Palmitoleic acid(POA)can be naturally found only in few oil seeds and has significant applications in pharmaceutical industry.Recently,the isolated oleaginous yeast Scheffersomyces segobiensis DSM 27193 was identified...Palmitoleic acid(POA)can be naturally found only in few oil seeds and has significant applications in pharmaceutical industry.Recently,the isolated oleaginous yeast Scheffersomyces segobiensis DSM 27193 was identified with high content of POA in its intracellular lipid(13.80%).In this study,process optimization focused on dissolved oxygen regulation to improve POA production was conducted.Dynamic agitation was found to do significant enhancement on POA-rich lipid production than aeration regulation.Under the best condition of 1000 r·min^(-1)of agitation and 1 vvm(airvolume/culture volume/min)of aeration,no ethanol was detected during the whole fermentation process,while a dry biomass concentration of 44.80 g·L^(-1)with 13.43 g·L^(-1)of lipid and 2.93 g·L^(-1)of POA was achieved.Transcription analysis revealed that the ethanol synthetic pathway was downregulated under the condition of high agitation,while the expression of the key enzymes responsible for lipid and POA accumulation were enhanced.展开更多
With the consumption of terrestrial metal resources,the exploitation of deep-sea polymetallic nodule minerals has been widely concerned around the world.Therefore,the environmental impact of deep-sea polymetallic nodu...With the consumption of terrestrial metal resources,the exploitation of deep-sea polymetallic nodule minerals has been widely concerned around the world.Therefore,the environmental impact of deep-sea polymetallic nodule mining cannot be ignored.However,duo to the lacks in stable and safe deep-sea(the depth>1000 m)vertical profile observation systems and consequently in long-term in-situ observation data,the sound speed and dissolved oxygen and the other water environment factors in the deposition areas of polymetallic nodules remains poorly understood.In this study,a deep-sea in-situ observation system was designed and deployed,and the water environment data of the polymetallic nodule deposition area were collected and analyzed.Result shows that the dissolved oxygen in the depth of 0–600 m was mainly affected by biological factors,while that in the area deeper than 600 m was affected by physical factors.The sound speed in the water body was mainly affected by temperature and pressure.At depths below 840 m,the sound speed is mainly controlled by temperature,and at depths between 840 m and 5700 m,the sound speed is mainly controlled by pressure.The correlations of sound speed vs.pressure and vs.temperature were regressed into equation.The resuspension of sediments rich in various metals may result in the reduction of dissolved oxygen and the improvement of redox potential.This environmental impact caused by a single sediment resuspension could last for 24 h or more.These findings enrich the understanding of the background value of the water environment in the polymetallic nodule deposition area.展开更多
Dissolved oxygen(DO)is one of most important factors which affect wide range physiologic features of including immune responses and intestinal bacterial community.However,the underlying mechanisms remain enigmatic.To ...Dissolved oxygen(DO)is one of most important factors which affect wide range physiologic features of including immune responses and intestinal bacterial community.However,the underlying mechanisms remain enigmatic.To address this question,the intestinal bacterial community compositions and the immune features of Atlantic salmon(Salmo salar)grown in recirculating aquaculture systems(RAS)were characterized.Fish were reared under different DO saturation levels,e.g.,200% saturation named high group(H),100%saturation named control group(CK),and 60%saturation named lower group(L).Large variations in the operational taxonomic units(OTUs)frequency distribution for the intestinal bacterial community of Atlantic salmon were observed.The intestinal bacterial community of all groups was dominated mainly by three phyla,e.g.,Proteobacteria.Firmicutes,and Bacteroidetes.Interestingly,Acinetobacter baumannii,an opportunistic pathogen of salmon was increased significantly in L group.We further monitored the immunity features of fish under different DO levels.The results show that leucocyte number,cortisol level,the expressions of interleukin-1β(IL-1β),Toll-like receptor 4(TLR4),and nucleotide-binding oligomerization domain like protein 2(NOD2)were higher at significant levels in the L group than those in the other two groups.TLR4 and NOD2 are usually related with the bacterial infections;therefore,it is reasonable to believe that the stronger immune responses observed in the L group might be related with the higher abundance of A.baumannii in the inte stine of Atlantic salmon.Overall,these findings demonstrated that low DO level may induce stronger immunity responses in Atlantic salmon.展开更多
Dissolved oxygen(DO)and apparent oxygen utilization(AOU)are crucial parameters for investigating marine ecosystem evolution and the marine environment.In this study,DO and AOU data were obtained and their spatial dist...Dissolved oxygen(DO)and apparent oxygen utilization(AOU)are crucial parameters for investigating marine ecosystem evolution and the marine environment.In this study,DO and AOU data were obtained and their spatial distribution characteristics were explored in the Cosmonaut Sea and Amundsen Sea in austral summer 2021.The standard deviation range of DO parallel samples was<0.1–3.7μmol·L–1,which met the accuracy requirements of the survey method.The DO concentration decreased sharply with water depth in the photic zone and increased slowly to the bottom.AOU in the surface layer of the two seas was significantly negatively correlated with chlorophyll a(p<0.01),and AOU was significantly lower in the south Cosmonaut Sea than in the north Cosmonaut Sea and Amundsen Sea(p<0.01).In austral summer,AOU was as low as<130μmol·L–1 in the nearshore Cosmonaut Sea with thicker Antarctic Surface Water down to ca.500 m.In early winter,AOU was lower than 50μmol·L–1 in the north Amundsen Sea in subsurface water(75–150 m).The unmodified Circumpolar Deep Water with high AOU(>160μmol·L–1)could surge up to ca.150–200 m in both seas,with stronger intrusion in the Amundsen Sea.The AOU in bottom water was significantly lower(p<0.01)in the Cosmonaut Sea(118.9±11.8μmol·L–1)than the Amundsen Sea(141.7±7.4μmol·L–1),indicating the stable existence of fresh oxygen-rich Antarctic Bottom Water in the Cosmonaut Sea.展开更多
Most of the water quality models previously developed and used in dissolved oxygen(DO) prediction are complex.Moreover,reliable data available to develop/calibrate new DO models is scarce.Therefore,there is a need to ...Most of the water quality models previously developed and used in dissolved oxygen(DO) prediction are complex.Moreover,reliable data available to develop/calibrate new DO models is scarce.Therefore,there is a need to study and develop models that can handle easily measurable parameters of a particular site,even with short length.In recent decades,computational intelligence techniques,as effective approaches for predicting complicated and significant indicator of the state of aquatic ecosystems such as DO,have created a great change in predictions.In this study,three different Al methods comprising:(1) two types of artificial neural networks(ANN) namely multi linear perceptron(MLP) and radial based function(RBF);(2) an advancement of genetic programming namely linear genetic programming(LGP);and(3) a support vector machine(SVM) technique were used for DO prediction in Delaware River located at Trenton,USA.For evaluating the performance of the proposed models,root mean square error(RMSE),Nash-Sutcliffe efficiency coefficient(NS),mean absolute relative error(MARE) and,correlation coefficient statistics(R) were used to choose the best predictive model.The comparison of estimation accuracies of various intelligence models illustrated that the SVM was able to develop the most accurate model in DO estimation in comparison to other models.Also,it was found that the LGP model performs better than the both ANNs models.For example,the determination coefficient was 0.99 for the best SVM model,while it was 0.96,0.91 and 0.81 for the best LGP,MLP and RBF models,respectively.In general,the results indicated that an SVM model could be employed satisfactorily in DO estimation.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
A full scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of COD Cr , TN and TP varied in a range of ...A full scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of COD Cr , TN and TP varied in a range of 352.9 mg/L—1338.2 mg/L, 34 4 mg/L —96.3 mg/L, and 2.21 mg/L—24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of COD Cr , BOD 5, NH 3 N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L, respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.展开更多
[Objective] The aim was to study the effects of dissolved oxygen(DO) on nitrogen release from Jialu River sediment.[Method] Based on the present pollution of Jialu River(in Zhengzhou),the effects of dissolved oxygen o...[Objective] The aim was to study the effects of dissolved oxygen(DO) on nitrogen release from Jialu River sediment.[Method] Based on the present pollution of Jialu River(in Zhengzhou),the effects of dissolved oxygen on nitrogen transformation in Jialu River sediment were analyzed through simulation test of original columnar sediment.[Result] DO was the main impact factor of nitrogen transformation in Jialu River sediment,and DO with different concentrations had various effects on the transformation time and transformation efficiency of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen.Under aerobic environment,ammoniation,nitrosification and nitrification conducted completely,and the transformation time of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen was less than that under anaerobic environment,while the transformation efficiency was higher than that under anaerobic environment.[Conclusion] The study could provide scientific references for the water pollution control of Jialu River.展开更多
Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effectively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is proposed that includ...Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effectively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is proposed that includes three stages:multi-factor analysis,adaptive decomposition,and an optimizationbased ensemble.First,considering the complex factors affecting DO,the grey relational(GR)degree method is used to screen out the environmental factors most closely related to DO.The consideration of multiple factors makes model fusion more effective.Second,the series of DO,water temperature,salinity,and oxygen saturation are decomposed adaptively into sub-series by means of the empirical wavelet transform(EWT)method.Then,five benchmark models are utilized to forecast the sub-series of EWT decomposition.The ensemble weights of these five sub-forecasting models are calculated by particle swarm optimization and gravitational search algorithm(PSOGSA).Finally,a multi-factor ensemble model for DO is obtained by weighted allocation.The performance of the proposed model is verified by timeseries data collected by the pacific islands ocean observing system(PacIOOS)from the WQB04 station at Hilo.The evaluation indicators involved in the experiment include the Nash–Sutcliffe efficiency(NSE),Kling–Gupta efficiency(KGE),mean absolute percent error(MAPE),standard deviation of error(SDE),and coefficient of determination(R^(2)).Example analysis demonstrates that:①The proposed model can obtain excellent DO forecasting results;②the proposed model is superior to other comparison models;and③the forecasting model can be used to analyze the trend of DO and enable managers to make better management decisions.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 distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem f...The distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem functions of rivers and lakes.In this work,the transport of high Schmidt number DO at the sediment-water interface of spanwise oscillating flow is investigated.The volume-averaged Navier-Stokes(VANS)equations and Monod equation are used to describe the flow in the sediment layer and the sediment oxygen demand of microorganisms.The phase-averaged velocities and concentrations of different amplitudes and periods are studied.The dependence of DO transfer on the amplitude and period is analyzed by means of phase-average statistical quantities.It is shown that the concentration in the sediment layer is positively correlated with the turbulence intensity,and the DO concentration and penetration depth in the sediment layer increases when the period and amplitude of the oscillating flow increase.Moreover,in the presence of oscillating flow,a specific scaling relationship exists between the Sherwood number/oxygen consumption of aerobic heterotrophs and the Reynolds number.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
Tropical storms(TSs)can induce sea surface cooling,freshening,and phytoplankton blooms.The dissolved oxygen(DO)concentration response to TSs within an anticyclone is still unclear due to the rarity of in situ observat...Tropical storms(TSs)can induce sea surface cooling,freshening,and phytoplankton blooms.The dissolved oxygen(DO)concentration response to TSs within an anticyclone is still unclear due to the rarity of in situ observations.In this study,we investi-gate the variations in DO concentration attributed to TS‘Haitang’within an anticyclonic eddy in the northern South China Sea based on Chinese underwater glider data.DO concentrations have a higher value at the edge of eddy than at the core.Influenced by TS,DO concentrations decrease remarkably in the subsurface layer in all three regions(inside,edge,and outside of the anticyclonic eddy).The mean DO concentrations decrease more at the edge of the anticyclone than those inside the anticyclone.The recovery time of DO concentration after TS is around one week at the edge of the anticyclone and is>10 days within the eddy.Our observations show that the DO concentrations decrease above the subsurface chlorophyll a maxima layer.Quantitative analysis shows that variations in DO concentration are dominated by horizontal advection and vertical advection terms in the subsurface layer.展开更多
To establish a immobilization method of oxygen sensitive dye, a dissolved oxygen sensor based on a sol-gel matrix doped with ruthenium complex ([Ru(bpy)3]2+) as the oxygen-sensitive material is reported. The results i...To establish a immobilization method of oxygen sensitive dye, a dissolved oxygen sensor based on a sol-gel matrix doped with ruthenium complex ([Ru(bpy)3]2+) as the oxygen-sensitive material is reported. The results indicate that the I0 /I100 value of the [Ru(bpy)3]2+-doped in tetraethylorthosilane (TEOS) composite films are estimated to be 10.6, where I0 and I100 correspond to the detected fluorescence intensities in pure nitrogen saturated water and pure oxygen saturated water, respectively. Also, the Stern-Volmer plot shows a very good linearity at low dissolved oxygen concentrations. The response time of the composite films is 5 s upon switching from nitrogen saturated water to oxygen saturated water and 10 s from oxygen saturated water to nitrogen saturated water. The dissolved oxygen sensors based on the ruthenium complex/TEOS composite films exhibit greater sensitivity, stability and faster response time as compared to the existing ones. Furthermore, the thin films possess greatly minimized dye leaching effect.展开更多
The lack of fresh water is one of the greatest challenges of our time.Increasing population and arid regions due to the temperature change limit the use of clean water.In this paper,Streeter-Phelps equation was used t...The lack of fresh water is one of the greatest challenges of our time.Increasing population and arid regions due to the temperature change limit the use of clean water.In this paper,Streeter-Phelps equation was used to find the levels of DO(Dissolved Oxygen)and the oxygen deficit which are the main criteria for the water body quality.Reaeration constants and deoxygenation coefficients were used to find how the DO and BOD(Biological Oxygen Demand)of the water bodies converge to equilibrium.Some pollutants cannot be removed from water efficiently via traditional water treatment.EDTA derivatives,owing to their engineered chemical properties,are also studied to be the potential metal ion chelator for enhancement of water quality.These molecules were tested for their thermodynamic stabilities,reactivities,and polarizations,and these characteristics are found to be important factors in selecting the most suitable chelator for metal ion chelation which is used for water quality control.展开更多
Clarifying the role of sulfate and dissolved oxygen (DO) in methane production may allow for precise and accurate modeling of methane emissions in eutrophic lakes.We conducted field observations of sulfate,methane,and...Clarifying the role of sulfate and dissolved oxygen (DO) in methane production may allow for precise and accurate modeling of methane emissions in eutrophic lakes.We conducted field observations of sulfate,methane,and DO concentrations in Lake Abashiri,a typical brackish and eutrophic lake in a cold region,to develop a DO-based method for quantitively estimating methane production in a eutrophic lake and analyzed the results.We found that sulfate concentrations decreased rapidly from 900.0 mg/L in water overlying the sediments to nearly 0.0 mg/L in the bottom sediment.Methane production was almost uniform across sediment depths of 0.05 to 0.25 m,ranging from 1400 to 1800μmol/m^(2)/day.Also,methane production was found to be a function of DO concentrations in water overlying the bottom and could be modeled by a logistic function:constant production at 1,400μmol/m^(2)/day for DO concentrations of 0.0 to 3.0 mg/L,rapidly decreasing to 0μmol/m^(2)/day for DO concentrations of 3.0 to 6.0 mg/L.This methane model was verified using a simple one-dimensional numerical model that showed good agreement with field observations.Our results thus suggest that the proposed methane model reduces uncertainty in estimating methane production in a eutrophic lake.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
The misuse of antibiotics and oxygen-lacking in aquaculture causes serious water environmental problems.Herein,a piezoelectic odd-layered MoS_(2)is prepared and applied to piezo-catalytic remove tinidazole(TNZ)and oth...The misuse of antibiotics and oxygen-lacking in aquaculture causes serious water environmental problems.Herein,a piezoelectic odd-layered MoS_(2)is prepared and applied to piezo-catalytic remove tinidazole(TNZ)and other antibiotic pollutants with aeration as a piezo-driving force.About 89.6%of TNZ can be degraded by MoS_(2)under aeration in the presence of dissolved oxygen with a reaction rate constant of0.15 min^(-1),which is 2.4 times higher than that under N2atmosphere and quiescence conditions.Quenching experiments and electron paramagnetic resonance(EPR)tests identify that singlet oxygen(^(1)O_(2))and superoxide radical(O_(2)^(·-))are dominant reactive oxygen species in MoS_(2)/aeration system.These results demonstrate that MoS2can trigger a piezoelectric effect and produce charge carriers to generate reactive oxygen species with dissolved oxygen(DO)for contaminant degradation with the turbulence and water bubbles rupture driven by aeration.展开更多
The Ediacaran Period(635–539 Ma)witnessed the largest negative excursion in inorganic carbon isotope(δ^(13)Ccarb)over the Earth’s geological history,also known as the Shuram Excursion(SE)event.The occurrence of the...The Ediacaran Period(635–539 Ma)witnessed the largest negative excursion in inorganic carbon isotope(δ^(13)Ccarb)over the Earth’s geological history,also known as the Shuram Excursion(SE)event.The occurrence of the SE has been widely attributed to an increase in atmospheric-oceanic oxygen levels and the subsequent oxidation of organic matters in Earth’s surface system.However,the oxygen levels in the Ediacaran ocean during the SE remain poorly constrained,limiting our ability to better understand the cause and mechanisms behind the SE.Recently,the ratio of I/(Ca+Mg)in carbonate has emerged as an effective proxy for quantifying dissolved oxygen([O_(2)])in the local surface seawaters.In this study,we analyzed I/(Ca+Mg)ratios in the Shuiquan Formation at the Mochia-Khutuk(MK)section,which records the SE event in the Tarim continent.The I/(Ca+Mg)ratio shows synchronous variation withδ^(13)Ccarbin the MK section,with the average value decreasing from 2.2μmol/mol at the bottom of the section to 0.8μmol/mol in the middle and then increasing to 3.4μmol/mol at the very top along with the decline and recovery ofδ^(13)Ccarb.According to the relationship between I/(Ca+Mg)and oxygen content in minimum oxygen zones of the modern ocean,we infer that[O_(2)]of surface water in the MK section decreased from>20–70μmol/L to<20–70μmol/L during the SE,which may reflect the upwelling of the deep seawater enriched dissolved organic carbon(DOC)and reduced substance(such as Fe^(2+))together with its subsequent consumption of[O2]in the surface ocean.The I/(Ca+Mg)pattern in the MK section is significantly different from those of other contemporaneous SE records on other continents,indicating the surface[O_(2)]in the Ediacaran ocean could have been temporally and spatially heterogeneous.Local factors,such as latitude,temperature,productivity,and input of anoxic water masses could play important roles in regulating the surface ocean redox conditions.This observation further suggests that the atmospheric oxygen level during the Ediacaran was relatively low and insufficient to dominate the regulation of[O_(2)]in the surface ocean.The results of our study imply that the oxidation of the ocean and in turn the DOC reservoir therein during the SE could be spatially restricted to the continental shelf,rather than the whole ocean.展开更多
In this article, the dissolved oxygen(DO) concentration control problem in wastewater treatment process(WWTP) is studied.Unlike existing control strategies that control DO concentration at a fixed value, here we devel...In this article, the dissolved oxygen(DO) concentration control problem in wastewater treatment process(WWTP) is studied.Unlike existing control strategies that control DO concentration at a fixed value, here we develop a different control framework.Under the proposed control framework, an intelligent control method of DO concentration based on reinforcement learning(RL)algorithm is presented to resolve the DO concentration control problem. By using the deep deterministic policy gradient(DDPG)algorithm, the DO concentration of the fifth tank in the activated sludge reactor can be adjusted dynamically. In addition, by designing two different reward functions and by analysing the relationships among effluent quality, energy consumption, and DO concentration, the target of energy-saving and emission-reducing is achieved. The simulation results indicate that the designed control method can reduce energy consumption while ensuring that the effluent quality meet the specified standards.展开更多
基金supported by the National Key Research & Development Program of China (2021YFC2101500, 2018YFA0902200)National Natural Science Foundation of China (22008115, 21978130)+4 种基金Jiangsu Province Natural Science Foundation for Youths (SBK2020044721)Jiangsu Provincial Agricultural Science and Technology Independent Innovation Fund Project (CX(21)3120)Jiangsu Planned Projects for Postdoctoral Research Funds (2021K085A)China Postdoctoral Science Foundation (2020M671467)Postdoctoral Research Funding Program of Jiangsu Province (2021K085A)
文摘Palmitoleic acid(POA)can be naturally found only in few oil seeds and has significant applications in pharmaceutical industry.Recently,the isolated oleaginous yeast Scheffersomyces segobiensis DSM 27193 was identified with high content of POA in its intracellular lipid(13.80%).In this study,process optimization focused on dissolved oxygen regulation to improve POA production was conducted.Dynamic agitation was found to do significant enhancement on POA-rich lipid production than aeration regulation.Under the best condition of 1000 r·min^(-1)of agitation and 1 vvm(airvolume/culture volume/min)of aeration,no ethanol was detected during the whole fermentation process,while a dry biomass concentration of 44.80 g·L^(-1)with 13.43 g·L^(-1)of lipid and 2.93 g·L^(-1)of POA was achieved.Transcription analysis revealed that the ethanol synthetic pathway was downregulated under the condition of high agitation,while the expression of the key enzymes responsible for lipid and POA accumulation were enhanced.
基金Supported by the National Natural Science Foundation of China(No.42107157)the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(No.MGQNLM-KF202101)+1 种基金the Fundamental Research Funds for the Central Universities,SCUT(No.21CX06016A)the Harbin Engineering University at Qingdao(No.2022-SXZN-CXJJ-04-06+01)。
文摘With the consumption of terrestrial metal resources,the exploitation of deep-sea polymetallic nodule minerals has been widely concerned around the world.Therefore,the environmental impact of deep-sea polymetallic nodule mining cannot be ignored.However,duo to the lacks in stable and safe deep-sea(the depth>1000 m)vertical profile observation systems and consequently in long-term in-situ observation data,the sound speed and dissolved oxygen and the other water environment factors in the deposition areas of polymetallic nodules remains poorly understood.In this study,a deep-sea in-situ observation system was designed and deployed,and the water environment data of the polymetallic nodule deposition area were collected and analyzed.Result shows that the dissolved oxygen in the depth of 0–600 m was mainly affected by biological factors,while that in the area deeper than 600 m was affected by physical factors.The sound speed in the water body was mainly affected by temperature and pressure.At depths below 840 m,the sound speed is mainly controlled by temperature,and at depths between 840 m and 5700 m,the sound speed is mainly controlled by pressure.The correlations of sound speed vs.pressure and vs.temperature were regressed into equation.The resuspension of sediments rich in various metals may result in the reduction of dissolved oxygen and the improvement of redox potential.This environmental impact caused by a single sediment resuspension could last for 24 h or more.These findings enrich the understanding of the background value of the water environment in the polymetallic nodule deposition area.
基金Supported by the Shandong Province Key Research and Invention Program(No.2017CXGC010K)the China Agriculture Research System(No.CARS-47)+7 种基金the National Key Research and Development Program(No.2018YFD0901204)the National Infrastructure of Fishery Germplasm Resource(No.2019DKA30470)the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2018SDKJ0502-2)the National Natural Science Foundation of China(Nos.31872606,31572657,U1701233,31402283,31802319)the Department of Agriculture and Rural Areas of Guangdong Province(No.KA1911101)the Natural Science Foundation of Shandong Province(No.ZR2018BC053)the Agricultural Application Technology Innovation Project of Shandong Province in 2018/2019(No.SD2019YY011)the Shandong Province Major Scientific and Technological Innovation Projects(No.2019JZZY020710)。
文摘Dissolved oxygen(DO)is one of most important factors which affect wide range physiologic features of including immune responses and intestinal bacterial community.However,the underlying mechanisms remain enigmatic.To address this question,the intestinal bacterial community compositions and the immune features of Atlantic salmon(Salmo salar)grown in recirculating aquaculture systems(RAS)were characterized.Fish were reared under different DO saturation levels,e.g.,200% saturation named high group(H),100%saturation named control group(CK),and 60%saturation named lower group(L).Large variations in the operational taxonomic units(OTUs)frequency distribution for the intestinal bacterial community of Atlantic salmon were observed.The intestinal bacterial community of all groups was dominated mainly by three phyla,e.g.,Proteobacteria.Firmicutes,and Bacteroidetes.Interestingly,Acinetobacter baumannii,an opportunistic pathogen of salmon was increased significantly in L group.We further monitored the immunity features of fish under different DO levels.The results show that leucocyte number,cortisol level,the expressions of interleukin-1β(IL-1β),Toll-like receptor 4(TLR4),and nucleotide-binding oligomerization domain like protein 2(NOD2)were higher at significant levels in the L group than those in the other two groups.TLR4 and NOD2 are usually related with the bacterial infections;therefore,it is reasonable to believe that the stronger immune responses observed in the L group might be related with the higher abundance of A.baumannii in the inte stine of Atlantic salmon.Overall,these findings demonstrated that low DO level may induce stronger immunity responses in Atlantic salmon.
基金supported by the National Polar Special Program“Impact and Response of Antarctic Seas to Climate Change”(Grant nos.IRASCC 01-01-02A,IRASCC 02-02)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 crucial parameters for investigating marine ecosystem evolution and the marine environment.In this study,DO and AOU data were obtained and their spatial distribution characteristics were explored in the Cosmonaut Sea and Amundsen Sea in austral summer 2021.The standard deviation range of DO parallel samples was<0.1–3.7μmol·L–1,which met the accuracy requirements of the survey method.The DO concentration decreased sharply with water depth in the photic zone and increased slowly to the bottom.AOU in the surface layer of the two seas was significantly negatively correlated with chlorophyll a(p<0.01),and AOU was significantly lower in the south Cosmonaut Sea than in the north Cosmonaut Sea and Amundsen Sea(p<0.01).In austral summer,AOU was as low as<130μmol·L–1 in the nearshore Cosmonaut Sea with thicker Antarctic Surface Water down to ca.500 m.In early winter,AOU was lower than 50μmol·L–1 in the north Amundsen Sea in subsurface water(75–150 m).The unmodified Circumpolar Deep Water with high AOU(>160μmol·L–1)could surge up to ca.150–200 m in both seas,with stronger intrusion in the Amundsen Sea.The AOU in bottom water was significantly lower(p<0.01)in the Cosmonaut Sea(118.9±11.8μmol·L–1)than the Amundsen Sea(141.7±7.4μmol·L–1),indicating the stable existence of fresh oxygen-rich Antarctic Bottom Water in the Cosmonaut Sea.
文摘Most of the water quality models previously developed and used in dissolved oxygen(DO) prediction are complex.Moreover,reliable data available to develop/calibrate new DO models is scarce.Therefore,there is a need to study and develop models that can handle easily measurable parameters of a particular site,even with short length.In recent decades,computational intelligence techniques,as effective approaches for predicting complicated and significant indicator of the state of aquatic ecosystems such as DO,have created a great change in predictions.In this study,three different Al methods comprising:(1) two types of artificial neural networks(ANN) namely multi linear perceptron(MLP) and radial based function(RBF);(2) an advancement of genetic programming namely linear genetic programming(LGP);and(3) a support vector machine(SVM) technique were used for DO prediction in Delaware River located at Trenton,USA.For evaluating the performance of the proposed models,root mean square error(RMSE),Nash-Sutcliffe efficiency coefficient(NS),mean absolute relative error(MARE) and,correlation coefficient statistics(R) were used to choose the best predictive model.The comparison of estimation accuracies of various intelligence models illustrated that the SVM was able to develop the most accurate model in DO estimation in comparison to other models.Also,it was found that the LGP model performs better than the both ANNs models.For example,the determination coefficient was 0.99 for the best SVM model,while it was 0.96,0.91 and 0.81 for the best LGP,MLP and RBF models,respectively.In general,the results indicated that an SVM model could be employed satisfactorily in DO estimation.
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.
文摘A full scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of COD Cr , TN and TP varied in a range of 352.9 mg/L—1338.2 mg/L, 34 4 mg/L —96.3 mg/L, and 2.21 mg/L—24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of COD Cr , BOD 5, NH 3 N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L, respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.
基金Supported by National Key Water Project of Huai River(2009ZX07010-010-003)
文摘[Objective] The aim was to study the effects of dissolved oxygen(DO) on nitrogen release from Jialu River sediment.[Method] Based on the present pollution of Jialu River(in Zhengzhou),the effects of dissolved oxygen on nitrogen transformation in Jialu River sediment were analyzed through simulation test of original columnar sediment.[Result] DO was the main impact factor of nitrogen transformation in Jialu River sediment,and DO with different concentrations had various effects on the transformation time and transformation efficiency of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen.Under aerobic environment,ammoniation,nitrosification and nitrification conducted completely,and the transformation time of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen was less than that under anaerobic environment,while the transformation efficiency was higher than that under anaerobic environment.[Conclusion] The study could provide scientific references for the water pollution control of Jialu River.
基金the National Natural Science Foundation of China(61873283)the Changsha Science&Technology Project(KQ1707017)the innovation-driven project of the Central South University(2019CX005).
文摘Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effectively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is proposed that includes three stages:multi-factor analysis,adaptive decomposition,and an optimizationbased ensemble.First,considering the complex factors affecting DO,the grey relational(GR)degree method is used to screen out the environmental factors most closely related to DO.The consideration of multiple factors makes model fusion more effective.Second,the series of DO,water temperature,salinity,and oxygen saturation are decomposed adaptively into sub-series by means of the empirical wavelet transform(EWT)method.Then,five benchmark models are utilized to forecast the sub-series of EWT decomposition.The ensemble weights of these five sub-forecasting models are calculated by particle swarm optimization and gravitational search algorithm(PSOGSA).Finally,a multi-factor ensemble model for DO is obtained by weighted allocation.The performance of the proposed model is verified by timeseries data collected by the pacific islands ocean observing system(PacIOOS)from the WQB04 station at Hilo.The evaluation indicators involved in the experiment include the Nash–Sutcliffe efficiency(NSE),Kling–Gupta efficiency(KGE),mean absolute percent error(MAPE),standard deviation of error(SDE),and coefficient of determination(R^(2)).Example analysis demonstrates that:①The proposed model can obtain excellent DO forecasting results;②the proposed model is superior to other comparison models;and③the forecasting model can be used to analyze the trend of DO and enable managers to make better management decisions.
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Project supported by the National Natural Science Foundation of China(Nos.91852111 and 92052201)and the Program of the Shanghai Municipal Education Commission(No.2019-01-07-00-09-E00018)。
文摘The distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem functions of rivers and lakes.In this work,the transport of high Schmidt number DO at the sediment-water interface of spanwise oscillating flow is investigated.The volume-averaged Navier-Stokes(VANS)equations and Monod equation are used to describe the flow in the sediment layer and the sediment oxygen demand of microorganisms.The phase-averaged velocities and concentrations of different amplitudes and periods are studied.The dependence of DO transfer on the amplitude and period is analyzed by means of phase-average statistical quantities.It is shown that the concentration in the sediment layer is positively correlated with the turbulence intensity,and the DO concentration and penetration depth in the sediment layer increases when the period and amplitude of the oscillating flow increase.Moreover,in the presence of oscillating flow,a specific scaling relationship exists between the Sherwood number/oxygen consumption of aerobic heterotrophs and the Reynolds number.
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 Natural Science Foundation of China(No.41976002)the National Key R&D Plan of China(Nos.2017YFC0305904,2016YFC0301201).
文摘Tropical storms(TSs)can induce sea surface cooling,freshening,and phytoplankton blooms.The dissolved oxygen(DO)concentration response to TSs within an anticyclone is still unclear due to the rarity of in situ observations.In this study,we investi-gate the variations in DO concentration attributed to TS‘Haitang’within an anticyclonic eddy in the northern South China Sea based on Chinese underwater glider data.DO concentrations have a higher value at the edge of eddy than at the core.Influenced by TS,DO concentrations decrease remarkably in the subsurface layer in all three regions(inside,edge,and outside of the anticyclonic eddy).The mean DO concentrations decrease more at the edge of the anticyclone than those inside the anticyclone.The recovery time of DO concentration after TS is around one week at the edge of the anticyclone and is>10 days within the eddy.Our observations show that the DO concentrations decrease above the subsurface chlorophyll a maxima layer.Quantitative analysis shows that variations in DO concentration are dominated by horizontal advection and vertical advection terms in the subsurface layer.
基金Funded by the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials of Sichuan Province (No.10zxfk23)Scientific Research Project of Sichuan Normal University (No.11KYL06)
文摘To establish a immobilization method of oxygen sensitive dye, a dissolved oxygen sensor based on a sol-gel matrix doped with ruthenium complex ([Ru(bpy)3]2+) as the oxygen-sensitive material is reported. The results indicate that the I0 /I100 value of the [Ru(bpy)3]2+-doped in tetraethylorthosilane (TEOS) composite films are estimated to be 10.6, where I0 and I100 correspond to the detected fluorescence intensities in pure nitrogen saturated water and pure oxygen saturated water, respectively. Also, the Stern-Volmer plot shows a very good linearity at low dissolved oxygen concentrations. The response time of the composite films is 5 s upon switching from nitrogen saturated water to oxygen saturated water and 10 s from oxygen saturated water to nitrogen saturated water. The dissolved oxygen sensors based on the ruthenium complex/TEOS composite films exhibit greater sensitivity, stability and faster response time as compared to the existing ones. Furthermore, the thin films possess greatly minimized dye leaching effect.
文摘The lack of fresh water is one of the greatest challenges of our time.Increasing population and arid regions due to the temperature change limit the use of clean water.In this paper,Streeter-Phelps equation was used to find the levels of DO(Dissolved Oxygen)and the oxygen deficit which are the main criteria for the water body quality.Reaeration constants and deoxygenation coefficients were used to find how the DO and BOD(Biological Oxygen Demand)of the water bodies converge to equilibrium.Some pollutants cannot be removed from water efficiently via traditional water treatment.EDTA derivatives,owing to their engineered chemical properties,are also studied to be the potential metal ion chelator for enhancement of water quality.These molecules were tested for their thermodynamic stabilities,reactivities,and polarizations,and these characteristics are found to be important factors in selecting the most suitable chelator for metal ion chelation which is used for water quality control.
基金supported by JSPS KAKENHI grant numbers JP26420491, JP14J03382, JP18KK0119, JP18H01545, JP18K13835, and JP21H05178。
文摘Clarifying the role of sulfate and dissolved oxygen (DO) in methane production may allow for precise and accurate modeling of methane emissions in eutrophic lakes.We conducted field observations of sulfate,methane,and DO concentrations in Lake Abashiri,a typical brackish and eutrophic lake in a cold region,to develop a DO-based method for quantitively estimating methane production in a eutrophic lake and analyzed the results.We found that sulfate concentrations decreased rapidly from 900.0 mg/L in water overlying the sediments to nearly 0.0 mg/L in the bottom sediment.Methane production was almost uniform across sediment depths of 0.05 to 0.25 m,ranging from 1400 to 1800μmol/m^(2)/day.Also,methane production was found to be a function of DO concentrations in water overlying the bottom and could be modeled by a logistic function:constant production at 1,400μmol/m^(2)/day for DO concentrations of 0.0 to 3.0 mg/L,rapidly decreasing to 0μmol/m^(2)/day for DO concentrations of 3.0 to 6.0 mg/L.This methane model was verified using a simple one-dimensional numerical model that showed good agreement with field observations.Our results thus suggest that the proposed methane model reduces uncertainty in estimating methane production in a eutrophic lake.
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.
基金financially supported by Open Project of State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(No.ESK202102)the Science and Technology Program of Guangzhou(No.202201020545)the Special Fund for Basic Scientific Research Business of Central Public Research Institutes(No.PM-zx703-202204-117)。
文摘The misuse of antibiotics and oxygen-lacking in aquaculture causes serious water environmental problems.Herein,a piezoelectic odd-layered MoS_(2)is prepared and applied to piezo-catalytic remove tinidazole(TNZ)and other antibiotic pollutants with aeration as a piezo-driving force.About 89.6%of TNZ can be degraded by MoS_(2)under aeration in the presence of dissolved oxygen with a reaction rate constant of0.15 min^(-1),which is 2.4 times higher than that under N2atmosphere and quiescence conditions.Quenching experiments and electron paramagnetic resonance(EPR)tests identify that singlet oxygen(^(1)O_(2))and superoxide radical(O_(2)^(·-))are dominant reactive oxygen species in MoS_(2)/aeration system.These results demonstrate that MoS2can trigger a piezoelectric effect and produce charge carriers to generate reactive oxygen species with dissolved oxygen(DO)for contaminant degradation with the turbulence and water bubbles rupture driven by aeration.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0800100)the National Natural Science Foundation of China(Grant Nos.42130208,41825019,42072335,42002027)。
文摘The Ediacaran Period(635–539 Ma)witnessed the largest negative excursion in inorganic carbon isotope(δ^(13)Ccarb)over the Earth’s geological history,also known as the Shuram Excursion(SE)event.The occurrence of the SE has been widely attributed to an increase in atmospheric-oceanic oxygen levels and the subsequent oxidation of organic matters in Earth’s surface system.However,the oxygen levels in the Ediacaran ocean during the SE remain poorly constrained,limiting our ability to better understand the cause and mechanisms behind the SE.Recently,the ratio of I/(Ca+Mg)in carbonate has emerged as an effective proxy for quantifying dissolved oxygen([O_(2)])in the local surface seawaters.In this study,we analyzed I/(Ca+Mg)ratios in the Shuiquan Formation at the Mochia-Khutuk(MK)section,which records the SE event in the Tarim continent.The I/(Ca+Mg)ratio shows synchronous variation withδ^(13)Ccarbin the MK section,with the average value decreasing from 2.2μmol/mol at the bottom of the section to 0.8μmol/mol in the middle and then increasing to 3.4μmol/mol at the very top along with the decline and recovery ofδ^(13)Ccarb.According to the relationship between I/(Ca+Mg)and oxygen content in minimum oxygen zones of the modern ocean,we infer that[O_(2)]of surface water in the MK section decreased from>20–70μmol/L to<20–70μmol/L during the SE,which may reflect the upwelling of the deep seawater enriched dissolved organic carbon(DOC)and reduced substance(such as Fe^(2+))together with its subsequent consumption of[O2]in the surface ocean.The I/(Ca+Mg)pattern in the MK section is significantly different from those of other contemporaneous SE records on other continents,indicating the surface[O_(2)]in the Ediacaran ocean could have been temporally and spatially heterogeneous.Local factors,such as latitude,temperature,productivity,and input of anoxic water masses could play important roles in regulating the surface ocean redox conditions.This observation further suggests that the atmospheric oxygen level during the Ediacaran was relatively low and insufficient to dominate the regulation of[O_(2)]in the surface ocean.The results of our study imply that the oxidation of the ocean and in turn the DOC reservoir therein during the SE could be spatially restricted to the continental shelf,rather than the whole ocean.
基金supported by the National Natural Science Foundation of China(Grant No.62173009)the National Key Research and Development Program of China(Grant No.2021ZD0112302)。
文摘In this article, the dissolved oxygen(DO) concentration control problem in wastewater treatment process(WWTP) is studied.Unlike existing control strategies that control DO concentration at a fixed value, here we develop a different control framework.Under the proposed control framework, an intelligent control method of DO concentration based on reinforcement learning(RL)algorithm is presented to resolve the DO concentration control problem. By using the deep deterministic policy gradient(DDPG)algorithm, the DO concentration of the fifth tank in the activated sludge reactor can be adjusted dynamically. In addition, by designing two different reward functions and by analysing the relationships among effluent quality, energy consumption, and DO concentration, the target of energy-saving and emission-reducing is achieved. The simulation results indicate that the designed control method can reduce energy consumption while ensuring that the effluent quality meet the specified standards.
