Unexpected slowdown of US pollutant emission reduction in the past decade

Zhe Jiang*, Brian C. McDonald, Helen Worden, John R. Worden, Kazuyuki Miyazaki, Zhen Qu, Daven K. Henze, Dylan B.A. Jones, Avelino F. Arellano, Emily V. Fischer, Liye Zhu, K. Folkert Boersma

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

49 Citations (Scopus)

Abstract

Ground and satellite observations show that air pollution regulations in the United States (US) have resulted in substantial reductions in emissions and corresponding improvements in air quality over the last several decades. However, large uncertainties remain in evaluating how recent regulations affect different emission sectors and pollutant trends. Here we show a significant slowdown in decreasing US emissions of nitrogen oxides (NOx) and carbon monoxide (CO) for 2011–2015 using satellite and surface measurements. This observed slowdown in emission reductions is significantly different from the trend expected using US Environmental Protection Agency (EPA) bottom-up inventories and impedes compliance with local and federal agency air-quality goals. We find that the difference between observations and EPA’s NOx emission estimates could be explained by: (i) growing relative contributions of industrial, area, and off-road sources, (ii) decreasing relative contributions of on-road gasoline, and (iii) slower than expected decreases in on-road diesel emissions.

Original languageEnglish
Pages (from-to)5099-5104
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number20
DOIs
Publication statusPublished - 15 May 2018

Keywords

  • Decadal scale variation
  • Emission regulations
  • Nitrogen oxides

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