追氮方式对夏玉米土壤N2O和NH3排放的影响

【目的】研究氮肥与硝化抑制剂撒施及条施覆土三种追施氮肥方式下土壤N2O和NH3排放规律、 O2浓度及土壤NH4+-N、 NO2--N和NO3--N的时空动态,揭示追氮方式对两种重要环境气体排放的影响及机制。【方法】试验设置3个处理: 1)农民习惯追氮方式撒施(BC); 2)撒施添加10%的硝化抑制剂(BC+DCD); 3) 条施后覆土(Band)。 3个处理均在施肥后均匀灌水20 mm。在夏玉米十叶期追施氮肥后的15天(2014年7月23日至8月8日)进行田间原位连续动态观测,并在玉米成熟期测定产量及吸氮量。采用静态箱-气相色谱法测定土壤N2O排放量,土壤气体平衡管-气相色谱法测定土壤N2O浓度,PVC管-通气法测定土壤NH3挥发,土壤气体平衡管-泵吸式O2浓度测定仪测定土壤O2浓度。【结果】农民习惯追氮方式N2O排放量为N 395 g/hm2,NH3挥发损失为N 22.9 kg/hm2,同时还导致土壤在一定程度上积累了NO2--N。与习惯追氮方式相比,添加硝化抑制剂显著减少N2O排放89.4%,使NH3挥发略有增加,未造成土壤NO2--N的累积。条施覆土使土壤N2O排放量显著增加将近1倍,但使NH3挥发显著减少69.4%,同时造成施肥后土壤局部高NO2--N累积。条施覆土的施肥条带上土壤NO2--N含量与N2O排放通量呈显著正相关。土壤气体的O2和N2O浓度受土壤含水量控制,当土壤WFPS大于60%时,020 cm土层中的O2浓度明显降低,而N2O浓度增加,土壤N2O浓度和土壤O2浓度间呈极显著负相关。各处理地上部产量及总吸氮量差异不显著。【结论】土壤NO2--N的累积与铵态氮肥施肥方式密切相关,NO2--N的累积能够促进土壤N2O的排放,且在条施覆土时达到显著水平(P0.05)。追氮方式对N2O和NH3两种气体的排放存在某种程度的此消彼长,添加硝化抑制剂在减少N2O排放的同时会增加NH3挥发,条施覆土在显著减少NH3挥发的同时会显著增加土壤N2O排放。在条施覆土基础上添加硝化抑制剂,有可能同时降低N2O排放和NH3挥发损失,此推论值得进一步研究。     

水稻根系生物特性与稻田温室气体排放相关性研究

通过湖南双季稻区温室气体排放差异的水稻品种田间试验,研究了不同品种温室气体排放与根系特征的相关性。结果表明,早稻分蘖盛期CH4排放通量与根干重、伤流量均呈显著负相关（P〈0.05）;晚稻CH4排放通量与根伤流量呈极显著负相关（P〈0.01）;早稻N2O排放通量在分蘖盛期与根伤流量相关性极显著（P〈0.01）,在齐穗期与根体积、干重、根伤流量均呈极显著负相关（P〈0.01）;晚稻分蘖盛期,根系干重与体积均与N2O排放通量呈显著正相关（P〈0.05）;齐穗期,根系体积与N2O排放通量呈显著负相关（P〈0.05）;早稻分蘖盛期CO2排放通量与根系干重和根伤流量呈显著正相关关系（P〈0.05）,晚稻齐穗期根系伤流量与CO2排放通量负相关性达到极显著水平（P〈0.01）。因此,根系特性是影响水稻温室气体排放的重要因素。     

强酸性茶园土壤中添加不同肥料氮后N2O释放量变化

茶园由于长期偏施氮肥，造成土壤酸化现象严重和 N2O 大量排放。本文对强酸性茶园土壤进行不同氮肥处理试验，结果表明， 通过31 d的好气培养，各施肥处理均显著提高N2O排放， 其中施硝酸钾（KNO3）处理平均每天排放的N2O最高，总排放量为对照（CK）的17倍，其次是硝酸铵（NH4NO3）处理， 尿素［CO（NH2）2］和硫酸铵［（NH4）2SO4］处理虽然能增加N2O 排放，但远远小于硝酸钾处理。对各氮肥处理硝化势的测定表明，尿素、 硫酸铵和硝酸铵处理均明显增加土壤硝化活性，而硝酸钾处理硝化势与对照相比显著降低。强酸性茶园土壤中N2O排放的主要来源是反硝化作用。氧化亚氮还原酶（nosZ）的定量PCR 分析表明，硝酸钾处理的nosZ 基因拷贝数与对照相比显著降低（P0.05）。因此，强酸性土壤中N2O还原酶活性被NO3-抑制是导致高N2O排放的重要原因之一。     

不同形态氮添加对长白山阔叶红松林土壤团聚体CO_2和N_2O排放的影响

以长白山阔叶红松林暗棕色森林土为研究对象,研究不同形态氮(N)添加对土壤不同粒级团聚体CO2和N2O排放的影响。采用室内短期培养试验(15 d),研究对照(CK)、氯化铵(NH4Cl,含N 150 mg kg-1)和硝酸钠(Na NO3,含N 150 mg kg-1)添加对全土(bulk soil)、大团聚体(250~1000μm)、微团聚体(53~250μm)、粉粒+黏粒(53μm)土壤组分CO2和N2O排放的影响。结果表明:CO2的排放量为大团聚体微团聚体全土粉粒+黏粒;NH4+-N添加对全土和各粒级团聚体的CO2排放没有显著影响;NO3--N添加对大团聚体和微团聚体的CO2排放有促进作用,并且在微团聚体中影响显著(P0.05),但对全土和粉粒+黏粒的CO2排放影响不显著。不同形态N添加对全土和各粒级团聚体N2O排放影响不同,NO3--N添加显著促进了N2O的排放,NO3--N添加后N2O排放量为全土大团聚体微团聚体粉粒+黏粒;NH4+-N的添加抑制了N2O的排放,NH4+-N添加后的土壤大团聚体、微团聚体和粉粒+黏粒的N2O排放量间无显著差异。由此可见,不同形态N添加影响土壤组分的CO2和N2O排放,且作用效果不一。     

农田土壤N2O和NO排放的影响因素及其作用机制

农田土壤作为N2O和NO的重要排放源而备受关注。硝化和反硝化是土壤N2O和NO产生的两个主要微生物过程,环境因子和农田管理措施等因素强烈影响着这两个过程以及N2O和NO的排放。本文重点论述了土壤水热状况、土壤质地、pH、肥料施用、耕作措施变更等关键性影响因素对农田土壤N2O和NO排放的影响及其影响机制。     

稻田CH4和N2O综合排放对控制灌溉的响应

为了揭示水稻控制灌溉对稻田CH4和N2O综合排放的影响,该文采用静态暗箱-气相色谱法对控制灌溉稻田CH4和N2O排放进行原位观测,分析稻田CH4和N2O综合排放对控制灌溉水分调控的动态响应。结果表明,控制灌溉稻田CH4排放通量多低于常规灌溉稻田,且主要集中在水稻分蘖前期,峰值出现在土壤脱水后第1～2d,排放总量较常规灌溉稻田减少81.2%～82.8%;N2O排放通量多高于常规灌溉稻田,峰值出现在肥后且土壤脱水后3～4d,排放总量较常规灌溉稻田增加了121.8%～144.3%。控制灌溉稻田CH4和N2O的综合全球增温潜势较常规灌溉稻田显著减少(p<0.05),减少幅度为15.0%～34.8%。控制灌溉显著降低了稻田CH4和N2O的综合温室效应。     

氢醌、双氰胺组合影响稻田甲烷和氧化亚氮排放研究进展

稻田是大气中CH4和N2O的重要来源。大量氮肥的施入不仅影响稻田CH4和N2O排放,且易造成NH3挥发、NO2-和NO3-淋溶及N2O、N2等形式的氮损失。脲酶抑制剂和硝化抑制剂通过缓解尿素水解及抑制硝化反硝化反应减少稻田N2O排放量,但对稻田CH4产生排放的影响报道不一。脲酶抑制剂氢醌(HQ)和硝化抑制剂双氰胺(DCD)是近年来研究较多的组合。本文试图在前人研究的基础上,综述HQ和DCD的基本性质及作用机理,总结HQ/DCD组合在稻田生态系统的应用状况、使用效果及存在问题,并特别讨论了HQ/DCD施用对稻田CH4排放的影响机理,旨在为合理使用脲酶/硝化抑制剂、有效减缓稻田温室气体排放和提高氮肥利用率等方面提供理论依据。     

耕作措施对双季稻田CH4与N2O排放的影响

随着全球气温的不断升高,温室气体减排成为研究的热点。该文旨在研究不同耕作措施下双季稻田CH4及N2O排放特征及其消长关系,为稻田温室气体减排及土壤固碳潜力评价提供依据。试验在湖南省宁乡县进行,通过静态箱法测定翻耕秸秆还田（CT）、旋耕秸秆还田（RT）、免耕秸秆还田（NT）的稻田CH4及N2O排放。结果表明：CH4排放主要来自于晚稻田,翻耕、旋耕和免耕晚稻田CH4排放分别占研究时段CH4排放的69%,67%,73%;各处理冬闲季CH4排放均不到研究时段排放量1%,冬闲CH4排放量为RT＞CT＞NT,差异显著;N2O排放时间变异性较大,早稻稻田N2O排放量为RT＞NT＞CT,晚稻稻田N2O排放量为NT＞RT＞CT,冬闲期各处理稻田N2O均为负排放;从研究时段排放量分析,翻耕秸秆还田有利于减少N2O排放,免耕秸秆还田有利于减少CH4排放;CH4与N2O排放呈显著负相关,冬闲季稻田CH4与N2O排放相关性不显著。总之,NT减少了CH4排放,虽N2O排放略有增加,但CH4与N2O引发的综合温室效应有所减弱。     

草甸草原模拟氮沉降抑制甲烷吸收、促进氧化亚氮排放

Few studies are conducted to quantify the effects of enhanced N deposition on soil nitrous oxide (N2O) emission and methane (CH4) uptake in the meadow steppe of Inner Mongolia,China.A two-year field experiment was conducted to assess the effects of nitrogen (N) deposition rates (0,10,and 20 kg N ha-1 year-1 as (NH4)2SO4) on soil N2O and CH4 fluxes.The seasonal and diurnal variations of soil N2O and CH4 fluxes were determined using the static chamber-gas chromatography method during the two growing seasons of 2008 and 2009.Soil temperature,moisture and mineral N (NH4+-N and NO3--N) concentration were simultaneously measured.Results showed that low level of (NH4)2SO4 (10 kg N ha-1 year-1) did not significantly affect soil CH4 and N2O fluxes and other variables.High level of (NH4)2SO4 (20 kg N ha-1 year-1) significantly increased soil NO3--N concentration by 24.1％ to 35.6％,decreased soil CH4 uptake by an average of 20.1％,and significantly promoted soil N2O emission by an average of 98.2％.Soil N2O emission responded more strongly to the added N compared to CH4 uptake.However,soil CH4 fluxes were mainly driven by soil moisture,followed by soil NO3--N concentration.Soil N2O fluxes were mainly driven by soil temperature,followed by soil moisture.Soil inorganic N availability was a key integrator of soil CH4 uptake and N2O emission.These results suggest that the changes of availability of inorganic N induced by the increased N deposition in soil may affect the CH4 and N2O fluxes in the cold semi-arid meadow steppe over the short term.     

接种蚯蚓对施加秸秆的旱作稻田N2O排放的影响

通过田间试验研究了秸秆不同施用方式下接种蚯蚓(威廉腔环蚓,Metaphire guillelmi)对水稻旱作土壤N2O排放通量的影响。结果显示施加秸秆和接种蚯蚓增加了N2O的排放量。在秸秆表施的情况下,接种蚯蚓处理显著提高了N2O的排放量,从12.54 kg/hm2提高到14.94 kg/hm2 (P<0.05);但是在秸秆混施的情况下,接种蚯蚓处理未显著提高N2O的排放量。蚯蚓的存在使土壤NO3--N的含量显著提高,尤其是在混施秸秆的情况下。由于栽培期内NH4+-N变化幅度较小,不同处理NO3--N含量的变化决定了土壤矿质氮的分异。农田生态系统中蚯蚓对N2O排放的贡献主要体现在促进秸秆混入土壤,从而加快秸秆的分解和N2O的排放。     

Towards bioremediation of toxic unresolved complex mixtures of hydrocarbons: identification of bacteria capable of rapid degradation of alkyltetralins

Background, aim and scope  Unresolved complex mixtures (UCMs) of aromatic hydrocarbons are widespread, but often overlooked, environmental contaminants. Since UCMs are generally rather resistant to bacterial degradation, bioremediation of UCM-contaminated sites by bacteria is a challenging goal. Branched chain alkyltetralins are amongst the individual classes of components of aromatic UCMs which have been identified in hydrocarbon-contaminated sediments and a number of synthetic alkyltetralins have proved toxic in laboratory studies. Thus, alkyltetralins should perhaps be amongst the targets for UCM bioremediation strategies. The slow degradation of several alkyltetralins by a microbial consortium has been reported previously; however, the bacteria involved remain unidentified and no single strain capable of alkyltetralin biodegradation has been isolated. The present project therefore aimed to enrich and identify bacterial consortia and single strains of bacteria from a naturally hydrocarbon-contaminated site (Whitley Bay, UK), which were capable of the degradation of two synthetic alkyltetralins (6-cyclohexyltetralin (CHT) and 1-(3’-methylbutyl)-7-cyclohexyltetralin (MBCHT)). Materials and methods  Bacteria were enriched from sediment collected from Whitley Bay, UK by culturing with CHT and MBCHT for a period of 4 months. Biodegradation experiments were then established and degradation of model compounds monitored by gas chromatography–mass spectrometry. Internal standards allowed the generation of quantitative data. 16S rRNA gene clone libraries were constructed from individual enrichments to allow assessment of microbial community structure. Selective media containing MBCHT were used to isolate single bacterial strains. These strains were then tested in liquid culture for their ability to degrade MBCHT. Results  The consortia obtained through enrichment culture were able to degrade 87% of CHT and 76% of MBCHT after only 46 days compared with abiotic controls. The 16S ribosomal RNA gene clone libraries of these bacteria were dominated by sequences of Rhodococcus spp. Using selective media, a strain of Rhodococcus was then isolated that was also able to biodegrade 63% of MBCHT in only 21 days. Discussion  The present report describes the isolation of a single bacterial strain able to degrade the resistant MBCHT. Although significant losses of MBCHT were observed, putative metabolites were not detectable. Rhodococcus sp. have been reported previously to be able to biodegrade a range of hydrocarbon compounds. Recommendations and perspectives  Due to their environmental persistence and toxicity, aromatic UCMs require bioremediation. The culturing and identification of such bacteria capable of rapid degradation of alkyltetralins may be an important step toward the development of bioremediation strategies for sites contaminated with toxic UCMs.     

食用仙人掌萎蔫气象条件分析

塑料大棚内种植的食用仙人掌在土壤墒情较好时也有萎蔫现象发生，通过试验观测和对仙人掌生理习性的分析，发现阴雨过后天气突然放晴温度急剧上升易使仙人掌发生萎蔫现象，并提出了田间管理的应对措施。     

姬松茸多糖提取工艺的优化

对姬松茸子实体多糖提取的工艺条件中的多糖提取温度、提取时间、浸提液pH值3因子的最优化组合问题进行了定量研究,建立了具有良好预测性能的姬松茸多糖提取条件的模型,并利用回归模型对工艺条件的最优化组合,对各单因子要素的多糖得率及其交互作用进行了探讨。试验表明,当浸提温度为100℃、浸提时间为3h、浸提液pH值为6.3时多糖得率处于较高水平     

植物恢复措施对鸡西矿区废弃地土壤养分的影响

以黑龙江省鸡西市矿区废弃地为研究区,对不同矿区废弃地的土壤养分元素进行含量分析。结果表明：应用植物恢复措施后的基质土壤各养分指标绝大多数要大大高于原废弃地土壤和经过自然恢复的土壤,说明该措施对石墨尾矿、矸石发电厂粉煤灰废弃地和平排矸石山土壤养分改善效果明显;其中石墨尾矿除全磷外,各种养分指标与林地土壤差距较大,而旱柳对石墨尾矿土壤的改善效果最好,其有机质含量为37．28g／kg,是残渣的2．6倍;种植大果沙棘对粉煤灰废弃地土壤养分的积累效果明显,有机质含量为48．25g／kg,是残渣的1．5倍;植物恢复措施使平排矸石山的土壤养分积累速度加快,已接近林地,混交种植兴安落叶松和家榆总体恢复效果最好,有机质含量分别为193．42和151．46g／kg,是自然恢复条件下的8．9和7倍。建议引入优势种群（如松科等）以加快演替速度,使矿区废弃地更快地恢复到原始状态。     

青海省耕地资源开发利用分析及对策研究

分析论述了青海省耕地资源开发利用的现状、特点和问题。在此基础上,提出了对青海省耕地资源进行研究的框架体系和思路,同时基于GIS/RS技术设计了相关的技术路线。最后依据所做设计对青海省耕地资源开发利用做了初步分析,并进行了相关的对策研究分析。     

济南山丘区土壤侵蚀潜在危险度景观格局分析

土壤侵蚀潜在危险度景观格局的形成及其变化是自然的和人为的多种因素相互作用的结果 ,运用景观生态学原理 ,通过分析景观斑块的类型、数量、面积大小和空间组合状况 ,揭示出济南市山丘区的土壤侵蚀潜在危险度分布特征及空间变异规律     

烘焙对生物质热解产物特性的影响

烘焙可有效地降低生物质中的水分和氧,对其热解过程有显著的影响。该文主要研究了烘焙温度（200,230,260,290℃）对生物质热解过程及产物特性的影响行为及影响机制;研究发现烘焙能改善热解产物的品质,随着烘焙温度的升高,热解合成气中CO含量由48%逐渐减少到34%,CH4和H2增加,其中H2含量最大增加了77.4%,而液体产物中,乙酸和水分含量逐渐减小,水分含量最大减少了42.8%,而酚类产物的含量明显增加,有利于生物油品质的提高。该研究为烘焙技术的发展和生物质高效热化学转化提供科学参考。     

氟对小鼠生精细胞凋亡的影响及锌的保护作用

为观察氟对成年雄性小鼠生精细胞凋亡的影响及锌的保护作用,通过腹腔注射氟化钠建立氟中毒动物模型及锌保护实验。采用石蜡切片、苏木精-伊红染色(HE染色)、末端原位标记(TUNEL)及琼脂糖凝胶电泳的方法检测小鼠生精细胞的凋亡情况。结果显示:(1)氟感染组无论是低剂量组(NaF10 mg/kg)或是高剂量组(NaF 20 mg/kg)生精细胞都发生了明显的凋亡。生精细胞凋亡主要发生在精母细胞和精原细胞,凋亡指数与对照组差异极显著(P<0.05)。(2)无论是高剂量锌(ZnSO430 mg/kg)和低剂量锌(ZnSO415 mg/kg)都可以使凋亡指数明显降低,高剂量锌组的凋亡指数与对照组差异不显著(P>0.05)。     

稀释介质种类对豆乳蛋白胶体粒子zeta电位测定效果的影响

蛋白粒子zeta电位是衡量豆乳体系稳定性的一个重要指标,而在电位分析前常采用稀释介质对豆乳进行预处理。为了确保zeta电位测定的准确性和科学性,必须选择合适的稀释介质。因此,该研究采用去离子水、豆乳超滤液两种稀释介质分别对豆乳进行稀释,并比较了这2种稀释介质对zeta电位、粒径分布、pH值以及电导率的影响。结果表明,若以去离子水为稀释介质,zeta电位的绝对值会随着稀释倍数的升高而显著增加（*P<0.05）,这主要是由于豆乳蛋白胶体粒子发生解聚导致粒径减小,而pH值的升高和电导率的降低则说明豆乳的离子强度显著降低。相比之下,选用豆乳超滤液稀释豆乳时,体系的 zeta 电位、粒径分布、pH值以及电导率都未随稀释倍数的增加而改变（*P>0.05）,说明此法能够较好地维持豆乳蛋白粒子的荷电稳定性。由此可知,豆乳超滤液可做为豆乳zeta电位测定的理想稀释介质。