the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 03 Mar 2025
Effectiveness of Emission Controls on Atmospheric Oxidation and Air Pollutant Concentrations: Uncertainties due to Chemical Mechanisms and Inventories
Abstract. In this study, three photochemical mechanisms of varying complexity from the Statewide Air Pollution Research Center (SAPRC) family and two widely used anthropogenic emission inventories are employed to quantify the discrepancies in the predicted effectiveness of nitrogen oxides (NOx) and volatile organic compound (VOC) emission controls on ozone (O3), secondary inorganic aerosols (SIA), and hydroxyl (OH) and nitrate (NO3) radicals using the Community Multiscale Air Quality (CMAQ) model. For maximum daily average 8-hour O3 (O3-8 h), relative reductions predicted using different emission inventory and mechanism combinations are consistent for up to 80 % NOx or VOC reductions, with maximum differences of approximately 15 %. For secondary inorganic aerosols (SIA), while the predicted relative changes in their daily average concentrations due to NOx reductions are quite similar, very large differences of up to 30 % occur for VOC reductions. Sometimes even the direction of change (i.e., increase or decrease) is different. For the oxidants OH and NO3 radicals, the uncertainties in the relative changes due to emission changes are even larger among different inventory-mechanism combinations, sometimes by as much as 200 %. Our results suggest that while the O3-8 h responses to emission changes are not sensitive to the choice of chemical mechanism and emission inventories, using a single model and mechanism to evaluate the effectiveness of emission controls on SIA and atmospheric oxidation capacity may have large errors. For these species, the evaluation of the control strategies may require an ensemble approach with multiple inventories and mechanisms.
- Preprint
(2980 KB) - Metadata XML
-
Supplement
(5265 KB) - BibTeX
- EndNote
Status: final response (author comments only)
-
RC1: 'Comment on egusphere-2025-255', Anonymous Referee #3, 08 May 2025
Overview comment
This manuscript provides the similarities and/or differences of responses due to the choice of chemical mechanism and emission inventories. I will agree with the final remark, “the evaluation of the control strategies may require an ensemble approach with multiple inventories and mechanisms,” for a better understanding of the model and clear guidance for policymakers. I could follow most parts of this manuscript; however, I am afraid that the manuscript may be hard to understand for those outside of modeling researcher. The fundamental revision, especially in the introduction and methodology, will be required. Please address the following comments.
Major comments
- Explanation of SAPRC mechanism: Lines 79-81, and even reading after Line 127-144 (Section 2.1), it was very hard to understand the SAPRC mechanism, especially for an unfamiliar researcher in modeling. Please rewrite and reorganize these parts to provide a clear introduction and explanation of the method.
- Configuration of experiments: Due to the inconsistency of the targeted year of the emission inventory, a large difference in the comparison is natural. What is the motivation for using different years? Because of this inconsistency of the year in the emission inventory and observation, how do we understand the result of the modeling evaluation (Section 3.1)? Unfortunately, without understanding this modeling comparison design, I cannot go on to read after Section 3.2.
Specific comments
- Line 100 and Lines 147-149: My simple question is why EDGAR was not used in this study. Please clarify the reason for the selection of MEIC and REAS in this study. From the website indicated in Line 148, REAS seems to be updated to 3.2.1. Why was the older version applied even though the release of the updated version?
- Line 161: The reason why July was analyzed in this study was unclear. Please clearly introduce this reason.
- Line 167: Why was S18-MEIC not conducted?
- Lines 172-195: Again, I wonder what the intention is of this discussion under the configuration of a different year’s emission inventory.
- Line 223: It is better to explicitly state “20, 40, 50, 60, and 80%”.
- Lines 251-253 (Figure 1): I understand that the emission outside China is unified by REAS. So, what stands for a larger difference over Mongolia, eastern Russia, Japan, and eastern India shown in Fig. 1(c)? Is this due to the different treatment in S11 and S18? Anyway, a detailed introduction to understand the differences in the SAPRC scheme is insufficient, and we do not follow these differences.
- Figures 3 and 4: The above comment could also be repeated for radicals of OH and NO3. A larger difference outside China was obvious in Fig. 3(c) and Fig. 4(c). However, there is no mention of these differences in Section 3.3. Please clarify.
- Figure 5: Same in Fig. 5(c).
Technical corrections
- Line 152: No need to spell out SAPRC.
- Lines 169-171: This sentence is redundant in Lines 155-156.
- Line 252 (and some parts in this manuscript): “summer” should be “July”.
Citation: https://doi.org/10.5194/egusphere-2025-255-RC1 -
AC1: 'Reply on RC1', Qi Ying, 21 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-255/egusphere-2025-255-AC1-supplement.pdf
-
CC1: 'Comment on egusphere-2025-255', Dazhong Yin, 09 Jun 2025
General comments
In the context modeling demonstration of emission control effectiveness, the general understanding is that models and model inputs all have uncertainties. The work presented in the manuscript investigated two aspects of these: gas-phase chemical mechanisms and emissions inventories. To certain extent, other factors such as meteorological driving fields could cause even larger uncertainties.
To address these uncertainties, some well-established approaches, such as those used in the United States for regulatory air quality modeling purposes, do not use model results in an absolute sense as done in this work. Rather, the emissions control effectiveness is assessed using the combination of observations and modeled relative changes. The appropriateness of the methodology in this work seems to be questionable.
Specific comments
Section 2.1: It will be good to add a table summarizing main features for CS07, S11, S18 mechanisms, for example, the number of species, the number of reactions, major updates.
Line 159: CMAQ also includes SAPRC07 mechanism, is CS07 different from the SAPRC07 mechanism in the CMAQ model?
Line 165: Is there any reason why S18-MEIC is not simulated?
Section 2.4: Are emission reductions limited to anthropogenic emissions, or it also applies to biogenic and fire emissions? The last sentence in this section needs some clarifications.
Page 7, first paragraph: Since inorganic aerosols are also investigated, in the emissions comparisons, particulate matter emissions should be included as well.
Section 3.1, model performance evaluation: is there any PM2.5 chemical component measurement that can be used to evaluate model performance for inorganic aerosols (i.e., ammonium sulfate and ammonium nitrate). Also how does the model perform for NOx, SO2, or selected VOCs (if possible)?
Line 242: The reference to the US EPA model performance criteria needs to be listed.
Figure 1: Why is O3-8hr noticeably lower over the yellow sea when comparing S11-REAS to S11-MEIC?
Line 274-286 and Figure 2: Model difference is presented for SIA (secondary inorganic aerosol). It is probably clearer if ammonium sulfate and ammonium nitrate are presented separately instead of being in a combined SIA. It will also help explain the impact of emission reductions on SIA concentrations. In addition, SIA is not clearly defined in the manuscript. What is included in SIA? How are the model primary inorganic aerosols separated from SIA?
Line 314, section 3.4: Is there any column concentrations data for HCHO that can be used to evaluate model performance for HCHO?
Figure 6: Why does Shenzhen seem to be least responsive to emission reductions?
Line 385-386: The explanation of the impact of VOC control on SIA concentrations seems to be too brief. More in-depth discussion will be helpful. For example, sulfate and nitrate probably need to be separated; maybe even PAN formation needs to be in the discussion.
Line 460: Why NO3 radical concentrations are much higher in northern China than southern China?
Section 3.5.4. HCHO concentration decreases duo to NOx emissions reductions are attributed to decrease of OH and NO3 levels. A conclusion is drawn indicating that secondary formation is the dominant source of HCHO. But the reduction of VOC emissions lead to steeper decreasing of HCHO. The VOC emissions reductions also cause OH and NO3 level increases as stated in the previous sections. These seem contradictory to the dominant secondary source conclusion.
Citation: https://doi.org/10.5194/egusphere-2025-255-CC1 -
AC3: 'Reply on CC1', Qi Ying, 21 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-255/egusphere-2025-255-AC3-supplement.pdf
-
AC3: 'Reply on CC1', Qi Ying, 21 Jun 2025
-
RC2: 'Comment on egusphere-2025-255', Anonymous Referee #4, 12 Jun 2025
This study investigated the uncertainties of emission controls on atmospheric oxidation and air pollutant concentrations by comparing different chemical mechanisms and inventories using an advanced CMAQ model. The manuscript is well-organized, clearly written, and the conclusions are well-supported by the presented data. These findings are timely and provide valuable insights for designing effective region-specific emission control strategies. I recommend this manuscript for publication in ACP after addressing the following minor revisions.
Minor suggestions:
- Line 28: Since the full name of SIA has already been introduced, the abbreviation can be used directly here.
- Lines 181-183: The statement “Note that OLE and TRP1 emissions are for the S11 mechanisms” is somewhat unclear. The authors should rephrase this sentence to improve clarity.
- Lines 241-243: The criteria suggested by the US EPA are better to be stated in the text for clarity.
- Lines 246-247: The current justification appears weak. The authors should revise this sentence.
- Lines 257-258: The authors attribute high O3 levels over water bodies to lower O3 dry deposition velocities over the ocean. Is there existing literature supporting this argument? A reference is need here.
- Line 274: The full term for SIA should be provided upon its first appearance in the main text. In addition, Figure 7 should explicitly list the SIA components for clarity.
- Lines 494 and 497: Since O3-8h and SIA have been previously defined, the abbreviation can be used directly without reintroducing the full terms.
Citation: https://doi.org/10.5194/egusphere-2025-255-RC2 -
AC2: 'Reply on RC2', Qi Ying, 21 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-255/egusphere-2025-255-AC2-supplement.pdf
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 192 | 40 | 19 | 251 | 18 | 12 | 14 |
- HTML: 192
- PDF: 40
- XML: 19
- Total: 251
- Supplement: 18
- BibTeX: 12
- EndNote: 14
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1