Predictions of NOx/N2O emissions from an ultra-supercritical CFB boiler using a 2-D comprehensive CFD combustion model

NOx and N2O emissions from an ultra-supercritical circulating fluidized bed(CFB)boiler were predicted using a two dimensional(2-D)comprehensive computational fluid dynamics(CFD)combustion model.This model was developed from a three dimensional model for a supercritical CFB boiler previously constructed by our group.Based on an analysis of the NOx and N2O conversion processes in a CFB boiler,the primary formation and destruction reactions were introduced into the 2-D model and coupled.The resulting model was validated using data from the Baima 600 MW supercritical CFB boiler,and then applied to a 660 MW ultra-supercritical CFB boiler.The effects of excess air,the secondary air(SA)to(primary air(PA)plus SA)ratio and the SA injection height on NOx and N2O emissions were investigated.The results show that a higher excess air volume increases both NOx and N2O emissions,while increasing the SA/(PA+SA)ratio somewhat reduces both the NOx and N2O concentrations.On the basis of the results of this work,optimal locations for SA injection ports so as to lower NOx and N2O emissions are recommended.

Managed grassland alters soil N dynamics and N2O emissions in temperate steppe

Reclamation of degraded grasslands as managed grasslands has been increasingly accelerated in recent years in China. Land use change affects soil nitrogen（N） dynamics and nitrous oxide（N2O） emissions. However, it remains unclear how large-scale grassland reclamation will impact the grassland ecosystem as a whole. Here, we investigated the effects of the conversion from native to managed grasslands on soil N dynamics and N2O emissions by field experiments in Hulunber in northern China. Soil（0-10 cm）, nitrate（NO3-）,ammonium（NH4＋）, and microbial N were measured in plots in a temperate steppe（Leymus chinensis grassland） and two managed grasslands（Medicago sativa and Bromus inermis grasslands） in 2011 and 2012. The results showed conversion of L. chinensis grassland to M.sativa or B. inermis grasslands decreased concentrations of NO3--N, but did not change NH4-N . Soil microbial N was slightly decreased by the conversion of L. chinensis grassland to M.sativa, but increased by the conversion to B. inermis. The conversion of L. chinensis grassland to M. sativa（i.e., a legume grass） increased N2O emissions by 26.2%, while the conversion to the B. inermis（i.e., a non-legume grass） reduced N2O emissions by 33.1%. The conversion from native to managed grasslands caused large created variations in soil NO3-＋-N and NH4-N concentrations. Net N mineralization rates did not change significantly in growing season or vegetation type, but to net nitrification rate. These results provide evidence on how reclamation may impact the grassland ecosystem in terms of N dynamics and N2O emissions.

Effects of Water Regime and Straw Application in Paddy Rice Season on N2O Emission from Following Wheat Growing Season

A split-plot experiment in a rice-winter wheat rotation system was performed to study the effects of water regime and wheat straw application in rice-growing season on N2O emission from following wheat growing season. Water regime in the rice-growing season was designed as the conventional irrigation (flooding/drainage cycle) and the permanent flooding. Wheat straw was incorporated with three rates of 0, 225 and 450 g m-2 into the paddy soil for each water regime just before rice was transplanted. N2O emission was measured by static chamber-gas chromatograph method. Results from the variance analysis indicated that the permanent flooding in rice-growing season markedly enhanced N2O emission in following wheat growing season (P=0. 003), and that the effect of straw application on N2O emission was distinguished between two water regimes. Under the conventional irrigation, incoporation of wheat straw reduced N2O emission in the following wheat growing season, while there were no significant differences in the emission for the straw application rates of 225 and 450 g m-2. No significant differences in N2O emissions were observed among the three rates of straw application for the permanent flooding regime. In addition, the seasonal variation of N2O emission was regulated by soil temperature and moisture. The daily N2O flux (Y, mg m-2 d-1) can be quantitatively described by soil temperature (T, ℃) and moisture (W, WFPS %) asY=A0+A1T+A2W+A3W2(n=23, R2 ≥0. 4159** )or y=C0+C1W+C2W2(n=23,R2≥0. 4074** ). Compared with the effect of soil temperature on N2O emission, soil moisture was an important factor regulating the seasonal pattern of N2O emission.

Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils

The soil type is a key factor influencing N(nitrogen)cycling in soil;however,gross N transformations and N_(2)O emission sources are still poorly understood.In this study,a laboratory 15N tracing experiment was carried out at 60%WHC(water holding capacity)and 25℃to evaluate the gross N transformation rates and N_(2)O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province,China.The results showed that the gross rates of N mineralization,immobilization,and nitrification were 3.60,1.90,and 5.63 mg N/(kg·d)in silt loam soil,respectively,which were 3.62,4.26,and 3.13 times those in sandy loam soil,respectively.The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia)in sandy loam soil and silt loam soil were all higher than 1.00,whereas the n/ia in sandy loam soil(4.36)was significantly higher than that in silt loam soil(3.08).This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil,and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_(3)–leaching.Under aerobic conditions,both nitrification and denitrification made contributions to N_(2)O emissions.Nitrification was the dominant pathway leading to N_(2)O production in soils and was responsible for 82.0%of the total emitted N_(2)O in sandy loam soil,which was significantly higher than that in silt loam soil(71.7%).However,the average contribution of denitrification to total N_(2)O production in sandy loam soil was 17.9%,which was significantly lower than that in silt loam soil(28.3%).These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.

Effects of Reduced Nitrogen Fertilization and Biochar Application on CO_2 and N_2O Emissions from a Summer Maize-Winter Wheat Rotation Field in North China

This experiment was conducted in Xinxiang, Henan from June 2013 to June 2014. Total four treatments were designed including farmers ’ common practice （F, 250 kg/hm^2）, 80% F （LF, 200 kg/hm^2）, 80% F＋biochar （LFC） and no fertilizer （CK） to measure the dynamic emissions of CO2 and N2O from a summer maize-winter wheat field by static chamber-gas chromatography method. The results showed that the soil CO2 emission was 21.8-1 022.7 mg/（m^2·h）, and was mainly influenced by soil temperature and moisture content. During the growth of summer maize, the soil CO2 emission was more significantly affected by soil moisture con-tent; and in winter wheat growing season, it was more significantly affected by soil temperature in the top 5 cm. The LF and LFC treatments significantly reduced the soil cumulative CO2 emission, especial y during the growth of winter wheat. Fertiliza-tion and irrigation were the main factors influencing the soil N2O emission. The soil N2O emission during the fertilization period accounted for 73.9%-74.5% and 40.5%-43.6% of the soil cumulative N2O emission during the summer maize-and winter wheat-growing season, respectively. The peak of emission fluxes was determined by fertilization amount, while the occurrence time of emission peak and emission re-duction effect were influenced by irrigation. The LF treatment reduced the soil cu-mulative N2O emission by 15.7%-16.8% and 18.1%-18.5% during the growth period of summer maize and winter wheat, respectively. Reduced nitrogen fertilization is an effective way for reducing N2O emission in intensive high-yielding farmland. Under a suitable nitrogen level （200 kg/hm^2）, the application of biochar showed no significant effect on the soil N2O emission in a short term. The N2O emission factors of the L and LF treatments were 0.60% and 0.56%, respectively. ln the intensive high-yield-ing farmland of North China, reducing the nitrogen application amount is an appro-priate measure to mitigate greenhouse gas emissions without crop yield loss.

Effect of water stress on N_2O emission rate of 5 tree species

The N2O emission rates, photosynthesis, respiration and stomatal conductance of the dominant tree species from broadleaf/Korean pine forest in Changbai Mountain were measured by simulated water stress with the closed bag-gas chromatography. A total of five species seedlings were involved in this study, i.e.,Pinus koraiensis Sieb. et Zucc,Fraxinus mandshurica Rupr,Juglans mandshurica Maxim,Tilia amurensis Rupr, andQuercus mongolica Fisch. ex Turcz.. The results showed that the stomatal conductance, net photosynthetic rate and N2O emission of leaves were significantly reduced under the water stress. The stoma in the leaves of trees is the main pathway of N2O emission. N2O emission in the trees mainly occurred during daytime. N2O emission rates were different in various tree specie seedlings at the same water status. In the same tree species, N2O emission rates decreased as the reduction of soil water contents. At different soil water contents (MW, LW) the N2O emission rates ofPinus koraiensis decreased by 34.43% and 100.6% of those in normal water condition, respectively. In broadleaf arbor decreased by 31.93% and 86.35%, respectively. Under different water stresses N2O emission rates in five tree species such asPinus koraiensis, Fraxinus mandshurica, Juglans mandshurica, Tilia amurensis, andQuercus mongolica were 38.22, 14.44, 33.02, 16.48 and 32.33 ngN2O·g?1DW·h?1, respectively. Keywords Trees - N2O emission rate - Soil water stress - broadleaf/Korean pine forest - Changbai Mountain CLC number S718.55 Document code A Foundation item: This project was supported by the National Natural Science Foundation of China (No. 30271068), the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ-CX-SW-01-01B-10), and the Special Funds for Major State Basic Research Program of China (No. G1999043407)Biography: Wang Miao (1964-), male, associate professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, P. R. China.Responsible editor: Song Funan

Effect of Light Quality and Intensity on N_2O and NO_X(NO, NO_2)Emissions from Rice Phyllosphere and Roots at Tillering Stage in a Liquid Culture Medium System

[Objective] N2Oand NOX（NO, NO2） are important nitrogen oxides gases（NOGs） in paddy fields, and rice plants play important roles in NOG emissions in paddy fields. However, the source of NOG emissions from rice phyllosphere and roots and their relationship to light quality and intensity still remain unclear. In this study, the relationship between light quality, intensity and N2 O, NOX（NO, NO2） emissions from rice phyllosphere and roots at tillering stage was investigated to clarify the contribution of rice plants to N2Oand NOX（NO, NO2） emissions and analyze the mechanism of light control, aiming at providing a scientific basis for revealing how light-control technology affects NOG emissions from rice at tillering stage in paddy fields. [Method] In this study, nitrogen content was controlled by a hydroponic system. A small electric incubator was used for light control. A simultaneous determination was designed to investigate the effect of different weak light qualities（yellow, green, white, red and blue lights） and intensities（dark, 0 lx; very weak, 2 000lx; weak, 4 000 lx; moderate, 6 000 lx; strong, 8 000 lx） on N2Oand NOXemissions from rice phyllosphere and roots at tillering stage in a liquid culture medium system. N2Oconcentration in air samples was determined by gas chromatography within 12 h, and NOX（NO, NO2） concentration was analyzed using 42 i NO- NO2-NOXgas analyzer. [Result] The results showed that：（1） Under a constant nitrogen condition（NH4NO3-N, 90 mg/L） when rice seedlings were treated with moderate（6 000lx） and strong（8 000 lx） light, the average emission rate of N2Oand NO from rice phyllosphere at tillering stage was 27.08, 32.33 μg/（pot·h） and 0.114, 0.057 μg/（pot·h）,respectively, accounting for 57.38%, 58.65% and 9.65%, 4.52% of the total release of N2Oand NO from the whole rice plant, respectively. It implicated that rice phyllosphere is an important source of N2Oemission at tillering stage in paddy fields.（2）When rice seedlings were treated with yellow, green, white, red and blue LED lights under a constant light intensity（1 600 lx）, the average emission rate of N2Ofrom rice phyllosphere was 6.83, 9.40, 9.73, 2.82 and 4.08 μg/（pot·h）, respectively. Compared with green and yellow LED lights, N2Oemission from rice phyllosphere and roots at tillering stage was inhibited markedly by red（3 000 lx） and blue（2 500 lx）LED lights（P0.01）. In addition, NO emission from rice phyllosphere was enhanced significantly by white and red LED lights, while NO emissions from rice phyllosphere and roots were inhibited by blue light synchronously. Nevertheless, no evident NO2 emission from rice phyllosphere and roots was detected under the same condition.（3） Within the range of 0-8 000 lx, NO and N2Oemissions from rice roots and N2Oemission from rice phyllosphere increased with the enhancement of light intensity. In contrast, NO emission from rice phyllosphere was inhibited remarkably by moderate（6 000 lx） and strong（8 000 lx） light（P〈 0.01）. [Conclusion] Rice seedlings mainly exhibited net emissions of NO2 from the phyllosphere and roots.N2Oand NOX（NO, NO2） emissions from rice phyllosphere and roots at tillering stage could be inhibited by adjusting the composition of visible light（synchronously increasing the proportions of red and blue lights） and appropriately controlling daytime light intensity.

N_2O emissions from forest and grassland soils in northern China

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Denitrification Losses and N_2O Emissions from Nitrogen Fertilizer Applied to a Vegetable Field

A field experiment was conducted on Chinese cabbage （Brassica campestris L. ssp. pekinensis （Lour.） Olsson） in a Nanjing suburb in 2003. The experiment included 4 treatments in a randomized complete block design with 3 replicates： zero chemical fertilizer N （CK）; urea at rates of 300 kg N ha^-1 （U300） and 600 kg N ha^-1 （U600）, both as basal and two topdressings; and polymer-coated urea at a rate of 180 kg N ha^-1 （PCU180） as a basal application. The acetylene inhibition technique was used to measure denitrification （N2 ＋ N2O） from intact soil cores and N2O emissions in the absence of acetylene. Results showed that compared to （3K total denitrification losses were significantly greater （P ≤ 0.05） in the PCU180, U300, and U600 treatments,while N2O emissions in the U300 and U600 treatments were significantly higher （P ≤ 0.05） than （3K. In the U300 and U600 treatments peaks of denitrification and N2O emission were usually observed after N application. In the polymer-coated urea treatment （PCU180） during the period 20 to 40 days after transplanting, higher denitrification rates and N2O fluxes occurred. Compared with urea, polymer-coated urea did not show any effect on reducing denitrification losses and N2O emissions in terms of percentage of applied N. As temperature gradually decreased from transplanting to harvest, denitrification rates and N2O emissions tended to decrease. A significant （P ≤0.01） positive correlation occurred between denitrification （r = 0.872） or N2O emission （r = 0.781） flux densities and soil temperature in the CK treatment with a stable nitrate content during the whole growing season.

Carbon Dioxide, Methane, and Nitrous Oxide Emissions from a Rice-Wheat Rotation as Affected by Crop Residue Incorporation and Temperature

Field measurements were made from June 2001 to May 2002 to evaluate the effect of crop residue application and temperature on CO2, CH4, and N2O emissions within an entire rice-wheat rotation season. Rapeseed cake and wheat straw were incorporated into the soil at a rate of 2.25 t hm(-2) when the rice crop was transplanted in June 2001. Compared with the control, the incorporation of rapeseed cake enhanced the emissions of CO2, CH4, and N2O in the rice-growing season by 12.3%, 252.3%, and 17.5%, respectively, while no further effect was held on the emissions of CO2 and N2O in the following wheat-growing season. The incorporation of wheat straw enhanced the emissions of CO2 and CH4 by 7.1% and 249.6%, respectively, but reduced the N2O emission by 18.8% in the rice-growing season. Significant reductions of 17.8% for the CO2 and of 12.9% for the N2O emission were observed in the following wheat-growing season. A positive correlation existed between the emissions of N2O and CO2 (R-2 = 0.445, n = 73,p < 0.001) from the rice-growing season when N2O was emitted. A trade-off relationship between the emissions of CH4 and N2O was found in the rice-growing season. The CH4 emission was significantly correlated with the CO2 emission for the period from rice transplantation to field drainage, but not for the entire rice-growing season. In addition, air temperature was found to regulate the CO2 emissions from the non-waterlogged period over the entire rice-wheat rotation season and the N2O emissions from the nonwaterlogged period of the rice-growing season, which can be quantitatively described by an exponential function. The temperature coefficient (Q(10)) was then evaluated to be 2.3+/-0.2 for the CO2 emission and 3.9+/-0.4 for the N2O emission, respectively.

Scenario analysis on abating industrial process greenhouse gas emissions from adipic acid production in China

Adipic acid is an important petrochemical product,and its production process emits a high concentration of greenhouse gas N_2 O.This paper aims to provide quantitative references for relevant authorities to formulate greenhouse gas control roadmaps.The forecasting method of this paper is consistent with the published national inventory in terms of caliber.Based on the N_2 O abatement technical parameters of adipic acid and the production trend,this paper combines the scenario analysis and provides a measurement of comprehensive N_2 O abatement effect of the entire industry in China.Four future scenarios are assumed.The baseline scenario(BAUS) is a frozen scenario.Three emission abatement scenarios(ANAS,SNAS,and ENAS) are assumed under different strength of abatement driving parameters.The results show that China's adipic acid production process can achieve increasingly significant N_2 O emission abatement effects.Compared to the baseline scenario,by 2030,the N_2 O emission abatements of the three emission abatement scenarios can reach 207-399 kt and the emission abatement ratios can reach 32.5%-62.6%.By 2050,the N_2 O emission abatements for the three emission abatement scenarios can reach 387-540 kt and the emission abatement ratios can reach 71.4%-99.6%.

Nitrous Oxide Emissions from Upland Farmland as Affected by Summer Legume Crop Cultivation

A field study was conducted to investigate the effects of leguminous crop cultivation on nitrous oxide (N2O) emissions from upland agricultural soils. Results demonstrated that N2O emission sequences were that peanut crop> soybean>upland rice in terms of N2O-N flux, being 25.9, 21.2 and 18.4μg/m2·h respectively . While in terms of seasonal emission, the sequence was that soybean > peanut crop > upland rice, being 0.77, 0.70 and 0.55 kg/ha respectively. Results also demonstrated that legume crop treatment emitted much more N2O than non-legume upland rice treatment and that N fertilized treatments emitted more than unfertilized treatments, average N2O-N flux being 25.8 and 17.9μg/m2·h respectively. Legume crop cultivation and N fertilizer, therefore, were one of the important sources of N2O emissions from agricultural fields.

N_2O emissions from a cultivated Andisol after application of nitrogen fertilizers with or without nitrification inhibitor under soil moisture regime

The aim of this work was to examine the emission of N 2O from soils following addition of nitrogen fertilizer with a nitrification inhibitor(+inh) or without the nitrification inhibitor(-inh) at different soil water regime. Higher soil moisture contents increased the total N 2O emissions in all treatments with total emissions being 7 times larger for the CK and >20 times larger for the fertilizer treatments at 85% WFPS(soil water filled pore space) than at 40% WFPS. The rates of N 2O emissions at 40% WFPS under all treatments were small. The maximum emission rate at 55% WFPS without the nitrification inhibitor(-inh) occurred later (day 11) than those of 70% WFPS (-inh) samples (day 8). The inhibition period was 4—22 d for 55% WFPS and 1—15 d for 70% WFPS comparing the rates of N 2O emissions treated (+inh) with (-inh). The maximum emission rates at 85% WFPS were higher than those at the other levels of soil water content for all treatments. The samples(+inh) released less N 2O than (-inh) samples at the early stage. Nevertheless, N 2O emissions from (+inh) samples lasted longer than in the (-inh) treatment. Changes in mineral N at 55%, 70% and 85% WFPS followed the same pattern. NH + 4-N concentrations decreased while NO - 3-N concentrations increased from the beginning of incubation. NH + 4-N concentrations from 40% WFPS treatment declined more slowly than those of the other three levels of soil water content. Nitrification was faster in the (-inh) samples with 100% NH + 4-N nitrified after 22 d(50% WFPS) and 15 d(70% and 85% WFPS). N 2O emissions increased with soil water content. Adding N-fertilizer increased emissions of N 2O. The application of the nitrification inhibitor significantly reduced total N 2O emissions from 30.5%(at 85%WFPS) to 43.6%(at 55% WFPS).

Effect of Vertical Distribution of Soil Water on N₂O Emission under Drip Irrigation

N2O emission has obvious water effect, but the current research is not deep enough. The soil wetting mode of drip irrigation technology is obviously different from that of conventional irrigation. Using the method of soil box indoor simulation, the N2O emission under different soil vertical water content was analyzed. Hydrus Software was used to simulate the soil wetting body under different drip irrigation technical parameters, the relationship between the combination of drip irrigation technical parameters and soil vertical water content was studied, and then the relationship between the N2O emission and the combination of drip irrigation technical parameters was proposed. The results showed that soil N2O emission flux increased with the increase of soil moisture, and the maximum emission flux was three times as much as the minimum emission flux. Under the condition of uniform distribution of soil moisture, soil N2O emission flux was smaller than that under non-uniform distribution of soil moisture. Hydrus software simulation results show that drip flow rate is 2.0 L/h, the irrigation period is 5 days, the irrigation quota is 12 mm, and the soil N2O emission flux is the largest. Adjusting the combination of technical parameters of drip irrigation can reduce soil N2O emission flux.

Research Progress on N₂O Emissions from Soil in Facility Vegetable Plot

N2O is one of the important greenhouse gases that cause global warming. N2O emissions from the soil of the facility vegetable land are an important source. It is important to summarize the research on the N2O emissions from the soil in the facility vegetable land, and is also of great significance to study on the emission mechanism of N2O in China’s agricultural fields. This paper summarizes the development status of the facility vegetable plot in China, tracks the progress of soil N2O emission research in the facility vegetable plot, and makes a prospect of the research in this field.

Short Report: Effects of Biochar Addition on Manure Composting and Associated N₂O Emissions

Recent interests in biochar stem from its agronomic benefits and carbon sequestration potentials in soil applications. As a not fully understood newer concept, adding biochar as a bulking agent to animal manure composting has the potential to enhance the performance of composting process and reduce associated N2O emissions. This short report presents emerging trends and knowledge gaps in this research area, and provides an introduction to understand the mechanism by which biochar impacts manure composting performance and N2O fluxes.

生物炭处理下干湿交替灌溉稻田活性氮气体排放特性

干湿交替灌溉具有节水稳产等优势,但也存在促进NH_(3)挥发和增加N_(2)O排放的风险。而生物炭具有改善土壤、蓄水保肥、降低温室气体排放等诸多正效应。为探究干湿交替灌溉条件下稻田活性氮气体排放(主要为NH_(3)和N_(2)O)对添加生物炭的响应机制,设置不同灌溉模式(淹灌和干湿交替灌溉)和生物炭用量(0和20 t/hm^(2))2个因素4个处理,通过2020和2021年大田原位试验,对稻田土壤环境、NH3挥发、N_(2)O排放、植物氮素吸收和产量等进行了研究。结果表明,2 a间,干湿交替灌溉对水稻产量均未产生显著影响(P>0.05),但却显著增加了NH3挥发(仅2020年)和N_(2)O排放(P<0.05),增幅分别达到8.9%和105.0%~115.0%;而添加生物炭显著降低了NH_(3)挥发(8.7%~20.5%)和N_(2)O排放(21.6%~24.2%)(P<0.05),减少9.0%~20.6%的活性氮气体排放(P<0.05)。较之无炭常规淹灌对照处理,干湿交替灌溉结合生物炭处理,可在实现增产0.2%~12.5%的同时,降低活性氮气体排放6.1%~11.7%。干湿交替灌溉促进N_(2)O排放的主要原因是频繁灌水-落干条件下稻田土壤NO_(3)^(−)-N浓度和氧化还原电位均得到了显著提升;而生物炭增产降氨的主要原因是无机氮固持量得到了显著提升,进而降低了NH3挥发损失,增加了水稻氮素吸收,最终实现增产。研究揭示了生物炭在干湿交替稻田的应用潜力,为实现稻田节水增产,增汇减排及降低活性氮排放带来的环境代价提供理论依据。

氮肥减量配施铁粉对稻麦轮作农田活性氮损失的影响

稻麦轮作农田是氨挥发、氧化亚氮(N_(2)O)排放和硝酸盐淋溶的重要来源。虽然减少氮肥用量能降低氮环境负效应,但会带来作物减产的风险。施用铁粉可刺激水稻田土壤铁还原细菌生长,增强其固氮活性。研究设置传统施氮量100%N、传统施氮量80%N、传统施氮量80%N+Fe、传统施氮量60%N、传统施氮量60%N+Fe、不施氮0%N、不施氮0%N+Fe共7个处理,通过田间原位试验研究氮肥减施和配施铁粉对作物产量、氨挥发、N_(2)O排放和硝酸盐淋溶的影响。结果表明,2021年麦季80%N+Fe处理的小麦产量较80%N处理提高了9.70%,水稻产量与传统施氮量处理相当,减氮20%配施铁粉具有稳产、增产的效果。水稻田氨挥发随着氮肥用量减少而明显降低(P<0.05);80%N+Fe处理与传统施氮量相比则进一步降低了累积氨挥发量与氨挥发强度(P<0.05),降幅分别为50.99%和47.41%。2021年麦季80%N+Fe处理的N_(2)O排放量较80%N处理显著降低78.16%(P<0.05),稻季与传统施氮量相比降低18.27%。同时,80%N+Fe处理也降低了土壤深层渗滤液硝态氮淋溶。因此,在传统氮肥用量基础上减氮20%配施Fe能起到作物稳产的效果,这可能是因为施加Fe增强了水稻田铁还原细菌固氮活性。农田氨挥发、N_(2)O排放和硝态氮淋溶减少主要是氮肥减施所致,相应的土壤微生物机理值得进一步探索。

玉米-小麦轮作系统中氮肥反硝化损失与N_2O排放量

应用乙炔抑制-原状土柱培养法研究了玉米-小麦轮作周年中氮肥的反硝化损失和N2O排放量。结果表明,氮肥产生的N2O为1.77～2.82kgN·hm-2,占施氮量的0.49%～0.76%;反硝化损失量为3～3.18kgN·hm-2,占施肥量的0.81%～0.86%。玉米与小麦生长期间的氮肥反硝化损失率很相近,分别为0.7%～0.99%和0.77%～0.88%。反硝化作用和N2O排放与土壤含水量密切相关,有机肥与氮肥混施增加N2O排放量。反硝化不是该旱作系统氮肥损失的主要途径,但施用氮肥大大增加了N2O的排放,对环境造成一定的影响。

固相萃取-反相高效液相色谱法测定水中的邻苯二甲酸酯

建立了固相萃取-反相高效液相色谱法检测水中3种邻苯二甲酸酯类物质邻苯二甲酸二甲酯、邻苯二甲酸二(2-乙基己基)酯、邻苯二甲酸二正辛酯的方法。考察了固相萃取柱、洗脱溶剂、洗脱体积、上样速度以及洗脱速度对萃取效率的影响。通过综合分析,选定SupelcleanLC-18 SPE Tube固相萃取柱,甲醇为洗脱剂,洗脱体积2mL,上样速度为4mL/min,洗脱速度为1mL/min。在此萃取条件下,萃取回收率在83.4%～121.2%之间。邻苯二甲酸二甲酯、邻苯二甲酸二(2-乙基己基)酯、邻苯二甲酸二正辛酯质量浓度在2～100mg/L之间均为线性。经萃取后,方法的最低检出限分别为邻苯二甲酸二甲酯0.06μg/L,邻苯二甲酸二(2-乙基己基)酯0.16μg/L,邻苯二甲酸二正辛酯0.08μg/L。方法的精密度在10%～15%之间。应用该方法测定自来水中酞酸酯类化合物的含量,加标回收率为83.6%～110.2%。