南美白对虾养殖系统中氨氧化菌多样性研究

[目的]为解决养殖水体的氨氮污染问题提供依据。[方法]研究南美白对虾养殖池塘底泥中的氨氧化菌的多样性和种群分布及其amoA基因的多样性,并与池塘周边土壤中的氨氧化菌群落结构进行比较。[结果]不同样品中氨氧化菌数量差异显著,其中池塘周边土壤中最多,达到4.5×105cfu/g,其次是池塘底泥和水体。来自土壤和底泥两个DNA样品均扩增到了预期长度(491 bp,517 bp)的amoA基因片段。底泥样品的DGGE条带数明显多于池塘周边土壤样品。土壤和底泥样品仅有1个共同的氨氧化菌种属,其序列与Nitrosospira sp.相似性达96%。池塘周边土壤的氨氧化菌种属序列与Nitrosospira sp.都有高度同源性。池塘底泥中Nitrosomonas sp.为氨氧化菌的优势菌群。[结论]构建的amoA基因克隆文库能较好反映南美白对虾养殖系统中氨氧化菌的多样性。     

Relationship between nitrifier and denitrifier community composition and abundance in predicting nitrous oxide emissions from ephemeral wetland soils

The link between differences in the community composition of nitrifiers and denitrifiers to differences in the emission of nitrous oxide (N₂O) from soils remains unclear. Nitrifier and denitrifier community composition, abundance and N₂O emission activity were determined for two common landscapes characteristic of the North American “prairie pothole region”: cultivated wetlands (CW) vs. uncultivated wetlands (UW). The hypotheses of this study were: (1) landscape selects for different nitrifier and denitrifier communities, (2) denitrification was the dominant N₂O emitting process, and (3) a relationship exists between nitrifier and denitrifier community composition, their abundance, and N₂O emission. Comparisons were made among soils from three CW and three UW at the St. Denis National Wildlife Area. Denaturing gradient gel electrophoresis was used to compare community composition, and quantitative polymerase chain reaction was used to estimate community size. Incubation experiments on re-packed soil cores with ¹⁵N-labeled nitrate were performed to assess the relative contributions of nitrification and denitrification to total N₂O emission. Results indicate: (1) nitrification was the primary source of N₂O emission, (2) cultivation increased nitrifier abundance but decreased nitrifier richness, (3) denitrifier abundance was not affected by cultivation but richness was increased by cultivation, and (4) differences in nitrifier and denitrifier communities composition and abundance between land-use and landform did not correspond to differences in N₂O emission.     

川中丘陵区紫色土冬小麦/夏玉米轮作氨挥发研究

大气中过量的氨会造成诸多环境问题并危害人类健康。我国农田氮肥施用后的氨挥发是一个重要的氨排放源。紫色土的土壤性质以及该区的气候条件导致其氨挥发潜力较大。与其他集约化农作区相比,该区农田氨挥发研究相对较少。本文探讨了川中丘陵区紫色土冬小麦/夏玉米轮作体系氨挥发情况,为开展陆地生态系统大气碳氮气体交换研究提供基础数据,同时也为氨排放清单的编制及农田氨减排措施研究提供依据。选取川中紫色土丘陵区典型的坡耕地作为研究对象,采用风洞法研究了紫色土冬小麦/夏玉米轮作体系的氨挥发动态过程。每次试验设置1个施肥处理,3次重复。风速、风向、大气温湿度、土壤温湿度等气象数据由试验田微型气象站获取。每隔2~3 d采集土壤样品用以测定土壤NH4+-N含量。两年的田间试验结果表明,受氮肥深施及低温的影响,冬小麦季氨挥发损失率明显低于夏玉米季;2013年和2014年冬小麦季氨挥发损失率分别为7.4%和8.8%;2013年夏玉米季三叶期氮肥撒施的氨挥发速率为34.1%;2014年夏玉米季三叶期氮肥条施覆土降低了氨挥发损失,损失率为21.4%;2014年夏玉米季十叶期出现极端干旱的气候条件,撒施氮肥后立即灌水使氨挥发损失率高达46.6%,这是由于干旱条件下施肥灌水提供了利于氨挥发的土壤水分条件。因此在极端干旱的气候条件下,应避免采用此施肥方式。综合分析两年的数据可得:紫色土冬小麦季氨挥发损失占施氮量的(8.1±1.0)%,夏玉米氨挥发损失占施氮量的(32.8±1.8)%。     

施氮量和田面水含氮量对紫色土丘陵区稻田氨挥发的影响

采用密闭室连续抽气法研究了四川省丘陵区紫色土上不同施氮量条件下(0、112.5、150、187.5、225 kg/hm2)稻田氨(NH3)挥发特征及田面水含氮量对其的影响。结果表明,施氮肥后的1~3天内出现NH3挥发峰值,随后逐渐下降。稻田NH3挥发总量随施氮量的增加而增加,二者呈极显著的相关关系(r=0.916 6***)。通过稻田NH3挥发损失的氮素占施氮量的比例为29.4%~38.0%。施氮肥后稻田田面水NH4+-N、可溶性氮和总氮浓度均迅速升高,稻田NH3挥发速率与田面水中的NH4+-N、可溶性氮和总氮浓度均具有显著的相关关系,观测期内的最高相关系数分别为0.926 9、0.841 2和0.881 3。因此,控制施氮量可有效降低田面水NH4+-N、可溶性氮和总氮浓度,以此来减少紫色土丘陵区稻田NH3挥发损失。     

华北农田土壤氨挥发原位测定研究

通过系数矫正后的双层海绵吸收法对不同N肥处理和NPK配施下氨气挥发损失特征研究结果表明,N肥施用方式、土壤温度以及灌溉是影响氨挥发的重要因素。施肥后氨挥发损失量为0.67~9.91kg/hm2,占施N量的0.41%~5.0%。玉米季氨挥发量占全年挥发损失的80%以上。尿素与过磷酸钙配施可显著降低氨挥发,在此基础上施用KCl,尿素氨挥发损失变化不明显。     

Injection of pig slurry and its effects on dynamics of nitrogen and carbon in a loamy soil unter laboratory conditions

Dynamics of nitrogen (N) and carbon (C) were investigated in a loamy soil amended or injected with pig slurry. Treatments were with or without acetylene C₂H₂ (which is assumed to inhibit reduction of nitrous oxide (N₂O) to dinitrogen (N₂), and soil cores were conditioned for 15 days at 25°C while pH, production of CO₂ and N₂O, ammonia (NH₃) emission and (nitrate) (NO₃ ^–) and (ammonium) (NH₄ ⁺) concentrations were monitored. There was no significant difference in CO₂ production between the injected and surface applied pig slurry treatments, and within 15 days ca. 5% of the C applied had been mineralized, if no priming effect was assumed. Neither the production of N₂O nor the total gaseous production of the denitrification process (N₂O plus N₂) were affected by the way the pig slurry was added to the soil. NH₃ volatilization, however, decreased by 90% when pig slurry was injected. The addition of C₂H₂ significantly increased the CO₂ production and the concentration of NH₄ ⁺, but significantly decreased the concentration of NO₃ ^–. It was concluded that the injection of pig slurry to a dry soil was an acceptable alternative to its application to the soil surface, as not only was NH₃ volatilization reduced, but the production of N₂O and N₂ through denitrification was not stimulated. It is also suggested that the composition of the organic C fraction in the pig slurry, most likely the concentration of fatty acids, had an important effect on the dynamics of N and C in the soil. Received: 12 May 1997     

镇江丘陵区稻田化肥氮的氨挥发及其影响因素

采用密闭室方法对镇江丘陵区典型稻麦轮作制度下的水稻插秧、分蘖和孕穗期施用尿素的氨挥发进行了测定，并对施肥后土壤pH的变化及其对氨挥发的影响进行了分析，结果表明稻田施用尿素有明显的氨挥发损失，氨挥发损失率在水稻不同生育期有很大的差异，分蘖肥的氨挥发显著高于基肥和孕穗肥，受温度、植株状况以及光照条件等因素的影响，氮挥发存在明显的年际差异。田面水的pH值在施肥后有明显的昼夜波动，而氨挥发损失受田面水pH值变化的显著影响。稻草对不同生育期施肥的氨挥发影响不同。     

改性沸石对氨氮去除效果与机理研究

[目的]研究改性沸石对废水中氨氮的去除效果及吸附机理。[方法]采用脱磷尿液作为试验废水,比较了不同改性沸石(NaCl沸石、HCl沸石、HCl-焙烧沸石和HCl-焙烧-微波沸石)对试验废水中氨氮的去除效果,并探讨了其吸附机理。[结果]在粒径为0.5～1.0 mm,投加量为200 g/L时,天然沸石和4种改性沸石对氨氮的平衡吸附量依次为天然沸石饱和NaCl改性沸石5.0%HCl改性沸石5.0%HCl-400℃焙烧改性沸石5.0%HCl-400℃焙烧-微波改性沸石。沸石扫描电镜影像和质量损失揭示吸附差异的主要原因是不同改性方法导致沸石孔隙大小和数量的差异。[结论]5.0%HCl-400℃焙烧-微波改性沸石对氨氮具有较高吸附能力,平衡吸附量为17.9 mg/g,是天然沸石的2.6倍。     

氮在河北平原褐土和地下水迁移转化机制

[目的]为了揭示氨氮、亚硝酸盐氮、硝酸盐氮在褐土和地下水中的迁移转化。[方法]以河北平原的褐土为主要的研究对象,通过室内土柱的淋滤实验,建立数学模型,预测其迁移规律。[结果]在施氮周期内,氨氮浓度最高为15.86 mg/L,最低为0.09 mg/L,平均为2.02 mg/L,超标10.1倍;亚硝酸盐氮最高浓度为37.456 mg/L,最低浓度为0.002 mg/L,平均浓度为4.854 mg/L,超标242.7倍;硝酸盐氮浓度最高为16.35 mg/L,最低浓度为2.12 mg/L,平均浓度为6.51 mg/L的未超标,占标率为32.57%。[结论]在浅层地下水中,硝酸盐氮和氨氮是污染地下水的主要2种氮素存在形态。在深层地下水中,氮素主要存在形态为硝酸盐氮。所建数学模型可以定量地预测氮在包气带和地下水中的迁移规律。