Soil nitrogen(N)is the main limiting nutrient for plant growth,which is sensitive to variations in the soil oxygen environment.To provide insights into plant N accumulation and yield under aerated and drip irrigation,...Soil nitrogen(N)is the main limiting nutrient for plant growth,which is sensitive to variations in the soil oxygen environment.To provide insights into plant N accumulation and yield under aerated and drip irrigation,a greenhouse tomato experiment was conducted with six treatments,including three fertilization types:inorganic fertilizer(NPK);organic fertilizer(OM);chemical(75%of applied N)+organic fertilizer(25%)(NPK+OM)under drip irrigation(DI)and aerated irrigation(AI)methods.Under Al,total soil carbon mineralization(C_(min))was significantly higher(by 5.7-7.0%)than under DI irrigation.C_(min)in the fertilizer treatments followed the order NPK+OM>OM>NPK under both AI and DI.Potentially mineralizable C(C_(0))and N(N_(0))was greater under AI than under DI.Gross N mineralization,gross nitrification,and NH_(4)^(+)immobilization rates were significantly higher under the AINPK treatment than the DINPK treatment by 2.58-3.27-,1.25-1.44-,and 1-1.26-fold,respectively.These findings demonstrated that AI and the addition of organic fertilizer accelerated the turnover of soil organic matter and N transformation processes,thereby enhancing N availability.Moreover,the combination of AI and organic fertilizer application was found to promote root growth(8.4-10.6%),increase the duration of the period of rapid N accumulation(ΔT),and increase the maximum N accumulation rate(V_(max)),subsequently encouraging aboveground dry matter accumulation.Consequently,the AI treatment yield was significantly greater(by 6.3-12.4%)than under the DI treatment.Further,N partial factor productivity(NPFP)and N harvest index(NHI)were greater under AI than under DI,by 6.3 to 12.4%,and 4.6 to 8.1%,respectively.The rankings of yield and NPFP remained consistent,with NPK+OM>OM>NPK under both AI and DI treatments.These results highlighted the positive impacts of AI and organic fertilizer application on soil N availability,N uptake,and overall crop yield in tomato.The optimal management measure was identified as the AINPK+OM treatment,which led to more efficient N management,better crop growth,higher yield,and more sustainable agricultural practices.展开更多
Electrochemical nitrogen transformation techniques represent a burgeoning avenue for nitrogen pollutant remediation and synthesizing valuable nitrogenous products from atmospheric nitrogen.Intermetallic compounds(IMCs...Electrochemical nitrogen transformation techniques represent a burgeoning avenue for nitrogen pollutant remediation and synthesizing valuable nitrogenous products from atmospheric nitrogen.Intermetallic compounds(IMCs)nanocrystals,featured with unique geometric,electronic and functional properties,have emerged as promising candidates.The review discusses various synthesis approaches for IMCs,including thermal annealing,wet chemical synthesis,electrochemical synthesis,and other emerging methods,analyzing their advantages and limitations.Then we summarized the recent advances of IMCs in electrocatalytic nitrogen transformation reactions,such as nitrate reduction reaction,nitric oxide reduction reaction,nitrogen reduction reaction,and hydrazine oxidation reaction.Despite significant progress,challenges remain in the field,particularly in adopting more refined strategies to improve catalyst performance and stability.This review aims to comprehensively understand the structural properties of IMCs and their structure-performance relationship,guiding the development of more efficient and stable catalysts for future nitrogen electrochemistry.展开更多
In order to address the evolving emission characteristics of oxygenated volatile organic compounds(OVOCs),it is essential to develop adsorbent materials specifically designed for the efficient adsorption of OVOCs with...In order to address the evolving emission characteristics of oxygenated volatile organic compounds(OVOCs),it is essential to develop adsorbent materials specifically designed for the efficient adsorption of OVOCs with large kinetic diameters.In this study,we used co-pyrolysis to prepare a series of graded porous carbon materials with well-developed micropores by adjusting the doping ratios of root nodules and pretreated cellulose.The material with root nodule to cellulose mass ratio of 1:1(TCC-RN-1)exhibited the highest saturated adsorption capacity for butyl acetate(834 mg/g).This can be attributed to enhanced pore size distribution from nodule doping,which facilitates the development of a micropore-graded structure.Additionally,the nodules acted as auxiliary activating agents that enhanced the KOH micropore regulation effect during the activation stage,resulting in the highest micropore volume(0.863 cm^(3)/g).The doping of root nodules facilitated the formation of additional defects on the surface of the porous carbon material,leading to a more disordered arrangement that improved pollutant adsorption.Furthermore,TCC-RN-1 demonstrated good thermal stability in an air atmosphere,main-taining a butyl acetate adsorption capacity exceeding 95%after five adsorption-desorption cycles.This indicates its favorable potential for industrial applications.展开更多
The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in m...The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in monsoon tropical climate. Clear felled area or burnt site and 15-21 year mixed plantation of native and exotic species, situated side by side on low hill having Typic Dystrochrepts soil was represented at each pair site. At all the three pair sites, clear felled area or burnt site showed very significantly （p~_0.001） lower population of actinomycetes, Rhizobium, Nitrosomonas, Nitrobacter and ammonifying as well as deni- trifying bacteria compared to their adjacent mixed plantation. From en- vironmental consideration, this finding has implication in managing natural ecosystem.展开更多
The effects of different species and concentrations’signal molecules on aerobic activated sludge system were investigated through batch experiments.Results showed that the fastest NH^(+)_(4)-N oxidization rate and th...The effects of different species and concentrations’signal molecules on aerobic activated sludge system were investigated through batch experiments.Results showed that the fastest NH^(+)_(4)-N oxidization rate and the most extracellular polymeric substances(EPS)secretion were obtained by adding 5 nmol/L N-hexanoyl-l-homoserine lactone(C_(6)-HSL)into the aerobic activated sludge.Further study investigated the correlation among N-acyl-homoserine lactones-mediated quorum sensing(AHLs-mediated QS),nutrient removal performances and microbial communities with the long-term addition of 5 nmol/L C_(6)-HSL.It was found that C_(6)-HSL-manipulation could enhance the stability and optimize the decontamination performance of aerobic granular sludge(AGS)system.Microbial compositions considerably shifted with long-term C_(6)-HSL-manipulation.Exogenous C_(6)-HSL-manipulation inhibited quorum quenching-related(QQ-related)activities and enhanced QS-related activities during the stable period.The proposed C_(6)-HSL-manipulation might be a potential technology to inhibit the growth of harmful bacteria in AGS,which could provide a theoretical foundation for the realization of more stable biological wastewater treatments.展开更多
This paper focused on nitrate fate in the vadose zone(VZ)and its implications for groundwater vulnerability under different soil types in the agricultural area of Huaihe River Basin,China.Isotopic compositions of nitr...This paper focused on nitrate fate in the vadose zone(VZ)and its implications for groundwater vulnerability under different soil types in the agricultural area of Huaihe River Basin,China.Isotopic compositions of nitrate(δ15N andδ18O)along with NO3-and Cl-concentrations were determined in the VZ-shallow groundwater continuum beneath silty-loam and silty-clay-loam,which are distinctive in texture and organic carbon(OC).In the soil zone(<1 m in depth),measuredδ18O-NO3-suggested the ubiquitous of nitrification regardless of soil types.In the subsoil zone(>1 m in depth),however,the concurrent enrichment ofδ15N-NO3-andδ18O-NO3-indicated the occurrence of denitrification,which showed a dependence on subsoil properties.Specifically,during wheat and maize land uses,denitrification removed as much as 76%-88%of the total nitrate where the subsoil was dominated by stratified OC-rich silty-clay-loam.In contrast,only 0%-28%of the nitrate was degraded via denitrification where the subsoil was composed of uniform,OC-depleted silty-loam.Furthermore,inactive denitrification and higher permeability in the silty-loam VZ implied higher groundwater vulnerability.This observation was consistent with the fact that groundwater NO3--N concentration beneath silty-loam(11.24 mg L-1)was over two times higher than that of the silty-clay-loam(5.32 mg L-1),where stricter fertilization management and conservation strategies should be applied to protect groundwater quality.展开更多
A better understanding of nitrogen transformation in soils could reveal the capacity for biological inorganic N supply and improve the efficiency of N fertilizers. In this study, a15 N tracing study was carried out to...A better understanding of nitrogen transformation in soils could reveal the capacity for biological inorganic N supply and improve the efficiency of N fertilizers. In this study, a15 N tracing study was carried out to investigate the effects of converting woodland to orchard, and orchard age on the gross rates of N transformation occurring simultaneously in subtropical soils in Eastern China. The results showed that inorganic N supply rate was remained constant with soil organic C and N contents increased after converting woodland into citrus orchard and with increasing orchard age. This phenomenon was most probably due to the increase in the turnover time of recalcitrant organic-N, which increased with decreasing soil p H along with increasing orchard age significantly. The amo A gene copy numbers of both archaeal and bacterial were stimulated by orchard planting and increased with increasing orchard age. The nitrification capacity（defined as the ratio of gross rate of nitrification to total gross rate of mineralization） increased following the Michaelis–Menten equation, sharply in the first 10 years after woodland conversion to orchard, and increased continuously but much more slowly till 30 years. Due to the increase in nitrification capacity and unchanged NO3-consumption, the dominance of ammonium in inorganic N in woodland soil was shifted to nitrate dominance in orchard soils. These results indicated that the risk of NO3-loss was expected to increase and the amount of N needed from fertilizers for fruit growth did not change although soil organic N accumulated with orchard age.展开更多
The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure （XANES） to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples w...The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure （XANES） to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples were collected from spruce, hemlock and pine forests in central Taiwan. Results showed that various organic N types could be revealed by XANES spectra. Amide and pyrrolic N are the major parts of the composition in the humic substance, soluble organic nitrogen and original soils. The relative distribution of N speciation differed in treatments and vegetations samples. The spruce had a significant difference from the hemlock in soluble organic nitrogen （SON） spectra at 402.3 eV energy peak. In the A-horizon soils, the relative amount of pyridinic N was much higher than that in the O-horizon soils, indicating N transformation in quantity in the mineral horizon was different from that in the organic horizon, which might play an important role in N cycling of forest ecosystems.展开更多
High concentrations of ammonium nitrogen released from tannery sludge during storage in open air may cause nitrogen pollution to soil and groundwater.To study the transformation mechanism of NH_(4)^(+)-N by nitrifying...High concentrations of ammonium nitrogen released from tannery sludge during storage in open air may cause nitrogen pollution to soil and groundwater.To study the transformation mechanism of NH_(4)^(+)-N by nitrifying functional bacteria in tannery sludge contaminated soils,a series of contaminated soil culture experiments were conducted in this study.The contents of ammonium nitrogen(as NH_(4)^(+)-N),nitrite nitrogen(as NO_(2)^(−)-N)and nitrate nitrogen(as NO_(3)^(−)-N)were analyzed during the culture period under different conditions of pollution load,soil particle and redox environment.Sigmodial equation was used to interpret the change of NO_(3)^(−)-N with time in contaminated soils.The abundance variations of nitrifying functional genes(amoA and nxrA)were also detected using the real-time quantitative fluorescence PCR method.The results show that the nitrification of NH_(4)^(+)-N was aggravated in the contaminated silt soil and fine sand under the condition of lower pollution load,finer particle size and more oxidizing environment.The sigmodial equation well fitted the dynamic accumulation curve of the NO_(3)^(−)-N content in the tannery sludge contaminated soils.The Cr(III)content increased with increasing pollution load,which inhibited the reproduction and activity of nitrifying bacteria in the soils,especially in coarse-grained soil.The accumulation of NO_(2)^(−)-N contents became more obvious with the increase of pollution load in the fine sand,and only 41.5%of the NH_(4)^(+)-N was transformed to NO_(3)^(−)-N.The redox environment was the main factor affecting nitrification process in the soil.Compared to the aerobic soil environment,the transformation of NH_(4)^(+)-N was significantly inhibited under anaerobic incubation condition,and the NO_(3)^(−)-N contents decreased by 37.2%,61.9%and 91.9%under low,medium and high pollution loads,respectively.Nitrification was stronger in the silt soil since its copy number of amoA and nxrA genes was two times larger than that of fine sand.Moreover,the copy numbers of amoA and nxrA genes in the silt soil under the aerobic environment were 2.7 times and 2.2 times larger than those in the anaerobic environment.The abundance changes of the amoA and nxrA functional genes have a positive correlation with the nitrification intensity in the tannery sludge-contaminated soil.展开更多
In order to provide basic design parameters for the industrial pyrolysis process,the transformation behavior of nitrogen was investigated using wheat straw as raw material.The distributions of nitrogen in pyrolysis ch...In order to provide basic design parameters for the industrial pyrolysis process,the transformation behavior of nitrogen was investigated using wheat straw as raw material.The distributions of nitrogen in pyrolysis char,oil,and gas were obtained and the nitrogenous components in the products were analyzed systematically by X-ray photoelectron spectroscopy(XPS),pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)and thermogravimetric-Fourier transform infrared spectrometry(TG-FTIR).The nitrogen distribution ranges of the pyrolysis char,oil,and gas were 37.34%–54.82%,32.87%–40.94%and 10.20%–28.83%,respectively.More nitrogen was retained in char at lower pyrolysis temperature and the nitrogen distribution of oil was from rise to decline with increasing temperature.The most abundant N-containing compounds in three-phase products were pyrrole-N,amines,and HCN,respectively.In addition,the transformation mechanism of nitrogen from wheat straw to pyrolysis products was concluded.展开更多
Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration...Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration on soil microbial nitrogen cycling in inland wetlands, we compared freshwater and brackish marsh(or non-marsh) wetlands in terms of sediment ammonia-oxidizing rate(AOR), denitrifying rate(DR), and related microbial communities in a typical inland basin, the Hulun Lake basin, in China. Results showed that marsh ecosystems(ME) exhibited 31% higher AOR and 65% higher DR than non-marsh ecosystems(NE). For NE, freshwater non-marsh wetland exhibited 12% higher AOR than brackish non-marsh wetland. This was probably due to the inhibitory effects of high NH_4~+ and salinity levels on ammonia-oxidizing archaea in brackish non-marsh wetland. Conversely, DR in brackish non-marsh wetland was 23% higher than that in freshwater non-marsh wetland, with total organic carbon(TOC) significantly influencing this difference,suggesting that the higher DR in brackish non-marsh wetland was mainly due to its higher TOC level. For ME, due to the direct and indirect interference of salinity, brackish marsh wetland displayed 26% lower AOR and 19% lower DR than freshwater marsh wetland. Besides, brackish wetlands harbored distinct ammonia-oxidizing and denitrifying microbial communities compared to freshwater wetlands. The assembly of these communities was dominated by stochastic processes, while brackish wetlands exhibited more prominent deterministic processes than freshwater wetlands. Overall, high evapotranspiration altered activities and community characteristics of ammonia oxidizers and denitrifiers in inland brackish wetlands by enhancing salinity and nutrient levels,while emergent plants occurring in ME could mitigate the adverse effects of salt stress of inland brackish wetlands on nitrogen cycling.展开更多
Soil nitrogen(N)transformation processes in the High Arctic tundra are poorly understood even though nitrogen is one of the main limiting nutrients.We analyzed soil samples collected along a High Arctic tundra transec...Soil nitrogen(N)transformation processes in the High Arctic tundra are poorly understood even though nitrogen is one of the main limiting nutrients.We analyzed soil samples collected along a High Arctic tundra transect to investigate spatial variability in key nitrogen transformation processes,functional gene abundances,ammonia-oxidizing archaea(AOA)community structures,and key nitrogen transformation regulators.The potential denitrification rates were higher than the nitrification rates in the soil samples,although nitrification may still regulate N2O emissions from tundra soil.The nutrient(total carbon,total organic carbon,total nitrogen,and NH_(4)^(+)-N)contents were important determinants of spatial variability in the potential denitrification rates of soil along the tundra transect.The total sulfurcontent was the main variable controlling potential nitrification processes,probably in association with sulfate-reducing bacteria.The nitrate content was the main variable affecting potential dissimilatory nitrate reduction to ammonium.AOA and ammonia-oxidizing bacteria amoA,nirS,and anammox 16S rRNA genes were found in all of the soil samples.AOA play more important roles than ammonia-oxidizing bacteria in soilnitrification.Anammox bacteria may utilize NO_(2)^(-)produced through nitrification.Phylogenetic analysis indicated that the AOA amoA sequences could be grouped into eight unique operational taxonomic units(OTUs)with a 97%sequence similarity and were affiliated with three group 1.1b Nitrososphaeraclusters.The results indicated that heterogeneous environmental factors(e.g.,the carbon and nitrogen contents of soil)along the High Arctic tundra transect strongly affected the nitrogen transformation rate and relevant functional gene abundances in soil.展开更多
Muddy water irrigation has been widely practiced in the Yellow River Basin for agricultural production and is an important method of economical and intensive utilization of water resources.In this study,the effects of...Muddy water irrigation has been widely practiced in the Yellow River Basin for agricultural production and is an important method of economical and intensive utilization of water resources.In this study,the effects of sediment gradation,sand content,and soil moisture content on nitrogen(N)transformation were studied through a series of experimental tests.The results indicated that muddy water irrigation significantly affected agricultural soil physical and biological properties as well as N transformation.Soil bulk density,total porosity,pH,and microbial enzyme activities significantly correlated with N transformation as affected by the interaction between sediment and soil moisture.Sediment addition generally increased the soil bulk density and reduced the soil porosity and pH significantly,and the optimum moisture for promotion of the N transformation rate was 80%of the water-filled pore space.Therefore,muddy water irrigation has a potentially long-term influence on agricultural N cycles in semi-arid regions of northwestern China.This could provide a theoretical basis for scientific and rational use of muddy water for irrigation.展开更多
As a recently emerging wastewater treatment technology,Algal-bacterial granular sludge(ABGS)process shows significant advantages.However,current research on the ABGS system is a lack of a clear and complete understand...As a recently emerging wastewater treatment technology,Algal-bacterial granular sludge(ABGS)process shows significant advantages.However,current research on the ABGS system is a lack of a clear and complete understanding of the potential mechanism of signal molecules on the growth of ABGS.This study comprehensively explores the variations in the ABGS under different N-acyl-homoserine lactone(AHL)conditions by constructing three sequencing batch reactor(SBR)systems.The results indicate that N-hexanoyl-l-homoserine lactone(C6-HSL)accelerates the granulation process in the early stages by promoting the loosely bound extracellular polymeric substances(LB-EPS)secretion and filamentous bacteria growth,thereby shortening required time for initial granule formation.On the other hand,N-(3-oxodecanoyl)-l-homoserine lactone(3-oxo-C12-HSL)expedites the granulation process by promoting the tightly bound extracellular polymeric substances(TB-EPS)and aromatic protein secretion,benefiting structural stability and nitrogen and phosphorus removal efficiency of mature ABGS.展开更多
To better understand the interaction of N transformation and exogenous C source and manage N fertilization, the effects of glucose addition on N transformation were determined in paddy soils with a gradient of soil or...To better understand the interaction of N transformation and exogenous C source and manage N fertilization, the effects of glucose addition on N transformation were determined in paddy soils with a gradient of soil organic C content. Changes in N mineralization, nitrification and denitrification, as well as their response to glucose addition were measured by incubation experiments in paddy soils derived from Quaternary red clay in subtropical China. Mineralization and denitrification were changed in order of increasing soil fertilities： high 〉 middle 〉 low. During the first week of incubation, net N mineralization and denitrification rates in paddy soil with high fertility were 1.9 and 1.1 times of those in soil with middle fertility and 5.3 and 2.9 times of those in soil with low fertility, respectively. Addition of glucose decreased net N mineralization by approximately 78.8, 109.2 and 177.4% in soils with high, middle and low fertility, respectively. However, denitrification rates in soils with middle and low fertility were increased by 14.4 and 166.2% respectively. The highest nitrate content among the paddy soils tested was 0.62 mg kg-1 and the highest nitrification ratio was 0.33%. Addition of glucose had no obvious effects on nitrate content and nitrification ratio. It was suggested that the intensity of mineralization and denitrification was quite different in soils with different fertility, and increased with increasing soil organic C content. Addition of glucose decreased mineralization, but increased denitrification, and the shifts were greater in soil with low than in soil with high organic C content. Neither addition of glucose nor inherent soil organic C had obvious effects on nitrification in paddy soils tested.展开更多
Reservoirs are regarded as hotspots of nitrogen transformation and potential sources of nitrous oxide(N_(2)O).However,it remains unclear how the hydrological conditions due to dam construction control the processes of...Reservoirs are regarded as hotspots of nitrogen transformation and potential sources of nitrous oxide(N_(2)O).However,it remains unclear how the hydrological conditions due to dam construction control the processes of nitrogen transformation in reservoir waters.To address this issue,we examined the spatial-temporal characteristics of nitrate concentrations,δ^(15)N-NO_(3)^(-),δ^(18)O-NO_(3)^(-),δ^(18)O-H_(2)O,relative water column stability(RWCS),and related environmental factors in a subtropical eutrophic reservoir(Hongfeng Reservoir,HFR),Southwest China.We found that denitrification was the most important nitrogen transformation process in the HFR and that higher denitrification intensity was associated with increased RWCS in summer,which suggested hydrological control of the denitrification process.In contrast,low RWCS conditions favored the nitrification process in the HFR in winter.Additionally,dissolved oxygen(DO;p<0.05)and nitrate concentrations(p<0.01)had significant impacts on the denitrification rate.We also found that the spatiotemporal RWCS variations were a prerequisite for regulating DO/nitrate stratification and the coupling/decoupling of nitrification-denitrification at the local and global scales.This study would advances our knowledge of the impacts of RWCS and thermal stratification on nitrogen transformation processes in reservoirs.展开更多
Imidacloprid is one of the most commonly used insecticides in agricultural practice, and its application poses a potential risk for soil microorganisms. The objective of this study was to assess whether changes in the...Imidacloprid is one of the most commonly used insecticides in agricultural practice, and its application poses a potential risk for soil microorganisms. The objective of this study was to assess whether changes in the structure of the soil microbial community after imidacloprid application at the field rate（FR, 1 mg/kg soil） and 10 times the FR（10 × FR, 10 mg/kg soil）may also have an impact on biochemical and microbial soil functioning. The obtained data showed a negative effect by imidacloprid applied at the FR dosage for substrate-induced respiration（SIR）, the number of total bacteria, dehydrogenase（DHA）, both phosphatases（PHOS-H and PHOS-OH）, and urease（URE） at the beginning of the experiment. In 10 × FR treated soil, decreased activity of SIR, DHA, PHOS-OH and PHOS-H was observed over the experimental period. Nitrifying and N2-fixing bacteria were the most sensitive to imidacloprid. The concentration of NO3-decreased in both imidacloprid-treated soils,whereas the concentration of NH4＋in soil with 10 × FR was higher than in the control.Analysis of the bacterial growth strategy revealed that imidacloprid affected the r- or K-type bacterial classes as indicated also by the decreased eco-physiological（EP） index.Imidacloprid affected the physiological state of culturable bacteria and caused a reduction in the rate of colony formation as well as a prolonged time for growth. Principal component analysis showed that imidacloprid application significantly shifted the measured parameters, and the application of imidacloprid may pose a potential risk to the biochemical and microbial activity of soils.展开更多
?15)N-labelled green manure was used to feed pigs. Its nitrogen recovery by pig body, feces and urine was23.5%, 23.8% and 28.8% respectively, totalling 76. 1%. Feces and green manure coordinated respectively withequal...?15)N-labelled green manure was used to feed pigs. Its nitrogen recovery by pig body, feces and urine was23.5%, 23.8% and 28.8% respectively, totalling 76. 1%. Feces and green manure coordinated respectively withequal amount of CO(NH_2)_2-N as well as urine alone were applied as basic fertilizer in microplot experiments.The ￣(15)N recovery from feces and urine was equivalent to 2.51% and 4.82% by rice grain, and 0.98% and1.94% by straw respectively, and soil residual ￣(15)N from them took 13.3% and 4.90% of the ￣(15)N in greenmanure. After feeding pigs with green manure and returning their feces and urine into soil, the ￣(15)N recoveryby pig body and rice grain was 30.8%, and that by pig body, and rice plant as well as soil residual took 52.7%of the ￣(15)N in feed. ￣(15)N loss was 23.9% in pig feeding and 23.4% in rice planting. When green manure wasincorporated directly into soil, its ￣(15)N recovery by grain was 26.65%, that by rice plant plus soil residual was65.2%, and the loss was 34.8%.展开更多
A new procedure of determining optimal C/N (the rate of carbon source to nitrogen source) of mixed distillers' grains for combined bacteria synergic fermentation is established. At the same time an improved method...A new procedure of determining optimal C/N (the rate of carbon source to nitrogen source) of mixed distillers' grains for combined bacteria synergic fermentation is established. At the same time an improved method evaluating bacteria growth, called method of dry cell weighing by filtering is developed. For each combination of C and N, their initial and residual contents before and after fermentation respectively are determined. Then followed the calculation of utilization of C and N sources by the compound bacteria. The optimal C/N is finally located from among the utilization of C and N of several combinations and the weight of produced mass of oven dried thallus. The conditions of fermentation are: inoculum size 10%, temperature 30 0℃, rotational speed 170 r/min, shake culture time 48h. The best results obtained from orthogonal experiments are: maximum mass of oven dried thallus is 14 693g in a liter liquid medium, maximum utilization rate of carbon source is 98 13% and maximum utilization rate of nitrogen is 78 14%. Optimal C/N is 5 1.展开更多
Background The forest-steppe ecotone,a critical transition zone sensitive to global change,faces increasing nitrogen deposition.However,the interplay between nitrogen conversion processes and soil enzyme activity rema...Background The forest-steppe ecotone,a critical transition zone sensitive to global change,faces increasing nitrogen deposition.However,the interplay between nitrogen conversion processes and soil enzyme activity remains unclear.We investigated the effects of nitrogen addition on plant nutrient dynamics,microbial functional genes,and enzyme activity in northwest Liaoning,China.Results Nitrogen addition significantly increased leaf nitrogen content in Potentilla tanacetifolia(peak under N40)and Artemisia frigida(peak under N40),while Lespedeza daurica showed a non-linear response(peak under N20).Phosphorus content remained unaffected across species.Soil enzyme activities(urease,nitrate reductase,dehydrogenase)increased with nitrogen input,with protease activity rising proportionally to nitrogen addition rate.Functional genes(nirK,nifH,AOB-amoA)exhibited dynamic responses:nirK abundance peaked under N40,nifH under N10,and AOB-amoA increased with nitrogen input.Structural equation modeling revealed that nirK gene abundance positively influenced enzyme activity(λ=0.512),while nifH negatively correlated with leaf N/P ratios(λ=-0.606).Soil protease activity directly drove leaf N/P ratios(λ=0.734).Conclusions Nitrogen addition enhances plant nitrogen uptake and enzyme-driven mineralization,but speciesspecific responses highlight ecological trade-offs.Soil pH and protease activity are pivotal in mediating nitrogen conversion and plant nutrient stoichiometry.These findings underscore the need to integrate microbial and enzymatic dynamics into nutrient management strategies for ecotones under nitrogen enrichment.展开更多
基金supported by the National Natural Science Foundation of China for Young Scholars(52109066)the Postdoctoral Science Foundation of Shaanxi Province,China(2023BSHTBZZ29)the China Postdoctoral Science Foundation(2022M712604 and 2023T160534).
文摘Soil nitrogen(N)is the main limiting nutrient for plant growth,which is sensitive to variations in the soil oxygen environment.To provide insights into plant N accumulation and yield under aerated and drip irrigation,a greenhouse tomato experiment was conducted with six treatments,including three fertilization types:inorganic fertilizer(NPK);organic fertilizer(OM);chemical(75%of applied N)+organic fertilizer(25%)(NPK+OM)under drip irrigation(DI)and aerated irrigation(AI)methods.Under Al,total soil carbon mineralization(C_(min))was significantly higher(by 5.7-7.0%)than under DI irrigation.C_(min)in the fertilizer treatments followed the order NPK+OM>OM>NPK under both AI and DI.Potentially mineralizable C(C_(0))and N(N_(0))was greater under AI than under DI.Gross N mineralization,gross nitrification,and NH_(4)^(+)immobilization rates were significantly higher under the AINPK treatment than the DINPK treatment by 2.58-3.27-,1.25-1.44-,and 1-1.26-fold,respectively.These findings demonstrated that AI and the addition of organic fertilizer accelerated the turnover of soil organic matter and N transformation processes,thereby enhancing N availability.Moreover,the combination of AI and organic fertilizer application was found to promote root growth(8.4-10.6%),increase the duration of the period of rapid N accumulation(ΔT),and increase the maximum N accumulation rate(V_(max)),subsequently encouraging aboveground dry matter accumulation.Consequently,the AI treatment yield was significantly greater(by 6.3-12.4%)than under the DI treatment.Further,N partial factor productivity(NPFP)and N harvest index(NHI)were greater under AI than under DI,by 6.3 to 12.4%,and 4.6 to 8.1%,respectively.The rankings of yield and NPFP remained consistent,with NPK+OM>OM>NPK under both AI and DI treatments.These results highlighted the positive impacts of AI and organic fertilizer application on soil N availability,N uptake,and overall crop yield in tomato.The optimal management measure was identified as the AINPK+OM treatment,which led to more efficient N management,better crop growth,higher yield,and more sustainable agricultural practices.
基金funded by the National Natural Science Foundation of China(No.22405173)the Shanghai Pujiang Program(No.23PJ1409100)the Project of Overseas Leading Talent of Shanghai.
文摘Electrochemical nitrogen transformation techniques represent a burgeoning avenue for nitrogen pollutant remediation and synthesizing valuable nitrogenous products from atmospheric nitrogen.Intermetallic compounds(IMCs)nanocrystals,featured with unique geometric,electronic and functional properties,have emerged as promising candidates.The review discusses various synthesis approaches for IMCs,including thermal annealing,wet chemical synthesis,electrochemical synthesis,and other emerging methods,analyzing their advantages and limitations.Then we summarized the recent advances of IMCs in electrocatalytic nitrogen transformation reactions,such as nitrate reduction reaction,nitric oxide reduction reaction,nitrogen reduction reaction,and hydrazine oxidation reaction.Despite significant progress,challenges remain in the field,particularly in adopting more refined strategies to improve catalyst performance and stability.This review aims to comprehensively understand the structural properties of IMCs and their structure-performance relationship,guiding the development of more efficient and stable catalysts for future nitrogen electrochemistry.
基金supported by the National Natural Science Foundation of China(No.52370112).
文摘In order to address the evolving emission characteristics of oxygenated volatile organic compounds(OVOCs),it is essential to develop adsorbent materials specifically designed for the efficient adsorption of OVOCs with large kinetic diameters.In this study,we used co-pyrolysis to prepare a series of graded porous carbon materials with well-developed micropores by adjusting the doping ratios of root nodules and pretreated cellulose.The material with root nodule to cellulose mass ratio of 1:1(TCC-RN-1)exhibited the highest saturated adsorption capacity for butyl acetate(834 mg/g).This can be attributed to enhanced pore size distribution from nodule doping,which facilitates the development of a micropore-graded structure.Additionally,the nodules acted as auxiliary activating agents that enhanced the KOH micropore regulation effect during the activation stage,resulting in the highest micropore volume(0.863 cm^(3)/g).The doping of root nodules facilitated the formation of additional defects on the surface of the porous carbon material,leading to a more disordered arrangement that improved pollutant adsorption.Furthermore,TCC-RN-1 demonstrated good thermal stability in an air atmosphere,main-taining a butyl acetate adsorption capacity exceeding 95%after five adsorption-desorption cycles.This indicates its favorable potential for industrial applications.
文摘The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in monsoon tropical climate. Clear felled area or burnt site and 15-21 year mixed plantation of native and exotic species, situated side by side on low hill having Typic Dystrochrepts soil was represented at each pair site. At all the three pair sites, clear felled area or burnt site showed very significantly （p~_0.001） lower population of actinomycetes, Rhizobium, Nitrosomonas, Nitrobacter and ammonifying as well as deni- trifying bacteria compared to their adjacent mixed plantation. From en- vironmental consideration, this finding has implication in managing natural ecosystem.
文摘The effects of different species and concentrations’signal molecules on aerobic activated sludge system were investigated through batch experiments.Results showed that the fastest NH^(+)_(4)-N oxidization rate and the most extracellular polymeric substances(EPS)secretion were obtained by adding 5 nmol/L N-hexanoyl-l-homoserine lactone(C_(6)-HSL)into the aerobic activated sludge.Further study investigated the correlation among N-acyl-homoserine lactones-mediated quorum sensing(AHLs-mediated QS),nutrient removal performances and microbial communities with the long-term addition of 5 nmol/L C_(6)-HSL.It was found that C_(6)-HSL-manipulation could enhance the stability and optimize the decontamination performance of aerobic granular sludge(AGS)system.Microbial compositions considerably shifted with long-term C_(6)-HSL-manipulation.Exogenous C_(6)-HSL-manipulation inhibited quorum quenching-related(QQ-related)activities and enhanced QS-related activities during the stable period.The proposed C_(6)-HSL-manipulation might be a potential technology to inhibit the growth of harmful bacteria in AGS,which could provide a theoretical foundation for the realization of more stable biological wastewater treatments.
基金This work was supported by the Key Program of the National Natural Science Foundation of China(41230640)Major Science and Technology Program for Water Pollution Control and Treatment(2017ZX07602003).
文摘This paper focused on nitrate fate in the vadose zone(VZ)and its implications for groundwater vulnerability under different soil types in the agricultural area of Huaihe River Basin,China.Isotopic compositions of nitrate(δ15N andδ18O)along with NO3-and Cl-concentrations were determined in the VZ-shallow groundwater continuum beneath silty-loam and silty-clay-loam,which are distinctive in texture and organic carbon(OC).In the soil zone(<1 m in depth),measuredδ18O-NO3-suggested the ubiquitous of nitrification regardless of soil types.In the subsoil zone(>1 m in depth),however,the concurrent enrichment ofδ15N-NO3-andδ18O-NO3-indicated the occurrence of denitrification,which showed a dependence on subsoil properties.Specifically,during wheat and maize land uses,denitrification removed as much as 76%-88%of the total nitrate where the subsoil was dominated by stratified OC-rich silty-clay-loam.In contrast,only 0%-28%of the nitrate was degraded via denitrification where the subsoil was composed of uniform,OC-depleted silty-loam.Furthermore,inactive denitrification and higher permeability in the silty-loam VZ implied higher groundwater vulnerability.This observation was consistent with the fact that groundwater NO3--N concentration beneath silty-loam(11.24 mg L-1)was over two times higher than that of the silty-clay-loam(5.32 mg L-1),where stricter fertilization management and conservation strategies should be applied to protect groundwater quality.
基金supported by the National Natural Science Foundation of China (Nos.41401339, 41330744)the Natural Science Foundation of Jiangsu Province (No.BK20140062)and Fujian Province (No.2014J01145)
文摘A better understanding of nitrogen transformation in soils could reveal the capacity for biological inorganic N supply and improve the efficiency of N fertilizers. In this study, a15 N tracing study was carried out to investigate the effects of converting woodland to orchard, and orchard age on the gross rates of N transformation occurring simultaneously in subtropical soils in Eastern China. The results showed that inorganic N supply rate was remained constant with soil organic C and N contents increased after converting woodland into citrus orchard and with increasing orchard age. This phenomenon was most probably due to the increase in the turnover time of recalcitrant organic-N, which increased with decreasing soil p H along with increasing orchard age significantly. The amo A gene copy numbers of both archaeal and bacterial were stimulated by orchard planting and increased with increasing orchard age. The nitrification capacity（defined as the ratio of gross rate of nitrification to total gross rate of mineralization） increased following the Michaelis–Menten equation, sharply in the first 10 years after woodland conversion to orchard, and increased continuously but much more slowly till 30 years. Due to the increase in nitrification capacity and unchanged NO3-consumption, the dominance of ammonium in inorganic N in woodland soil was shifted to nitrate dominance in orchard soils. These results indicated that the risk of NO3-loss was expected to increase and the amount of N needed from fertilizers for fruit growth did not change although soil organic N accumulated with orchard age.
基金This paper was supported by Front Project of Knowl-edge Innovation Program, Chinese Academy of Sciences (ISSASIP0205)
文摘The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure （XANES） to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples were collected from spruce, hemlock and pine forests in central Taiwan. Results showed that various organic N types could be revealed by XANES spectra. Amide and pyrrolic N are the major parts of the composition in the humic substance, soluble organic nitrogen and original soils. The relative distribution of N speciation differed in treatments and vegetations samples. The spruce had a significant difference from the hemlock in soluble organic nitrogen （SON） spectra at 402.3 eV energy peak. In the A-horizon soils, the relative amount of pyridinic N was much higher than that in the O-horizon soils, indicating N transformation in quantity in the mineral horizon was different from that in the organic horizon, which might play an important role in N cycling of forest ecosystems.
基金supported jointly by Natural Science Foundation of Hebei Province(D2020504003)National Key Research and Development Program of China(No.2019YFC1805300).
文摘High concentrations of ammonium nitrogen released from tannery sludge during storage in open air may cause nitrogen pollution to soil and groundwater.To study the transformation mechanism of NH_(4)^(+)-N by nitrifying functional bacteria in tannery sludge contaminated soils,a series of contaminated soil culture experiments were conducted in this study.The contents of ammonium nitrogen(as NH_(4)^(+)-N),nitrite nitrogen(as NO_(2)^(−)-N)and nitrate nitrogen(as NO_(3)^(−)-N)were analyzed during the culture period under different conditions of pollution load,soil particle and redox environment.Sigmodial equation was used to interpret the change of NO_(3)^(−)-N with time in contaminated soils.The abundance variations of nitrifying functional genes(amoA and nxrA)were also detected using the real-time quantitative fluorescence PCR method.The results show that the nitrification of NH_(4)^(+)-N was aggravated in the contaminated silt soil and fine sand under the condition of lower pollution load,finer particle size and more oxidizing environment.The sigmodial equation well fitted the dynamic accumulation curve of the NO_(3)^(−)-N content in the tannery sludge contaminated soils.The Cr(III)content increased with increasing pollution load,which inhibited the reproduction and activity of nitrifying bacteria in the soils,especially in coarse-grained soil.The accumulation of NO_(2)^(−)-N contents became more obvious with the increase of pollution load in the fine sand,and only 41.5%of the NH_(4)^(+)-N was transformed to NO_(3)^(−)-N.The redox environment was the main factor affecting nitrification process in the soil.Compared to the aerobic soil environment,the transformation of NH_(4)^(+)-N was significantly inhibited under anaerobic incubation condition,and the NO_(3)^(−)-N contents decreased by 37.2%,61.9%and 91.9%under low,medium and high pollution loads,respectively.Nitrification was stronger in the silt soil since its copy number of amoA and nxrA genes was two times larger than that of fine sand.Moreover,the copy numbers of amoA and nxrA genes in the silt soil under the aerobic environment were 2.7 times and 2.2 times larger than those in the anaerobic environment.The abundance changes of the amoA and nxrA functional genes have a positive correlation with the nitrification intensity in the tannery sludge-contaminated soil.
基金supported by the National Key Research and Development Program of China(2019YFC1906700)the Natural Science Foundation of Sichuan,China(2022NSFSC0308).
文摘In order to provide basic design parameters for the industrial pyrolysis process,the transformation behavior of nitrogen was investigated using wheat straw as raw material.The distributions of nitrogen in pyrolysis char,oil,and gas were obtained and the nitrogenous components in the products were analyzed systematically by X-ray photoelectron spectroscopy(XPS),pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)and thermogravimetric-Fourier transform infrared spectrometry(TG-FTIR).The nitrogen distribution ranges of the pyrolysis char,oil,and gas were 37.34%–54.82%,32.87%–40.94%and 10.20%–28.83%,respectively.More nitrogen was retained in char at lower pyrolysis temperature and the nitrogen distribution of oil was from rise to decline with increasing temperature.The most abundant N-containing compounds in three-phase products were pyrrole-N,amines,and HCN,respectively.In addition,the transformation mechanism of nitrogen from wheat straw to pyrolysis products was concluded.
基金supported by the Natural Science Foundation of Shandong Province,China(Nos.ZR2022QC146and ZR2021YQ22)the National Natural Science Foundation of China(Nos.31872242,32070405,32270444,and32200349)he Colleges and Universities Youth Innovation Science and Technology Teams Support Program of Shandong Province,China(No.2021KJ015)。
文摘Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration on soil microbial nitrogen cycling in inland wetlands, we compared freshwater and brackish marsh(or non-marsh) wetlands in terms of sediment ammonia-oxidizing rate(AOR), denitrifying rate(DR), and related microbial communities in a typical inland basin, the Hulun Lake basin, in China. Results showed that marsh ecosystems(ME) exhibited 31% higher AOR and 65% higher DR than non-marsh ecosystems(NE). For NE, freshwater non-marsh wetland exhibited 12% higher AOR than brackish non-marsh wetland. This was probably due to the inhibitory effects of high NH_4~+ and salinity levels on ammonia-oxidizing archaea in brackish non-marsh wetland. Conversely, DR in brackish non-marsh wetland was 23% higher than that in freshwater non-marsh wetland, with total organic carbon(TOC) significantly influencing this difference,suggesting that the higher DR in brackish non-marsh wetland was mainly due to its higher TOC level. For ME, due to the direct and indirect interference of salinity, brackish marsh wetland displayed 26% lower AOR and 19% lower DR than freshwater marsh wetland. Besides, brackish wetlands harbored distinct ammonia-oxidizing and denitrifying microbial communities compared to freshwater wetlands. The assembly of these communities was dominated by stochastic processes, while brackish wetlands exhibited more prominent deterministic processes than freshwater wetlands. Overall, high evapotranspiration altered activities and community characteristics of ammonia oxidizers and denitrifiers in inland brackish wetlands by enhancing salinity and nutrient levels,while emergent plants occurring in ME could mitigate the adverse effects of salt stress of inland brackish wetlands on nitrogen cycling.
基金This study was funded by the National Key Research and Development Program of China(Grant no.2020YFA0608501)the National Natural Science Foundation of China(Grant no.41976220)the State Key Laboratory of NBC Protection of Civilians(Grant no.SKLNBC2020-10).
文摘Soil nitrogen(N)transformation processes in the High Arctic tundra are poorly understood even though nitrogen is one of the main limiting nutrients.We analyzed soil samples collected along a High Arctic tundra transect to investigate spatial variability in key nitrogen transformation processes,functional gene abundances,ammonia-oxidizing archaea(AOA)community structures,and key nitrogen transformation regulators.The potential denitrification rates were higher than the nitrification rates in the soil samples,although nitrification may still regulate N2O emissions from tundra soil.The nutrient(total carbon,total organic carbon,total nitrogen,and NH_(4)^(+)-N)contents were important determinants of spatial variability in the potential denitrification rates of soil along the tundra transect.The total sulfurcontent was the main variable controlling potential nitrification processes,probably in association with sulfate-reducing bacteria.The nitrate content was the main variable affecting potential dissimilatory nitrate reduction to ammonium.AOA and ammonia-oxidizing bacteria amoA,nirS,and anammox 16S rRNA genes were found in all of the soil samples.AOA play more important roles than ammonia-oxidizing bacteria in soilnitrification.Anammox bacteria may utilize NO_(2)^(-)produced through nitrification.Phylogenetic analysis indicated that the AOA amoA sequences could be grouped into eight unique operational taxonomic units(OTUs)with a 97%sequence similarity and were affiliated with three group 1.1b Nitrososphaeraclusters.The results indicated that heterogeneous environmental factors(e.g.,the carbon and nitrogen contents of soil)along the High Arctic tundra transect strongly affected the nitrogen transformation rate and relevant functional gene abundances in soil.
基金supported by the Open Fund of the Key Laboratory of Lower Yellow River Channel and Estuary Regulation of Ministry of Water Resources of China(Grant No.HHNS202001)the Fundamental Research Funds for the Central Universities(Grants No.B200204033 and B210202117).
文摘Muddy water irrigation has been widely practiced in the Yellow River Basin for agricultural production and is an important method of economical and intensive utilization of water resources.In this study,the effects of sediment gradation,sand content,and soil moisture content on nitrogen(N)transformation were studied through a series of experimental tests.The results indicated that muddy water irrigation significantly affected agricultural soil physical and biological properties as well as N transformation.Soil bulk density,total porosity,pH,and microbial enzyme activities significantly correlated with N transformation as affected by the interaction between sediment and soil moisture.Sediment addition generally increased the soil bulk density and reduced the soil porosity and pH significantly,and the optimum moisture for promotion of the N transformation rate was 80%of the water-filled pore space.Therefore,muddy water irrigation has a potentially long-term influence on agricultural N cycles in semi-arid regions of northwestern China.This could provide a theoretical basis for scientific and rational use of muddy water for irrigation.
基金financially supported by the Open Project of Sanya Science and Education Innovation Park of Wuhan University of Technology(No.2022KF0005)Researchers Supporting Project(No.RSP-2024-R20)King Saud University,Riyadh,Saudi Arabia.
文摘As a recently emerging wastewater treatment technology,Algal-bacterial granular sludge(ABGS)process shows significant advantages.However,current research on the ABGS system is a lack of a clear and complete understanding of the potential mechanism of signal molecules on the growth of ABGS.This study comprehensively explores the variations in the ABGS under different N-acyl-homoserine lactone(AHL)conditions by constructing three sequencing batch reactor(SBR)systems.The results indicate that N-hexanoyl-l-homoserine lactone(C6-HSL)accelerates the granulation process in the early stages by promoting the loosely bound extracellular polymeric substances(LB-EPS)secretion and filamentous bacteria growth,thereby shortening required time for initial granule formation.On the other hand,N-(3-oxodecanoyl)-l-homoserine lactone(3-oxo-C12-HSL)expedites the granulation process by promoting the tightly bound extracellular polymeric substances(TB-EPS)and aromatic protein secretion,benefiting structural stability and nitrogen and phosphorus removal efficiency of mature ABGS.
基金supported by the National Basic Research Program of China (2007CB109301)the National Natural Science Foundation of China(40871 122)
文摘To better understand the interaction of N transformation and exogenous C source and manage N fertilization, the effects of glucose addition on N transformation were determined in paddy soils with a gradient of soil organic C content. Changes in N mineralization, nitrification and denitrification, as well as their response to glucose addition were measured by incubation experiments in paddy soils derived from Quaternary red clay in subtropical China. Mineralization and denitrification were changed in order of increasing soil fertilities： high 〉 middle 〉 low. During the first week of incubation, net N mineralization and denitrification rates in paddy soil with high fertility were 1.9 and 1.1 times of those in soil with middle fertility and 5.3 and 2.9 times of those in soil with low fertility, respectively. Addition of glucose decreased net N mineralization by approximately 78.8, 109.2 and 177.4% in soils with high, middle and low fertility, respectively. However, denitrification rates in soils with middle and low fertility were increased by 14.4 and 166.2% respectively. The highest nitrate content among the paddy soils tested was 0.62 mg kg-1 and the highest nitrification ratio was 0.33%. Addition of glucose had no obvious effects on nitrate content and nitrification ratio. It was suggested that the intensity of mineralization and denitrification was quite different in soils with different fertility, and increased with increasing soil organic C content. Addition of glucose decreased mineralization, but increased denitrification, and the shifts were greater in soil with low than in soil with high organic C content. Neither addition of glucose nor inherent soil organic C had obvious effects on nitrification in paddy soils tested.
基金supported by the National Natural Science Foundation of China(No.U1612442)the National Key Research and Development Program of China(No.2016YFA0601000)。
文摘Reservoirs are regarded as hotspots of nitrogen transformation and potential sources of nitrous oxide(N_(2)O).However,it remains unclear how the hydrological conditions due to dam construction control the processes of nitrogen transformation in reservoir waters.To address this issue,we examined the spatial-temporal characteristics of nitrate concentrations,δ^(15)N-NO_(3)^(-),δ^(18)O-NO_(3)^(-),δ^(18)O-H_(2)O,relative water column stability(RWCS),and related environmental factors in a subtropical eutrophic reservoir(Hongfeng Reservoir,HFR),Southwest China.We found that denitrification was the most important nitrogen transformation process in the HFR and that higher denitrification intensity was associated with increased RWCS in summer,which suggested hydrological control of the denitrification process.In contrast,low RWCS conditions favored the nitrification process in the HFR in winter.Additionally,dissolved oxygen(DO;p<0.05)and nitrate concentrations(p<0.01)had significant impacts on the denitrification rate.We also found that the spatiotemporal RWCS variations were a prerequisite for regulating DO/nitrate stratification and the coupling/decoupling of nitrification-denitrification at the local and global scales.This study would advances our knowledge of the impacts of RWCS and thermal stratification on nitrogen transformation processes in reservoirs.
文摘Imidacloprid is one of the most commonly used insecticides in agricultural practice, and its application poses a potential risk for soil microorganisms. The objective of this study was to assess whether changes in the structure of the soil microbial community after imidacloprid application at the field rate（FR, 1 mg/kg soil） and 10 times the FR（10 × FR, 10 mg/kg soil）may also have an impact on biochemical and microbial soil functioning. The obtained data showed a negative effect by imidacloprid applied at the FR dosage for substrate-induced respiration（SIR）, the number of total bacteria, dehydrogenase（DHA）, both phosphatases（PHOS-H and PHOS-OH）, and urease（URE） at the beginning of the experiment. In 10 × FR treated soil, decreased activity of SIR, DHA, PHOS-OH and PHOS-H was observed over the experimental period. Nitrifying and N2-fixing bacteria were the most sensitive to imidacloprid. The concentration of NO3-decreased in both imidacloprid-treated soils,whereas the concentration of NH4＋in soil with 10 × FR was higher than in the control.Analysis of the bacterial growth strategy revealed that imidacloprid affected the r- or K-type bacterial classes as indicated also by the decreased eco-physiological（EP） index.Imidacloprid affected the physiological state of culturable bacteria and caused a reduction in the rate of colony formation as well as a prolonged time for growth. Principal component analysis showed that imidacloprid application significantly shifted the measured parameters, and the application of imidacloprid may pose a potential risk to the biochemical and microbial activity of soils.
基金Project supported by the Laboratory of Material CycHng in Ped osphere，Chinese Academy of Sciences
文摘?15)N-labelled green manure was used to feed pigs. Its nitrogen recovery by pig body, feces and urine was23.5%, 23.8% and 28.8% respectively, totalling 76. 1%. Feces and green manure coordinated respectively withequal amount of CO(NH_2)_2-N as well as urine alone were applied as basic fertilizer in microplot experiments.The ￣(15)N recovery from feces and urine was equivalent to 2.51% and 4.82% by rice grain, and 0.98% and1.94% by straw respectively, and soil residual ￣(15)N from them took 13.3% and 4.90% of the ￣(15)N in greenmanure. After feeding pigs with green manure and returning their feces and urine into soil, the ￣(15)N recoveryby pig body and rice grain was 30.8%, and that by pig body, and rice plant as well as soil residual took 52.7%of the ￣(15)N in feed. ￣(15)N loss was 23.9% in pig feeding and 23.4% in rice planting. When green manure wasincorporated directly into soil, its ￣(15)N recovery by grain was 26.65%, that by rice plant plus soil residual was65.2%, and the loss was 34.8%.
文摘A new procedure of determining optimal C/N (the rate of carbon source to nitrogen source) of mixed distillers' grains for combined bacteria synergic fermentation is established. At the same time an improved method evaluating bacteria growth, called method of dry cell weighing by filtering is developed. For each combination of C and N, their initial and residual contents before and after fermentation respectively are determined. Then followed the calculation of utilization of C and N sources by the compound bacteria. The optimal C/N is finally located from among the utilization of C and N of several combinations and the weight of produced mass of oven dried thallus. The conditions of fermentation are: inoculum size 10%, temperature 30 0℃, rotational speed 170 r/min, shake culture time 48h. The best results obtained from orthogonal experiments are: maximum mass of oven dried thallus is 14 693g in a liter liquid medium, maximum utilization rate of carbon source is 98 13% and maximum utilization rate of nitrogen is 78 14%. Optimal C/N is 5 1.
基金supported by the Liaoning Provincial Scientific Research Fund (JYTYB2024046)
文摘Background The forest-steppe ecotone,a critical transition zone sensitive to global change,faces increasing nitrogen deposition.However,the interplay between nitrogen conversion processes and soil enzyme activity remains unclear.We investigated the effects of nitrogen addition on plant nutrient dynamics,microbial functional genes,and enzyme activity in northwest Liaoning,China.Results Nitrogen addition significantly increased leaf nitrogen content in Potentilla tanacetifolia(peak under N40)and Artemisia frigida(peak under N40),while Lespedeza daurica showed a non-linear response(peak under N20).Phosphorus content remained unaffected across species.Soil enzyme activities(urease,nitrate reductase,dehydrogenase)increased with nitrogen input,with protease activity rising proportionally to nitrogen addition rate.Functional genes(nirK,nifH,AOB-amoA)exhibited dynamic responses:nirK abundance peaked under N40,nifH under N10,and AOB-amoA increased with nitrogen input.Structural equation modeling revealed that nirK gene abundance positively influenced enzyme activity(λ=0.512),while nifH negatively correlated with leaf N/P ratios(λ=-0.606).Soil protease activity directly drove leaf N/P ratios(λ=0.734).Conclusions Nitrogen addition enhances plant nitrogen uptake and enzyme-driven mineralization,but speciesspecific responses highlight ecological trade-offs.Soil pH and protease activity are pivotal in mediating nitrogen conversion and plant nutrient stoichiometry.These findings underscore the need to integrate microbial and enzymatic dynamics into nutrient management strategies for ecotones under nitrogen enrichment.
