Genus Microcystis is the most common dominant species of bloom-forming cyanobacteria.Growth and colony formation are critical processes for the occurrence of Microcystis blooms.To identify allelochemicals that can inh...Genus Microcystis is the most common dominant species of bloom-forming cyanobacteria.Growth and colony formation are critical processes for the occurrence of Microcystis blooms.To identify allelochemicals that can inhibit the growth and colony formation of Microcystis,Microcystis aeruginosa was cultivated and treated with various concentrations of gramine,catechol,berberine,and sanguinarine in laboratory.Results indicate that the growth,colony formation,and extracellular polysaccharides(EPS)content of Microcystis were significantly inhibited when treated with gramine,catechol,and berberine in appropriate concentrations at high iron level(6.8 mg/L).Microcystis growth was inhibited and colony formation and EPS content were promoted when treated with sanguinarine at high iron level.These findings suggest that cyanobacterial blooms can be controlled by regulating the input of gramine,catechol,and berberine.Furthermore,this study revealed that plant allelochemicals could affect the growth and morphology of algae in aquatic ecological restoration,which may be potentially important for improving water quality.展开更多
Global warming and algal blooms have been two of the most pressing problems faced by the world today.In recent decades,numerous studies indicated that global warming promoted the expansion of algal blooms.However,rese...Global warming and algal blooms have been two of the most pressing problems faced by the world today.In recent decades,numerous studies indicated that global warming promoted the expansion of algal blooms.However,research on how algal blooms respond to global warming is scant.Global warming coupled with eutrophication promoted the rapid growth of phytoplankton,which resulted in an expansion of algal blooms.Algal blooms are affected by the combined effects of global warming,including increases in temperatures,CO_(2)concentration,and nutrient input to aquatic systems by extreme weather events.Since the growth of phytoplankton requires CO_(2),they appear to act as a carbon sink.Unfortunately,algal blooms will release CH4,CO_(2),and inorganic nitrogen when they die and decompose.As substrate nitrogen increases from decompose algal biomass,more N2O will be released by nitrification and denitrification.In comparison to CO_(2),CH4has 28-fold and N2O has 265-fold greenhouse effect.Moreover,algal blooms in the polar regions may contribute to melting glaciers and sea ice(will release greenhouse gas,which contribute to global warming)by reducing surface albedo,which consequently would accelerate global warming.Thus,algal blooms and global warming could form feedback loops which prevent human survival and development.Future researches shall examine the mechanism,trend,strength,and control strategies involved in this mutual feedback.Additionally,it will promote global projects of environmental protection combining governance greenhouse gas emissions and algal blooms,to form a geoengineering for regulating the cycles of carbon,nitrogen,and phosphorus.展开更多
In order to characterize the oxygen isotopic composition of internal phosphate and explore the possibility of using these data to identify phosphate sources, we measured oxygen isotopic compositions of phosphate(δ^(1...In order to characterize the oxygen isotopic composition of internal phosphate and explore the possibility of using these data to identify phosphate sources, we measured oxygen isotopic compositions of phosphate(δ^(18)O_p) in sediment pore water in Hongfeng Lake, a typical deep-water lake in a mountainous area. These data, in combination with δ^(18)O_p in surface water samples and water column samples, were successfully used to identify phosphate sources. The δ^(18)O_p value of sediment pore water ranged from 15.2% to 15.8%, with an average value of 15.5%—the δ^(18)O_p value of internal phosphate. The δ^(18)O_p values decreased gradually through the water column from 19.4% in surface water to 16.4% in deeper water, implying that internal phosphate had more negative δ^(18)O_p values than external phosphate. This finding was substantiated by horizontal variations in δ^(18)O_p values, which decreased with increasing distance from inflowing rivers. All collected evidence suggests that external and internal phosphate have distinctly different isotopic signatures and that these signatures have not been considerably altered by biological mediation in Hongfeng Lake. Therefore, δ^(18)O_p can be used to distinguish phosphate sources. A two-endmember mixing model showed that internal phosphate had an average contribution of 40%, highlighting the influence of internal phosphorus loading on aqueous phosphate and eutrophication. This study illustrates the need to reduce the internal phosphorus load from sediment and provides guidance for nutrient management and in-lake restoration treatment in Hongfeng Lake. The data presented here are limited, but serve to highlight the great potential of δ^(18)O_p as an effective tracer for identifying phosphate sources. Systematic investigations of the oxygen isotopic compositions of external phosphate, internal phosphate, and phosphate through the water column, in combination with in-lake P biogeochemical cycle study, would be desirable in further research.展开更多
The design of an integral pressurized water reactor (IPWR) focuses on enhancing the safety and reliability of the reactor by incorporating a number of inherent safety features and engineered safety features. However, ...The design of an integral pressurized water reactor (IPWR) focuses on enhancing the safety and reliability of the reactor by incorporating a number of inherent safety features and engineered safety features. However, the characteristics of passive safety systems for the marine reactors are quiet different from those for the land nuclear power plant because of the more formidable and dangerous operation environments of them. This paper presents results of marine black out accident analyses. In the case of a transient, the passive residual heat removal system (PRHRS) is designed to cool the reactor coolant system (RCS) from a normal operation condition to a hot shutdown condition by a natural circulation, and the shutdown cooling system (SCS) is designed to cool the primary system from a hot shutdown condition to a refueling condition by a forced circulation. A realistic calculation has been carried out by using the RELAP5/MOD3.4 code and a sensitivity analysis has been performed to evaluate a passive cooldown capability. The results of the accident analyses show that the reactor coolant system and the passive residual heat removal system adequately remove the core decay heat by a natural circulation.展开更多
In situ microscale distributions of 02, H2S, pH and redox potential in sediments of Hongfeng Lake, SW China, were investigated using the powerful microsensor technique. Our results show that O2 was depleted within the...In situ microscale distributions of 02, H2S, pH and redox potential in sediments of Hongfeng Lake, SW China, were investigated using the powerful microsensor technique. Our results show that O2 was depleted within the top 3.9 mm in surface sediments, and H2S was subsequently detected at -6.0 mm depth, and reached its maximum concentrations at -25 mm. The degradation of organic matter and reduction of sulfate might be the major pathways of producing H2S in sediments, pH rapidly reduced in surface layers mainly due to H＋ release in the oxidation of organic matter. Eh also decreased sharply in surface sediments, probabl indicating the coexistence of Fe and Mn oxides with O2 in aerobic region. Furthermore, the programme of PROFILE was applied to model the 02 gradient, and good fit was obtained between the simulative values and the factual values both in sediments and in the diffusive boundary layer （DBL）. The results indicate that the depth-integrated O2 consumption rates within sediments were 0.083 and 0.134 nmol·m-3·s-1 in site S1 and site S2, respectively. In addition, there were distinct DBL in two sediment profiles, with 1.2 mm thickness in S1 and 0.9 mm thickness in S2. The diffusive fluxes of O2 within the DBL were 67.13 nmol·m-2·s-1 in S1 and 88.54 nmol·m-2·s-1 in S2.展开更多
基金Supported by the Chongqing Water Conservancy Bureau Project(No.5000002021BF40001)the National Natural Science Foundation of China(No.41601537)the Science and Technology Support Project of Guizhou Province,China(No.[2022]General 148)。
文摘Genus Microcystis is the most common dominant species of bloom-forming cyanobacteria.Growth and colony formation are critical processes for the occurrence of Microcystis blooms.To identify allelochemicals that can inhibit the growth and colony formation of Microcystis,Microcystis aeruginosa was cultivated and treated with various concentrations of gramine,catechol,berberine,and sanguinarine in laboratory.Results indicate that the growth,colony formation,and extracellular polysaccharides(EPS)content of Microcystis were significantly inhibited when treated with gramine,catechol,and berberine in appropriate concentrations at high iron level(6.8 mg/L).Microcystis growth was inhibited and colony formation and EPS content were promoted when treated with sanguinarine at high iron level.These findings suggest that cyanobacterial blooms can be controlled by regulating the input of gramine,catechol,and berberine.Furthermore,this study revealed that plant allelochemicals could affect the growth and morphology of algae in aquatic ecological restoration,which may be potentially important for improving water quality.
基金Supported by the Chongqing Water Conservancy Bureau Project(No.5000002021BF40001)the National Natural Science Foundation of China(No.41601537)+1 种基金the Opening Fund of the State Key Laboratory of Environmental Geochemistry(No.SKLEG2021202)the Strategic Pilot Science and Technology(Class A,No.XDA23040303)。
文摘Global warming and algal blooms have been two of the most pressing problems faced by the world today.In recent decades,numerous studies indicated that global warming promoted the expansion of algal blooms.However,research on how algal blooms respond to global warming is scant.Global warming coupled with eutrophication promoted the rapid growth of phytoplankton,which resulted in an expansion of algal blooms.Algal blooms are affected by the combined effects of global warming,including increases in temperatures,CO_(2)concentration,and nutrient input to aquatic systems by extreme weather events.Since the growth of phytoplankton requires CO_(2),they appear to act as a carbon sink.Unfortunately,algal blooms will release CH4,CO_(2),and inorganic nitrogen when they die and decompose.As substrate nitrogen increases from decompose algal biomass,more N2O will be released by nitrification and denitrification.In comparison to CO_(2),CH4has 28-fold and N2O has 265-fold greenhouse effect.Moreover,algal blooms in the polar regions may contribute to melting glaciers and sea ice(will release greenhouse gas,which contribute to global warming)by reducing surface albedo,which consequently would accelerate global warming.Thus,algal blooms and global warming could form feedback loops which prevent human survival and development.Future researches shall examine the mechanism,trend,strength,and control strategies involved in this mutual feedback.Additionally,it will promote global projects of environmental protection combining governance greenhouse gas emissions and algal blooms,to form a geoengineering for regulating the cycles of carbon,nitrogen,and phosphorus.
基金financially supported by the National Key Research and Development Project by MOST of China(No.2016YFA0601003)the National Natural Science Foundation of China(Nos.U1612441 and 41173125)Science and Technology Project of Guizhou Province
文摘In order to characterize the oxygen isotopic composition of internal phosphate and explore the possibility of using these data to identify phosphate sources, we measured oxygen isotopic compositions of phosphate(δ^(18)O_p) in sediment pore water in Hongfeng Lake, a typical deep-water lake in a mountainous area. These data, in combination with δ^(18)O_p in surface water samples and water column samples, were successfully used to identify phosphate sources. The δ^(18)O_p value of sediment pore water ranged from 15.2% to 15.8%, with an average value of 15.5%—the δ^(18)O_p value of internal phosphate. The δ^(18)O_p values decreased gradually through the water column from 19.4% in surface water to 16.4% in deeper water, implying that internal phosphate had more negative δ^(18)O_p values than external phosphate. This finding was substantiated by horizontal variations in δ^(18)O_p values, which decreased with increasing distance from inflowing rivers. All collected evidence suggests that external and internal phosphate have distinctly different isotopic signatures and that these signatures have not been considerably altered by biological mediation in Hongfeng Lake. Therefore, δ^(18)O_p can be used to distinguish phosphate sources. A two-endmember mixing model showed that internal phosphate had an average contribution of 40%, highlighting the influence of internal phosphorus loading on aqueous phosphate and eutrophication. This study illustrates the need to reduce the internal phosphorus load from sediment and provides guidance for nutrient management and in-lake restoration treatment in Hongfeng Lake. The data presented here are limited, but serve to highlight the great potential of δ^(18)O_p as an effective tracer for identifying phosphate sources. Systematic investigations of the oxygen isotopic compositions of external phosphate, internal phosphate, and phosphate through the water column, in combination with in-lake P biogeochemical cycle study, would be desirable in further research.
文摘The design of an integral pressurized water reactor (IPWR) focuses on enhancing the safety and reliability of the reactor by incorporating a number of inherent safety features and engineered safety features. However, the characteristics of passive safety systems for the marine reactors are quiet different from those for the land nuclear power plant because of the more formidable and dangerous operation environments of them. This paper presents results of marine black out accident analyses. In the case of a transient, the passive residual heat removal system (PRHRS) is designed to cool the reactor coolant system (RCS) from a normal operation condition to a hot shutdown condition by a natural circulation, and the shutdown cooling system (SCS) is designed to cool the primary system from a hot shutdown condition to a refueling condition by a forced circulation. A realistic calculation has been carried out by using the RELAP5/MOD3.4 code and a sensitivity analysis has been performed to evaluate a passive cooldown capability. The results of the accident analyses show that the reactor coolant system and the passive residual heat removal system adequately remove the core decay heat by a natural circulation.
基金supported by the National Natural Science Foundation of China (Nos.41173125 and 41403113)
文摘In situ microscale distributions of 02, H2S, pH and redox potential in sediments of Hongfeng Lake, SW China, were investigated using the powerful microsensor technique. Our results show that O2 was depleted within the top 3.9 mm in surface sediments, and H2S was subsequently detected at -6.0 mm depth, and reached its maximum concentrations at -25 mm. The degradation of organic matter and reduction of sulfate might be the major pathways of producing H2S in sediments, pH rapidly reduced in surface layers mainly due to H＋ release in the oxidation of organic matter. Eh also decreased sharply in surface sediments, probabl indicating the coexistence of Fe and Mn oxides with O2 in aerobic region. Furthermore, the programme of PROFILE was applied to model the 02 gradient, and good fit was obtained between the simulative values and the factual values both in sediments and in the diffusive boundary layer （DBL）. The results indicate that the depth-integrated O2 consumption rates within sediments were 0.083 and 0.134 nmol·m-3·s-1 in site S1 and site S2, respectively. In addition, there were distinct DBL in two sediment profiles, with 1.2 mm thickness in S1 and 0.9 mm thickness in S2. The diffusive fluxes of O2 within the DBL were 67.13 nmol·m-2·s-1 in S1 and 88.54 nmol·m-2·s-1 in S2.
