Environmental microbes and gas fluxes: A systematic study of volatile reactive nitrogen oxides

一系列的污染气体，特别是氮(N)化合物（N2O， NO， NO2等）从陆地来源排放到大气中，包括农业和自然生态系统这些气体极其重要的原因有很多，包括它们对气候变化和城市空气污染的贡献。施肥和灌溉等常见农业做法将继续增加，可能导致高排放。在自然生态系统中，氮的大气沉降变得越来越普遍，也刺激了土壤的排放。然而，来自陆地来源的氮气预测受到以下因素的阻碍：(1)缺乏实地测量；(2)对这些气体的生产和消耗过程的不完全理解。该项目旨在更好地量化来自陆地系统的氮气体通量，并绘制与土壤中排放和消耗相关的各种机制。氮循环是大气氮气体的重要来源；然而，导致排放和消耗的条件是极其复杂的。对于NOz气体（HONO、HNO3、有机硝酸盐和颗粒硝酸盐）来说尤其如此，它们的研究比N2O、NO和NO2少得多，但通过它们对大气氧化能力的贡献，它们是气候的重要驱动因素。此外，氮循环微生物与碳循环微生物之间存在潜在的交集，这可能会影响土壤中氮的转化。例如，N循环产物（如NH2OH和NO）可以在细胞外与异养微生物产生的活性氧（ROS = OH, O2, HO2, H2O2）发生反应，生成亚硝酸盐和NO2等活性N化合物。这些类型的土壤中未充分研究的反应代表了我们对n循环的理解中的一个主要差距，这阻碍了我们将这些过程扩展到区域和全球尺度。本研究将探索不同陆地生态系统中N-气体对土壤N和碳(C)修正的响应，并系统地评估负责排放的过程。

A range of pollutant gases, and especially nitrogen (N) compounds (N2O, NO, NO2, etc.) are emitted to the atmosphere from terrestrial sources, including agriculture and natural ecosystems.1,2,3 These gases are extremely important for a myriad of reason including their contribution to climate change and urban air pollution. Common agricultural practices such as fertilization and irrigation will continue to increase, likely resulting in high emissions. In natural ecosystems, atmospheric deposition of N has become increasing prevalent, also stimulating emissions from soil. However, N-gas forecasts from terrestrial sources are hampered by (1) a lack of field-based measurements and (2) an incomplete understanding of the processes associated with production and consumption of these gases. This project aims to better quantify N-gas fluxes from terrestrial systems as well as map the various mechanisms associated with emission and consumption in soil.The N-cycle is a significant source of atmospheric N-gases; however, the conditions leading to both emission and consumption are extremely complex. This is particularly true for the suite of NOz gases (HONO, HNO3, organic nitrates, and particulate nitrates), which are much less studied than N2O, NO, and NO2, but represent an important driver of climate via their contribution to the oxidizing capacity of the atmosphere. Additionally, there are potential intersections between N-cycling microbes and those involved in carbon-cycling, which may affect transformations of N in the soil. For example, N-cycle products (e.g., NH2OH and NO) can react extracellularly with reactive oxygen species (ROS = OH, O2, HO2, H2O2) generated by heterotrophic microbes to produce reactive N compounds such as nitrite and NO2. These types of understudied reactions in soil represent a major gap in our understanding of the N-cycle which prevents us from scaling these processes to the regional and global scales. This study will explore the response of N-gases to soil N and carbon (C) amendments in various terrestrial ecosystems and systematically evaluate the processes responsible for emissions.