EAGER: Collaborative Research: Development of a New Technique to Measure Ecosystem-level Soil Nitrous Oxide Fluxes using Micrometeorological Towers

EAGER：合作研究：开发利用微气象塔测量生态系统水平土壤一氧化二氮通量的新技术

• 批准号: 1359138
• 负责人: Ilya Gelfand
• 金额: $ 7万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1359138&HistoricalAwards=false
• 关键词: EAGER; Collaborative; Research; Development; New

Nitrous oxide is the third most important greenhouse gas in the atmosphere, with an atmospheric lifetime of about 114 years and a global warming impact per molecule that is about 300 times greater than that of carbon dioxide. Atmospheric concentrations of nitrous oxide are increasing, primarily due to agriculture, which is thought to be responsible for about half of the total output to the atmosphere that can be attributed to human activities. Current trends in land-use change and agricultural intensification (in particular increasing fertilizer use) suggest that an additional 20% increase in global nitrous oxide emissions will occur by 2030. However, difficulties in measuring the output of nitrous oxide from ecosystems make it hard to manage and predict nitrous oxide production from major human sources. This project we will test a promising new technique to measure the ecosystem-level exchange of nitrous oxide with the atmosphere using a laser sensor. This novel approach will provide opportunities to measure whole system nitrous oxide dynamics at hourly to daily time scales over areas that are too large to effectively sample with traditional techniques. With this novel approach, a new understanding of the factors that control the production and consumption of nitrous oxide in forests, grasslands, and agricultural lands may be possible. This would lead to much better ability to manage and minimize the production of this important greenhouse gas, because management is currently hampered by significant uncertainties in the measurement of nitrous oxide. A major barrier to understanding and mitigating emissions of nitrous oxide from agricultural and other managed soils is the difficulty with which fluxes are measured, given temporal and spatial variability that often exceeds an order of magnitude at scales of meters and hours. In this project, open-path quantum cascade laser sensors will be integrated with standard micrometeorological measurements to develop a solar-powered measurement system to quantify nitrous oxide fluxes. This novel approach will provide opportunities to measure whole system nitrous oxide fluxes at hourly to daily time scales over multi-hectare areas, and thereby resolve and integrate the spatial and temporal variability that makes this flux so difficult to quantify and model in situ. A newly developed open-path quantum cascade laser (OP-QCL) sensor will be used on each of two existing carbon dioxide micrometeorological eddy covariance towers to measure ecosystem-level nitrous oxide exchange. In addition to the OP-QCL sensors, multiple standard static chambers will be deployed within the study area to perform ground based validation of the OP-QCL measurements. One of the sensors will be deployed in a high-emission fertilized continuous corn system; the other will be deployed in grassland that has not been farmed for 25 years. In addition to validating the micrometeorological method, the project will test hypotheses related to the temporal variability of fluxes at diurnal to seasonal scales, which cannot be answered without continuous observations. Specific project objectives include 1) to develop, test, and validate an OP-QCL sensor for ecosystem-level measurements of nitrous oxide fluxes using micrometeorological towers; and 2) to relate and assess the significance of changes in nitrous oxide flux with temporal environmental variability, including daily, seasonal, and episodic events such as large rain events and management activities such as tillage and fertilization in cropped systems.

一氧化二氮是大气中第三大温室气体，在大气中的寿命约为114年，每分子对全球变暖的影响约为二氧化碳的300倍。一氧化二氮在大气中的浓度正在增加，这主要是由于农业造成的，据认为，农业造成了可归因于人类活动的大气总排放量的大约一半。 目前土地使用变化和农业集约化（特别是增加化肥使用）的趋势表明，到2030年，全球一氧化二氮排放量将再增加20%。 然而，由于难以测量生态系统的一氧化二氮产量，因此很难管理和预测主要人为来源的一氧化二氮产量。 在这个项目中，我们将测试一种有前途的新技术，使用激光传感器测量生态系统水平的一氧化二氮与大气的交换。这种新的方法将提供机会，以每小时到每天的时间尺度测量整个系统的一氧化二氮动态，这些区域太大，无法用传统技术进行有效采样。有了这种新的方法，对控制森林、草原和农田中一氧化二氮的生产和消费的因素有了新的认识。 这将大大提高管理和尽量减少这一重要温室气体的生产的能力，因为目前在测量一氧化二氮方面存在很大的不确定性，这妨碍了管理工作。 理解和减少农业土壤和其他管理土壤的一氧化二氮排放的一个主要障碍是难以测量通量，因为在米和小时的尺度上，时间和空间的变化往往超过一个数量级。 在该项目中，开放路径量子级联激光传感器将与标准微气象测量相结合，以开发一个太阳能测量系统，量化一氧化二氮通量。这种新的方法将提供机会来测量整个系统的一氧化二氮通量在每小时到每天的时间尺度超过多公顷的地区，从而解决和整合的空间和时间的变化，使这种通量很难量化和模拟原位。一个新开发的开路量子级联激光（OP-QCL）传感器将用于两个现有的二氧化碳微气象涡动协方差塔，以测量生态系统一级的一氧化二氮交换。除了OP-QCL传感器外，还将在研究区域内部署多个标准静态室，以对OP-QCL测量值进行地面验证。其中一个传感器将部署在高排放的连续施肥玉米系统中;另一个将部署在25年未耕种的草地上。除了验证微气象学方法外，该项目还将检验与日至季节尺度通量的时间变化有关的假设，如果不进行连续观测，就无法回答这些假设。 具体项目目标包括：1）开发、测试和验证一种OP-QCL传感器，用于使用微气象塔在生态系统一级测量一氧化二氮通量; 2）将一氧化二氮通量变化与时间环境变异性联系起来并评估其重要性，包括每日、季节和偶发事件，如大雨事件和管理活动，如耕作系统中的耕作和施肥。