Source contribution to ozone pollution during June 2021 fire events in Arizona: insights from WRF-Chem-tagged O<sub>3</sub> and CO
<p>This study quantifies wildfire contributions to O<span class="inline-formula"><sub>3</sub></span> pollution in Arizona, relative to local and regional emissions. Using WRF-Chem with O<span class="inline-formula"><sub>3</sub></...
Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-06-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/5591/2025/acp-25-5591-2025.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | <p>This study quantifies wildfire contributions to O<span class="inline-formula"><sub>3</sub></span> pollution in Arizona, relative to local and regional emissions. Using WRF-Chem with O<span class="inline-formula"><sub>3</sub></span> and CO tags, we analyzed emissions during June 2021, a period of drought, extreme heat, and wildfires. Our results show that background O<span class="inline-formula"><sub>3</sub></span> accounted for <span class="inline-formula">∼50</span> % of total O<span class="inline-formula"><sub>3</sub></span>, while local anthropogenic emissions contributed 24 %–40 %, consistent with recent estimates for Phoenix. During peak smoke conditions, fire-related O<span class="inline-formula"><sub>3</sub></span> ranged from 5 to 23 ppb (5 %–21 % of total O<span class="inline-formula"><sub>3</sub></span>), averaging 15 ppb (15 %). These estimates were compared with model sensitivity tests excluding fire emissions, which confirmed the spatiotemporal pattern of fire-driven O<span class="inline-formula"><sub>3</sub></span>, though the model underestimated the magnitude by a factor of 1.4. The results further demonstrate that wildfires exacerbate O<span class="inline-formula"><sub>3</sub></span> exceedances over urban areas. Our analysis reveals key differences in O<span class="inline-formula"><sub>3</sub></span> sources: Phoenix's O<span class="inline-formula"><sub>3</sub></span> was mainly driven by local emissions, while Yuma's was heavily influenced by transboundary transport from California and Mexico. Wildfires not only boosted O<span class="inline-formula"><sub>3</sub></span> formation but also altered winds and atmospheric chemistry in Phoenix and downwind areas. O<span class="inline-formula"><sub>3</sub></span> increases along the smoke plume resulted from NO<span class="inline-formula"><sub><i>X</i></sub></span> and volatile organic compound (VOC) interactions, with fire-driven O<span class="inline-formula"><sub>3</sub></span> forming in NO<span class="inline-formula"><sub><i>X</i></sub></span>-limited zones near the urban interface. Downwind, O<span class="inline-formula"><sub>3</sub></span> chemistry shifted, shaped by higher NO<span class="inline-formula"><sub><i>X</i></sub></span> in central Phoenix and more VOCs in suburban and rural areas. Winds weakened and turned westerly near fire-affected areas. This study highlights the value of high-resolution modeling with tagging to disentangle wildfire and regional O<span class="inline-formula"><sub>3</sub></span> sources, particularly in arid regions, where extreme heat intensifies O<span class="inline-formula"><sub>3</sub></span> pollution, making accurate source attribution essential.</p> |
|---|---|
| ISSN: | 1680-7316 1680-7324 |