Understanding Reactive Nitrogen Recycling on Soil and Mineral Dust Surfaces
EMSL Project ID
49808
Abstract
A fundamental understanding of the factors controlling the lifetime and fate of reactive nitrogen oxides (NOy = NO, NO2, HNO2, N2O5, etc.) in the atmosphere is critical for accurately representing ozone (O3) and aerosol formation rates in air pollution and climate change models. Bare soil is a substrate with high reactivity and surface area that comprises 28% of terrestrial surfaces, while soil-derived dust is an important aerosol constituent. Thus, interactions between NOy reservoir species and soil likely play a more important role in NOy recycling than previously realized. Despite the importance of soil to the global terrestrial-atmospheric cycling of nitrogen affecting air pollution and climate, interactions of N2O5 and HNO2 with soil are not well understood. Uncertainty in these processes is problematic because it means that NOy is not properly represented in the Earth-systems models used for prediction and regulation. The objective of this project is to understand the reactivity of N2O5 and HNO2 with soil and mineral dust surfaces, with a particular emphasis on quantifying reactive uptake on the role of soil organic matter (SOM = humic substances) and elucidating the mechanisms that return NOy back to the atmosphere where it can contribute to aerosol and O3 formation. The central hypothesis is that reactions of N2O5 and HNO2 with soil organic matter lead to the incorporation of N into SOM, which is photolabile and can release NOy back into the atmosphere during the following day. The hypothesis will be tested via reactivity studies using a coated-wall flow reactor and surface-sensitive analytical methods such as nanospray desorption electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy, Raman microscopy, and high spatial resolution secondary ion mass spectrometry, that are uniquely available at EMSL. Results from our kinetic studies will be used in the WRF-Chem chemical transport model to evaluate the impact of atmospheric N2O5 and HNO2 deposition to aerosol and soil surfaces and subsequent daytime photochemistry. It is anticipated that this work will yield: (1) Unprecedented molecular-level insights into the mechanisms of NOy reaction with soil organic matter; (2) critical insight into an abiotic mechanism associated with daytime NOy release from soil organic matter; (3) new parameterizations for N2O5 reactive uptake onto soil surfaces. The proposed work is significant because, in addition to revealing new mechanisms of NOy uptake and release from soil dust, it will provide the kinetics data needed to advance our ability to model the fate of NOy in soil and the atmosphere.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2017-10-01
End Date
2019-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Hansen R.F., R.B. Abney, M.H. Engelhard, D.P. Veghte, S. China, and J.D. Raff. 12/12/2018. "Investigation of the Mechanism of the Reaction of Soil Organic Matter with N2O5." Presented by R.F. Hansen at AGU Fall 2018, Washington, District Of Columbia. PNNL-SA-140108.