利用膜进样质谱仪测定水稻土几种厌氧氮转化速率

为了在同一体系下区分和测定水稻土反硝化、厌氧氨氧化(Anammox)和硝酸根异化还原成铵(DNRA)过程发生速率和相互关系,并获取近似原位情况下的净脱氮速率,本研究通过将~(15)NH_4~+化学氧化法测定DNRA速率和添加尿素模拟原位土柱测定净脱氮速率与膜进样质谱法(MIMS)进行联用,完善了一套基于膜进样质谱法(MIMS)的稻田硝态氮转化测定方法体系,利用该方法测定了5种典型的水稻土[辽宁营口(YK)、江苏宜兴(YX)、浙江金华(JH)、广西桂林(GL)和四川广安(GA)]的反硝化、Anammox、DNRA和净脱氮4种氮转化速率。结果显示:基于MIMS的方法体系可实现对水稻土中反硝化、Anammox、DNRA和净脱氮速率的测定,5种水稻土反硝化、Anammox、DNRA和净脱氮速率范围分别为(358.63±25.37)～(479.96±22.12)、(-14.81±0.22)～(5.29±1.22)、(25.76±12.71)～(109.87±3.88)g N·hm~(-2)·h~(-1)和(33.33±11.16)～(72.74±14.18)g N·hm~(-2)·h~(-1),相关结果与其他方法研究结果具有可比性。相关性分析显示:水稻土NO_3~-、可溶性有机碳(DOC)和土壤Fe~(2+)含量是反硝化过程的主要限制因素;NO_3~-是Anammox的关键限制因素;而土壤DOC和Fe~(2+)含量是DNRA过程的主要限制因素。基于MIMS的方法体系可以在短时间内(1周)测定水稻土四种厌氧氮转化速率,且所需样品量低、精确度高,在稻田或湿地土壤厌氧氮转化过程研究中有很好的应用前景。     

Depth-specific distribution and importance of nitrite-dependent anaerobic ammonium and methane-oxidising bacteria in an urban wetland

Anaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) are two recently discovered processes in the nitrogen cycle that are catalysed by anammox bacteria and n-damo bacteria, respectively. Here, the depth-specific distribution and importance of anammox bacteria and n-damo bacteria were studied in an urban wetland, Xixi Wetland, Zhejiang Province (China). Anammox bacteria related to Candidatus Brocadia, Candidatus Kuenenia and Candidatus Anammoxoglobus, and n-damo bacteria related to “Candidatus Methylomirabilis oxyfera” were present in the collected soil samples. The abundance of anammox bacteria (2.6–8.6 × 10⁶ copies g⁻¹ dry soil) in the shallow soils (0–10 cm and 20–30 cm) was higher than that (2.5–9.8 × 10⁵ copies g⁻¹ dry soil) in the deep soils, whereas the abundance of n-damo bacteria (0.6–1.3 × 10⁷ copies g⁻¹ dry soil) in the deep soils (50–60 cm and 90–100 cm) was higher than that (3.4–4.5 × 10⁶ copies g⁻¹ dry soil) in the shallow soils. Anammox activity was detected at all depths, and higher potential rates (12.1–21.4 nmol N₂ g⁻¹ dry soil d⁻¹) were observed at depths of 0–10 cm and 20–30 cm compared with the rates (3.5–8.7 nmol N₂ g⁻¹ dry soil d⁻¹) measured at depths of 50–60 and 90–100 cm. In contrast, n-damo was mainly occurred at depths of 50–60 cm and 90–100 cm with potential rates of 0.7–5.0 nmol CO₂ g⁻¹ dry soil d⁻¹. This study suggested the niche segregation of the anammox bacteria and n-damo bacteria in wetland soils, with anammox bacteria being active primarily in deep soils and n-damo bacteria being active primarily in shallow soils.     

猪场废水中氮的去除研究现状

规模化猪场废水中含有高浓度的氨氮,如不加以去除,将给环境造成很大的压力。本文分析了国内外现阶段几种去除猪场废水中氨氮的技术:包括物理吹脱、沸石离子交换、还田利用、人工湿地处理、生物硝化反硝化处理。此外,着重介绍了两种极具发展前景的新工艺:短程硝化反硝化、短程硝化--厌氧氨氧化工艺。     

猪场废水厌氧消化液的厌氧氨氧化脱氮研究进展

传统生物脱氮工艺在处理猪场废水厌氧消化液时,存在着能耗高、脱氮效果差、需要补充碳源、投加碱等缺点。与传统方法相比,厌氧氨氧化工艺作为一种新型生物脱氮工艺,因具有不需供给有机碳源、无需供氧等优势而受到广泛关注。本文在分析厌氧氨氧化反应机理、厌氧氨氧化工艺优点的基础上,主要综述了厌氧氨氧化的影响因素(温度、pH值、溶解氧、有机物、基质抑制),重点介绍了厌氧氨氧化工艺在猪场废水厌氧消化液处理方面的应用现状,指出了目前研究的难点,并对今后研究的方向作了一定的展望。     

稻田厌氧氨氧化菌群落结构对氮肥的响应

为探明稻田厌氧氨氧化菌多样性及其对氮肥用量的响应状况,利用厌氧氨氧化菌16S rRNA基因特异引物对定位试验稻田土壤DNA进行PCR-DGGE(聚合酶链反应变性梯度凝胶电泳)并结合DNA克隆测序,研究了氮肥供应量对厌氧氨氧化菌群落结构的影响。DGGE图谱及依据其条带位置和亮度数值计算的多样性指数均显示:高氮处理[N3:225 kg(N).hm 2]的厌氧氨氧化菌群落结构多样性在表层或根层土壤中均显著(P<0.05)高于中、低氮[N2:150 kg(N).hm 2;N1:75 kg(N).hm 2]处理和不施肥对照(CK);同时,高氮处理下表层土壤厌氧氨氧化菌群落多样性指数显著高于根层土壤(P<0.05)。冗余分析(RDA)结果表明,表层土壤中厌氧氨氧化菌群落结构组成与不同氮肥水平处理存在显著相关性(P=0.006)。此外,本试验获得厌氧氨氧化菌DGGE条带DNA序列18条,登录GenBank并获得登录号。研究表明稻田厌氧氨氧化菌群落结构对高氮水平具有较强的响应,尤其是在表层土壤中。     

稻田土壤厌氧氨氧化菌群落结构对长期不同施肥的响应

研究长期不同施肥稻田土壤厌氧氨氧化微生物丰度和群落结构组成,深入认识稻田厌氧氨氧化菌对不同施肥的响应机理,可为合理施肥和理解湿地生态系统厌氧氨氧化过程提供科学依据。设置不施肥(CK)、单施无机肥(NPK)、无机肥配施牛粪(NPKM)、无机肥加秸秆还田(NPKS)四个处理,采用荧光定量PCR和高通量测序对不同施肥模式下水稻土厌氧氨氧化细菌丰度和群落结构进行分析。结果发现,不同处理之间厌氧氨氧化细菌丰度具有显著差异(p0.05),表现为NPKMNPKSNPKCK,且与有机质、全氮和铵态氮含量具有显著相关性(p0.05)。高通量测序结果表明,不同施肥处理主要的厌氧氨氧化菌为Candidatus Brocadia、Candidatus Anammoxoglobus和Candidatus Scalindua,其中优势种群为Candidatus Brocadia。菌群的多样性分析表明,CK和NPKS处理的厌氧氨氧化菌群落结构多样性香农指数(Shannon index)、辛普森指数(Simpson index)和丰富度指数(Chao 1 index)显著高于NPKM和NPK处理(p0.05)。上述结果表明,长期施肥改变了厌氧氨氧化菌的数量和群落结构。有机无机肥配施更有利于提高厌氧氨氧化菌丰度。然而,不同施肥措施对厌氧氨氧化菌的多样性影响不同,无机肥加秸秆还田提高了厌氧氨氧化菌多样性,但单施无机肥和无机肥配牛粪降低了厌氧氨氧化菌多样性。厌氧氨氧化菌的数量和群落结构对不同施肥的响应不同。     

厌氧氨氧化研究进展

厌氧氨氧化的发现使人们对微生物氮循环的认识更加全面,本文综述了厌氧氨氧化菌的生物学特性及其活性的影响因素,介绍了厌氧氨氧化在废水生物脱氮方面的应用前景.     

水稻土厌氧氨氧化对不同耕作方式与秸秆还田的响应

【目的】研究稻田土壤厌氧氨氧化微生物活性、丰度和群落结构对不同耕作方式与秸秆还田的响应,为稻田土壤氮素管理提供科学依据。【方法】设置3个不同耕作方式(翻耕、旋耕、免耕)+秸秆还田处理,同时设置翻耕+秸秆不还田处理作为对照,采用_¹⁵N示踪法、荧光定量PCR及Illumina测序分别分析厌氧氨氧化菌潜在活性、功能基因hzsB拷贝数及群落组成。【结果】秸秆还田条件下,厌氧氨氧化菌潜在活性表现为免耕>旋耕>翻耕(p<0.05),对照与旋耕+秸秆还田处理无显著性差异。各处理之间厌氧氨氧化菌功能基因(hzsB)拷贝数无显著性差异。Illumina测序从属水平鉴定出Kuenenia和Scalindua两种已知的厌氧氨氧化菌及部分未鉴定属,且各处理间二者的相对丰度具有负相关关系(p<0.05)。相关性分析结果表明,厌氧氨氧化菌活性与土壤反硝化活性显著相关,与功能基因拷贝数及群落组成无显著相关性。【结论】水稻田长期秸秆还田和不同耕作方式改变了厌氧氨氧化菌活性和群落组成,但其数量未发生显著变化。水稻田秸秆还田加翻耕可一定程度上抑制土壤氮损失,而秸秆还田与免耕结合的田间管理方式提高了土壤氮素损失潜力。     

Formation of hybrid N2O and hybrid N2 due to codenitrification: First review of a barely considered process of microbially mediated N-nitrosation

At the end of the 19th century an experimental study had already reported N gas production during microbial nitrate reduction, which significantly exceeded the amount of nitrate N supplied to the microorganism. The observed excess gas production was suggested to be caused by a reaction of nitrous acid (produced during microbial nitrate reduction) with amino acids contained in the nutrient solution. Since the 1980’s a number of ¹⁵N tracer experiments revealed that this biotic excess gas production was based on the formation of hybrid N₂O and/or hybrid N₂. It was shown that the N-N linkage forms due to a microbially mediated N-nitrosation reaction by which one N atom of nitrite or nitric oxide combines via a nitrosyl intermediate with one N atom of another N species (e.g., amino compound). Because of its cooccurrence with conventional denitrification this process was later on termed “codenitrification”. Although the phenomenon of N₂O and N₂ formation by codenitrification was recognised over a century ago its impact on global N cycling is still unclear today. Nonetheless, the present literature review reveals codenitrification as a potentially important process of biospheric N cycling since (i) most codenitrifying species are already known as typical denitrifiers (e.g., Pseudomonas sp., Fusarium sp. etc.) and (ii) codenitrification was already reported to occur within the three domains archaea, bacteria, and eukarya (kingdom fungi). Furthermore, the present literature suggests that codenitrification acts not only as an additional source of N gas formation due to a mobilisation of organic N by N-nitrosation, but also acts as an N immobilising process due to a bonding of inorganic N (e.g., from NO₃⁻ or NO₂⁻) onto organic compounds due to e.g., N- or even C-nitrosation reactions. From this it can be concluded that N gas formation by codenitrification represents a sub-phenomenon of a variety of possible biotic nitrosation reactions. Moreover, the review reveals that biotic nitrosation also occurs among nitrifying species, even under aerobic conditions. Furthermore, recent studies support the assumption that even anaerobic ammonium oxidation (anammox) appears to be based on biotically mediated N-nitrosation. Therefore, we propose to introduce the term BioNitrosation, which includes all biotically mediated nitrosation reactions resulting either in N gas release or in N immobilisation, independently from the acting microbial species or the environmental conditions.     

人工湿地中生物脱氮新路径分析

综述了人工湿地中除氮的传统路径和新型路径,包括氨化、硝化反硝化、短程硝化反硝化、厌氧氨氧化和全程自养脱氮等脱氮方式,对生物脱氮的机理、优越性、影响因素以及在人工湿地中的应用现状进行分析,为采用新型脱氮路径,建立脱氮效果更好的人工湿地奠定了基础.