Harmful algal blooms(HABs)have emerged as a critical global environmental and ecological concern.Timely and accurate monitoring of the prevalent bloom-forming genera is crucial for HABmanagement.Conventional microscop...Harmful algal blooms(HABs)have emerged as a critical global environmental and ecological concern.Timely and accurate monitoring of the prevalent bloom-forming genera is crucial for HABmanagement.Conventional microscope-based methods are time-consuming,laborintensive,and specialized expertise-dependent,often making them impractical for largescale surveillance.Molecular methods,such as metabarcoding,provide efficient technical solutions;however,the lack of competent PCR primers and further field validation present obstacles to their wide use.Here,we successfully developed Aphanizomenon-specific primers and validated the application of environmental DNA(eDNA)metabarcoding for field-based monitoring of Aphanizomenon in 37 sites across lentic and lotic freshwater ecosystems in Beijing.The sensitivity and specificity tests of newly developed primers demonstrated high performance-comprehensive recovery of biodiversity in Aphanizomenon communities and high ratios(>95%)of Aphanizomenon sequences in datasets.We observed significant correlations between the sequence abundance derived fromeDNAmetabarcoding and the total cell density determined through microscopic identification across all the sampling sites,both in the spring(r=0.8086,p<0.0001)and summer(r=0.7902,p<0.0001),thus validating the utility of eDNA metabarcoding based on the newly developed primers for monitoring in the field.Further,we identified key environmental variables that were primary drivers responsible for the spatiotemporal distribution of Aphanizomenon abundance.These variables included temperature,total nitrogen,and dissolved oxygen in lentic ecosystems,and total phosphorus in lotic ecosystems.The method developed and validated here offers an accurate,efficient,and high-throughput tool for the monitoring of Aphanizomenon blooms in freshwater ecosystems.展开更多
During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configura...During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.展开更多
The 2016–2022 monitoring data from three ecological buoys in the Wenzhou coastal region of Zhejiang Province and the dataset European Centre for Medium-Range Weather Forecasts were examined to clarify the elaborate r...The 2016–2022 monitoring data from three ecological buoys in the Wenzhou coastal region of Zhejiang Province and the dataset European Centre for Medium-Range Weather Forecasts were examined to clarify the elaborate relationship between variations in ecological parameters during spring algal bloom incidents and the associated changes in temperature and wind fields in this study.A long short-term memory recurrent neural network was employed,and a predictive model for spring algal bloom in this region was developed.This model integrated various inputs,including temperature,wind speed,and other pertinent variables,and chlorophyll concentration served as the primary output indicator.The model training used chlorophyll concentration data,which were supplemented by reanalysis and forecast temperature and wind field data.The model demonstrated proficiency in forecasting next-day chlorophyll concentrations and assessing the likelihood of spring algal bloom occurrences using a defined chlorophyll concentration threshold.The historical validation from 2016 to 2019 corroborated the model's accuracy with an 81.71%probability of correct prediction,which was further proven by its precise prediction of two spring algal bloom incidents in late April 2023 and early May 2023.An interpretable machine learning-based model for spring algal bloom prediction,displaying effective forecasting with limited data,was established through the detailed analysis of the spring algal bloom mechanism and the careful selection of input variables.The insights gained from this study offer valuable contributions to the development of early warning systems for spring algal bloom in the Wenzhou coastal area of Zhejiang Province.展开更多
In eutrophic shallow lakes,cyanobacterial blooms will occur frequently and then settle into sediment,leading the formation of fluid sediment.Several factors including temperature can influence surface sediment propert...In eutrophic shallow lakes,cyanobacterial blooms will occur frequently and then settle into sediment,leading the formation of fluid sediment.Several factors including temperature can influence surface sediment properties.In this study,the influence of temperatures on surface sediment properties was determined in microcosm experiments through monitoring sediment physicochemical and rheological properties.During one-month incubation,it was found that surface sediment density and water content varied exponentially with increase in temperatures from 10 to 35℃.The results of particle size distribution indicated that cyanobacterial blooms biomass(CBB)degradation in sediment led to sediment flocculation and agglomeration.In themeantime,therewere high ratios polysaccharide/protein in extracellular polymeric substances(EPSs),which enhanced the sediment particle agglomeration.Further,the yield stress in rheological test for sediment with(R^(2)=0.97)and without(R^(2)=0.85)CBB presented an exponential decay with increase in temperatures.And a threshold value at 20℃ for sediment critical shear stress(τ_(cr))indicated that sediment could be resuspended easier when temperature was more than 20℃.Altogether,this study showed that the increase in temperatures with a threshold at 20℃,can cause sediment particle flocculation,resulting in a loose and fragile structure.And the results would be helpful to sediment management considering environmental effects of sediment suspension for eutrophication shallow lakes.展开更多
Harmful macroalgal blooms caused by Ulva prolifera and Sargassum horneri are increasing in the Yellow Sea and East China Sea.However,our understanding of macroalgal blooms before 2008 is fragmented and unclear.Using t...Harmful macroalgal blooms caused by Ulva prolifera and Sargassum horneri are increasing in the Yellow Sea and East China Sea.However,our understanding of macroalgal blooms before 2008 is fragmented and unclear.Using time-series Landsat imagery from 1984 to 2008,we examined macroalgal bloom events and their evolutionary patterns.The results suggest that no macroalgal blooms were observed before 1999.Ulva blooms could be traced back to 1999 and occurred on a small scale in 2000,2004 and 2005,before escalating into large green tides in 2007 and 2008.Notably,these Ulva blooms were confined to the southern Yellow Sea from May to August.In comparison,Sargassum blooms were first detected in the East China Sea in March 2000 and occurred almost every year thereafter,although the size of the blooms showed significant interannual variation.The distribution areas generally moved northwards from March until the bloom dissipated in May or June,suggesting the influence of the monsoon and currents.Our investigation provided some insight into the bloom history of these two harmful macroalgal blooms in the Yellow Sea and East China Sea.展开更多
A coupled computational model of molten steel within the mold was developed,encompassing electromagnetic fields,fluid flow,heat transfer,shell formation,stress,and strain.The model was verified through comparison with...A coupled computational model of molten steel within the mold was developed,encompassing electromagnetic fields,fluid flow,heat transfer,shell formation,stress,and strain.The model was verified through comparison with plant measurements,showing reasonable agreement in electromagnetic field distribution,solidification endpoint,and shell thickness.Results indicate that coordinating the submerged entry nozzle(SEN)and mold electromagnetic stirring(M-EMS)effectively regulates the solidification quality of the initial shell.Adjusting M-EMS current frequency changes the impact position of the molten steel jet from the four-port SEN,while increasing current intensity reduces the jet impact intensity.Adjusting the M-EMS parameters can enhance the initial shell uniformity.Furthermore,in areas directly impacted by the steel jet from the four-port SEN,a relationship between brittle temperature range(BTR)width and total mechanical strain was found,and the larger the BTR width,the smaller the corresponding total mechanical strain.The BTR width provides a discriminant method to avoid hot tearing.Appropriate M-EMS parameters are obtained and applied,and the plant trials show a significant improvement in hot tearing near the surface of round blooms.展开更多
Inexpensive flocculant-modified iron tailings sand(ITS)were converted into effective flocculation materials for cyanobacteria blooms.After composite modification with polyaluminum chloride(PAC)and polyacrylamide(PAM),...Inexpensive flocculant-modified iron tailings sand(ITS)were converted into effective flocculation materials for cyanobacteria blooms.After composite modification with polyaluminum chloride(PAC)and polyacrylamide(PAM),the surface charge of ITS was altered from negative to positive,and surface adhesion was increased by~1.5 times.PAC/PAM-modified ITS(PP-ITS)had strong flocculating effects on cyanobacteria,facilitating their removal.When the dosage of PP-ITS was 150 mg/L and the ratio of flocculant to ITS was 1:20,the elimination rate of cyanobacteria was as high as 90%.The flocs formed were better than those with chitosan-modified clays(CS-CA)and PAC-modified ITS(PAC-ITS)in terms of settling velocity,size,and recovery ability.The positively charged groups in the flocculant,such as-NH_(2) and Al^(3+),are attracted to negatively charged ions on the surface of ITS,altering the surface charge.Additionally,hydrogen bonds could form between amide side groups,and surface adhesion was improved through molecular association.Coupled with the strong bridging and sweeping effects of the flocculant,the flocs generated by PP-ITS formed rapidly and were large and resilient.The use of PP-ITS could effectively treat cyanobacteria blooms as well as solve the problem of ore tailings disposal.These results are of practical importance for engineering strategies to control cyanobacteria blooms,though there are still some issues that need to be addressed,such as how cyanobacteria flocs are collected and utilized after settling.展开更多
基金supported by the National Key R&D Program of China(No.2021YFC3200102)Yunnan Collaborative Innovation Center for Plateau Lake Ecology and Environmental Healththe Key Research and Development Project of Shandong Province(No.2020CXGC011202).
文摘Harmful algal blooms(HABs)have emerged as a critical global environmental and ecological concern.Timely and accurate monitoring of the prevalent bloom-forming genera is crucial for HABmanagement.Conventional microscope-based methods are time-consuming,laborintensive,and specialized expertise-dependent,often making them impractical for largescale surveillance.Molecular methods,such as metabarcoding,provide efficient technical solutions;however,the lack of competent PCR primers and further field validation present obstacles to their wide use.Here,we successfully developed Aphanizomenon-specific primers and validated the application of environmental DNA(eDNA)metabarcoding for field-based monitoring of Aphanizomenon in 37 sites across lentic and lotic freshwater ecosystems in Beijing.The sensitivity and specificity tests of newly developed primers demonstrated high performance-comprehensive recovery of biodiversity in Aphanizomenon communities and high ratios(>95%)of Aphanizomenon sequences in datasets.We observed significant correlations between the sequence abundance derived fromeDNAmetabarcoding and the total cell density determined through microscopic identification across all the sampling sites,both in the spring(r=0.8086,p<0.0001)and summer(r=0.7902,p<0.0001),thus validating the utility of eDNA metabarcoding based on the newly developed primers for monitoring in the field.Further,we identified key environmental variables that were primary drivers responsible for the spatiotemporal distribution of Aphanizomenon abundance.These variables included temperature,total nitrogen,and dissolved oxygen in lentic ecosystems,and total phosphorus in lotic ecosystems.The method developed and validated here offers an accurate,efficient,and high-throughput tool for the monitoring of Aphanizomenon blooms in freshwater ecosystems.
文摘During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.
基金the Zhejiang Provincial Natural Science Foundation of China(No.LY21D 060003)the Project of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Ocean-ography,MNR(No.SOEDZZ2103)+1 种基金the National Natural Science Foundation of China(No.42076216)the Open Research Fund of the Key Laboratory of Marine Ecological Monitoring and Restoration Technologies,MNR(No.MEMRT202210)。
文摘The 2016–2022 monitoring data from three ecological buoys in the Wenzhou coastal region of Zhejiang Province and the dataset European Centre for Medium-Range Weather Forecasts were examined to clarify the elaborate relationship between variations in ecological parameters during spring algal bloom incidents and the associated changes in temperature and wind fields in this study.A long short-term memory recurrent neural network was employed,and a predictive model for spring algal bloom in this region was developed.This model integrated various inputs,including temperature,wind speed,and other pertinent variables,and chlorophyll concentration served as the primary output indicator.The model training used chlorophyll concentration data,which were supplemented by reanalysis and forecast temperature and wind field data.The model demonstrated proficiency in forecasting next-day chlorophyll concentrations and assessing the likelihood of spring algal bloom occurrences using a defined chlorophyll concentration threshold.The historical validation from 2016 to 2019 corroborated the model's accuracy with an 81.71%probability of correct prediction,which was further proven by its precise prediction of two spring algal bloom incidents in late April 2023 and early May 2023.An interpretable machine learning-based model for spring algal bloom prediction,displaying effective forecasting with limited data,was established through the detailed analysis of the spring algal bloom mechanism and the careful selection of input variables.The insights gained from this study offer valuable contributions to the development of early warning systems for spring algal bloom in the Wenzhou coastal area of Zhejiang Province.
基金supported by the National Natural Science Foundation of China(Nos.52209102 and U2240208)the Doctoral Program of Entrepreneurship and Innovation in Jiangsu Province(No.JSSCBS20211393)+1 种基金the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20190050)the Science and Technology Innovation Project of Jiang Province,China(No.BK20220043).
文摘In eutrophic shallow lakes,cyanobacterial blooms will occur frequently and then settle into sediment,leading the formation of fluid sediment.Several factors including temperature can influence surface sediment properties.In this study,the influence of temperatures on surface sediment properties was determined in microcosm experiments through monitoring sediment physicochemical and rheological properties.During one-month incubation,it was found that surface sediment density and water content varied exponentially with increase in temperatures from 10 to 35℃.The results of particle size distribution indicated that cyanobacterial blooms biomass(CBB)degradation in sediment led to sediment flocculation and agglomeration.In themeantime,therewere high ratios polysaccharide/protein in extracellular polymeric substances(EPSs),which enhanced the sediment particle agglomeration.Further,the yield stress in rheological test for sediment with(R^(2)=0.97)and without(R^(2)=0.85)CBB presented an exponential decay with increase in temperatures.And a threshold value at 20℃ for sediment critical shear stress(τ_(cr))indicated that sediment could be resuspended easier when temperature was more than 20℃.Altogether,this study showed that the increase in temperatures with a threshold at 20℃,can cause sediment particle flocculation,resulting in a loose and fragile structure.And the results would be helpful to sediment management considering environmental effects of sediment suspension for eutrophication shallow lakes.
基金funded by the National Key R&D Program of China(No.2022YFC3106005)the Shandong Provincial Natural Science Foundation(No.ZR2021MD 122)+2 种基金the MNR Key Laboratory of Eco-Environmental Science and Technology,China(No.MEEST-2023-04)the Taishan Scholars Program(No.tstp20230642)the Shandong Provincial Key Laboratory of Marine Ecological Environment and Disaster Prevention and Mitigation(Nos.201708,202209,202314)。
文摘Harmful macroalgal blooms caused by Ulva prolifera and Sargassum horneri are increasing in the Yellow Sea and East China Sea.However,our understanding of macroalgal blooms before 2008 is fragmented and unclear.Using time-series Landsat imagery from 1984 to 2008,we examined macroalgal bloom events and their evolutionary patterns.The results suggest that no macroalgal blooms were observed before 1999.Ulva blooms could be traced back to 1999 and occurred on a small scale in 2000,2004 and 2005,before escalating into large green tides in 2007 and 2008.Notably,these Ulva blooms were confined to the southern Yellow Sea from May to August.In comparison,Sargassum blooms were first detected in the East China Sea in March 2000 and occurred almost every year thereafter,although the size of the blooms showed significant interannual variation.The distribution areas generally moved northwards from March until the bloom dissipated in May or June,suggesting the influence of the monsoon and currents.Our investigation provided some insight into the bloom history of these two harmful macroalgal blooms in the Yellow Sea and East China Sea.
基金supported by Zhongyuan Special Steel Equipment Manufacturing Co.,Ltd.,China.
文摘A coupled computational model of molten steel within the mold was developed,encompassing electromagnetic fields,fluid flow,heat transfer,shell formation,stress,and strain.The model was verified through comparison with plant measurements,showing reasonable agreement in electromagnetic field distribution,solidification endpoint,and shell thickness.Results indicate that coordinating the submerged entry nozzle(SEN)and mold electromagnetic stirring(M-EMS)effectively regulates the solidification quality of the initial shell.Adjusting M-EMS current frequency changes the impact position of the molten steel jet from the four-port SEN,while increasing current intensity reduces the jet impact intensity.Adjusting the M-EMS parameters can enhance the initial shell uniformity.Furthermore,in areas directly impacted by the steel jet from the four-port SEN,a relationship between brittle temperature range(BTR)width and total mechanical strain was found,and the larger the BTR width,the smaller the corresponding total mechanical strain.The BTR width provides a discriminant method to avoid hot tearing.Appropriate M-EMS parameters are obtained and applied,and the plant trials show a significant improvement in hot tearing near the surface of round blooms.
基金Supported by the National Key Research and Development Program of China(No.2022 YFC 3202700)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX 24_0904)。
文摘Inexpensive flocculant-modified iron tailings sand(ITS)were converted into effective flocculation materials for cyanobacteria blooms.After composite modification with polyaluminum chloride(PAC)and polyacrylamide(PAM),the surface charge of ITS was altered from negative to positive,and surface adhesion was increased by~1.5 times.PAC/PAM-modified ITS(PP-ITS)had strong flocculating effects on cyanobacteria,facilitating their removal.When the dosage of PP-ITS was 150 mg/L and the ratio of flocculant to ITS was 1:20,the elimination rate of cyanobacteria was as high as 90%.The flocs formed were better than those with chitosan-modified clays(CS-CA)and PAC-modified ITS(PAC-ITS)in terms of settling velocity,size,and recovery ability.The positively charged groups in the flocculant,such as-NH_(2) and Al^(3+),are attracted to negatively charged ions on the surface of ITS,altering the surface charge.Additionally,hydrogen bonds could form between amide side groups,and surface adhesion was improved through molecular association.Coupled with the strong bridging and sweeping effects of the flocculant,the flocs generated by PP-ITS formed rapidly and were large and resilient.The use of PP-ITS could effectively treat cyanobacteria blooms as well as solve the problem of ore tailings disposal.These results are of practical importance for engineering strategies to control cyanobacteria blooms,though there are still some issues that need to be addressed,such as how cyanobacteria flocs are collected and utilized after settling.
