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Title: Regional scale analysis of nitrous oxide emissions within the U.S. Corn Belt and the potential role of episodic hot spots

item GRIFFIS, T - University Of Minnesota
item LEE, X - Yale University
item Baker, John
item Russelle, Michael
item XHANG, X - Yale University
item MILLET, D - University Of Minnesota
item Venterea, Rodney - Rod

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2012
Publication Date: 12/3/2012
Citation: Griffis, T.J., Lee, X., Baker, J.M., Russelle, M.P., Xhang, X., Millet, D., Venterea, R.T. 2012. Regional scale analysis of nitrous oxide emissions within the U.S. Corn Belt and the potential role of episodic hot spots [abstract]. American Geophysical Union, San Francisco, CA. December 3-7, 2012. Abstract B52B-03.

Interpretive Summary:

Technical Abstract: Nitrous oxide (N2O) is a long-lived greenhouse gas that has the third largest radiative forcing on the Earth-Atmosphere system and has become the most important stratospheric ozone depleting substance of the 21st century. The rapid increase in N2O concentrations over the last century is primarily attributed to the Haber-Bosch process and the green revolution. Predicting future concentrations and developing mitigation strategies for N2O is a critical environmental challenge as pressure mounts on agricultural ecosystems to deliver more products to a burgeoning population. Bottom-up (process/inventory) and top-down (global) strategies are used to constrain the global N2O budget, but have been inadequately tested by data collected at the appropriate spatial and temporal scales. Two-years of tall tower (regional-scale) high-frequency N2O concentration data and boundary layer budget techniques were used to quantify the regional budget and assess bottom-up and top-down emission factors within the U.S. Corn Belt. Here we show that regional flux estimates were 2 to 9-fold greater than bottom-up emission estimates provided by the EDGAR, IPCC, and GEIA assessments. Using our regional flux data we derived “internal” and “external” emission factors that relate directly to the bottom-up and top-down perspectives on constraining the global N2O cycle. The internal and external emission factors were 4.0 and 5.6%, respectively, and significantly larger than that derived from bottom-up approaches. It is hypothesized that this bias is caused by episodic leakage mechanisms that can only be accounted for at the appropriate spatial and temporal scales. N2O emission hot spots from agricultural drainage ditches are shown to exceed 60 nmol m-2 s-1 and, at times, are about 60-fold greater than typical field-scale fluxes. Our data and analyses suggest that many field-scale studies that quantify greenhouse gas emissions will significantly underestimate the true net radiative forcing of agricultural ecosystems because of offsite leakage mechanisms.