Changing aerosol chemistry is redefining HONO sources
Abstract Heterogeneous reactions of NO2 on particulate matter have been considered an important source of HONO (Nitrous acid) in the troposphere, whereas its contribution is controversial due to the lack of uptake coefficient of NO2 (γNO2) on the surfaces of ambient particulate matter (PM). Here we...
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-06-01
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| Series: | Nature Communications |
| Online Access: | https://doi.org/10.1038/s41467-025-60614-7 |
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| Summary: | Abstract Heterogeneous reactions of NO2 on particulate matter have been considered an important source of HONO (Nitrous acid) in the troposphere, whereas its contribution is controversial due to the lack of uptake coefficient of NO2 (γNO2) on the surfaces of ambient particulate matter (PM). Here we investigate the the γNO2 to form HONO and its evolution based on long-term comprehensive field observations (2019–2023) in Beijing and a random forest model with Shapley additive explanations. The γNO2 on ambient PM is on the order of 10−6, decreasing markedly from 3.07 ± 5.99 × 10−6 in 2019 to 1.43 ± 3.22 × 10−6 in 2023. This decrease is driven by the increase in aerosol pH, linked to increased ratio of NH4NO3 to (NH4)2SO4, resulting from an unbalanced desulfurization and denitrification. This study implies that the role of the heterogeneous reaction of NO2 on aerosol surfaces in HONO production is declining in Beijing, providing valuable insights into the atmospheric chemistry in urban environments. |
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| ISSN: | 2041-1723 |