Creative Commons License

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

Abstract

Widespread efforts to abate ozone (O3) smog have significantly reduced emissions of nitrogen oxides (NOx) over the past 2 decades in the Southeast US, a place heavily influenced by both anthropogenic and biogenic emissions. How reactive nitrogen speciation responds to the reduction in NOx emissions in this region remains to be elucidated. Here we exploit aircraft measurements from ICARTT (July–August 2004), SENEX (June–July 2013), and SEAC4RS (August–September 2013) and long-term ground measurement networks alongside a global chemistry–climate model to examine decadal changes in summertime reactive oxidized nitrogen (RON) and ozone over the Southeast US. We show that our model can reproduce the mean vertical profiles of major RON species and the total (NOy) in both 2004 and 2013. Among the major RON species, nitric acid (HNO3) is dominant (∼ 42–45%), followed by NOx (31%), total peroxy nitrates (ΣPNs; 14%), and total alkyl nitrates (ΣANs; 9–12%) on a regional scale. We find that most RON species, including NOx, ΣPNs, and HNO3, decline proportionally with decreasing NOx emissions in this region, leading to a similar decline in NOy. This linear response might be in part due to the nearly constant summertime supply of biogenic VOC emissions in this region. Our model captures the observed relative change in RON and surface ozone from 2004 to 2013. Model sensitivity tests indicate that further reductions of NOxemissions will lead to a continued decline in surface ozone and less frequent high-ozone events.

Department

Earth Systems Research Center

Publication Date

2-16-2018

Journal Title

Atmospheric Chemistry and Physics

Publisher

European Geosciences Union (EGU)

Digital Object Identifier (DOI)

https://doi.org/10.5194/acp-18-2341-2018

Document Type

Article

Rights

© Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License.

Comments

This is an article published by European Geosciences Union in Atmospheric Chemistry and Physics in 2018, available online: https://doi.org/10.5194/acp-18-2341-2018

Share

COinS