Related Experiment Video
Updated: Jun 8, 2026
07:14
Automated, High-resolution Mobile Collection System for the Nitrogen Isotopic Analysis of NOx
Published on: December 20, 2016
11.6K
Improved Spatial Resolution in Modeling of Nitrogen Oxide Concentrations in the Los Angeles Basin
Katelyn A Yu1,2, Meng Li2,3, Colin Harkins2,3
1Department of Civil and Environmental Engineering, University of California, Berkeley, Berkeley, California 94720, United States.
Environmental Science & Technology
|November 30, 2023
Summary
This study reveals on-road vehicles contribute significantly to nitrogen oxide (NOx) emissions in Southern California, with a fuel-based inventory suggesting higher emissions than official estimates. These findings impact air quality policy and vehicle emission control strategies.
Area of Science:
- Atmospheric Chemistry
- Environmental Science
- Transportation Emissions
Background:
- Accurate estimation of anthropogenic nitrogen oxide (NOx) emissions from motor vehicles is crucial for effective air quality management.
- Uncertainty exists regarding the actual impact of emission control technologies and policies on reducing vehicle NOx emissions.
Purpose of the Study:
- To evaluate a novel fuel-based emission inventory for Southern California during the RECAP-CA field campaign in June 2021.
- To assess the contribution of on-road vehicles to NOx emissions in the South Coast Air Basin and compare it with existing inventories.
Main Methods:
- A modified Fuel-based Inventory of Vehicle Emissions (FIVE) model with 1.3 km resolution and a new light-/medium-duty diesel category was utilized.
- The WRF-Chem model predicted NOx concentrations and weekday-weekend differences, validated with satellite and aircraft observations.
- Comparison of the fuel-based inventory with the South Coast Air Quality Management District's planning inventory and the EMFAC model.
Main Results:
- The fuel-based inventory indicates on-road vehicles accounted for 55-72% of NOx emissions in the South Coast Air Basin, higher than the planning inventory's 43%.
- Weekend decreases in NOx were primarily attributed to changes in on-road vehicle emissions.
- The fuel-based inventory suggests on-road NOx emissions are 1.5x (gasoline), 2.8x (light-/medium-duty diesel), and 1.3x (heavy-duty diesel) higher than EMFAC estimates.
Conclusions:
- On-road vehicles are a dominant source of NOx emissions in Southern California, potentially underestimated by current planning inventories.
- The developed fuel-based inventory provides a more refined estimate of vehicle NOx emissions, crucial for targeted air pollution control strategies.
- Findings highlight the need to re-evaluate emission control effectiveness and inform future transportation and air quality policies.
