voyage surveys in the Bohai Sea during 2008-2017,the seasonal variability in dissolved oxygen(DO)and its controlling mechanisms were studied.The results indicated that in spring and autumn,the DO distributions exhibited similar spatial patterns in the surface and bottom layers,while in summer,its spatial distribution was characterized by large-scale oxygen-poor zones distributed off the Qinhuangdao Coast and the central southern Bohai Sea in the bottom layer.The controlling mechanisms of the DO distribution varied from season to season.Spring and autumn DO distributions were dominated by the seawater temperature.Under the combined eff ects of stratifi cation and decomposition,the summer bottom DO exhibited dual-core distribution.On the one hand,stratifi cation could greatly impede vertical mixing,resulting in reduced bottom DO replenishment.On the other hand,the increased bottom organic matter intensifi ed the decomposition processes,inducing massive DO consumption and elevated dissolved inorganic nitrogen concentrations.In addition,the stronger stratifi cation might be the reason for the more severe deoxygenation in the southern oxygen-poor zones in summer.Our study provides guidance for an in-depth understanding of the DO seasonality in the Bohai Sea and the mechanisms that modulate it and for the improvement of hypoxia forecasts in ocean models.展开更多
The intrusion of the Kuroshio into the East China Sea(ECS)aff ects the development of hypoxia off the Changjiang(Yangtze)River estuary;however,quantitative analysis of its impacts is lacking.In this study,the Regional...The intrusion of the Kuroshio into the East China Sea(ECS)aff ects the development of hypoxia off the Changjiang(Yangtze)River estuary;however,quantitative analysis of its impacts is lacking.In this study,the Regional Ocean Modeling Systems(ROMS)model coupled with the Carbon,Silicate and Nitrogen Ecosystem(CoSiNE)model was used to investigate the relative importance of dissolved oxygen(DO)and diff erent nutrients(silicate,nitrate,and phosphate)in the Kuroshio on hypoxia in the ECS.Results show that changes in DO concentrations in the Kuroshio modify the distribution and intensity of hypoxia through direct onshore transport by hydrodynamic processes.An increase in Kuroshio DO concentration by 25%or 50%would result in a decrease of the maximum hypoxia extent(MHE)in the ECS by 76%or 86%,respectively,while a 25%decrease in Kuroshio DO would increase the MHE by up to 219%.The contribution of DO in the Taiwan Strait is almost negligible.In contrast to Kuroshio DO,nutrients aff ect hypoxia in the ECS through onshore transport by hydrodynamic and biochemical processes.Changes in phosphate and nitrate concentrations by 25%in the Kuroshio would change the MHE by up to 30%and 18%,respectively,accompanied by apparent changes in surface chlorophyll-a concentrations.The eff ect of silicate on hypoxia is negligible because a 25%change in silicate concentrations in the Kuroshio would result in less than 1%change in the MHE.Our results reveal a hierarchical rank of importance for environmental variables in the Kuroshio(i.e.,DO>phosphate>nitrate>silicate)in modifying the development of hypoxia in the ECS.展开更多
The corrosion form and mechanical properties deterioration of mooring chain steel in simulated deep-sea environments were investigated.With the increase of ocean depth,not only the pressure increases,but also the diss...The corrosion form and mechanical properties deterioration of mooring chain steel in simulated deep-sea environments were investigated.With the increase of ocean depth,not only the pressure increases,but also the dissolved oxygen content decreases.These two factors affect corrosion evolution of mooring chain steel in simulated deep-sea environments,which was studied for the first time.Compared with uniform corrosion of mooring chain steel in shallow sea with sufficient oxygen,low dissolved oxygen leads to the corrosion dominated by pitting with pit covers.Meanwhile,hydrostatic pressure distinctly accelerates pitting initiation and propagation.The higher the hydrostatic pressure is,the more serious the pitting is.For failure mechanism of unstressed mooring chain steel serving in simulated deep-sea environments,both absorbed hydrogen and corrosion morphology can degrade the ductility of mooring chain steel,in which the leading factor depends on the service time.The severe pitting is the main factor and causes remarkable ductility loss of the steel after long-term immersion.But hydrogen plays an important role on elongation loss in early stage.展开更多
基金supported by the Central Guiding Local Science and Technology Development Fund of Shandong-Yellow River Basin(No.YDZX2023019)Shandong Natural Science Foundation of China(Nos.ZR2020QF067 and ZR2023QD073)+6 种基金the Discipline Cluster Research Project of Qingdao University“Deep mining and intelligent prediction of multimodal big data for marine ecological disasters”(No.20240604)sourced from the International Argo Program and the national programs that contribute to it(https://argo.ucsd.edu)the CMEMS(http://marine.copernicus.eu/)the CDS(https://cds.climate.copernicus.eu/)the EMODnet(https://www.emodnet-chemistry.eu/)obtained from the ERA5(https://www.ecmwf.int)derived from the Glob Colour Project(http://globcolour.info).
文摘Oceanic dissolved oxygen(DO)concentration is crucial for assessing the status of marine ecosystems.Against the backdrop of global warming,DO shows a general decrease,posing a threat to the health of marine ecosystems.Therefore,there is an urgent need to develop advanced tools to characterize the spatio-temporal variations of three-dimensional(3D)DO.To address this challenge,this study introduces the Light Gradient Boosting Machine(Light-GBM),combining satellite remote sensing and reanalysis data with Biogeochemical Argo data to accurately reconstruct the 3D DO structure in the Mediterranean Sea from 2010 to 2022.Various environmental parameters are incorporated as inputs,including spatiotemporal features,meteorological characteristics,and ocean color properties.The LightGBM model demonstrates excellent performance on the testing dataset with R^(2) of 0.958.The modeled DO agrees better with in-situ measurements than products from numerical models.Using the Shapley Additive exPlanations method,the contributions of input features are assessed.Sea surface temperatures provide a correlation with DO at the sea surface,while spatial coordinates supplement the view of the ocean interior.Based on the reconstructed 3D DO structure,we identify an oxygen minimum zone in the western Mediterranean that expands continuously,reaching depths of approximately 300–800 m.The western Mediterranean exhibits a significant declining trend.This study enhances marine environmental evidence by proposing a precise and cost-effective approach for reconstructing 3D DO,thereby offering insights into the dynamics of DO variations under changing climatic conditions.
基金Open Access funding provided by Kobe UniversityThis research was partially performed by the Environment Research and Technology Development Fund(2RL-2301)of the Environmental Restoration and Conservation Agency provided by Ministry of the Environment of Japan.
文摘This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessment Report,including CCP scenarios,projecting a significant temperature rise of 3.3–5.7℃in the case o very high GHG emission power,the research investigates how these shifts may influence dissolved oxygen levels in Lake Biwa.Through a one-dimensional model incorporat ing sediment redox reactions,various scenarios where ai temperature and wind speed are changed are simulated.I is revealed that a 5℃increase in air temperature leads to decreasing 1-2 mg/L of dissolved oxygen concentrations from the surface layer to the bottom layer,while a decrease in air temperature tends to elevate 1–3 mg/L of oxygen lev els.Moreover,doubling wind speed enhances surface laye oxygen but diminishes it in deeper layers due to increased mixing.Seasonal variations in wind effects are noted with significant surface layer oxygen increases from 0.4to 0.8 mg/L during summer to autumn,increases from 0.4 to 0.8 mg/L in autumn to winter due to intensified vertica mixing.This phenomenon impacts the lake’s oxygen cycle year-round.In contrast,precipitation changes show limited impact on oxygen levels,suggesting minor influence com pared to other meteorological factors.The study suggests the necessity of comprehensive three-dimensional models that account for lake-specific and geographical factors fo accurate predictions of future water conditions.A holistic approach integrating nutrient levels,water temperature,and river inflow is deemed essential for sustainable management of Lake Biwa’s water resources,particularly in addressing precipitation variations.
基金supported by the National Natural Science Foundation of China(Nos.52171236,51971062,52231005)Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,Southeast University,China(No.AMM2024A01)+3 种基金Suzhou Science and Technology Project,China(Nos.SJC2023005,SZS2023023)City University of Hong Kong Donation Research Grant,China(No.DON-RMG 9229021)City University of Hong Kong Strategic Research Grant,China(No.SRG 7005505)City University of Hong Kong Donation Grant,China(No.9220061)。
文摘To investigate the influence of oxygen content in a physiological liquid environment on the corrosion behavior of biomedical zinc-based alloys,a simulated bodily fluid environment with varying dissolved oxygen was established in vitro using external oxygen supply equipment.The influence of dissolved oxygen concentration on the corrosion behavior of pure Zn and Zn−Cu alloys was studied with scanning electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectrometry,and electrochemical analysis.Due to oxygen absorption corrosion,the increase in dissolved oxygen concentration increases the pH value of the solution and promotes the accumulation of corrosion product layer.Compared with the environment without additional oxygen supply,the corrosion rate of the sample under the continuous oxygen supply condition is increased by one order of magnitude.Because the Zn−Cu alloy has micro-galvanic corrosion,its corrosion rate is about 1.5 times that of pure zinc under different dissolved oxygen conditions.
基金The National Natural Science Foundation of China under contract Nos T2421002, 623B2071,and 42125601the National Key R&D Program of China under contract No. 2023YFF0805300
文摘Oceanic dissolved oxygen(DO)in the ocean has an indispensable role on supporting biological respiration,maintaining ecological balance and promoting nutrient cycling.According to existing research,the total DO has declined by 2%of the total over the past 50 a,and the tropical Pacific Ocean occupied the largest oxygen minimum zone(OMZ)areas.However,the sparse observation data is limited to understanding the dynamic variation and trend of ocean using traditional interpolation methods.In this study,we applied different machine learning algorithms to fit regression models between measured DO,ocean reanalysis physical variables,and spatiotemporal variables.We demonstrate that extreme gradient boosting(XGBoost)model has the best performance,hereby reconstructing a four-dimensional DO dataset of the tropical Pacific Ocean from 1920 to 2023.The results reveal that XGBoost significantly improves the reconstruction performance in the tropical Pacific Ocean,with a 35.3%reduction in root mean-squared error and a 39.5%decrease in mean absolute error.Additionally,we compare the results with three Coupled Model Intercomparison Project Phase 6(CMIP6)models data to confirm the high accuracy of the 4-dimensional reconstruction.Overall,the OMZ mainly dominates the eastern tropical Pacific Ocean,with a slow expansion.This study used XGBoost to efficiently reconstructing 4-dimensional DO enhancing the understanding of the hypoxic expansion in the tropical Pacific Ocean and we foresee that this approach would be extended to reconstruct more ocean elements.
基金supported by the National Key Research and Development Program of China(2021YFC2103300)the National Natural Science Foundation of China(22078148)the Natural Science Foundation of Jiangsu Province(BK20220002).
文摘Dissolved oxygen(DO)usually refers to the amount of oxygen dissolved in water.In the environment,medicine,and fermentation industries,the DO level needs to be accurate and capable of online monitoring to guide the precise control of water quality,clinical treatment,and microbial metabolism.Compared with other analytical methods,the electrochemical strategy is superior in its fast response,low cost,high sensitivity,and portable device.However,an electrochemical DO sensor faces a trade-off between sensitivity and long-term stability,which strongly limits its practical applications.To solve this problem,various advanced nanomaterials have been proposed to promote detection performance owing to their excellent electrocatalysis,conductivity,and chemical stability.Therefore,in this review,we focus on the recent progress of advanced nanomaterial-based electrochemical DO sensors.Through the comparison of the working principles on the main analysis techniques toward DO,the advantages of the electrochemical method are discussed.Emphasis is placed on recently developed nanomaterials that exhibit special characteristics,including nanostructures and preparation routes,to benefit DO determination.Specifically,we also introduce some interesting research on the configuration design of the electrode and device,which is rarely introduced.Then,the different requirements of the electrochemical DO sensors in different application fields are included to provide brief guidance on the selection of appropriate nanomaterials.Finally,the main challenges are evaluated to propose future development prospects and detection strategies for nanomaterial-based electrochemical sensors.
基金funding support from National Natural Science Foundation of China(Project No.61574091)Wuxi River and Lake Management and Water Resources Management Center(Project No.JSXXCG2022-004).
文摘The structure of liquid water is primarily composed of three-dimensional networks of water clusters formed by hydrogen bonds,and dis-solved oxygen is one of the most important indicators for assessing water qual-ity.In this work,distilled water with different concentration of dissolved oxygen were prepared,and a clear negative correlation between the size of water clus-ters and dissolved oxygen concentration was observed.Besides,a phenomenon of rapid absorption and release of oxygen at the water interfaces was unveiled,suggesting that oxygen molecules predominantly exist at the interfaces of water clusters.Oxygen molecules can move rapidly through the interfaces among water clusters,allowing dissolved oxygen to quickly reach a saturation level at certain partial pressure of oxygen and temperature.Further exploration into the mechanism by molecular dynamics simulations of oxygen and water clusters found that oxygen molecules can only exist stably at the interfaces among water clusters.A semi-empirical formula relating the average number of water molecules in a cluster(n)to ^(17)O NMR half-peak width(W)was summarized:n=0.1 W+0.85.These findings provide a foundation for exploring the structure and properties of water.
基金The National Key Research&Development Program of China under contract No.2023YFC3108003 in Project No.2023YFC3108000the National Natural Science Foundation of China under contract No.41876026+3 种基金the Scientific Research Fund of the Second Institute of Oceanography,Ministry of Natural Resources under contract No.YJJC2201the National Programme on Global Change and Air–Sea Interaction Phase Ⅱ under contract No.GASI-01-CJKthe Zhejiang Provincial Ten Thousand Talents Program under contract No.2020R52038the Project of State Key Laboratory of Satellite Ocean Environment Dynamics under contract No.SOEDZZ2105。
文摘Hypoxia off the Changjiang River Estuary has been the subject of much attention,yet systematic observations have been lacking,resulting in a lack of knowledge regarding its long-term change and drivers.By revisiting the repeated surveys of dissolved oxygen(DO) and other relevant hydrographic parameters along the section from the Changjiang River Estuary to the Jeju-do in the summer from 1997 to 2014,rather different trends were revealed for the dual low-DO cores.The nearshore low-DO core,located close to the river mouth and relatively stable,shows that hypoxia has become more severe with the lowest DO descen ding at a rate of -0.07 mg/(L·a) and the thickness of low-DO zone rising at a rate of 0.43 m/a.The offshore core,centered around 40-m isobath but moving back and forth between 123.5°-125°E,shows large fluctuations in the minimum DO concentration,with the thickness of low-DO zone falling at a rate of -1.55 m/a.The probable factors affecting the minimum DO concentration in the two regions also vary.In the nearshore region,the decreasing minimum DO is driven by the increase in both stratification and primary productivity,with the enhanced extension of the Changjiang River Diluted Water(CDW) strengthening stratification.In the offshore region,the fluctuating trend of the minimum DO concentration indicates that both DO loss and DO supplement are distinct.The DO loss is primarily attributed to bottom apparent oxygen utilization caused by the organic matter decay and is also relevant to the advection of low-DO water from the nearshore region.The DO supplement is primarily due to weakened stratification.Our analysis also shows that the minimum DO concentration in the nearshore region was extremely low in 1998,2003,2007 and 2010,related to El Ni?o signal in these summers.
基金The Major Projects of the National Natural Science Foundation of China under contract No.U20A20105the Guangdong Key Project under contract No.2019BT2H594+2 种基金the National Key Research and Development Program of China under contract No.2022YFC3105000the State Key Laboratory of Tropical Oceanography Independent Research Fund under contract No.LTOZZ2103the Guangxi Key Laboratory of Marine Environmental Change and Disaster in Beibu Gulf,Beibu Gulf University under contract No.2023KF01。
文摘Oxygen facilitates the breakdown of the organic material to provide energy for life.The concentration of dissolved oxygen(DO) in the water must exceed a certain threshold to support the normal metabolism of marine organisms.Located in the northern B eibu Gulf,Qinzhou B ay receives abundant freshwater and nutrients from several rivers which significantly influence the level of the dissolved oxygen.However,the spatial-temporal variations of DO as well as the associated driving mechanisms have been rarely studied through field observations.In this study,a three-dimension al coupled physical-biogeochemical model is used to investigate the spatial and seasonal variations of the DO and the associated driving mechanisms in Qinzhou B ay.The validation against observations indicates that the model can capture the seasonal and inter-annual variability of the DO concentration with the range of 5-10 mg/L.Sensitivity experiments show that the river discharges,winds and tides play crucial roles in the seasonal variability of the DO by changing the vertical mixing and stratification of the water column and the circulation pattern.In winter,the tide and wind forces have strong effects on the DO distribution by enhancing the vertical mixing,especially near the bay mouth.In summer,the river discharges play a dominant role in the DO distribution by inhibiting the vertical water exchange and delivering more nutrients to the Bay,which increases the DO depletion and results in lower DO on the bottom of the estuary salt wedge.These findings can contribute to the preservation and management of the coastal environment in the northern Beibu Gulf.
基金supported by the Scientific Research Fund of the Second Institute of Oceanography,MNR(Grant nos.JG2211 and JG2212)the National Polar Special Program“Impact and Response of Antarctic Seas to Climate Change”(Grant nos.IRASCC 01-01-02A and IRASCC 02-02)+1 种基金the National Key Research and Development Program of China(Grant no.2022YFE0136500)the National Natural Science Foundation of China(Grant no.41976228)。
文摘Dissolved oxygen(DO)and apparent oxygen utilization(AOU)are essential parameters for evaluating the impact of climate change on marine ecosystems.In this study,we utilized data on DO and AOU collected from the Amundsen Sea(western Antarctic)and the Cosmonaut Sea(eastern Antarctic)during the 38th Chinese National Antarctic Research Expedition,along with chlorophyll a(Chl a)data,to analyze the impact of primary production and the spatial distribution and structural features of water masses in these regions.The findings show that the standard deviation range of parallel DO samples is between 0.1 and 3.9μmol·L^(-1),meeting the precision criteria of the survey method.AOU values lower than 0.0μmol·L^(-1) were commonly observed in the surface waters of both regions,with the highest incidence in the polynya of Amundsen Sea,indicating a strong influence of high primary production.The Cosmonaut Sea exhibited the highest AOU values(higher than 160.0μmol·L^(-1))in the 75-500 m layer,while AOU value in the Amundsen Sea did not exceed 160.0μmol·L^(-1),suggesting potential upwelling of Circumpolar Deep Water to 100 m in the Cosmonaut Sea with minimal changes in its properties,whereas significant changes were noted in the properties of upwelling modified Circumpolar Deep Water in the Amundsen Sea.AOU values lower than 125.0μmol·L^(-1)were detected in the near-bottom waters of the Cosmonaut Sea,indicating the presence of Antarctic Bottom Water.
基金Supported by National Natural Science Foundation of China (40801227)Open Foundation of Marine and Estuarine Fisheries Resources of Ministry of Agriculture and the Key Laboratory of Ecology (Open-2-04-09)~~
文摘A dissolved oxygen fuzzy system predicting model based on neural network was put forward in this study. 106 groups of data were used to confirm the fitness of the predicting model. The first 80 groups of data were acted as training input and the other 26 groups of data were acted as the confirmed data in the system. The result showed that the testing data was approximately the same as the predicted data. So it gave a new way to solve the problem that the status of the water quality couldn＇t be predicted in time and it＇s hard to watching and measuring the factors dynamic.
文摘Influence of the combination of nutrient feed with dissolved oxygen control on taxol production in suspension cultures of Taxus chinensis (Pilg.) Rehd. was investigated in bioreactors. Addition of feeding medium with 20 g/L sucrose on day 16 enhanced both the biomass and taxol production in 5-L bioreactors. Further investigation of the fed-batch cultures in a 20-L bioreactor showed that cultivation under a low dissolved oxygen tension (DOT) of 20% for the entire culture resulted in the highest taxol content of 0.98 mg/g DW, while the taxol production was lower than that with 40% and 60% DOT. Moreover, taxol accumulation was remarkably improved by the cultivation of cells initially under DOT of 60% for 20 d followed by changing the DOT to 20% for another 12 d. By combining the use of these two strategies, a maximum taxol content of 18.7 mg/L was obtained in a 20-L bioreactor.
基金supported by the National Natural Science Foundation of China(No.51878011)
文摘Dissolved oxygen(DO)concentration is regarded as one of the crucial factors to influence partial nitrification process.However,achieving and keeping stable partial nitrification under different DO concentrations were widely reported.The mechanism of DO concentration influencing partial nitrification is still unclear.Therefore,in this study two same sequencing batch reactors(SBRs)cultivated same seeding sludge were built up with realtime control strategy.Different DO concentrations were controlled in SBRs to explore the effect of DO concentration on the long-term stability of partial nitrification process at room temperature.It was discovered that ammonium oxidation rate(AOR)was inhibited when DO concentration decreased from 2.5 to 0.5 mg/L.The abundance of Nitrospira increased from 1011.5 to 1013.7 copies/g DNA,and its relative percentage increased from 0.056%to 3.2%during 190 operational cycles,causing partial nitrification gradually turning into complete nitrification process.However,when DO was 2.5 mg/L the abundance of Nitrospira was stable and AOB was always kept at 1010.7 copies/g DNA.High AOR was maintained,and stable partial nitrification process was kept.Ammonia oxidizing bacteria(AOB)activity was significantly higher than nitrite oxidizing bacteria(NOB)activity at DO of 2.5 mg/L,which was crucial to maintain excellent nitrite accumulation performance.
文摘The Changjiang Estuary and its adjacent waters form one of the most important estuarine and coastal areas in China. Multi source and long-term data are assembled to examine the temporal-spatial distribution features of dissolved oxygen （DO） in the Changjiang Estuary and its adjacent waters for the past SO a. The results show that the DO concentration in the surface of different seasons generally stays stable, while the DO concentration in winter displays a slight increase for the last 50 a. The DO average concentration in winter and spring varies from 7 to 11 rag/L, and in summer and autumn from 6 to 8 mg/L. Hypoxic values first appear in May, and low DO value plume can be observed on the bottom in spring along coastal areas of Zhejiang and Fujian Provinces, China. In summer, the plume advances northward, and the hypoxic intensity of northern transects is much higher than southern transects. Until autumn, hypoxia areas fade away little by little, and completely disappear in winter. Within last 50 a, hypoxia in the Changjiang Estuary and its adjacent waters starts to appear in the 1980s. Since 2000, the degree of hypoxia has increased seriously and the distribution depth has become smaller. It is performed based on a large amount of historical data, and the research results will be of great significance to further study on the dynamic development of hypoxia around the Changjiang Estuary.
基金financially supported by the National Natural Science Foundation of China(No.51471175)
文摘The effect of residual dissolved oxygen （DO） on the corrosion behavior of carbon steel in 0.1 M NaHCO3 solution was investigated by electrochemical measurements, corrosion mass loss test, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. In the initial immersion stage, the increase of the dissolved oxygen concentration led to the change of from a reductive state of active dissolution to an oxidizing state of pseudo passivation in low carbon steel. While in the final stage, all the steels transformed into the steady state of pseudo passivation. In the anaerobic solution, the formation of c^-FeOOH was attributed to the chemical oxidization of the ferrous corrosion products and the final cathodic process only included the reduction of c^-FeOOH, while in the aerobic solution, it included the reduction of oxygen and （x-FeOOH simultaneously. As the main corrosion products, the content of （x-FeOOH was increased while that of Fe6（OH）12CO3 was decreased with increasing concentration of dissolved oxygen. The total corrosion mass loss of the steel was promoted with the increase of dissolved oxygen concentration.
基金supported financially by the National Natural Science Foundation of China (Nos. U1960103 and 51571139)。
文摘The corrosion behavior of 2205 duplex stainless steel was investigated in hot concentrated seawater with different dissolved oxygen(DO) concentration by electrochemical measurement techniques and surface analysis methods. DO obviously enhances the cathodic reaction process, the formation of passive film and polarization resistance. With increasing the DO concentration from 0.34 to 3.06 mg L^(-1), the relative contents of Fe_(2)O_(3) and Cr_(2)O_(3) and the Cr-enrichment gradually enlarge in the passive film. The higher DO concentrations result in lower defect densities and thicker of space charge layers in the passive films,whichmayeffectively inhibit the intrusion of aggressive chloride ions. The increment inDOconcentration clearly increases the pitting potential, but decreases the repassivation potential. It may weaken both the occurrence and repassviation tendencies of stable pitting corrosion.
基金supported by the National Natural Science Foundation of China(Grant No.30571102)the Key Projects in the National Science & Technology Pillar Program of China(Grant No.2006BAD02A13)the Provincial Natural Science Foundation of Zhejiang(Grant No.Y3100270)
文摘Dissolved oxygen and nitrogen form have important effects on rice root growth and nitrogen availability.An indica hybrid rice,Guodao 1,and a conventional japonica rice,Xiushui 09,were cultured in hypoxic nutrient solution with NH4NO3 or(NH4)2SO4 as the nitrogen source for six weeks in pools.A portion of the Guodao 1 seedlings after treatment in the pools for four weeks were transferred to a split-root system at different dissolved oxygen contents and cultured for an additional two weeks.Biomass,root morphological traits and nitrogen accumulation were recorded.Under the low rhizosphere dissolved oxygen content(0-1.0 mg/L),plant biomass was significantly increased under NH4NO3-N supply by about 69% in Guodao 1 and 41% in Xiushui 09 compared with those under NH4+-N alone.Similar results were observed for root number,maximum root length,root dry weight and root activity.Nitrogen accumulations in roots and shoots were increased by 60% and 52% for Guodao 1,and by 41% and 33% for Xiushui 09,respectively,in the NH4NO3-N treatment.In the split-root system,the high rhizosphere dissolved oxygen content(8.0-9.0 mg/L) promoted root growth and development.Root biomass was increased by 21.6%,root number by 27%,maximum root length by 14%,and root volume by 10%.Moreover,nitrogen accumulation in roots was increased by 11% under high rhizosphere oxygen conditions.In conclusion,enhanced dissolved oxygen content and combined ammonium-nitrate nitrogen source have positive effects on root growth and nitrogen accumulation of rice plants.
基金supported by the National Natural Science Foundation of China (No. 51138009)the Major Science and Technology Program for Water Pollution Control and Treatment (No. 2012ZX07203-001)
文摘In the Orbal oxidation ditch, denitrification is primarily accomplished in the outer channel. However, the detailed characteristics of the flow field and dissolved oxygen （DO） distribution in the outer channel are not well understood. Therefore, in this study, the flow velocity and DO concentration in the outer channel of an Orbal oxidation ditch system in a wastewater treatment plant in Beijing （China） were monitored under actual operation conditions. The flow field and DO concentration distributions were analyzed by computed fluid dynamic modeling. In situ monitoring and modeling both showed that the flow velocity was heterogeneous in the outer channel. As a result, the DO was also heterogeneously distributed in the outer channel, with concentration gradients occurring along the flow direction as well as in the cross-section. This heterogeneous DO distribution created many anoxic and aerobic zones, which may have facilitated simultaneous nitrificafion-denitrification in the channel. These findings may provide supporting information for rational optimization of the performance of the Orbal oxidation ditch.
基金Supported by the National Natural Science Foundation of China(No.41776012)the Key R&D Project of Zhejiang Province(No.2020C03012)+4 种基金the Shandong Provincial Natural Science Foundation(No.ZR2020MD059)the Key R&D Project of Guangdong Province(No.2020B1111030002)the Major Science and Technology Project of Sanya YZBSTC(No.SKJC-KJ-2019KY03)the National Key R&D Program of China(No.2019YFD0901305)the Marine Science and Technology Project of North China Sea Bureau in 2020:Tempo-Spatial Distribution and Its Mechanisms of the Bottom Oxygen-Poor Zones in the Bohai Sea(No.202001)。
文摘Deoxygenation has frequently appeared in coastal ecosystems over the past century due to the joint infl uence of increasing anthropogenically induced nutrient inputs and global warming.The semi-enclosed Bohai Sea is a typical system that is prone to deoxygenation,with regular hypoxia events consistently recorded in recent decades.Based on in-situ observation data collected in large-scale voyage surveys in the Bohai Sea during 2008-2017,the seasonal variability in dissolved oxygen(DO)and its controlling mechanisms were studied.The results indicated that in spring and autumn,the DO distributions exhibited similar spatial patterns in the surface and bottom layers,while in summer,its spatial distribution was characterized by large-scale oxygen-poor zones distributed off the Qinhuangdao Coast and the central southern Bohai Sea in the bottom layer.The controlling mechanisms of the DO distribution varied from season to season.Spring and autumn DO distributions were dominated by the seawater temperature.Under the combined eff ects of stratifi cation and decomposition,the summer bottom DO exhibited dual-core distribution.On the one hand,stratifi cation could greatly impede vertical mixing,resulting in reduced bottom DO replenishment.On the other hand,the increased bottom organic matter intensifi ed the decomposition processes,inducing massive DO consumption and elevated dissolved inorganic nitrogen concentrations.In addition,the stronger stratifi cation might be the reason for the more severe deoxygenation in the southern oxygen-poor zones in summer.Our study provides guidance for an in-depth understanding of the DO seasonality in the Bohai Sea and the mechanisms that modulate it and for the improvement of hypoxia forecasts in ocean models.
基金Supported by the National Key Research and Development Project of China(No.2016YFC1401603)the Scientifi c Research Fund of the Second Institute of Oceanography,MNR(No.JG2008)+7 种基金the National Program on Global Change and Air-Sea Interaction(No.GASI-04-WLHY-01)the National Natural Science Foundation of China(Nos.41705048,41876026)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(No.SL2020MS032)the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences(No.LTO2007)the CEES Visiting Fellowship Program(No.CEESRS202001)the Zhejiang Provincial Natural Science Foundation(No.LR16D060001)the Zhejiang Provincial Key Research and Development Project(No.2021C03186)the Sino-German Mobility Program:CHESS-Chinese and European Coastal Shelf Seas Ecosystem Dynamics-A Comparative Assessment(No.M-0053)。
文摘The intrusion of the Kuroshio into the East China Sea(ECS)aff ects the development of hypoxia off the Changjiang(Yangtze)River estuary;however,quantitative analysis of its impacts is lacking.In this study,the Regional Ocean Modeling Systems(ROMS)model coupled with the Carbon,Silicate and Nitrogen Ecosystem(CoSiNE)model was used to investigate the relative importance of dissolved oxygen(DO)and diff erent nutrients(silicate,nitrate,and phosphate)in the Kuroshio on hypoxia in the ECS.Results show that changes in DO concentrations in the Kuroshio modify the distribution and intensity of hypoxia through direct onshore transport by hydrodynamic processes.An increase in Kuroshio DO concentration by 25%or 50%would result in a decrease of the maximum hypoxia extent(MHE)in the ECS by 76%or 86%,respectively,while a 25%decrease in Kuroshio DO would increase the MHE by up to 219%.The contribution of DO in the Taiwan Strait is almost negligible.In contrast to Kuroshio DO,nutrients aff ect hypoxia in the ECS through onshore transport by hydrodynamic and biochemical processes.Changes in phosphate and nitrate concentrations by 25%in the Kuroshio would change the MHE by up to 30%and 18%,respectively,accompanied by apparent changes in surface chlorophyll-a concentrations.The eff ect of silicate on hypoxia is negligible because a 25%change in silicate concentrations in the Kuroshio would result in less than 1%change in the MHE.Our results reveal a hierarchical rank of importance for environmental variables in the Kuroshio(i.e.,DO>phosphate>nitrate>silicate)in modifying the development of hypoxia in the ECS.
基金supported by the National Key R&D Program of China(No.2021YFB3702200)National Natural Science Foundation of China(No.52271050).
文摘The corrosion form and mechanical properties deterioration of mooring chain steel in simulated deep-sea environments were investigated.With the increase of ocean depth,not only the pressure increases,but also the dissolved oxygen content decreases.These two factors affect corrosion evolution of mooring chain steel in simulated deep-sea environments,which was studied for the first time.Compared with uniform corrosion of mooring chain steel in shallow sea with sufficient oxygen,low dissolved oxygen leads to the corrosion dominated by pitting with pit covers.Meanwhile,hydrostatic pressure distinctly accelerates pitting initiation and propagation.The higher the hydrostatic pressure is,the more serious the pitting is.For failure mechanism of unstressed mooring chain steel serving in simulated deep-sea environments,both absorbed hydrogen and corrosion morphology can degrade the ductility of mooring chain steel,in which the leading factor depends on the service time.The severe pitting is the main factor and causes remarkable ductility loss of the steel after long-term immersion.But hydrogen plays an important role on elongation loss in early stage.
