Measurement report: Observation-based formaldehyde production rates and their relation to OH reactivity around the Arabian Peninsula
<p>Formaldehyde (<span class="inline-formula">HCHO</span>) is the most abundant aldehyde in the troposphere. While its background mixing ratio is mostly determined by the oxidation of methane, in many environments, especially in the boundary layer, <span class="in...
Guardado en:
| Autores principales: | , , , , , , , , , , , , , , , , , , , , |
|---|---|
| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
|
| Materias: | |
| Acceso en línea: | https://doaj.org/article/6f0bd171a3334f9cb6d8cf85efa34ee8 |
| Etiquetas: |
Agregar Etiqueta
Sin Etiquetas, Sea el primero en etiquetar este registro!
|
| Sumario: | <p>Formaldehyde (<span class="inline-formula">HCHO</span>) is the most abundant aldehyde in the troposphere. While its background mixing ratio is mostly determined by the oxidation
of methane, in many environments, especially in the boundary layer, <span class="inline-formula">HCHO</span> can have a large variety of precursors, in particular biogenic and
anthropogenic volatile organic compounds (VOCs) and their oxidation products. Here we present shipborne observations of <span class="inline-formula">HCHO</span>, hydroxyl radical (OH)
and OH reactivity (<span class="inline-formula">R(OH)</span>), which were obtained during the Air Quality and Climate Change in the Arabian Basin (AQABA) campaign in summer 2017. The loss
rate of <span class="inline-formula">HCHO</span> was inferred from its reaction with OH, measured photolysis rates and dry deposition. In photochemical steady state, the <span class="inline-formula">HCHO</span> loss is
balanced by production via OH-initiated degradation of VOCs, photolysis of oxygenated VOCs (<span class="inline-formula">OVOCs</span>) and the ozonolysis of alkenes. The slope
<span class="inline-formula"><i>α</i><sub>eff</sub></span> from a scatter plot of the <span class="inline-formula">HCHO</span> production rate versus the product of OH and <span class="inline-formula">R(OH)<sub>eff</sub></span> (excluding inorganic
contribution) yields the fraction of OH reactivity that contributes to <span class="inline-formula">HCHO</span> production. Values of <span class="inline-formula"><i>α</i><sub>eff</sub></span> varied between less than
2 % in relatively clean air over the Arabian Sea and the southern Red Sea and up to 32 % over the polluted Arabian Gulf (also known as
Persian Gulf), signifying that polluted areas harbor a larger variety of <span class="inline-formula">HCHO</span> precursors. The separation of <span class="inline-formula">R(OH)<sub>eff</sub></span> into individual
compound classes revealed that elevated values of <span class="inline-formula"><i>α</i><sub>eff</sub></span> coincided with increased contribution of alkanes and OVOCs, with the highest
reactivity of all VOCs over the Arabian Gulf.</p> |
|---|