Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning
Chamber secondary organic aerosol (SOA) from low-NO<sub>x</sub> photooxidation of naphthalene by hydroxyl radical was examined with respect to its redox cycling behaviour using the dithiothreitol (DTT) assay. Naphthalene SOA was highly redox-active, consuming DTT at an average rate of 11...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2013-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/13/9731/2013/acp-13-9731-2013.pdf |
| _version_ | 1818586755705602048 |
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| author | R. D. McWhinney S. Zhou J. P. D. Abbatt |
| author_facet | R. D. McWhinney S. Zhou J. P. D. Abbatt |
| author_sort | R. D. McWhinney |
| collection | DOAJ |
| description | Chamber secondary organic aerosol (SOA) from low-NO<sub>x</sub> photooxidation of naphthalene by hydroxyl radical was examined with respect to its redox cycling behaviour using the dithiothreitol (DTT) assay. Naphthalene SOA was highly redox-active, consuming DTT at an average rate of 118 ± 14 pmol per minute per μg of SOA material. Measured particle-phase masses of the major previously identified redox active products, 1,2- and 1,4-naphthoquinone, accounted for only 21 ± 3% of the observed redox cycling activity. The redox-active 5-hydroxy-1,4-naphthoquinone was identified as a new minor product of naphthalene oxidation, and including this species in redox activity predictions increased the predicted DTT reactivity to 30 ± 5% of observations. These results suggest that there are substantial unidentified redox-active SOA constituents beyond the small quinones that may be important toxic components of these particles. A gas-to-SOA particle partitioning coefficient was calculated to be (7.0 ± 2.5) × 10<sup>−4</sup> m<sup>3</sup> μg<sup>−1</sup> for 1,4-naphthoquinone at 25 °C. This value suggests that under typical warm conditions, 1,4-naphthoquinone is unlikely to contribute strongly to redox behaviour of ambient particles, although further work is needed to determine the potential impact under conditions such as low temperatures where partitioning to the particle is more favourable. Also, higher order oxidation products that likely account for a substantial fraction of the redox cycling capability of the naphthalene SOA are likely to partition much more strongly to the particle phase. |
| first_indexed | 2024-12-16T08:58:01Z |
| format | Article |
| id | doaj.art-cdda3af93c174311a7885d020b065996 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-16T08:58:01Z |
| publishDate | 2013-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-cdda3af93c174311a7885d020b0659962022-12-21T22:37:14ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242013-10-0113199731974410.5194/acp-13-9731-2013Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioningR. D. McWhinneyS. ZhouJ. P. D. AbbattChamber secondary organic aerosol (SOA) from low-NO<sub>x</sub> photooxidation of naphthalene by hydroxyl radical was examined with respect to its redox cycling behaviour using the dithiothreitol (DTT) assay. Naphthalene SOA was highly redox-active, consuming DTT at an average rate of 118 ± 14 pmol per minute per μg of SOA material. Measured particle-phase masses of the major previously identified redox active products, 1,2- and 1,4-naphthoquinone, accounted for only 21 ± 3% of the observed redox cycling activity. The redox-active 5-hydroxy-1,4-naphthoquinone was identified as a new minor product of naphthalene oxidation, and including this species in redox activity predictions increased the predicted DTT reactivity to 30 ± 5% of observations. These results suggest that there are substantial unidentified redox-active SOA constituents beyond the small quinones that may be important toxic components of these particles. A gas-to-SOA particle partitioning coefficient was calculated to be (7.0 ± 2.5) × 10<sup>−4</sup> m<sup>3</sup> μg<sup>−1</sup> for 1,4-naphthoquinone at 25 °C. This value suggests that under typical warm conditions, 1,4-naphthoquinone is unlikely to contribute strongly to redox behaviour of ambient particles, although further work is needed to determine the potential impact under conditions such as low temperatures where partitioning to the particle is more favourable. Also, higher order oxidation products that likely account for a substantial fraction of the redox cycling capability of the naphthalene SOA are likely to partition much more strongly to the particle phase.http://www.atmos-chem-phys.net/13/9731/2013/acp-13-9731-2013.pdf |
| spellingShingle | R. D. McWhinney S. Zhou J. P. D. Abbatt Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning Atmospheric Chemistry and Physics |
| title | Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning |
| title_full | Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning |
| title_fullStr | Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning |
| title_full_unstemmed | Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning |
| title_short | Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning |
| title_sort | naphthalene soa redox activity and naphthoquinone gas particle partitioning |
| url | http://www.atmos-chem-phys.net/13/9731/2013/acp-13-9731-2013.pdf |
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