Baseflow is one of the major pathways of runoff in hilly areas,and its contributions to surface water resources and pollutant loads cannot be ignored.In this study,based on water quantity and quality data from 1988 to...Baseflow is one of the major pathways of runoff in hilly areas,and its contributions to surface water resources and pollutant loads cannot be ignored.In this study,based on water quantity and quality data from 1988 to 2019 in hilly and low rainfall watersheds,we focused on the impact of long-term baseflow on nitrogen load using the load allocation based on the baseflow separation method.We also constructed a nitrogen balance model for the Chaohe River Basin of China from 2012 to 2021 to analyze the nitrogen accumulation in the basin.We used the baseflow nitrogen load lag analysis method to study the lag characteristics of the baseflow discharge process and analyzed the response and periodicity of baseflow nitrogen to precipitation and soil accumulation using time delay analysis.The res-ults showed that the contribution rate of baseflow nitrogen reached 69%and showed a slight increasing trend from 1988 to 2019.The ef-fects of changes in precipitation and nitrogen accumulation on the baseflow contribution was observed after 1-2 and 2 yr,respectively.After nitrogen accumulation,it entered the river channel through baseflow,which was already the main and continuous source of nitro-gen in rivers in hilly areas.展开更多
This study of Mikasa City in 2001, which analyzed N flow between N production and N load in seven agricultural and settlement subsystems, i.e., paddy, onion, wheat, vegetable, dairy, chicken, and citizen subsystems, a...This study of Mikasa City in 2001, which analyzed N flow between N production and N load in seven agricultural and settlement subsystems, i.e., paddy, onion, wheat, vegetable, dairy, chicken, and citizen subsystems, aimed to compare N flow in each subsystem, to determine the main sources of the N load, and to evaluate the influence of agricultural production and food consumption on N cycling in a rural area. The results showed that in Mikasa city, 38.5% of the N load came from point sources and the remainder from non-point sources with intensive vegetable farming imparting a serious N load. Because of the internal N cycling in the dairy subsystem, chemical fertilizer application was reduced by 70.2%, and 23.72 Mg manure N was recycled to the field; therefore, the N utilization efficiency was raised from 18.1% to 35.1%. If all the manure N in the chicken subsystem was recycled, chemical fertilizer application would be reduced by 8.1% from the present level, and the point sources of N pollution would be reduced by 20.8%.展开更多
The effectiveness of controlling nitrogen(N)loading(in addition to phosphorus[P])to manage the eutrophication of aquatic ecosystems has been debated despite the role of N in producing algal biomass and toxins.Longterm...The effectiveness of controlling nitrogen(N)loading(in addition to phosphorus[P])to manage the eutrophication of aquatic ecosystems has been debated despite the role of N in producing algal biomass and toxins.Longterm,controlled tests of the efficacy of N loading reductions are largely missing from the scientific record,perhaps due to the historical focus on P control.To address this knowledge gap,we examined the results from a unique,long-term study conducted in 24 flow-through(2.5-month retention time)lake ecosystem-scale mesocosms in Denmark,operating since 2003 at two contrasting nutrient loading levels crossed with three temperature scenarios(ambient,IPCC(Intergovernmental Panel on Climate Change)A2 scenario,and A2+50%).For 1 year,the N loading,apart from groundwater inputs,was stopped in high nutrient loading mesocosms,while P loading was maintained.Wefollowed the changes in key environmental variables and systemmetabolismfor 5 years,including the 2 years prior to N loading reduction and 2 years after N loading resumption.The low nutrient loading treatments,which only received N and P fromgroundwater,were used as a reference.We found a strong effect of N loading on total N(TN),N oxides(NO_(2)+NO_(3)),and N:P ratios.After reducing the excess external N loading,which had lasted for 15 years,TN and N oxides declined to similar levels as those in the low nutrient treatments at all temperature scenarios and increased quickly when N loading was resumed.Algal biomass(as chlorophyll a)and ecosystem production and respiration were also affected.The results showed(1)a rapid response of water N concentrations to external N loading,(2)major ecosystem effects,including reduced algal biomass and system metabolism,and(3)overall low sensitivity in response to the IPCC temperature scenarios.This study was conducted under semi-natural conditions,providing strong experimental support for the key role of N at the ecosystem level in shallow lakes.Our results have profound implications for lake management and suggest that external N loading reductions may strengthen the recovery of shallow lakes from eutrophication.展开更多
Background Previous studies into the interactions between native and invasive species under nitrogen(N)deposition have often overlooked the presence of co-occurring native species,a factor that could influence the out...Background Previous studies into the interactions between native and invasive species under nitrogen(N)deposition have often overlooked the presence of co-occurring native species,a factor that could influence the outcomes of interspecific competition.Furthermore,publication bias may lead researchers to focus on rare native species with limited adaptability.In this study,we examined how two levels of N deposition affected the physiological and ecological traits and the interspecies interactions between three invasive and three common native species.Results N deposition promoted the growth of both invasive and native species.The relative dominance index(RDI)of invasive species was consistently higher than that of native species.Invasive species had an advantage over common native species in using the increased N effectively.The biomass distribution of invasive species was biased toward the aboveground parts,indicating competition for light resources.Conclusions N deposition conferred a stronger competitive advantage to invasive species than to native species,suggesting that the distribution range of invasive species may expand further under increased N deposition.展开更多
This article reports pollutant removal performances of baffled subsurface flow, and integrated surface flow-floating treatment wetland units, when arranged in series for the treatment of municipal wastewater in Bangla...This article reports pollutant removal performances of baffled subsurface flow, and integrated surface flow-floating treatment wetland units, when arranged in series for the treatment of municipal wastewater in Bangladesh. The wetland units （of the hybrid system） included organic, inorganic media, and were planted with nineteen types of macrophytes. The wetland train was operated under hydraulic loading fluctuation and seasonal variation. The performance analyses （across the wetland units） illustrated simultaneous denitrification and organics removal rates in the first stage vertical flow wetland, due to organic carbon leaching from the employed organic media. Higher mean organics removal rates （656.0 g COD]（m2.day）） did not completely inhibit nitrification in the first stage vertical flow system; such pattern could be linked to effective utilization of the trapped oxygen, as the flow was directed throughout the media by the baffle walls. Second stage horizontal flow wetland showed enhanced biodegradable organics removal, which depleted organic carbon availability for denitrification. The final stage integrated wetland system allowed further nitrogen removal from wastewater, via nutrient uptake by plant roots （along with nitrification）, and generation of organic carbon （by the dead macrophytes） to support denitrification. The system achieved higher E. coli mortality through protozoa predation, E. coli oxidation, and destruction by UV radiation. In general, enhanced pollutant removal efflciencies as demonstrated by the structurally modified hybrid wetland system signify the necessity of such modification, when operated under adverse conditions such as： substantial input organics loading, hydraulic loading fluctuation, and seasonal variation.展开更多
Road dust is one of the most common pollutants and causes a series of negative effects on plant physiology. Dust＇s impacts on plants can be regarded as a combination of load,composition and grain size impacts on plan...Road dust is one of the most common pollutants and causes a series of negative effects on plant physiology. Dust＇s impacts on plants can be regarded as a combination of load,composition and grain size impacts on plants; however, there is a lack of integrated dust effect studies involving these three aspects. In our study, Sophora japonica seedlings were artificially dusted with road dust collected from the road surface of Beijing so that we could study the impacts of this dust on nitrogen/carbon allocation, biomass allocation and photosynthetic pigments from the three aspects of composition, load and grain size. The results showed that the growth characteristics of S. japonica seedlings were mostly influenced by dust composition and load. Leaf N, root–shoot ratio and chlorophyll a/b were significantly affected by dust composition and load; leaf C/N, shoot biomass, total chlorophyll and carotenoid were significantly affected by dust load; stem N and stem C/N were significantly affected by dust composition; while the dust grain size alone did not affect any of the growth characteristics. Road dust did influence the growth characteristics more extensively than loam. Therefore, a higher dust load could increase the differences between road dust and loam treatments. The elements in dust are well correlated to the shoot N, shoot C/N, and root–shoot ratio of S. japonica seedlings. This knowledge could benefit the management of urban green spaces.展开更多
Fertilizer N use in Japan has decreased by about 30% from 1960 to 2000, while keeping a little increase in cereal yields. This has resulted in a significant increase in apparent nitrogen use efficiency, in particular ...Fertilizer N use in Japan has decreased by about 30% from 1960 to 2000, while keeping a little increase in cereal yields. This has resulted in a significant increase in apparent nitrogen use efficiency, in particular for rice. On the other hand, national N load on the environment associated with the production and consumption of domestic and imported agricultural products has almost tripled during this period, mainly due to the dramatic increase of imports of food and feedstuffs. The environmental problems, including water and air pollution, caused by the excessive loads of N are serious public concerns and there is an urgent need to minimize N losses from agricultural production. In order to meet the necessity for reducing the environmental impacts by excess N, political and technological measures have been taken at regional and country levels. In recent years, the Japanese government has embarked on a series of policies to encourage transition to an environmentally conscious agriculture. Promoting proper material circulation with reducing fertilizer impact and utilizing biomass and livestock wastes is emphasized in these policies. The effectiveness of environmental assessment and planning for reducing regional and national N load has been discussed. Implementation of environmentally friendly technologies and management, both conventional and innovational, have been developed and adopted in Japanese agriculture. The effectiveness of conventional technologies in reducing environmental reactive N has been re-evaluated. Innovative technologies, such as use of controlled availability fertilizers and livestock wastes compost pellets, are being investigated and extended. A comprehensive approach that applies political and technological measures with closer cooperation is necessary to control reactive N in the environment.展开更多
As an essential component of proteins and genetic material for all organisms, nitrogen(N) is one of the major limiting factors that control the dynamics, biodiversity and functioning of lacustrine wetlands, in which i...As an essential component of proteins and genetic material for all organisms, nitrogen(N) is one of the major limiting factors that control the dynamics, biodiversity and functioning of lacustrine wetlands, in which intensified N biogeochemical activities take place. Reactive N loaded into wetland ecosystems has been doubled due to various human activities, including industrial, agricultural activities and urbanization. The main driving mechanisms of N transport and transformation in lacustrine wetlands are categorized to pushing forces and pulling forces in this study. Geomorphology, wetland age, N concentrations, and temperature are the main pushing forces(passive forces); whereas water table variation, oxygen concentration, other elements availability, oxidation-reduction potential(Eh) and p H, and microorganisms are the predominant pulling forces(active forces). The direction and kinetic energy of reactions are determined by pulling forces and then are stimulated by pushing forces. These two types of forces are analyzed and discussed separately. Based on the analysis of driving mechanisms, possible solutions to wetland N pollutions are proposed at individual, regional and global scales, respectively. Additional research needs are addressed to obtain a thorough understanding of N transport and transformations in wetlands and to reduce detrimental impacts of excessive N on such fragile ecosystems.展开更多
基金Under the auspices of the National Natural Science Foundation of China(No.52221003,42277044)。
文摘Baseflow is one of the major pathways of runoff in hilly areas,and its contributions to surface water resources and pollutant loads cannot be ignored.In this study,based on water quantity and quality data from 1988 to 2019 in hilly and low rainfall watersheds,we focused on the impact of long-term baseflow on nitrogen load using the load allocation based on the baseflow separation method.We also constructed a nitrogen balance model for the Chaohe River Basin of China from 2012 to 2021 to analyze the nitrogen accumulation in the basin.We used the baseflow nitrogen load lag analysis method to study the lag characteristics of the baseflow discharge process and analyzed the response and periodicity of baseflow nitrogen to precipitation and soil accumulation using time delay analysis.The res-ults showed that the contribution rate of baseflow nitrogen reached 69%and showed a slight increasing trend from 1988 to 2019.The ef-fects of changes in precipitation and nitrogen accumulation on the baseflow contribution was observed after 1-2 and 2 yr,respectively.After nitrogen accumulation,it entered the river channel through baseflow,which was already the main and continuous source of nitro-gen in rivers in hilly areas.
基金Project supported by the Science Research Foundation, Japan (No. 11460028).
文摘This study of Mikasa City in 2001, which analyzed N flow between N production and N load in seven agricultural and settlement subsystems, i.e., paddy, onion, wheat, vegetable, dairy, chicken, and citizen subsystems, aimed to compare N flow in each subsystem, to determine the main sources of the N load, and to evaluate the influence of agricultural production and food consumption on N cycling in a rural area. The results showed that in Mikasa city, 38.5% of the N load came from point sources and the remainder from non-point sources with intensive vegetable farming imparting a serious N load. Because of the internal N cycling in the dairy subsystem, chemical fertilizer application was reduced by 70.2%, and 23.72 Mg manure N was recycled to the field; therefore, the N utilization efficiency was raised from 18.1% to 35.1%. If all the manure N in the chicken subsystem was recycled, chemical fertilizer application would be reduced by 8.1% from the present level, and the point sources of N pollution would be reduced by 20.8%.
基金supported by the AQUACOSM and AQUACOSM-plus projects funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement nos.731065 and 871081 and AnaEE Denmark(anaee.dk)supported by the TÜB_ITAK-B_IDEB 2232 program(grant/award no.118C250)+3 种基金supported by the National Science Foundation of China(no.32371629)the Jiangxi Provincial Natural Science Foundation(20232ACB215006)supported by the Estonian Research Council(PRG1954 and PRG709)AQUACOSM/AQUACOSM-plus.
文摘The effectiveness of controlling nitrogen(N)loading(in addition to phosphorus[P])to manage the eutrophication of aquatic ecosystems has been debated despite the role of N in producing algal biomass and toxins.Longterm,controlled tests of the efficacy of N loading reductions are largely missing from the scientific record,perhaps due to the historical focus on P control.To address this knowledge gap,we examined the results from a unique,long-term study conducted in 24 flow-through(2.5-month retention time)lake ecosystem-scale mesocosms in Denmark,operating since 2003 at two contrasting nutrient loading levels crossed with three temperature scenarios(ambient,IPCC(Intergovernmental Panel on Climate Change)A2 scenario,and A2+50%).For 1 year,the N loading,apart from groundwater inputs,was stopped in high nutrient loading mesocosms,while P loading was maintained.Wefollowed the changes in key environmental variables and systemmetabolismfor 5 years,including the 2 years prior to N loading reduction and 2 years after N loading resumption.The low nutrient loading treatments,which only received N and P fromgroundwater,were used as a reference.We found a strong effect of N loading on total N(TN),N oxides(NO_(2)+NO_(3)),and N:P ratios.After reducing the excess external N loading,which had lasted for 15 years,TN and N oxides declined to similar levels as those in the low nutrient treatments at all temperature scenarios and increased quickly when N loading was resumed.Algal biomass(as chlorophyll a)and ecosystem production and respiration were also affected.The results showed(1)a rapid response of water N concentrations to external N loading,(2)major ecosystem effects,including reduced algal biomass and system metabolism,and(3)overall low sensitivity in response to the IPCC temperature scenarios.This study was conducted under semi-natural conditions,providing strong experimental support for the key role of N at the ecosystem level in shallow lakes.Our results have profound implications for lake management and suggest that external N loading reductions may strengthen the recovery of shallow lakes from eutrophication.
基金supported by the National Natural Science Foundation of China(32271588 and 31971718)Qingdao Agricultural University Doctoral Start-Up Fund(6631120094)the Talent Introduction Program for YouthInnovation Team of Shandong Higher Learning(018-1622001).
文摘Background Previous studies into the interactions between native and invasive species under nitrogen(N)deposition have often overlooked the presence of co-occurring native species,a factor that could influence the outcomes of interspecific competition.Furthermore,publication bias may lead researchers to focus on rare native species with limited adaptability.In this study,we examined how two levels of N deposition affected the physiological and ecological traits and the interspecies interactions between three invasive and three common native species.Results N deposition promoted the growth of both invasive and native species.The relative dominance index(RDI)of invasive species was consistently higher than that of native species.Invasive species had an advantage over common native species in using the increased N effectively.The biomass distribution of invasive species was biased toward the aboveground parts,indicating competition for light resources.Conclusions N deposition conferred a stronger competitive advantage to invasive species than to native species,suggesting that the distribution range of invasive species may expand further under increased N deposition.
文摘This article reports pollutant removal performances of baffled subsurface flow, and integrated surface flow-floating treatment wetland units, when arranged in series for the treatment of municipal wastewater in Bangladesh. The wetland units （of the hybrid system） included organic, inorganic media, and were planted with nineteen types of macrophytes. The wetland train was operated under hydraulic loading fluctuation and seasonal variation. The performance analyses （across the wetland units） illustrated simultaneous denitrification and organics removal rates in the first stage vertical flow wetland, due to organic carbon leaching from the employed organic media. Higher mean organics removal rates （656.0 g COD]（m2.day）） did not completely inhibit nitrification in the first stage vertical flow system; such pattern could be linked to effective utilization of the trapped oxygen, as the flow was directed throughout the media by the baffle walls. Second stage horizontal flow wetland showed enhanced biodegradable organics removal, which depleted organic carbon availability for denitrification. The final stage integrated wetland system allowed further nitrogen removal from wastewater, via nutrient uptake by plant roots （along with nitrification）, and generation of organic carbon （by the dead macrophytes） to support denitrification. The system achieved higher E. coli mortality through protozoa predation, E. coli oxidation, and destruction by UV radiation. In general, enhanced pollutant removal efflciencies as demonstrated by the structurally modified hybrid wetland system signify the necessity of such modification, when operated under adverse conditions such as： substantial input organics loading, hydraulic loading fluctuation, and seasonal variation.
基金supported by the National Natural Science Foundation of China(Project 41430638 to KMM)
文摘Road dust is one of the most common pollutants and causes a series of negative effects on plant physiology. Dust＇s impacts on plants can be regarded as a combination of load,composition and grain size impacts on plants; however, there is a lack of integrated dust effect studies involving these three aspects. In our study, Sophora japonica seedlings were artificially dusted with road dust collected from the road surface of Beijing so that we could study the impacts of this dust on nitrogen/carbon allocation, biomass allocation and photosynthetic pigments from the three aspects of composition, load and grain size. The results showed that the growth characteristics of S. japonica seedlings were mostly influenced by dust composition and load. Leaf N, root–shoot ratio and chlorophyll a/b were significantly affected by dust composition and load; leaf C/N, shoot biomass, total chlorophyll and carotenoid were significantly affected by dust load; stem N and stem C/N were significantly affected by dust composition; while the dust grain size alone did not affect any of the growth characteristics. Road dust did influence the growth characteristics more extensively than loam. Therefore, a higher dust load could increase the differences between road dust and loam treatments. The elements in dust are well correlated to the shoot N, shoot C/N, and root–shoot ratio of S. japonica seedlings. This knowledge could benefit the management of urban green spaces.
文摘Fertilizer N use in Japan has decreased by about 30% from 1960 to 2000, while keeping a little increase in cereal yields. This has resulted in a significant increase in apparent nitrogen use efficiency, in particular for rice. On the other hand, national N load on the environment associated with the production and consumption of domestic and imported agricultural products has almost tripled during this period, mainly due to the dramatic increase of imports of food and feedstuffs. The environmental problems, including water and air pollution, caused by the excessive loads of N are serious public concerns and there is an urgent need to minimize N losses from agricultural production. In order to meet the necessity for reducing the environmental impacts by excess N, political and technological measures have been taken at regional and country levels. In recent years, the Japanese government has embarked on a series of policies to encourage transition to an environmentally conscious agriculture. Promoting proper material circulation with reducing fertilizer impact and utilizing biomass and livestock wastes is emphasized in these policies. The effectiveness of environmental assessment and planning for reducing regional and national N load has been discussed. Implementation of environmentally friendly technologies and management, both conventional and innovational, have been developed and adopted in Japanese agriculture. The effectiveness of conventional technologies in reducing environmental reactive N has been re-evaluated. Innovative technologies, such as use of controlled availability fertilizers and livestock wastes compost pellets, are being investigated and extended. A comprehensive approach that applies political and technological measures with closer cooperation is necessary to control reactive N in the environment.
基金the National Natural Science Foundation of China (Grant No. 41272249)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110072110020)
文摘As an essential component of proteins and genetic material for all organisms, nitrogen(N) is one of the major limiting factors that control the dynamics, biodiversity and functioning of lacustrine wetlands, in which intensified N biogeochemical activities take place. Reactive N loaded into wetland ecosystems has been doubled due to various human activities, including industrial, agricultural activities and urbanization. The main driving mechanisms of N transport and transformation in lacustrine wetlands are categorized to pushing forces and pulling forces in this study. Geomorphology, wetland age, N concentrations, and temperature are the main pushing forces(passive forces); whereas water table variation, oxygen concentration, other elements availability, oxidation-reduction potential(Eh) and p H, and microorganisms are the predominant pulling forces(active forces). The direction and kinetic energy of reactions are determined by pulling forces and then are stimulated by pushing forces. These two types of forces are analyzed and discussed separately. Based on the analysis of driving mechanisms, possible solutions to wetland N pollutions are proposed at individual, regional and global scales, respectively. Additional research needs are addressed to obtain a thorough understanding of N transport and transformations in wetlands and to reduce detrimental impacts of excessive N on such fragile ecosystems.
