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| 厌氧条件下土壤反硝化气体(N2、N2O、NO)和CO2排放——氦环境培养—气体同步直接测定法的应用初探 | |
| 引用本文： | 冯琪,王睿,郑循华,张伟,邹建文.厌氧条件下土壤反硝化气体(N2、N2O、NO)和CO2排放——氦环境培养—气体同步直接测定法的应用初探[J].气候与环境研究,2013,18(3):297-310. |
| 作者姓名： | 冯琪 王睿 郑循华 张伟 邹建文 |
| 作者单位： | 1. 南京农业大学资源与环境科学学院，南京210095; 中国科学院大气物理研究所大气边界层物理和大气化学国家重点实验室，北京100029 2. 中国科学院大气物理研究所大气边界层物理和大气化学国家重点实验室,北京,100029 3. 南京农业大学资源与环境科学学院,南京,210095 |
| 基金项目： | 公益性行业(农业)科研专项项目200803036;国家自然科学基金国际合作项目40711130636 |
| 摘 要： | 反硝化过程是维系闭合氮循环所必需的氮素形态转化环节。土壤反硝化过程速率及产物比的直接测定是研究氮循环过程机理的基础，但却是一个难题。为解决此难题，德国卡尔斯鲁厄技术研究所与中国科学院大气物理研究所最近合作新建了一套通过氦环境培养-气体同步直接测定土壤反硝化气体--氮气（N2）、氧化亚氮（N2O）、一氧化氮（NO）和二氧化碳（CO2）排放的系统和与之配套的三阶段培养方法。为检验该新建系统和配套方法测定土壤反硝化过程的准确性和可靠性，以华北地区广泛分布的盐碱地农田土壤（采自山西运城）为研究对象开展实验室培养试验，在初始可溶性有机碳（DOC）供应比较充足约300 mgC kg–1干土（d.s.）的条件下，测试了不同初始土壤硝态氮含量水平（10、100 mgN kg–1d.s.左右，分别表示为10N和100N）的反硝化气体和CO2排放过程。结果显示：100N的反硝化速率（定义为N2、N2O 和NO 排放速率之和）显著高于10N 处理（统计检验显著水平p＜0.01）；两个处理的反硝化产物均以N2为主（质量比分别占77%和75%），产物的NO/N2O摩尔比分别为1.2和1.5，N2O/N2摩尔比均为0.19；土壤反硝化气体动态排放速率及相关指标的测定结果表明，培养土壤中消失的硝态氮被回收81%～87%，培养前后的氮平衡率达92%～95%。因此，该新建方法测定土壤反硝化速率和产物比的结果具有很好的可靠性，为定量研究土壤反硝化过程提供了有效的直接测定手段。研究中检测到的土壤反硝化产物NO/N2O摩尔比大于1，不同于以往用液体培养基纯培养反硝化细菌得出的NO/N2O摩尔比远小于1的结论。这意味着，不能用NO/N2O摩尔比小于1与否来推断土壤排放的N2O和NO是主要来源于反硝化作用还是硝化作用。 |
| 关 键 词： | 氦环境培养-气体同步直接测定法 反硝化作用 N2 N2O NO和CO2排放 NO/N2O比 N2O/N2比 回收率 |
| 收稿时间： | 2011/1/27 0:00:00 |
| 修稿时间： | 2013/2/25 0:00:00 |
Direct Measurements of Denitrification Gas (N2, N2O, NO) and CO2 Emissions Using the Gas-Flow-Soil-Core Technique with Helium Environment Incubation |
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| FENG Qi,WANG Rui,ZHENG Xunhu,ZHANG Wei and ZOU Jianwen.Direct Measurements of Denitrification Gas (N2, N2O, NO) and CO2 Emissions Using the Gas-Flow-Soil-Core Technique with Helium Environment Incubation[J].Climatic and Environmental Research,2013,18(3):297-310. | |
| Authors: | FENG Qi WANG Rui ZHENG Xunhu ZHANG Wei and ZOU Jianwen |
| Institution: | College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095;State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 |
| Abstract: | Denitrification is the key process of nitrogen transformation to close the global nitrogen cycle. Quantification of microbial denitrification rate and its ratios of products is the key step for obtaining insights into nitrogen cycling processes, though it is very difficult. To enable precise quantification of the rates of the entire process, as well as individual products, a system of gas-flow-soil-core technique with helium-environment incubation was recently established and a three-period incubation method was set up by the Karlsruhe Institute of Technology and the Institute of Atmospheric Physics, Chinese Academy of Sciences. Using this system, dynamic emission rates of dinitrogen (N2), nitrous oxide (N2O), nitric oxide (NO) and carbon dioxide (CO2), which are the gaseous products of microbial denitrification, can be simultaneously and directly measured. In this study, we conducted the first soil incubation experiment to test the reliability of the measurements by this system in association with the newly proposed incubation method. Our experiment included two levels of initial soil nitrate (NO3-) content, which were around 10 and 100 mgN kg-1d.s. (dry soil), respectively (hereinafter referred to as 10N and 100N). For either nitrate level, sufficient dissolved organic carbon (DOC) was initially supplied (glucose was added to establish an initial DOC content of around 300 mgC kg-1d.s.). The incubated fresh soil was a silty clay loam of the northern China. It was sampled from a typical cropland rotationally cultivated with a double cropping system of summer maize and winter wheat and a single cropping system of cotton. Our results show that the microbial denitrification rate was significantly higher for the 100N than 10N treatments (p<0.01), and N2 was the main product in both treatments (with mass fractions of 77% and 75%, respectively). The molar ratios were 1.2 (10N) to 1.5 (100N) for NO/N2O and were 0.19 (both treatments) for N2O/N2. The measurements of individual denitrification gases recovered 81%-87% of disappeared nitrate during incubation. The direct dynamic detection of individual denitrification gases and the measurements of DOC, ammonium, nitrate, microbial biomass carbon, and microbial biomass nitrogen at the beginning and end of incubation gave mass balance rates of 92%-95% for nitrogen. These results suggest that the tested system, in association with the proposed incubation method, could precisely determine the dynamical rate of microbial denitrification. The molar ratios of NO/N2O given by our data were greater than 1. This differs from previous knowledge of much lower ratios yielded by denitrifiers. This difference implicates that the NO/N2O ratio of 1 may not be used as the threshold to indicate nitrification or denitrification processes. |
| Keywords: | Gas-flow-soil-core technique with helium-environment incubation Denitrification Dynamics of N2 N2O NO and CO2 emissions NO/N2O N2O/N2 Recovery rate |
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