Legume green manure can intensify the function of chemical nitrogen fertilizer substitution via increasing nitrogen supply and uptake of wheat

Achieving the green development of agriculture requires the reduction of chemical nitrogen(N)fertilizer input.Previous studies have confirmed that returning green manure to the field is an effective measure to improve crop yields while substituting partial chemical N fertilizer.However,it remains unclear how to further intensify the substituting function of green manure and elucidate its underlying agronomic mechanism.In a split-plot field experiment in spring wheat,different green manures returned to the field under reduced chemical N supply was established in an oasis area since 2018,in order to investigate the effect of green manure and reduced N on grain yield,N uptake,N use efficiency(NUE),N nutrition index,soil organic matter,and soil N of wheat in 2020-2022.Our results showed that mixed sown common vetch and hairy vetch can substitute 40%of chemical N fertilizer without reducing grain yield or N accumulation.Noteworthily,mixed sown common vetch and hairy vetch under reduced N by 20%showed the highest N agronomy efficiency and recovery efficiency,which were 92.0%and 46.0%higher than fallow after wheat harvest and conventional N application rate,respectively.The increase in NUE of wheat was mainly attributed to mixed sown common vetch and hairy vetch,which increased N transportation quantity and transportation rate at pre-anthesis,enhanced N harvest index,optimized N nutrition index,and increased activities of nitrate reductase and glutamine synthetase of leaf,respectively.Meanwhile,mixed sown common vetch and hairy vetch under reduced N by 20%improved soil organic matter and N contents.Therefore,mixed sown common vetch and hairy vetch can substitute 40%of chemical N fertilizer while maintaining grain yield and N accumulation,and it combined with reduced chemical N by 20%or 40%improved NUE of wheat via enhancing N supply and uptake.

Atmospheric nitrogen deposition affects forest plant and soil system carbon:nitrogen:phosphorus stoichiometric flexibility:A meta-analysis

Background:Nitrogen(N)deposition affects forest stoichiometric flexibility through changing soil nutrient availability to influence plant uptake.However,the effect of N deposition on the flexibility of carbon(C),N,and phosphorus(P)in forest plant-soil-microbe systems remains unclear.Methods:We conducted a meta-analysis based on 751 pairs of observations to evaluate the responses of plant,soil and microbial biomass C,N and P nutrients and stoichiometry to N addition in different N intensity(050,50–100,>100 kg·ha^(-1)·year^(-1)of N),duration(0–5,>5 year),method(understory,canopy),and matter(ammonium N,nitrate N,organic N,mixed N).Results:N addition significantly increased plant N:P(leaf:14.98%,root:13.29%),plant C:P(leaf:6.8%,root:25.44%),soil N:P(13.94%),soil C:P(10.86%),microbial biomass N:P(23.58%),microbial biomass C:P(12.62%),but reduced plant C:N(leaf:6.49%,root:9.02%).Furthermore,plant C:N:P stoichiometry changed significantly under short-term N inputs,while soil and microorganisms changed drastically under high N addition.Canopy N addition primarily affected plant C:N:P stoichiometry through altering plant N content,while understory N inputs altered more by influencing soil C and P content.Organic N significantly influenced plant and soil C:N and C:P,while ammonia N changed plant N:P.Plant C:P and soil C:N were strongly correlated with mean annual precipitation(MAT),and the C:N:P stoichiometric flexibility in soil and plant under N addition connected with soil depth.Besides,N addition decoupled the correlations between soil microorganisms and the plant.Conclusions:N addition significantly increased the C:P and N:P in soil,plant,and microbial biomass,reducing plant C:N,and aggravated forest P limitations.Significantly,these impacts were contingent on climate types,soil layers,and N input forms.The findings enhance our comprehension of the plant-soil system nutrient cycling mechanisms in forest ecosystems and plant strategy responses to N deposition.

Effects of tree size and organ age on variations in carbon,nitrogen,and phosphorus stoichiometry in Pinus koraiensis

Carbon(C),nitrogen(N),and phosphorus(P)are of fundamental importance for growth and nutrient dynamics within plant organs and deserve more attention at regional to global scales.However,our knowledge of how these nutrients vary with tree size,organ age,or root order at the individual level remains limited.We determined C,N,and P contents and their stoichiometric ratios(i.e.,nutrient traits)in needles,branches,and fine roots at different organ ages(0-3-year-old needles and branches)and root orders(1st-4th order roots)from 64 Pinus koraiensis of varying size(Diameter at breast height ranged from 0.3 to 100 cm)in northeast China.Soil factors were also measured.The results show that nutrient traits were regulated by tree size,organ age,or root order rather than soil factors.At a whole-plant level,nutrient traits decreased in needles and fine roots but increased in branches with tree size.At the organ level,age or root order had a negative effect on C,N,and P and a positive effect on stoichiometric ratios.Our results demonstrate that nutrient variations are closely related to organ-specific functions and ecophysiological processes at an individual level.It is suggested that the nutrient acquisition strategy by younger trees and organ fractions with higher nutrient content is for survival.Conversely,nutrient storage strategy in older trees and organ fractions are mainly for steady growth.Our results clarified the nutrient utilization strategies during tree and organ ontogeny and suggest that tree size and organ age or root order should be simultaneously considered to understand the complexities of nutrient variations.

Effects of Temperature and Nitrogen Input on Nitrogen Mineralization in Alpine Soils on Tibetan Plateau

[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conducted using three alpine soils.These soils were collected from the top 10 cm depth in three grassland types：alpine meadow in Haibei,alpine steppe in Naqu and alpine wetland in Dangxiong.[Result] Temperature significantly affected nitrogen mineralization in alpine soils of three grassland types.The mineralization rate in alpine steppe soil rose with the rise of temperature,while the mineralization rate in the alpine meadow soil and alpine wetland soil decreased with the rise of temperature.Nitrogen input had no significant effect on nitrogen mineralization in the alpine meadow soil,but significantly increased nitrogen mineralization in the alpine steppe soil and the alpine wetland soil.Grassland types significantly affected nitrogen mineralization in alpine grasslands.[Conclusion] The effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau were significant.And those different effects depended on different types of grassland.

N-Calculator与NUFER耦合模型和组合预测法在食物氮足迹研究中的应用

为改善传统N-Calculator模型的局限性,加强食物氮足迹核算结果与环境影响的联系,提高活性氮管理预见性,将N-Calculator模型与食物系统养分流动(Nutrient Flows in Food Chains,Environment and Resources Use,NUFER)模型进行耦合,以估算我国2001—2020年人均食物氮足迹,建立组合预测体系。结果显示:2001—2020年,我国人均食物氮足迹由16.04 kg N/a增至18.95 kg N/a;全国食物氮足迹由20.47 Mt N/a增至26.76 Mt N/a;居民饮食结构正由以植物源食物为主的低氮消费模式转向以动物源食物为主的高氮消费模式;食物生产过程产生的活性氮的最终归宿为大气(64.3%)、水体和深层土壤(35.7%);我国食物氮足迹与人均可支配收入、城市化率、动物源食物消费氮占比呈正相关性,与恩格尔系数呈负相关性;未来10 a我国人均食物氮足迹呈增长趋势,预测结果显示年均增幅为0.16 kg N/a。

稻麦复种模式下氮肥与稻秸互作对小麦产量和N_(2)O排放影响及推荐施肥研究

优化氮肥施用和秸秆还田技术为途径的农业管理措施被认为是提升农业可持续性的有效手段,然而当前关于氮肥和秸秆还田对小麦产量和N_(2)O排放影响的研究仍十分有限。为此,本研究基于2000—2022年发表的关于长江中下游流域氮肥和秸秆投入下小麦产量和N_(2)O排放变化的文献,运用随机森林建模,定量分析氮肥和秸秆还田对小麦产量和N_(2)O排放的影响,并结合情景设置进行了特定地点的小麦产量和N_(2)O排放模拟,同时评估了碳排放强度(CEE)和净生态系统经济效益(NEEB)。结果表明,建立的区域尺度小麦产量与N_(2)O排放对氮秸互作响应的随机森林模型,验证结果R^(2)分别为0.66和0.65,RMSE分别为0.70和1.11。结果表明施氮量和土壤有机质是影响小麦产量和N_(2)O排放的重要因素。综合来看,达到最大产量所需的氮肥量为208~212 kg hm^(-2),达到最小CEE所需的氮肥量为113~130 kg hm^(-2),达到最高的NEEB所需的氮肥量为202~205 kg hm^(-2),其中在6.75 t hm^(-2)的秸秆投入下施用202 kg hm^(-2)的氮肥可以获得最高的生态收益1.37万元。优化氮肥和秸秆投入具备减少作物碳排放强度并获得最大净生态环境效益的潜力。

Differing responses of root morphology and physiology to nitrogen application rates and their relationships with grain yield in rice

Root morphology and physiology influence aboveground growth and yield formation in rice.However,root morphological and physiological differences among rice varieties with differing nitrogen(N)sensitivities and their relationship with grain yield are still unclear.In this study,rice varieties differing in N sensitivity over many years of experiments were used.A field experiment with multiple N rates(0,90,180,270,and 360 kg ha^(-1))was conducted to elucidate the effects of N application on root morphology,root physiology,and grain yield.A pot experiment with root excision and exogenous application of 6-benzyladenine(6-BA)at heading stage was used to further verify the above effects.The findings revealed that(1)under the same N application rate,N-insensitive varieties(NIV)had relatively large root biomass(root dry weight,length,and number).Grain yield was associated with root biomass in NIV.The oxidation activity and zeatin(Z)+zeatin riboside(ZR)contents in roots obviously and positively correlated with grain yield in N-sensitive varieties(NSV),and accounted for its higher grain yield than that of NIV at lower N application rates(90 and 180 kg ha^(-1)).(2)The root dry weight required for equal grain yield of NIV was greater than that of NSV.Excision of 1/10 and 1/8 of roots at heading stage had no discernible effect on the yield of Liangyoupeijiu(NIV),and it significantly reduced yield by 11.5%and 21.3%in Tianyouhuazhan(NSV),respectively,compared to the treatment without root excision.The decrease of filled kernels and grain weight after root excision was the primary cause for the yield reduction.Root excision and exogenous 6-BA application after root excision had little influence on the root activity of NIV.The oxidation activity and Z+ZR contents in roots of NSV decreased under root excision,and the increase in the proportion of excised roots aggravated these effects.The application of exogenous 6-BA increased the root activity of NSV and increased filled kernels and grain weight,thereby reducing yield loss after root excision.Thus,the root biomass of NIV was large,and there may be a phenomenon of"root growth redundancy."Vigorous root activity was an essential feature of NSV.Selecting rice varieties with high root activity or increasing root activity by cultivation measures could lead to higher grain yield under lower N application rates.

Maize straw application as an interlayer improves organic carbon and total nitrogen concentrations in the soil profile: A four-year experiment in a saline soil

Soil salinization is a critical environmental issue restricting agricultural production.Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress.However,the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive.Therefore,a four-year (2015–2018) field experiment was conducted with four levels (i.e.,0,6,12and 18 Mg ha~(–1)) of straw returned as an interlayer.Compared with no straw interlayer (CK),straw addition increased SOC concentration by 14–32 and 11–57%in the 20–40 and 40–60 cm soil layers,respectively.The increases in soil TN concentration (8–22 and 6–34%in the 20–40 and 40–60 cm soil layers,respectively) were lower than that for SOC concentration,which led to increased soil C:N ratio in the 20–60 cm soil depth.Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm),which promoted uniform distributions of SOC and TN in the soil profile.Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield.Generally,compared with other treatments,the application of 12 Mg ha~(–1) straw had higher SOC,TN and C:N ratio,and lower soil stratification ratio in the2015–2017 period.The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years,and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.

^(15)N同位素标记氮肥减施棉田养分利用效率分析

【目的】研究氮肥减施对棉花氮素吸收、转运及利用效率的影响,为绿洲滴灌棉田氮肥合理施用提供参考依据。【方法】利用^(15)N同位素示踪技术,采用盆栽试验,设置不施氮肥(N_(0))、氮肥减施(N_(1),225 kg/hm^(2))、当地推荐施肥(N 2,300 kg/hm^(2))3个处理,研究氮肥减施对棉花生物量、氮素吸收量、肥料氮吸收量以及氮肥利用率的影响。【结果】氮肥减施处理的棉花干物质积累量和氮素吸收量均显著高于不施氮处理(N_(0)),而与当地推荐施肥处理差异均不显著;氮肥减施处理棉花壳、籽的干物质量和籽的氮素吸收量均显著高于当地推荐施肥处理,分别增加了7.02%、6.81%和16.59%;2个施肥处理棉籽的肥料氮(^(15)N)积累量占比最高,占全株的26.02%~35.99%,其次为叶(22.40%~23.81%)和茎(14.48%~18.98%),絮中最少(3.05%~6.62%);氮肥减施处理生殖器官的肥料氮吸收量比当地推荐施肥处理高19.02%;2个施肥处理的棉株吸收的氮素来源于肥料氮的比例(Ndff%)为21.14%~21.70%;氮肥减施处理的氮肥利用率和表观利用率均显著高于当地推荐施肥处理,分别增加2.36%和3.12%。【结论】氮肥减施(225 kg/hm^(2))可以显著提高棉籽中的干物质量、氮素吸收量、肥料氮(^(15)N)吸收量、Ndff%以及棉花整株的氮肥利用率,在确保棉花产量不降低的前提下,适度的减少化肥施用量是提高化肥利用率最有效的措施之一。

基于^(15)N稳定同位素示踪技术的植物组合湿地对氨氮去除途径研究

人工湿地是生态修复受污染水体的重要手段,对氮的去除效果显著,但不同植物湿地对氮去除效果差异明显,因此不同类型植物组合后的湿地对氮去除效果及去除途径值得进一步研究。通过室内控制试验,以常见浮水植物绿狐尾藻(Myriophyllum elatinoides)和挺水植物梭鱼草(Pontederia cordata)为研究对象,利用^(15)N稳定同位素示踪技术探究绿狐尾藻、梭鱼草及绿狐尾藻+梭鱼草植物组合对氨氮(NH_(4)^(+)-N)的去除途径。结果表明,绿狐尾藻+梭鱼草植物组合处理相较于单一绿狐尾藻和梭鱼草处理对氮的脱除量分别提高1.8%和3.6%。基于^(15)N质量平衡,绿狐尾藻、梭鱼草和绿狐尾藻+梭鱼草植物组合处理氮去除途径的底泥吸附贡献分别为8.30%、7.96%和6.94%,植物吸收贡献分别为41.76%、35.34%和48.67%,微生物作用去除贡献分别为49.94%、56.71%和44.39%。微生物作用在湿地脱氮过程中占主导地位。相较于单一植物湿地,植物组合湿地对氮的去除效果得到提升,同时促进了植物对水体NH 4+-N的吸收。该研究有助于更好地理解植物组合湿地对氨氮的脱除途径。

人造沸石对低C/N污水中氮的去除性能及机理

以人造沸石为吸附剂,处理低C/N高速服务区污水。考察了沸石投加量对人造沸石去除污水中氮效果的影响,利用正交实验探讨了影响人造沸石吸附污水中NH_(3)-N效果的因素,并结合吸附动力学和热力学、比表面积分析(BET)、扫描电子显微镜(SEM)等手段探讨了人造沸石去除NH_(3)-N的机理。结果表明:人造沸石可在短时间内实现对污水中NH_(3)-N和TN的显著去除,并可有效提升污水C/N,反应24 h后,40 g/L人造沸石可使污水中NH_(3)-N和TN分别降至(13.45±0.39)、(19.23±0.21)mg/L,去除率分别达到(91.14±0.32)%和(87.12±0.10)%,C/N由1.30±0.01提升至5.47±0.07;正交实验表明各因素影响人造沸石脱氮效果的程度表现为沸石投加量>曝气量>NH_(3)-N初始浓度;人造沸石对NH_(3)-N的吸附过程符合准二级反应动力学模型(R^(2)=0.990),且该吸附行为是吸热过程;BET和SEM显示,人造沸石对NH_(3)-N的高效去除主要得益于其较大的比表面积(493.23 m^(2)/g)以及以介孔为主且分布范围较宽的孔道,吸附后沸石表面的颗粒变得光滑、紧密且数量减少。

Fate of fertilizer nitrogen and residual nitrogen in paddy soil in Northeast China

The relationship between the fate of nitrogen (N) fertilizer and the N application rate in paddy fields in Northeast China is unclear,as is the fate of residual N.To clarify these issues,paddy field and15N microplot experiments were carried out in 2017 and 2018,with N applications at five levels:0,75,105,135 and 165 kg N ha–1(N0,N75,N105,N135 and N165,respectively).15N-labeled urea was applied to the microplots in 2017,and the same amount of unlabeled urea was applied in 2018.Ammonia (NH3) volatilization,leaching,surface runoff,rice yield,the N contents and15N abundances of both plants and soil were analyzed.The results indicated a linear platform model for rice yield and the application rate of N fertilizer,and the optimal rate was 135 kg N ha–1.N uptake increased with an increasing N rate,and the recovery efficiency of applied N (REN) values of the difference subtraction method were 45.23 and 56.98%on average in 2017and 2018,respectively.The RENwas the highest at the N rate of 135 kg ha–1in 2017 and it was insignificantly affected by the N application rate in 2018,while the agronomic efficiency of applied N (AEN) and physiological efficiency of applied N (PEN) decreased significantly when excessive N was applied.N loss through NH3volatilization,leaching and surface runoff was low in the paddy fields in Northeast China.NH3volatilization accounted for 0.81 and 2.99%of the total N application in 2017 and 2018,respectively.On average,the leaching and surface runoff rates were 4.45% and less than 1.05%,respectively,but the apparent denitrification loss was approximately 42.63%.The residual N fertilizer in the soil layer (0–40 cm) was 18.37–31.81 kg N ha–1in 2017,and the residual rate was 19.28–24.50%.Residual15N from fertilizer in the soil increased significantly with increasing N fertilizer,which was mainly concentrated in the 0–10 cm soil layer,accounting for 58.45–83.54% of the total residual N,and decreased with increasing depth.While the ratio of residual N in the 0–10 cm soil layer to that in the 0–40 cm soil layer was decreased with increasing N application.Furthermore,of the residual N,approximately 5.4%was taken up on average in the following season and 50.2%was lost,but 44.4%remained in the soil.Hence,the amount of applied N fertilizer should be reduced appropriately due to the high residual N in paddy fields in Northeast China.The appropriate N fertilizer rate in the northern fields in China was determined to be 105–135 kg N ha–1in order to achieve a balance between rice yield and high N fertilizer uptake.

Global and Comparative Proteome Analysis of Nitrogen-Stress Responsive Proteins in the Root, Stem and Leaf of Brassica napus

Nitrogen(N)is one of the basic nutrients and signals for plant development and deficiency of it would always limit the productions of crops in the field.Quantitative research on expression of N-stress responsive proteins on a proteome level remains elusive.In order to gain a deep insight into the proteins responding to nitrogen stress in rapeseed(Brassica napus L.),comparative proteomic analysis was performed to investigate changes of protein expression profiles from the root,stem and leaf under different N concentrations,respectively.More than 200 differential abundance proteins(DAPs)were detected and categorized into groups according to annotations,including“binding and catalytic activity”,“involved in primary metabolism and cellular processes”,“stress-response”and so on.Variation in chlorophyll(Chl)content and antioxidant activities further revealed that oxidative stress raised with the increase of N concentration.Bioinformatics analysis based on the expression level of total proteins suggested these DAPs might play important roles in adaptation to N-stress conditions.Generally,these results provides a new aspect into N-stress responding proteins in Brassica plants.

Nitrogen application levels based on critical nitrogen absorption regulate processing tomatoes productivity, nitrogen uptake, nitrate distributions, and root growth in Xinjiang, China

The unreasonable nitrogen(N)supply and low productivity are the main factors restricting the sustainable development of processing tomatoes.In addition,the mechanism by which the N application strategy affects root growth and nitrate distributions in processing tomatoes remains unclear.In this study,we applied four N application levels to a field(including 0(N0),200(N200),300(N300),and 400(N400)kg/hm^(2))based on the critical N absorption ratio at each growth stage(planting stage to flowering stage:22%;fruit setting stage:24%;red ripening stage:45%;and maturity stage:9%).The results indicated that N300 treatment significantly improved the aboveground dry matter(DM),yield,N uptake,and nitrogen use efficiency(NUE),while N400 treatment increased nitrate nitrogen(NO_(3)^(-)-N)residue in the 20–60 cm soil layer.Temporal variations of total root dry weight(TRDW)and total root length(TRL)showed a single-peak curve.Overall,N300 treatment improved the secondary root parameter of TRDW,while N400 treatment improved the secondary root parameter of TRL.The grey correlation coefficients indicated that root dry weight density(RDWD)in the surface soil(0–20 cm)had the strongest relationship with yield,whereas root length density(RLD)in the middle soil(20–40 cm)had a strong relationship with yield.The path model indicated that N uptake is a crucial factor affecting aboveground DM,TRDW,and yield.The above results indicate that N application levels based on critical N absorption improve the production of processing tomatoes by regulating N uptake and root distribution.Furthermore,the results of this study provide a theoretical basis for precise N management.

基于模糊n-cell数的非线性投入产出模型解的存在性

将混合单调以及耦合不动点的概念引入到模糊n-cell数空间中,给出此空间上的混合单调型不动点定理。考虑到模糊n-cell数具有表示n维不确定信息的特点,将非线性投入产出模型与模糊n-cell数相结合,建立模糊非线性投入产出模型并给出相应的平衡方程。最后利用本文中所给的不动点定理讨论此模型解存在的条件,验证模型的合理性。

钙钛矿结构氧氮化物SrTaO_(2)N的高温高压结构稳定性研究

N2是地球大气的主要组分,N元素是生命起源的基础元素,了解N在地球深部高温高压环境中的赋存形式是探讨全球N循环和宜居性地球大气环境的重要基础。本研究应用金刚石对顶砧(DAC)高压装置和激光加温技术模拟地球深部的压力和温度环境,通过高压原位同步辐射X射线衍射和拉曼光谱对钙钛矿结构氧氮化物SrTaO_(2)N开展高温高压结构稳定性研究。高压X射线衍射结果表明,在0~40.5 GPa的压力范围内,四方结构SrTaO_(2)N没有发生相变,其体积模量为K_(0)=290(3) GPa,并具有a轴和c轴的压缩各向异性。压缩过程中,Ta(O,N)_(6)八面体主要发生刚性旋转,旋转角为0.25°~12.64°,但保持四方结构稳定。常温高压(300 K,40.2 GPa)与高温高压(1800±200 K,41.3 GPa)拉曼对比实验结果显示,在高温高压条件下,SrTaO_(2)N仍保持初始的拉曼谱特征,结构稳定。本研究结果揭示,常压高温条件下通过N^(3-)替代O^(2-)合成的钙钛矿结构氧氮化物,能够在地球内部下地幔上部的温压环境下稳定存在。这种以钙钛矿结构存在的氧氮化物可能是地球深部隐藏的N储库,为解释地球N亏损现象提供了重要线索,同时也为探索N在地球深部中的赋存及其对全球N循环和宜居性大气环境的影响提供了新的研究方向。

我国典型水源地N-DBPs生成势及生态风险评价

随着含氮消毒副产物(N-DBPs)的基因毒性和细胞毒性受到重视,饮用水中的N-DBPs产生和生态风险的研究成为近年的关注热点。文章基于前人研究分析,研究了我国典型水源地中N-DBPs生成势的空间分布特征,采用风险熵值法,对我国典型水源地N-DBPs的潜在生成生态风险进行了评估,还关注了有机物指标与N-DBPs生成势之间的关系。结果表明:DON与N-DBPs生成势的分布特点均存在地域差异,总体表现为在东部沿海城市呈现南北高、中部低、东部地区高于其他地区、经济发达地区高于其他地区、珠三角地区高于其他地区的特点。结合生态风险的评价方法,利用现有数据进行初步估计,发现部分城市水源地生态风险呈现低风险,水库水源N-DBPs的生态风险一般高于河流水源。UV_(254)与N-DBPs生成势相关性较好,可以作为N-DBPs生成势的替代性指标。研究结果将为做好我国水源地的修复与保护、保障居民饮水安全提供重要的支撑。

The fate of ^(15)N-labeled nitrogen inputs to pot cultured beech seedlings

The partitioning of nitrogen deposition among forest soil （including forest floor）, leachate and above- and belowground biomass of pot cultured beech seedlings in comparison to non-cultured treatments were investigated by adding 1.92 g.m^-2 ^15N tracer in throughfall for two successive growing seasons at a greenhouse experiment. Ammonium and nitrate depositions were simulated on four treatments （cultured and non-cultured） and each treatment was labeled with either ^15N-NH4^＋ or ^15N-NO3^-. Total recovery rates of the applied ^15N in the whole system accounted for 74.9% to 67.3% after ^15N-NH4^＋ and 85.3% to 88.1% after ^15N-NO3^-in cultured and non-cultured treatments, respectively. The main sink for both ^15N tracers was the forest soil （including forest floor）, where 34.6% to 33.7% of ^15N-NH4^＋ and 13.1% to 9.0% of ^15N-NO3^-were found in cultured and non-cultured treatments, respectively, suggesting strong immobilization of both N forms by hetero- trophic microorganisms. Nitrogen immobilization by microorganisms in the forest soil （including forest floor） was three times higher when ^15N-NH4^＋ was applied compared to ^15N-NO3^-. The preferential heterotrophic use of ammonium resulted in a two times higher retention of deposited ^15N-NH4^＋ in the forest soil as compared to plants. In contrast, nitrate immobilization in the forest soil was lower compared to plants, although statistically it was not significantly different. In total the immobilization of ammonium in the plant-soil system was about 60% higher than nitrate, indicating the importance of the N-forms deposition for retention in forest ecosystems.

水力停留时间强化复合载体基固定化藻菌系统处理低C/N废水脱氮

为探索一种低C/N废水脱氮新技术,本研究将绿沸石和玉米芯组成复合载体,以小球藻和活性污泥为接种物,通过吸附法构建固定化藻菌系统(IABS),探究了装置的脱氮效果及水力停留时间(HRT)对脱氮效率的影响。研究结果表明,复合载体可有效改善废水的C/N,构建的固定化藻菌系统可实现低C/N废水中氮素的有效去除。装置脱氮效果随着HRT的延长而提升,当HRT达18h时,装置的总氮去除率最高可达98%;氨氮去除率可达100%。综合而言,绿沸石和玉米芯复合载体构建的固定化藻菌系统具有脱氮效率高、无需连续投加碳源、出水水质稳定等优点。

丛枝菌根对植物叶片δ^(15) N含量影响的数据挖掘分析

为明确丛枝菌根(AM)对植物叶片稳定氮同位素(δ^(15)N)含量的影响,探索丛枝菌根在调控植物应对全球变化方面的重要功能,通过数据挖掘,建立了AM植物和非AM(non-AM)植物叶片δ^(15)N含量数据库,探究了AM对植物叶片δ^(15)N含量的影响。结果表明:AM植物叶片δ^(15)N含量为0.86‰,显著高于non-AM植物叶片的0.50‰。丛枝菌根针对不同植物功能群而言,将植物的AM状况与植物的固氮状况和生长周期结合作为影响因素时,AM都显著影响着植物叶片的δ^(15)N含量。虽然AM没有显著提高固氮植物叶片δ^(15)N含量,但却把非固氮植物叶片δ^(15)N的含量从0.58‰提高到了0.99‰。AM使多年生植物叶片δ^(15)N含量的增加最显著,从0.49‰增加到了0.82‰。可见,丛枝菌根作为与植物长期共生进化的最广泛共生体,对植物叶片δ^(15)N含量有不同程度的影响。