土壤氮循环微生物过程的分子生态学研究进展

固氮作用、硝化作用和反硝化作用是土壤微生物参与氮素循环的三个重要方面。自分子生态学方法应用于土壤学后,土壤微生物作用于氮素循环过程的机理研究取得了若干重要进展。包括:1)利用固氮菌的nifH基因作为分子标记研究有机质、氮素与固氮微生物之间的关系,发现固氮微生物的丰度和群落结构与土壤有机质含量呈正相关。然而,固氮微生物的丰度和群落结构与土壤速效N含量呈负相关,施用氮肥会抑制固氮微生物的生长,施氮土壤固氮微生物数量减少,多样性降低。2)以氨氧化微生物功能基因为探针,揭示了土壤pH与氨氧化微生物分布关系密切,碱性土壤中氨氧化细菌是硝化作用主要参与者,而酸性土壤中氨氧化古菌是硝化作用的主导者。土壤中N素的含量也影响氨氧化微生物的数量和群落结构,施入氮肥后氨氧化微生物的数量和活性增加。3)利用反硝化功能基因为分子标记研究土壤因子对反硝化细菌群落的影响,阐明了土壤可溶性有机碳、pH和土壤水分是影响反硝化细菌数量和群落结构的重要因子,并且发现土壤反硝化细菌与土壤反硝化能力和氧化亚氮释放之间存在着一定的联系,但这种联系在不同研究对象中存在差异,需要进一步确认。目前,利用分子生物学技术解析土壤氮素循环微生物生态功能取得了重要的进展,但还需进一步深入。今后,将采用包括同位素在内的示踪技术与分子生物学方法相结合共同分析氮循环不同代谢过程微生物种群间的相互关系以及氧化亚氮产生与硝化和反硝化微生物之间的关系。     

Difference in diffusion coefficients of 14NO3 −-N and 15NO3 −-N affects the apparent fractionation factor associated with denitrification in soil

Abstract

We previously analyzed the effect of nitrate dispersion on the apparent nitrogen isotope fractionation factor associated with denitrification in soil (Kawanishi et al. 1993), and found that the dispersion effect was significant when the water flow was slow. In the previous report, we assumed that the dispersion coefficients of ¹⁴NO₃ ^? and ¹⁵NO₃ ^? were similar. However, when the water flow is slow, molecular diffusion will dominate mechanical dispersion and the above assumption may not be valid.     

盐度对序批式生物反应器污泥膨胀的影响

为了研究盐度对污泥膨胀的影响,采用序批式生物反应器（sequencing batch reactor,SBR）处理含盐废水,考察NaCl、NA₂SO₄和Na₃PO₄盐度变化对污泥沉降性和污染物去除效果的影响。结果表明,当NaCl和NA₂SO₄盐度由0升高至30 g/L时,污泥容积指数（sludge volume index,SVI）由135 mL/g下降至71⁷3 mL/g,总氮（total nitrigen,TN）去除率由80%下降到60%,胞外聚合物（extracellular polymeric substance,EPS）质量浓度由521⁵23 mg/L升高到896⁹17 mg/L,污泥沉降性良好;当Na₃PO₄盐度由0升高至8 g/L时,SVI由135 mL/g升高至198 mL/g,TN去除率由80%下降至60%,EPS质量浓度由549 mg/L升高到674 mg/L,发生污泥膨胀。随着NaCl和NA₂SO₄盐度的提高,污泥沉降性能提高,TN去除率下降,EPS质量浓度升高。随着Na₃PO₄盐度的提高,污泥沉降性能和TN去除率均下降,EPS质量浓度升高。然而,随着NaC（l30⁰ g/L）、NA₂SO₄（30⁰ g/L）和Na₃PO₄（8⁰ g/L）盐度的降低,SVI值分别由71 mL/g升高至298 mL/g,73 mL/g升高至291 mL/g和198 mL/g升高至241 mL/g,TN去除率分别由62%下降至43%,65%下降至44%,70%下降至35%,EPS质量浓度分别由917 mg/L升高至1 092 mg/L,896 mg/L升高至1 078 mg/L,674 mg/L升高至759 mg/L。随着NaCl、NA₂SO₄和Na₃PO₄盐度由高降低后,污泥沉降性能和TN去除率均下降,EPS质量浓度继续升高,盐度降低后发生了污泥膨胀。     

Integrated Nitrogen Fertilization for Intensive and Sustainable Agriculture

Summary

Increased efficiency of land use and resource-use are critical for agriculture to feed the ever increasing population and yet remain sustainable for the future generations. Mineral fertilizers, particularly, nitrogen (N) fertilizer has played a very important role in meeting the increased food demand and in saving millions of hectares of marginal and wildlife reserves from coming under cultivation. Apart from higher yields per unit land, N application also results in higher protein content. Improper use of N fertilizers due to high application rates, incorrect source and method of application, and poor timing of application have led to air and water pollution and economic losses. Integrated and balanced N fertilization results in a win-win situation with intensive and sustainable agriculture that feed the world without harming the environment. Since multitude of management, soil, crop, and weather-related factors control soil and plant N dynamics, N management recommendations based on field trials alone are too costly and time-consuming. Dynamic N management recommendations that are both site— and season-specific combine field trials with decision support systems (DSS) that simulate crop growth and N transformations as a function of above-mentioned factors. Innovative N fertilizer products and N efficient plant types will further improve N use efficiency.     

空间位置对聚丁二酸丁二醇酯固相反硝化脱氮性能的影响

采用室内装置以可生物降解聚合物(BDPs)聚丁二酸丁二醇酯[Poly (butylene succinate),PBS]为碳源和载体构建固相反硝化系统,研究反应器内上、中、下3层PBS颗粒表面所附着的生物量、质量损耗以及反硝化脱氮速率.结果表明,在进水硝酸盐浓度为50 mg/L、水力停留时间(HRT)为4h的条件下,反应器具有良好的脱氮能力,第20d时出水硝酸盐浓度降到0.2476 mg/L,去除率为99.50％.在生物量和质量损耗的试验中发现,PBS的空间物理结构对表面附着的生物量和PBS质量损耗有着显著的影响,随高度的增加呈递减趋势;上、中、下3层PBS表面所附着生物量分别为7.65×108、1.48×109、3.64×109 CFU/cm3,质量损耗量分别为0.3517、0.6749、3.9336 g.反硝化脱氮速率测试结果表明,上、中、下3层PBS颗粒的硝酸盐去除能力存在极显著差异,去除率分别为38.479％、72.128％和99.233％;在前9h内亚硝酸盐的含量都呈升高趋势,浓度分别为9.7075、7.2982、10.0527 mg/L,随后的14h内开始下降,终浓度分别为6.9351、5.3473、0.2119 mg/L;总氮的去除率分别为58.3449％、70.0623％和99.1570％.     

Treatment of Wastewater with High Concentration of Ammonia Nitrogen through ASBR Combining with Pulsed SBR

In order to analyze the nitrogen removal performance of anaerobic-aerobic process treating landfill leachate, a system combining ASBR with pulsed SBR was applied to treat real landfill leachate with high concentration of ammonia nitrogen. The HRT of ASBR was 2 d; middle water tank regulated the COD/NH +4-N (3～5) and NH +4-N concentration of pulsed SBRs influent; the cycle of pulsed SBR consisted of four anoxic stages and three oxic stages in which three equal feeds model was applied. In the fourth anoxic stage (An4), internal carbon source was used to implement denitrification without any extra carbon source addition. The results indicate that efficient nitrogen removal performance of this system was achieved in the series running period (157 d). Influent chemical oxygen demand (COD) concentration of ASBR was from 7 338 mg·L -1 to 1 0445 mg·L -1 of which above 83% was removed; pulsed SBRs influent NH +4-N concentration could be divided into four phases in which improving from 296.1±14.5 mg·L -1 to 912.0±41.7 mg·L -1, and the effluent total nitrogen (TN) concentration of pulsed SBR was below 40 mg·L -1 all the time, which means TN removal rate reached over 90%. To sum up, the COD and TN removal rate of the combined system were above 87% and 97%, respectively. Endogenous denitrification rate(DNR) of An4 changed from the fast one to the slow one, and the mean value of theoretical denitrification rate (TDNRm) of pulsed SBRs An4 could reach 1.531 mg N·h -1·gMLVSS -1. Advanced nitrogen removal of the system was realized without extra carbon source addition and physicochemical pre-treatment.     

除氮生物反应器净化农田排水的研究及应用潜力分析

农田排水氮素输出是造成水环境污染的重要原因。近年来涌现的生物反应器除氮技术通过在排水末端增设固体碳源装置,将农田排水部分或全部导入后,使其中的硝态氮通过反硝化反应得到去除。该文回顾了国际上现有生物反应器净化农田排水的研究进展,并分析了农田生物反应器在中国南方湿润区应用的潜力。现有研究结果表明,除氮生物反应器可以有效净化排水水质,平均每年可降低23%～98%的氮素负荷;是一种占地面积少且水质净化效率高的农田控污措施。生物反应器的除氮效果与农田排水过程密切相关,并受到介质特性、入流、出流条件以及环境因子等的影响。中国南方平原作物生长及排水过程相对集中,气象等环境条件非常适于生物反应器的反硝化反应。如何因地制宜确定反应器安装位置与设计尺寸,筛选填料介质,并通过对排水过程的调控来优化生物反应器的除氮效果是需要进一步研究的问题。生物反应器系统后期管理与内部反应动态监测是保证系统正常运行的重要手段。利用生物反应器来净化农田排水具有良好的应用前景,该文可为推动生物反应器在中国的应用研究以及排水污染治理提供理论依据与技术支撑。     

Effects of Rhizosphere and Long-Term Fertilization Practices on the Activity and Community Structure of Denitrifiers Under Double-Cropping Rice Field

The soil physicochemical properties, soil denitrification rates (PDR), denitrifiers via nitrite reductases (nirK and nirS) and nitrous oxide reductase (nosZ), abundance and community composition of denitrifiers in both the rhizosphere and bulk soil from a long-term (32 year) fertilizer field experiment conducted during late rice season were investigated by using the MiSeq sequencing, quantitative PCR, terminal restriction fragment polymorphism (T-RFLP). The experiment including four treatments: without fertilizer input (CK), chemical fertilizer alone (MF), rice straw residue and chemical fertilizer (RF), and organic manure and chemical fertilizer (OM). The results showed that the application of rice straw residue and organic manure increased soil organic carbon (C), total nitrogen (N), and NH₄⁺-N contents. The nirK, nirS, and nosZ copy numbers with OM and RF treatments were significant higher than that of the MF and CK treatments in the rhizosphere and bulk soil (p < 0.05). The principal coordinate analysis (PCoA) analysis showed that the different parts of root zone are the most important factors for the variation of denitrifying bacteria community, and the different fertilization treatments is the second important factors for the variation of denitrifying bacteria community. The MiSeq sequencing result showed that nirK, nirS and nosZ-type denitrifiers communities within bulk soil had lower species diversity compared with rhizosphere soil, and were dominated by Rhizobiales, Rhodobacterales, Burkholderiales, and Pseudomonadales. As a result, the application of fertilization practices had significant effects on soil N and PDR levels, and affected the abundance and community composition of N-functional microbes.