SOURCE APPORTIONMENT OF URBAN AND RURAL REACTIVE NITROGEN EMISSIONS

Reactive nitrogen emissions, including NO_x and NH₃, are significant contributors to global water and air quality degradation. The atmospheric lifetimes of NO_x and NH₃ (and their oxidation products) allow transport of reactive N across large urban to rural regions. Thus, it is important to improve our understanding of the sources, transport, and fate of reactive N in the environment. This research lays the foundation for using isotopic data to apportion sources of reactive nitrogen deposition. Here, we present a comprehensive inventory of the isotopic composition of reactive N sources. To accomplish this reactive N source sampling locations included a concentrated animal feeding operation (CAFO), livestock barns, a conventionally managed cornfield, coal-fired power plants, a tallgrass prairie, and a highly trafficked tunnel. In particular, we address the largest NO_x emission source in the U.S., fossil fuel combustion. We characterize the isotopic composition of NO_x derived from both mobile and stationary source NO_x. Further, we use transects radiating out from agricultural emission sources to demonstrate how reactive N sources can be traced across landscapes using isotopes.