Faculty Publications

Document Type

Article

Publication Version

Published Version

Journal/Book/Conference Title

Atmospheric Chemistry and Physics

Volume

21

Issue

2

First Page

951

Last Page

971

Abstract

We apply airborne measurements across three seasons (summer, winter and spring 2017-2018) in a multi-inversion framework to quantify methane emissions from the US Corn Belt and Upper Midwest, a key agricultural and wetland source region. Combing our seasonal results with prior fall values we find that wetlands are the largest regional methane source (32 %, 20 [16-23] Gg/d), while livestock (enteric/manure; 25 %, 15 [14-17] Gg/d) are the largest anthropogenic source. Natural gas/petroleum, waste/landfills, and coal mines collectively make up the remainder. Optimized fluxes improve model agreement with independent datasets within and beyond the study timeframe. Inversions reveal coherent and seasonally dependent spatial errors in the WetCHARTs ensemble mean wetland emissions, with an underestimate for the Prairie Pothole region but an overestimate for Great Lakes coastal wetlands. Wetland extent and emission temperature dependence have the largest influence on prediction accuracy; better representation of coupled soil temperature-hydrology effects is therefore needed. Our optimized regional livestock emissions agree well with the Gridded EPA estimates during spring (to within 7 %) but are g≈ 25 % higher during summer and winter. Spatial analysis further shows good top-down and bottom-up agreement for beef facilities (with mainly enteric emissions) but larger (g≈ 30 %) seasonal discrepancies for dairies and hog farms (with > 40 % manure emissions). Findings thus support bottom-up enteric emission estimates but suggest errors for manure; we propose that the latter reflects inadequate treatment of management factors including field application. Overall, our results confirm the importance of intensive animal agriculture for regional methane emissions, implying substantial mitigation opportunities through improved management.

Department

Department of Earth and Environmental Sciences

Comments

First published in Atmospheric Chemistry and Physics, v.21, pp. 951-971 (2021), by the European Geosciences Union. DOI: 10.5194/acp-21-951-2021

Original Publication Date

1-25-2021

Object Description

1 PDF file

DOI of published version

10.5194/acp-21-951-2021

Repository

UNI ScholarWorks, Rod Library, University of Northern Iowa

Copyright

©2021 by the Authors. CC BY license.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Language

en

File Format

application/pdf

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