Postdoctoral Fellowship: EAR-PF: Shifting Paradigms in Atmospheric Deposition: The Rise of Organic Solutes

Nitrogen (N) is essential for life, yet most of it exists as inert atmospheric N2, inaccessible to most living organisms. Only a small fraction of N – reactive N (Nr)– is biologically available and directly usable by plants and microbes. Bioavailable forms of N are exchanged between the atmosphere and terrestrial environments primarily through emission and precipitation, or wet deposition. Understandings of deposition are shifting, from a general focus on inorganic acidic solutes such as nitrate to a more complex and dynamic picture inclusive of dissolved organic N which encompasses any molecule with an organic carbon (C) backbone that also contains N. The chemical composition of precipitation can reveal landscape-scale emission sources of organic C, and by association N, to the atmosphere and the degree to which these complex organic molecules may participate in C and/or N cycles once deposited into ecosystems. The goal of this postdoctoral fellowship project is to advance the understanding of how organic C and N in precipitation originate, transform, and impact ecosystems. The research will explicitly test whether events such as forest fires, transpiration, and agricultural soil decomposition may individually or collectively drive the trends in organic matter deposition. The broader impacts of this research encompass quantifying biogeochemical links between the atmosphere and biosphere while also achieving stakeholder engagement, interdisciplinary collaboration, and teaching and mentoring of graduate and undergraduate students. The overarching research goal is to determine the contribution of organic matter in wet deposition, quantify how it impacts forested ecosystems, and identify the role of emission sources. During this fellowship, new atmospheric deposition samples will be collected and an archive of existing deposition samples will be leveraged, precipitation bioavailability and airmass origin will be evaluated, high-resolution molecular analyses will be conducted, and an Earth system model will be utilized to address several research questions. (1) What is the concentration, flux, and relative abundance of bioavailable organic compounds in wet deposition? (2) How does incorporating organic N into total deposition fluxes alter deposition gradients and the extent of area exceeding an ecosystems capacity to process N? (3) How responsive are wet deposition organic matter fluxes to landscape emissions from biogenic and anthropogenic sources? This interdisciplinary approach integrates atmospheric science, Earth systems science, and ecology by examining how climate dynamics, land use, and wildfire activity shape wet deposition chemistry and the cycling of essential elements. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.