Reactive nitrogen in and around the northeastern and mid-Atlantic US: sources, sinks, and connections with ozone
<p>This study describes the application of a regional Earth system model with updated parameterizations for selected land–atmosphere exchange processes and multiplatform, multidisciplinary observations. We estimate reactive nitrogen (Nr <span class="inline-formula">=</span&g...
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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/1449/2025/acp-25-1449-2025.pdf |
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| Summary: | <p>This study describes the application of a regional Earth system model with updated parameterizations for selected land–atmosphere exchange processes and multiplatform, multidisciplinary observations. We estimate reactive nitrogen (Nr <span class="inline-formula">=</span> NO<span class="inline-formula"><sub><i>y</i></sub>+</span> NH<span class="inline-formula"><sub><i>x</i></sub></span>) emissions from various sources, surface and column nitrogen dioxide (NO<span class="inline-formula"><sub>2</sub></span>), and total and speciated Nr dry and wet deposition during 2018–2023 over the northeastern and mid-Atlantic US where nitrogen-oxide-limited or transitional chemical regimes dominate. The estimated Nr concentrations and deposition fluxes are related to ozone (O<span class="inline-formula"><sub>3</sub></span>) in terms of spatiotemporal variability and its key drivers as well as possible ecosystem impacts. Modeled surface O<span class="inline-formula"><sub>3</sub></span> persistently agrees well with observations, with root mean square errors staying within 4–7 ppbv for individual years in May–June–July. Model-based surface O<span class="inline-formula"><sub>3</sub></span>–NO<span class="inline-formula"><sub>2</sub></span> column correlation, which shows a dependency on column formaldehyde <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="880d1b22cfae9b4167ff115d05c6894c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-1449-2025-ie00001.svg" width="8pt" height="14pt" src="acp-25-1449-2025-ie00001.png"/></svg:svg></span></span> NO<span class="inline-formula"><sub>2</sub></span>, is higher in 2020 (<span class="inline-formula"><i>r</i>=0.62</span>) than in other years (<span class="inline-formula"><i>r</i>=0.47</span>–0.56). Ozone vegetative uptake overall dropped by <span class="inline-formula">∼10 <i>%</i></span> from 2018 to 2023, displaying clearer downward temporal changes than total Nr deposition as declining NO<span class="inline-formula"><sub><i>y</i></sub></span> emission and deposition competed with increasing NH<span class="inline-formula"><sub><i>x</i></sub></span> fluxes. It is highlighted that temporal variabilities of Nr and O<span class="inline-formula"><sub>3</sub></span> concentrations and fluxes on subregional to local scales respond to hydrological variability that can be influenced by precipitation and controllable human activities like irrigation. Deposition and biogenic emissions that are highly sensitive to interconnected environmental and plant physiological conditions, plus extra-regional sources (e.g., O<span class="inline-formula"><sub>3</sub></span>-rich stratospheric air and dense wildfire plumes from upwind regions), have been playing increasingly important roles in controlling pollutant budgets as local emissions decline owing to effective emission regulations and COVID lockdowns.</p> |
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| ISSN: | 1680-7316 1680-7324 |