In recent years,in order to improve nutrient use efficiency,especially nitrogen use efficiency,fertilizer valueadded technology has been developed rapidly.However,the mechanism of the effect of synergistic fertilizer ...In recent years,in order to improve nutrient use efficiency,especially nitrogen use efficiency,fertilizer valueadded technology has been developed rapidly.However,the mechanism of the effect of synergistic fertilizer on plant nitrogen utilization is not clear.A study was,therefore,conducted to explore the activities and gene expression of key enzymes for nitrogen assimilation and the gene expression of nitrogen transporters in wheat after the application of synergistic fertilizer.Soil column experiment was set up in Qingdao Agricultural University experimental base from October 2018 to June 2019.Maleic acid and itaconic acid were copolymerized with acrylic acid as cross-linking monomer to make a fluid gel,which was sprayed on the fertilizer surface to make nitrogen and phosphorus synergistic fertilizer.A total of 6 treatments was set according to different nitrogen and phosphorus fertilizer ratios:(1)100%common nitrogen fertilizer+100%common phosphate fertilizer(2)70%nitrogen synergistic fertilizer+100%phosphorus synergistic fertilizer;(3)100%nitrogen synergistic fertilizer+70%phosphorus synergistic fertilizer;(4)100%nitrogen synergistic fertilizer+100%phosphorus synergistic fertilizer;(5)70%nitrogen synergistic fertilizer+70%phosphorus synergistic fertilizer;(6)100%commercial nitrogen synergistic fertilizer+100%commercial phosphorus synergistic fertilizer.The results are as follows:(1)the enzyme activities of wheat plants under synergistic fertilizer condition were higher than those under ordinary fertilizer,except under the treatment that nitrogen and phosphorus synergistic fertilizer were both reduced;(2)the expression level of the genes under the treatment“100%nitrogen synergistic fertilizer+100%phosphorus synergistic fertilizer”was significantly higher than those in other treatments.Combined with the higher performance of nitrogen concentration in various parts of the plant under the condition of applying synergistic fertilizer,this study indicated that the application of synergistic fertilizer can improve the nitrogen metabolism of the plant by increasing the nitrogen level in the rhizosphere soil,inducing the expression of nitrogen transporter genes and key assimilation enzymes genes.展开更多
Hydrological and hydro-chemical monitoring of nitrogen(N) and phosphorus(P) in a small urbanized catchment was conducted in the hilly area of the central Sichuan Basin,China,from 2010 through 2011.The diffuse N and P ...Hydrological and hydro-chemical monitoring of nitrogen(N) and phosphorus(P) in a small urbanized catchment was conducted in the hilly area of the central Sichuan Basin,China,from 2010 through 2011.The diffuse N and P loadings in different forms of total nitrogen(TN) and phosphorus(TP),dissolved nitrogen(DN) and phosphorus(DP),as well as particulate nitrogen(PN) and phosphorus(PP) were calculated based on runoff discharges and chemical analyses.The results revealed that the diffuse pollution concentrations of TN,DN,PN,TP,DP and PP exhibited large variations during rainfall events,with peak concentrations occurring during the initial period.For all of the measured parameters,the event mean concentrations(EMCs) were observed to clearly vary among rainfall events.The EMCs of TN,DN,PN,TP,DP and PP(for all of the observed rainfall events) were 10.04,6.62,3.42,1.30,0.47 and0.83 mg/L,respectively.The losses of diffuse N and P exhibited clear seasonal patterns and mainly occurred during the period from July through September,when the losses totaled 99.3 and 9.6 kg/ha for TN and TP,respectively,accounting for 75% and 74% of the total annual loadings.The mean annual loadings of TN and TP were 124.6 and 12.9 kg/ha,respectively.The results indicate that residential areas in the hilly areaof the central Sichuan Basin are subject to high diffuse N and P loadings,posing a serious risk to the receiving water quality.Ecological buffering belts are recommended to incorporate into the urbanized catchment to reduce diffuse pollution.展开更多
We established a budget model of nitrogen （N） inputs and outputs between watersheds and waterbodies to determine the sources of riverine N in the Changjiang （Yangtze） River drainage area. Nitrogen inputs in the bu...We established a budget model of nitrogen （N） inputs and outputs between watersheds and waterbodies to determine the sources of riverine N in the Changjiang （Yangtze） River drainage area. Nitrogen inputs in the budget included N from synthetic fertilizer, biological fixation by leguminous and other crops, wet/dry atmospheric deposition, excreta from humans and animals, and crop residues. The total N input was estimated to be 17.6 Tg, of which 20% or 3.5 Tg N was transported into waterbodies. Of the total N transported into waterbodies, the largest proportion was N from animal waste （26%）, followed by N from atmospheric wet/dry deposition （25%）, synthetic fertilizer N （17%）, N in sewage wastes （17%）, N in human waste from rural areas （6%） and industrial wastewater N （9%）. We studied the spatial patterns of N inputs and outputs by dividing the Changjiang River drainage area into four sub-basins, from upstream to downstream： the Tongtian River drainage area （TTD, the headwater drainage area, 138 000 l^n2, less disturbed by human activities）; the Jinsha River drainage area （JSD, 347 000 km2, less disturbed by human activities, approx. 3 500 km upstream of the Changjiang estuary）; the Pingshan-Yichang drainage area （PYD, 520 500 krn2, large-scale human disturbance, about 2 000 km upstream of the Changjiang estuary）; and the Yichang-Datong drainage area （YDD, 699 900 km^2, large-scale httman disturbance, approx. 620 km upstream of the Changjiang estuary）. The average N input into waterbodies was 2.3, 7.3, 24.1, and 28.2 kg N/ha in the TTD, JSD, PYD, and YDD sub-basins, respectively, suggesting an increase of N-components of more than 10 times from upstream to downstream areas.展开更多
We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-princ...We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-principles method based on density functional theory. Among the three models M1–M3, M1 is not doped with a heteroatom. In the left parts of M2 and M3, nitrogen atoms are doped at two edges of the nanoribbon. In the right parts, nitrogen atoms are doped at one center and at the edges of M2 and M3, respectively. Comparisons of M1, M2 and M3 show obvious rectifying characteristics, and the maximum rectification ratios are up to 42.9 in M2. The results show that the rectifying behavior is strongly dependent on the doping position of electrodes. A higher rectification ratio can be found in the dipyrimidinyl-diphenyl molecular device with asymmetric doping of left and right electrodes, which suggests that this system has a broader application in future logic and memory devices.展开更多
Ion-absorbed rare earth mines,leached in situ,retain a large amount of ammonium nitrogen(NH4–N)that continuously releases into the surrounding environments.However,quantitative descriptions and predictions of the tra...Ion-absorbed rare earth mines,leached in situ,retain a large amount of ammonium nitrogen(NH4–N)that continuously releases into the surrounding environments.However,quantitative descriptions and predictions of the transport of NH4–N across mining area with hill slopes are not fully established.Here,laboratory column experiments were designed with an inclined slope(a sand box)to examine the spatial temporal transport of NH4–N in soils collected from the ionic rare earth elements(REE)mining area.An HYDRUS-2D model simulation of the experimental data over time showed that soils had a strong adsorption capacity toward NH4–N.Chemical non-equilibrium model(CNEM)could well simulate the transport of NH4–N through the soil-packed columns.The simulation of the transport-adsorption processes at three flow rates of leaching agents revealed that low flow rate enabled a longer residence time and an increased NH4-N adsorption,but reduced the extraction efficiency for REE.During the subsequent rainwater washing process,the presence of slope resulted in the leaching of NH4–N on the surface of the slope,while the leaching of NH4–N deep inside the column was inhibited.Furthermore,the high-intensity rainfall significantly increased the leaching,highlighting the importance of considering the impact of extreme weather conditions during the leaching process.Overall,our study advances the understanding of the transport of NH4–N in mining area with hills,the impact of flow rates of leaching agents and precipitation intensities,and presents as a feasible modeling method to evaluate the environmental risks of NH4–N pollution during and post REE in situ mining activities.展开更多
Nitrate-nitrogen （NO3-N） dynamics and nitrogen （N） budgets in rice （0ryza sativa L.）-wheat （Triticum aestivum L.） rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer...Nitrate-nitrogen （NO3-N） dynamics and nitrogen （N） budgets in rice （0ryza sativa L.）-wheat （Triticum aestivum L.） rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer management over a two-year period. The experiment included four N rates for rice and wheat, respectively： N1 （125 and 94 kg N ha-1）, N2 （225 and 169 kg N ha-1）, N3 （325 and 244 kg N ha-1）, and NO （0 kg N ha-1）. The results showed that an overlying water layer during the rice growing seasons contributed to moderate concentrations of NO3-N in sampled waters and the concentrations of NO3-N only showed a rising trend during the field drying stage. The NO3-N concentrations in leachates during the wheat seasons were much higher than those during the rice seasons, particularly in the wheat seedling stage. In the wheat seedling stage, the NO3-N concentrations of leachates were significantly higher in N treatments than in NO treatment and increased with increasing N rates. As the NO3-N content （below 2 mg N L-1） at a depth of 80 cm during the rice-wheat rotations did not respond to the applied N rates, the high levels of NO3-N in the groundwater of paddy fields might not be directly related to NO3-N leaching. Crop growth trends were closely related to variations of NO3-N in leachates. A reduction in N application rate, especially in the earlier stages of crop growth, and synchronization of the peak of N uptake by the crop with N fertilizer application are key measures to reduce N loss. Above-ground biomass for rice and wheat increased significantly with increasing N rate, but there was no significant difference between N2 and N3. Increasing N rates to the levels greater than N2 not only decreased N use efficiency, but Mso significantly increased N loss. After two cycles of rice-wheat rotations, the apparent N losses of N1, N2 and N3 amounted to 234, 366 and 579 kg N ha-1, respectively. With an increase of N rate from NO to N3, the percentage of N uptake in total N inputs decreased from 63.9% to 46.9%. The apparent N losses during the rice seasons were higher than those during the wheat seasons and were related to precipitation; therefore, the application of fertilizer should take into account climate conditions and avoid application before heavy rainfall.展开更多
Film hole irrigation has been widely adopted as an effective water-saving irrigation technology in the arid and semiarid areas of China.To investigate the effects of initial soil moisture content(θ0)on soil water and...Film hole irrigation has been widely adopted as an effective water-saving irrigation technology in the arid and semiarid areas of China.To investigate the effects of initial soil moisture content(θ0)on soil water and nitrogen transport characteristics under muddy water film hole infiltration,the laboratory experiments were conducted with muddy water film hole infiltration,using five initial soil moisture content treatments.The models for describing the relationships between the cumulative infiltration(I(t))and infiltration duration(t);the relationship among the horizontal and vertical migration distances of the wetting front(Fx,Fz),θ0 and t,were established.The results showed that the initial soil moisture content had a significant effect on I(t),Fx,Fz and moisture content distribution in the wetted body.The change of I(t)over t conformed to Kostiakov model.With the increase ofθ0,the infiltration coefficient(K)gradually decreased.NO-3-N was mainly distributed in the range of the wetting radius of 15 cm,while NH+4-N was mainly distributed in the range of the wetting radius of 8 cm.This study can provide a theoretical basis and technical support for film hole irrigation.展开更多
To investigate the nitrogen transport and conversion inside activated sludge flocs,micro-profiles of O2,NHt 4,NO-2,NO-3,and pH were measured under different operating conditions.The flocs were obtained from a laborato...To investigate the nitrogen transport and conversion inside activated sludge flocs,micro-profiles of O2,NHt 4,NO-2,NO-3,and pH were measured under different operating conditions.The flocs were obtained from a laboratory-scale sequencing batch reactor.Nitrification,as observed from interfacial ammonium and nitrate fluxes,was higher at pH 8.5,than at pH 6.5 and 7.5.At pH 8.5,heterotrophic bacteria used less oxygen than nitrifying bacteria,whereas at lower pH heterotrophic activity dominated.When the ratio of C to N was decreased from 20 to 10,the ammonium uptake increased.When dissolved oxygen(DO)concentration in the bulk liquid was decreased from 4 to 2 mg·L^(-1),nitrification decreased,and only 25%of the DO influx into the flocs was used for nitrification.This study indicated that nitrifying bacteria became more competitive at a higher DO concentration,a higher pH value(approximately 8.5)and a lower C/N.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
Electrochemical fixation of nitrogen to ammonia with highly active,highly selective and low cost electrocatalysts is a sustainable alternative to the extremely energy-and capital-intensive Haber-Bosch process.Herein,w...Electrochemical fixation of nitrogen to ammonia with highly active,highly selective and low cost electrocatalysts is a sustainable alternative to the extremely energy-and capital-intensive Haber-Bosch process.Herein,we demonstrate a near electroneutral WO3 nanobelt catalyst to be a promising electrocatalyst for selective and efficient nitrogen reduction.The concept of near electroneutral interface is demonstrated by fabricating WO3 nanobelts with small zeta potential value on carbon fiber paper,which ensures a loose double layer structure of the electrode/electrolyte interface and allows nitrogen molecules access the active sites more easily and regulates proton transfer to increase the catalytic selectivity.The WO3/CFP electrode with optimal surface charge achieves a NH3 yield rate of 4.3μg·h-1·mg-1 and a faradaic efficiency of 37.3%at-0.3 V vs.RHE,rivalling the performance of the state-of-the-art nitrogen reduction reaction electrocatalysts.The result reveals that an unobstructed gas-diffusion pathway for continually supplying enough nitrogen to the active catalytic sites is of great importance to the overall catalytic performance.展开更多
基金supported by the Program of Shandong Modern Agricultural Technology and Industry System–Cultivation and Soil Fertilizer(SDAIT0107)the Major Application Technology Innovation Projects in Shandong Province and the Key Research and Development Projects of Shandong Province.
文摘In recent years,in order to improve nutrient use efficiency,especially nitrogen use efficiency,fertilizer valueadded technology has been developed rapidly.However,the mechanism of the effect of synergistic fertilizer on plant nitrogen utilization is not clear.A study was,therefore,conducted to explore the activities and gene expression of key enzymes for nitrogen assimilation and the gene expression of nitrogen transporters in wheat after the application of synergistic fertilizer.Soil column experiment was set up in Qingdao Agricultural University experimental base from October 2018 to June 2019.Maleic acid and itaconic acid were copolymerized with acrylic acid as cross-linking monomer to make a fluid gel,which was sprayed on the fertilizer surface to make nitrogen and phosphorus synergistic fertilizer.A total of 6 treatments was set according to different nitrogen and phosphorus fertilizer ratios:(1)100%common nitrogen fertilizer+100%common phosphate fertilizer(2)70%nitrogen synergistic fertilizer+100%phosphorus synergistic fertilizer;(3)100%nitrogen synergistic fertilizer+70%phosphorus synergistic fertilizer;(4)100%nitrogen synergistic fertilizer+100%phosphorus synergistic fertilizer;(5)70%nitrogen synergistic fertilizer+70%phosphorus synergistic fertilizer;(6)100%commercial nitrogen synergistic fertilizer+100%commercial phosphorus synergistic fertilizer.The results are as follows:(1)the enzyme activities of wheat plants under synergistic fertilizer condition were higher than those under ordinary fertilizer,except under the treatment that nitrogen and phosphorus synergistic fertilizer were both reduced;(2)the expression level of the genes under the treatment“100%nitrogen synergistic fertilizer+100%phosphorus synergistic fertilizer”was significantly higher than those in other treatments.Combined with the higher performance of nitrogen concentration in various parts of the plant under the condition of applying synergistic fertilizer,this study indicated that the application of synergistic fertilizer can improve the nitrogen metabolism of the plant by increasing the nitrogen level in the rhizosphere soil,inducing the expression of nitrogen transporter genes and key assimilation enzymes genes.
基金provided by the Innovative Team Program of Chinese Academy of Sciences (Grant No.KZZD-EW-TZ-06)the National Natural Science Foundation of China (Grant No.41430750)the National Science & Technology Pillar Program (Grant No.2011BAD31B03)
文摘Hydrological and hydro-chemical monitoring of nitrogen(N) and phosphorus(P) in a small urbanized catchment was conducted in the hilly area of the central Sichuan Basin,China,from 2010 through 2011.The diffuse N and P loadings in different forms of total nitrogen(TN) and phosphorus(TP),dissolved nitrogen(DN) and phosphorus(DP),as well as particulate nitrogen(PN) and phosphorus(PP) were calculated based on runoff discharges and chemical analyses.The results revealed that the diffuse pollution concentrations of TN,DN,PN,TP,DP and PP exhibited large variations during rainfall events,with peak concentrations occurring during the initial period.For all of the measured parameters,the event mean concentrations(EMCs) were observed to clearly vary among rainfall events.The EMCs of TN,DN,PN,TP,DP and PP(for all of the observed rainfall events) were 10.04,6.62,3.42,1.30,0.47 and0.83 mg/L,respectively.The losses of diffuse N and P exhibited clear seasonal patterns and mainly occurred during the period from July through September,when the losses totaled 99.3 and 9.6 kg/ha for TN and TP,respectively,accounting for 75% and 74% of the total annual loadings.The mean annual loadings of TN and TP were 124.6 and 12.9 kg/ha,respectively.The results indicate that residential areas in the hilly areaof the central Sichuan Basin are subject to high diffuse N and P loadings,posing a serious risk to the receiving water quality.Ecological buffering belts are recommended to incorporate into the urbanized catchment to reduce diffuse pollution.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX2-YW-Q07-02)the National Basic Research Program of China (973Program)(No.2010CB428706)+1 种基金the Fund for Creative Research Groups of NSFC(No.41121064)the National Natural Science Foundation of China (No.41106090)
文摘We established a budget model of nitrogen （N） inputs and outputs between watersheds and waterbodies to determine the sources of riverine N in the Changjiang （Yangtze） River drainage area. Nitrogen inputs in the budget included N from synthetic fertilizer, biological fixation by leguminous and other crops, wet/dry atmospheric deposition, excreta from humans and animals, and crop residues. The total N input was estimated to be 17.6 Tg, of which 20% or 3.5 Tg N was transported into waterbodies. Of the total N transported into waterbodies, the largest proportion was N from animal waste （26%）, followed by N from atmospheric wet/dry deposition （25%）, synthetic fertilizer N （17%）, N in sewage wastes （17%）, N in human waste from rural areas （6%） and industrial wastewater N （9%）. We studied the spatial patterns of N inputs and outputs by dividing the Changjiang River drainage area into four sub-basins, from upstream to downstream： the Tongtian River drainage area （TTD, the headwater drainage area, 138 000 l^n2, less disturbed by human activities）; the Jinsha River drainage area （JSD, 347 000 km2, less disturbed by human activities, approx. 3 500 km upstream of the Changjiang estuary）; the Pingshan-Yichang drainage area （PYD, 520 500 krn2, large-scale human disturbance, about 2 000 km upstream of the Changjiang estuary）; and the Yichang-Datong drainage area （YDD, 699 900 km^2, large-scale httman disturbance, approx. 620 km upstream of the Changjiang estuary）. The average N input into waterbodies was 2.3, 7.3, 24.1, and 28.2 kg N/ha in the TTD, JSD, PYD, and YDD sub-basins, respectively, suggesting an increase of N-components of more than 10 times from upstream to downstream areas.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11504283 and 21503153the Natural Science Foundation of Shaanxi Province under Grant No 2014JM1025the Science and Technology Star Project of Shaanxi Province under Grant No 2016KJXX-45
文摘We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-principles method based on density functional theory. Among the three models M1–M3, M1 is not doped with a heteroatom. In the left parts of M2 and M3, nitrogen atoms are doped at two edges of the nanoribbon. In the right parts, nitrogen atoms are doped at one center and at the edges of M2 and M3, respectively. Comparisons of M1, M2 and M3 show obvious rectifying characteristics, and the maximum rectification ratios are up to 42.9 in M2. The results show that the rectifying behavior is strongly dependent on the doping position of electrodes. A higher rectification ratio can be found in the dipyrimidinyl-diphenyl molecular device with asymmetric doping of left and right electrodes, which suggests that this system has a broader application in future logic and memory devices.
基金the Financial of National Key Research and Development Project of China(No.2019YFC1805102)Partial supports are from the National Natural Science Foundation of China(Nos.42107228 and 41977266)Shanghai Pujiang Program(No.21PJ1401000)。
文摘Ion-absorbed rare earth mines,leached in situ,retain a large amount of ammonium nitrogen(NH4–N)that continuously releases into the surrounding environments.However,quantitative descriptions and predictions of the transport of NH4–N across mining area with hill slopes are not fully established.Here,laboratory column experiments were designed with an inclined slope(a sand box)to examine the spatial temporal transport of NH4–N in soils collected from the ionic rare earth elements(REE)mining area.An HYDRUS-2D model simulation of the experimental data over time showed that soils had a strong adsorption capacity toward NH4–N.Chemical non-equilibrium model(CNEM)could well simulate the transport of NH4–N through the soil-packed columns.The simulation of the transport-adsorption processes at three flow rates of leaching agents revealed that low flow rate enabled a longer residence time and an increased NH4-N adsorption,but reduced the extraction efficiency for REE.During the subsequent rainwater washing process,the presence of slope resulted in the leaching of NH4–N on the surface of the slope,while the leaching of NH4–N deep inside the column was inhibited.Furthermore,the high-intensity rainfall significantly increased the leaching,highlighting the importance of considering the impact of extreme weather conditions during the leaching process.Overall,our study advances the understanding of the transport of NH4–N in mining area with hills,the impact of flow rates of leaching agents and precipitation intensities,and presents as a feasible modeling method to evaluate the environmental risks of NH4–N pollution during and post REE in situ mining activities.
基金Supported by the National Basic Research Program (973 Program) of China (No. 2011CB100506)the National Natural Science Foundation of China (Nos. 41171179 and 40871105)
文摘Nitrate-nitrogen （NO3-N） dynamics and nitrogen （N） budgets in rice （0ryza sativa L.）-wheat （Triticum aestivum L.） rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer management over a two-year period. The experiment included four N rates for rice and wheat, respectively： N1 （125 and 94 kg N ha-1）, N2 （225 and 169 kg N ha-1）, N3 （325 and 244 kg N ha-1）, and NO （0 kg N ha-1）. The results showed that an overlying water layer during the rice growing seasons contributed to moderate concentrations of NO3-N in sampled waters and the concentrations of NO3-N only showed a rising trend during the field drying stage. The NO3-N concentrations in leachates during the wheat seasons were much higher than those during the rice seasons, particularly in the wheat seedling stage. In the wheat seedling stage, the NO3-N concentrations of leachates were significantly higher in N treatments than in NO treatment and increased with increasing N rates. As the NO3-N content （below 2 mg N L-1） at a depth of 80 cm during the rice-wheat rotations did not respond to the applied N rates, the high levels of NO3-N in the groundwater of paddy fields might not be directly related to NO3-N leaching. Crop growth trends were closely related to variations of NO3-N in leachates. A reduction in N application rate, especially in the earlier stages of crop growth, and synchronization of the peak of N uptake by the crop with N fertilizer application are key measures to reduce N loss. Above-ground biomass for rice and wheat increased significantly with increasing N rate, but there was no significant difference between N2 and N3. Increasing N rates to the levels greater than N2 not only decreased N use efficiency, but Mso significantly increased N loss. After two cycles of rice-wheat rotations, the apparent N losses of N1, N2 and N3 amounted to 234, 366 and 579 kg N ha-1, respectively. With an increase of N rate from NO to N3, the percentage of N uptake in total N inputs decreased from 63.9% to 46.9%. The apparent N losses during the rice seasons were higher than those during the wheat seasons and were related to precipitation; therefore, the application of fertilizer should take into account climate conditions and avoid application before heavy rainfall.
基金This study was financially supported by the National Key Research and Development Program of China(Grant No.2016YFC0400204)the National Natural Science Foundation of China(Grant No.52079105,51779205 and 51479161)+1 种基金and the Public welfare industry research special project(Grant No.201203003)The authors acknowledge the anonymous reviewers and the editor for their valuable comments and suggestions.
文摘Film hole irrigation has been widely adopted as an effective water-saving irrigation technology in the arid and semiarid areas of China.To investigate the effects of initial soil moisture content(θ0)on soil water and nitrogen transport characteristics under muddy water film hole infiltration,the laboratory experiments were conducted with muddy water film hole infiltration,using five initial soil moisture content treatments.The models for describing the relationships between the cumulative infiltration(I(t))and infiltration duration(t);the relationship among the horizontal and vertical migration distances of the wetting front(Fx,Fz),θ0 and t,were established.The results showed that the initial soil moisture content had a significant effect on I(t),Fx,Fz and moisture content distribution in the wetted body.The change of I(t)over t conformed to Kostiakov model.With the increase ofθ0,the infiltration coefficient(K)gradually decreased.NO-3-N was mainly distributed in the range of the wetting radius of 15 cm,while NH+4-N was mainly distributed in the range of the wetting radius of 8 cm.This study can provide a theoretical basis and technical support for film hole irrigation.
基金This work was supported by Program for Changjiang Scholars and Innovative Research Team in University(No.IRT0853)State Commission of Science Technology of China(No.2009ZX07212-002)+1 种基金State Key Laboratory of Western Architecture and Technology(No.10KF08)Foundation of Shaanxi Educational Committee(No.11JK0759).
文摘To investigate the nitrogen transport and conversion inside activated sludge flocs,micro-profiles of O2,NHt 4,NO-2,NO-3,and pH were measured under different operating conditions.The flocs were obtained from a laboratory-scale sequencing batch reactor.Nitrification,as observed from interfacial ammonium and nitrate fluxes,was higher at pH 8.5,than at pH 6.5 and 7.5.At pH 8.5,heterotrophic bacteria used less oxygen than nitrifying bacteria,whereas at lower pH heterotrophic activity dominated.When the ratio of C to N was decreased from 20 to 10,the ammonium uptake increased.When dissolved oxygen(DO)concentration in the bulk liquid was decreased from 4 to 2 mg·L^(-1),nitrification decreased,and only 25%of the DO influx into the flocs was used for nitrification.This study indicated that nitrifying bacteria became more competitive at a higher DO concentration,a higher pH value(approximately 8.5)and a lower C/N.
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.
基金supported by Shenzhen Science and Technology Research Grant(ZDSYS201707281026184)Natural Science Foundation of Shenzhen(JCYJ20190813110605381)。
文摘Electrochemical fixation of nitrogen to ammonia with highly active,highly selective and low cost electrocatalysts is a sustainable alternative to the extremely energy-and capital-intensive Haber-Bosch process.Herein,we demonstrate a near electroneutral WO3 nanobelt catalyst to be a promising electrocatalyst for selective and efficient nitrogen reduction.The concept of near electroneutral interface is demonstrated by fabricating WO3 nanobelts with small zeta potential value on carbon fiber paper,which ensures a loose double layer structure of the electrode/electrolyte interface and allows nitrogen molecules access the active sites more easily and regulates proton transfer to increase the catalytic selectivity.The WO3/CFP electrode with optimal surface charge achieves a NH3 yield rate of 4.3μg·h-1·mg-1 and a faradaic efficiency of 37.3%at-0.3 V vs.RHE,rivalling the performance of the state-of-the-art nitrogen reduction reaction electrocatalysts.The result reveals that an unobstructed gas-diffusion pathway for continually supplying enough nitrogen to the active catalytic sites is of great importance to the overall catalytic performance.
