the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Apr 2024
Source analyses of ambient VOCs considering reactive losses: methods of reducing loss effects, impacts of losses, and sources
Abstract. Chemical losses of ambient reactive volatile organic compounds (VOCs) is a long-term issue yet to be resolved in VOC source apportionments. These losses substantially reduce the concentrations of highly reactive species in the apportioned factor profiles and result in the underestimation of source contributions. This review assesses the common methods and existing issues in ways to reduce losses and loss impacts in source analyses and suggest research directions for improved VOC source apportionments. Positive Matrix Factorization (PMF) is now the main VOC source analysis method compared to other mathematical models. The issue in using any apportionment tool is the processing of the data to be analyzed to reduce the impacts of reactive losses. Estimating the initial concentrations of ambient VOCs based on photochemical age has become the primary approach to reduce reactive loss effects in PMF except for selecting low reactivity species or nighttime data into the analysis. Currently, the initial concentration method only considers daytime reactions with hydroxyl (•OH) radicals. However, the •OH rate constants vary with temperature and that has not been considered. Losses from reactions with O3 and NO3 radicals especially for alkene species remain to be included. Thus, the accuracy of the photochemical-age estimation is uncertain. Beyond developing accurate quantitative approaches for reactive losses, source analyses methods for the consumed VOCs and the accurate quantification of different source contributions to O3 and secondary organic aerosols are important additional directions for future research.
- Preprint
(1296 KB) - Metadata XML
-
Supplement
(959 KB) - BibTeX
- EndNote
Status: open (until 01 Jul 2024)
-
RC1: 'Comment on egusphere-2024-916', Anonymous Referee #1, 16 May 2024
reply
Liu et al., reviews publications that focus on addressing chemical loss from source analyses. They summarize the methods and their limitations for reducing losses and addressing the loss impact. They also discuss the chemical losses of VOCs in different cities in China and the source contributions of consumed VOCs. The authors need to reconsider the type of the manuscript, as this article is better suited to “Review article” than “Research articles”.
- The title can be re-phrased to clearly convey the message of this review article.
- The sections 3.1.1 and 3.1.3 describe the methods for reducing the impact of reactive losses in PMF and CMB, respectively. Why does section 3.1.2 only discuss OVOC? Similarly, for Figure 1, why is PAPM presented as a method parallel to PMF and CMB while it only focuses on OVOCs?
- Section 3.1.1.1: To my understanding, incorporating night only data into PMF is a way to diagnose emissions at night, and it is not considered as a method to reduce the reactive loss in PMF source analyses.
- Section 3.2: this section discusses the impact of quantifying reactive losses on source analyses, however, not many studies have described the impacts. I don’t think it should be a result section, instead, it could be moved up to introduction.
- Section 3.3: the authors should clarify the difference between “reducing the impact of chemical losses in section 3.1” and “estimating VOC reactive losses in Section 3.3”. For instance, both sections discuss the photochemical age-based parametrization method, which may be redundant.
- Line 487-488: why were studies on VOC photochemical losses mainly conducted in Chinese cities? How does these studies differ from those in other cities? I would suspect that the impact of VOC chemical losses would be larger over cities with higher BVOC abundance, such as those in Southeast US.
Citation: https://doi.org/10.5194/egusphere-2024-916-RC1 -
RC2: 'Comment on egusphere-2024-916', Anonymous Referee #2, 01 Jun 2024
reply
Liu et al. present a review of methods used to estimate and account for reactive losses when assessing VOC emission sources and production of secondary pollutants. They also advocate for further investigations regarding consumed VOCs to elucidate secondary pollution. Overall, this article fits the scope of the journal as it addresses important questions regarding emission source characterization and photochemical processing. I would recommend publication after addressing the comments below.
- Title should incorporate “review” for the sake of the reader.
- Section 2 – Give more details of the literature search rather than make the reader go to the SI for more information. You note that 41% of the articles were in the last 5 years. Explicitly note that this fact suggests you’re including some of the most up-to-date analyses in your review. Separately, how many of the 151 papers were on studies done in China vs N America vs Europe vs other (provides context for your statement on lines 487-488 about most studies being conducted in Chinese cities)? Are you missing major journal publishers (e.g., ACS or AGU)?
- Line 161 – specify evaporative gasoline sources were not resolved.
- Line 240 – revise this sentence “…species had no the change…”
- Line 340 – Formed by oxidation of precursors with OH radicals, …
- Line 343 – Is there a reason why this tracer method is presented as only used with OVOCs? The same method can be used to retrieve emission ratios of hydrocarbons by simply removing the precursor term. In general, you should note equation 8 (and similar can be said for many other methods discussed here) represents one use case and can be adapted to an individual study. For example, more than one tracer can be used to address multiple emissions sources and apportion a VOC of interest.
- Line 386-389 – Of the references used just here, Wang et al., 2017 introduced the m coefficient, not Huang et al., nor Zhu et al. Also, I think you mis-cite de Gouw et al., 2005 when mentioning that photolysis is proportional to OH – given that you mention that de Gouw et al., 2005 don’t consider photolytic losses in the first place. Perhaps you meant de Gouw et al., 2018 (cited alongside Wang et al, 2017 by Huang et al.’s discussion of this topic)?
- Section 3.2 – there is no real discussion/synthesis of ideas here. This section reads more like an introduction than results.
- Figure 2 – I may be misunderstanding; should the sum of the measured concentration and reactive loss bars add up to the initial concentration bar?
- Figure 2 – it would reduce ambiguity to add a line between the panels and the dots representing the cities.
- Figure 3 – Some clean-up is necessary. Beijing b panel, some percentages overlap. All pie charts, the small fractions (e.g., 0.2% in the Tianjin panel) are impossible to see the color/VOC class. Also, be mindful of red/green colorblind readers.
- Table S6 – specify local time in the table header.
References
de Gouw, J. A., Gilman, J. B., Kim, S.-W., Alvarez, S. L., Dusanter, S., Graus, M., Griffith, S. M., Isaacman‐VanWertz, G., Kuster, W. C., Lefer, B. L., Lerner, B. M., McDonald, B. C., Rappenglück, B., Roberts, J. M., Stevens, P. S., Stutz, J., Thalman, R., Veres, P. R., Volkamer, R., Warneke, C., Washenfelder, R. A., and Young, C. J.: Chemistry of Volatile Organic Compounds in the Los Angeles Basin: Formation of Oxygenated Compounds and Determination of Emission Ratios, J. Geophys. Res. Atmospheres, 123, 2298–2319, https://doi.org/10.1002/2017JD027976, 2018.
Citation: https://doi.org/10.5194/egusphere-2024-916-RC2
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 290 | 92 | 22 | 404 | 36 | 12 | 14 |
- HTML: 290
- PDF: 92
- XML: 22
- Total: 404
- Supplement: 36
- BibTeX: 12
- EndNote: 14
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1