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

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.