the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Opinion: Atmospheric Multiphase Chemistry: Past, Present, and Future
Akkihebbal Ravishankara
Abstract. Multiphase chemistry occurs between chemicals in different atmospheric phases, typically involving gas-solid and gas-liquid interactions. The importance of atmospheric multiphase chemistry has long been recognized. Its central role extends from acid precipitation and stratospheric ozone depletion, to its impact on the oxidizing capacity of the troposphere, and to the roles that aerosol particles play in driving chemistry-climate interactions and affecting human health. This opinion article briefly introduces the subject of multiphase chemistry and tracks its development before and after the start of Atmospheric Chemistry and Physics. Most of the article focuses on research opportunities and challenges in the field. Central themes are that a fundamental understanding of the chemistry at the molecular level underpins the ability of atmospheric chemistry to accurately predict environmental change, and that the discipline of multiphase chemistry is strongest when tightly connected to atmospheric modeling and field observations.
Jonathan Abbatt and Akkihebbal Ravishankara
Status: open (until 17 Apr 2023)
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RC1: 'Comment on egusphere-2023-334', Anonymous Referee #1, 26 Mar 2023
reply
This is a well-written paper summarizing the area of multiphase chemistry and some important remaining challenges. It is difficult to appropriately reference all of the contributions to such a broad topic but overall, they have done a good job at this and the paper will be a valuable resource, especially to those not familiar with this area.
That said, a general comment is that there is some inconsistency in the referencing. In some cases, references are made to the original, foundational papers (e.g. line 77, Hoffmann and Edwards, 1975; Penkett et al., 1979; also references on lines 128, 130). In this reviewer’s opinion, this is excellent as there is an increasing tendency in the literature to only cite the last few years work that would not have happened without the seminal papers such as these. Since this paper will undoubtedly be read and highly cited, referencing the early work is important.
On the other hand, there are a number of instances where only recent papers are cited, and references to the earlier work would be helpful to a reader, e.g.,
Line 137: While Carpenter et al. (2013) have done very nice work on the ozone-iodide reaction, there are foundational papers on this that go back many decades before this that would be helpful to cite.
Line 167: Pankow et al. published many papers on partitioning and volatility starting in the 1980’s, which laid the foundation for the Donahue et al. subsequent studies, and should be cited.
Line 206: Optical properties and photodegradation of brown carbon are discussed in detail in a 2015 Chem Rev article by Laskin et al and should be cited in addition to Hems et al.
Line 249: Gligorovski et al published a number of papers on indoor OH (e.g. Atmos. Env., 2014) and indoor chemistry, long before the Sloan Foundation funding pushed this area to the fore. Some of his work should be cited.
Line 267: Some of the original work on particles translocating to the brain, e.g. Oberdorster et al., should be cited.
Line 306: Zelenyuk et al field measurements on shielding of PAH inside particles should also be cited.
Other reference suggestions:
Line 161: Citing broader treatments of health effects of particles would be appropriate, e.g. some of the Landrigan et al articles summarizing the results from the commission on pollution and health.
Lines 351-353: Adding some references supporting the statements about absorption spectra and quantum yields being different from those in the gas phase would be helpful to the reader. Also mentioning the effects of viscosity and matrix on these (e.g. Nizkorodov et al)
Line 359: Zelenyuk and their SPLAT should be included here.
Other comments:
Line 180: The impact of temperature on SOA formation is mentioned. However, growth of particles is also affected and should be mentioned.
Lines 211, 212: A brief description of what is meant by the deposition and immersion modes would be helpful to non-experts in the field.
Lines 256-259: I think this statement regarding the impacts on health is grossly understated. Particles have not been “implicated” as harmful, there is a ton of evidence showing they are. The statement that the toxicity mechanisms are not known is also somewhat misleading. For example, it has been known for decades that particles initiate an inflammatory response.
Line 291: The last sentence “It is not clear whether this effect is related to multiphase chemistry at biological surfaces” seems out of place. What is meant by this needs to be amplified or the sentence omitted.
Lines 309-311: The authors might want to mention that freezing also concentrates soluble species in the shrinking liquid layer, which can have significant impacts on the chemistry.
Section on chemical complexity: This is a nicely written section. In the complexity listed on lines 402-403, the authors might also want to mention the importance of the surface composition vs the bulk, e.g. Wingen et al, Chem Sci (2019).
Citation: https://doi.org/10.5194/egusphere-2023-334-RC1
Jonathan Abbatt and Akkihebbal Ravishankara
Jonathan Abbatt and Akkihebbal Ravishankara
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