Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxy
<p>The toxicity of particulate matter (PM) is highly related to the concentration of particle-bound reactive oxygen species (ROS). Chemical properties, including dissolved metals and the sources of PM, influence ROS production and ROS oxidative potential. Here, the photochemical aging of a sec...
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Copernicus Publications
2025-06-01
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| Series: | Aerosol Research |
| Online Access: | https://ar.copernicus.org/articles/3/337/2025/ar-3-337-2025.pdf |
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| author | K. Kilchhofer K. Kilchhofer K. Kilchhofer A. Barth B. Utinger M. Kalberer M. Ammann |
| author_facet | K. Kilchhofer K. Kilchhofer K. Kilchhofer A. Barth B. Utinger M. Kalberer M. Ammann |
| author_sort | K. Kilchhofer |
| collection | DOAJ |
| description | <p>The toxicity of particulate matter (PM) is highly related to the concentration of particle-bound reactive oxygen species (ROS). Chemical properties, including dissolved metals and the sources of PM, influence ROS production and ROS oxidative potential. Here, the photochemical aging of a secondary organic aerosol proxy (citric acid, CA) with metal complexes (iron–citrate, Fe<span class="inline-formula"><sup>III</sup></span>(Cit)) is assessed toward the production of particle-bound ROS with an online instrument (OPROSI). We studied the photochemically induced redox chemistry in iron/copper–citrate particles experimentally with an aerosol flow tube (AFT), mimicking atmospheric UV aging. Experiments were performed at different relative humidity (RH) levels, leading to variation in the physicochemical properties of the particles, e.g., viscosity. We found that UV-aged CA aerosol containing 10 mol % Fe<span class="inline-formula"><sup>III</sup></span> generated ROS concentrations on the order of 0.1 <span class="inline-formula">nmol</span> <span class="inline-formula">H<sub>2</sub>O<sub>2</sub></span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">eq</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">µ</mi><msup><mi mathvariant="normal">g</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="dd43093c6f886134690f4611b85d85eb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ar-3-337-2025-ie00001.svg" width="41pt" height="15pt" src="ar-3-337-2025-ie00001.png"/></svg:svg></span></span>, indicating the photochemically driven formation of peroxides. An increase in RH leads to only a slight but overall lower concentration of ROS, possibly due to a loss of volatile <span class="inline-formula">HO<sub>2</sub></span> and <span class="inline-formula">H<sub>2</sub>O<sub>2</sub></span> in the gas phase in the less viscous particles. The RH effect is enhanced in absence of oxygen. Compared to the Fe<span class="inline-formula"><sup>III</sup></span>(Cit)/CA particles, the iron/copper–citrate samples show a uniformly decreased ROS level. Interestingly, in the high-RH nitrogen experiment with copper, we found an enhanced drop in the ROS concentration down to 0.02 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">nmol</mi><mspace width="0.125em" linebreak="nobreak"/><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mn mathvariant="normal">2</mn></msub><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">2</mn></msub></mrow><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">eq</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><mi mathvariant="normal">µ</mi></mrow><msup><mi mathvariant="normal">g</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="94pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="f5add010be387b3a06e915873c59efcf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ar-3-337-2025-ie00002.svg" width="94pt" height="16pt" src="ar-3-337-2025-ie00002.png"/></svg:svg></span></span> compared to all other irradiation experiments. We suggest that copper may suppress radical redox reactions, and when particles are more viscous, ROS are still produced with photochemistry, but the levels are more sensitive to the presence of copper than under humid or lower-viscosity conditions.</p> |
| format | Article |
| id | doaj-art-4b09814ce9b147ce82b9103672a86e1c |
| institution | Kabale University |
| issn | 2940-3391 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Aerosol Research |
| spelling | doaj-art-4b09814ce9b147ce82b9103672a86e1c2025-08-20T03:45:14ZengCopernicus PublicationsAerosol Research2940-33912025-06-01333734910.5194/ar-3-337-2025Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxyK. Kilchhofer0K. Kilchhofer1K. Kilchhofer2A. Barth3B. Utinger4M. Kalberer5M. Ammann6PSI Center for Energy and Environmental Sciences, Paul Scherrer Institute, 5232 Villigen, SwitzerlandDepartment of Environmental System Science, Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerlandnow at: Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center (PMOD/WRC), 7260 Davos, SwitzerlandDepartment of Environmental Sciences, University of Basel, 4056 Basel, SwitzerlandDepartment of Environmental Sciences, University of Basel, 4056 Basel, SwitzerlandDepartment of Environmental Sciences, University of Basel, 4056 Basel, SwitzerlandPSI Center for Energy and Environmental Sciences, Paul Scherrer Institute, 5232 Villigen, Switzerland<p>The toxicity of particulate matter (PM) is highly related to the concentration of particle-bound reactive oxygen species (ROS). Chemical properties, including dissolved metals and the sources of PM, influence ROS production and ROS oxidative potential. Here, the photochemical aging of a secondary organic aerosol proxy (citric acid, CA) with metal complexes (iron–citrate, Fe<span class="inline-formula"><sup>III</sup></span>(Cit)) is assessed toward the production of particle-bound ROS with an online instrument (OPROSI). We studied the photochemically induced redox chemistry in iron/copper–citrate particles experimentally with an aerosol flow tube (AFT), mimicking atmospheric UV aging. Experiments were performed at different relative humidity (RH) levels, leading to variation in the physicochemical properties of the particles, e.g., viscosity. We found that UV-aged CA aerosol containing 10 mol % Fe<span class="inline-formula"><sup>III</sup></span> generated ROS concentrations on the order of 0.1 <span class="inline-formula">nmol</span> <span class="inline-formula">H<sub>2</sub>O<sub>2</sub></span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">eq</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">µ</mi><msup><mi mathvariant="normal">g</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="dd43093c6f886134690f4611b85d85eb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ar-3-337-2025-ie00001.svg" width="41pt" height="15pt" src="ar-3-337-2025-ie00001.png"/></svg:svg></span></span>, indicating the photochemically driven formation of peroxides. An increase in RH leads to only a slight but overall lower concentration of ROS, possibly due to a loss of volatile <span class="inline-formula">HO<sub>2</sub></span> and <span class="inline-formula">H<sub>2</sub>O<sub>2</sub></span> in the gas phase in the less viscous particles. The RH effect is enhanced in absence of oxygen. Compared to the Fe<span class="inline-formula"><sup>III</sup></span>(Cit)/CA particles, the iron/copper–citrate samples show a uniformly decreased ROS level. Interestingly, in the high-RH nitrogen experiment with copper, we found an enhanced drop in the ROS concentration down to 0.02 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">nmol</mi><mspace width="0.125em" linebreak="nobreak"/><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mn mathvariant="normal">2</mn></msub><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">2</mn></msub></mrow><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">eq</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><mi mathvariant="normal">µ</mi></mrow><msup><mi mathvariant="normal">g</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="94pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="f5add010be387b3a06e915873c59efcf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ar-3-337-2025-ie00002.svg" width="94pt" height="16pt" src="ar-3-337-2025-ie00002.png"/></svg:svg></span></span> compared to all other irradiation experiments. We suggest that copper may suppress radical redox reactions, and when particles are more viscous, ROS are still produced with photochemistry, but the levels are more sensitive to the presence of copper than under humid or lower-viscosity conditions.</p>https://ar.copernicus.org/articles/3/337/2025/ar-3-337-2025.pdf |
| spellingShingle | K. Kilchhofer K. Kilchhofer K. Kilchhofer A. Barth B. Utinger M. Kalberer M. Ammann Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxy Aerosol Research |
| title | Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxy |
| title_full | Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxy |
| title_fullStr | Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxy |
| title_full_unstemmed | Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxy |
| title_short | Reactive oxygen species buildup in photochemically aged iron- and copper-doped secondary organic aerosol proxy |
| title_sort | reactive oxygen species buildup in photochemically aged iron and copper doped secondary organic aerosol proxy |
| url | https://ar.copernicus.org/articles/3/337/2025/ar-3-337-2025.pdf |
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