Measurement report: The 10-year trend of PM<sub>2.5</sub> major components and source tracers from 2008 to 2017 in an urban site of Hong Kong, China

Chow, Wing Sze; Liao, Kezheng; Huang, X. H. Hilda; Leung, Ka Fung; Lau, Alexis K. H.; Yu, Jian Zhen

doi:https://doi.org/10.5194/acp-22-11557-2022

Articles | Volume 22, issue 17

https://doi.org/10.5194/acp-22-11557-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-22-11557-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 22, issue 17

Measurement report

|

08 Sep 2022

Measurement report |

| 08 Sep 2022

Measurement report: The 10-year trend of PM_2.5 major components and source tracers from 2008 to 2017 in an urban site of Hong Kong, China

Wing Sze Chow, Kezheng Liao, X. H. Hilda Huang, Ka Fung Leung, Alexis K. H. Lau, and Jian Zhen Yu

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Final revised paper (published on 08 Sep 2022)
Supplement to the final revised paper
Preprint (discussion started on 07 Mar 2022)
Supplement to the preprint

Interactive discussion

Status: closed

RC1:
'Comment on acp-2022-100', Anonymous Referee #1, 22 Mar 2022
The essential information for major sources as well as evaluation and planning of control measures in Hong Kong, China, was proposed based on 10 years of long-term monitoring data of PM_2.5. Overall, it is an interesting study. The test and analysis procedures are reliable and the amount of data are sufficient. The manuscript can be accepted with the following revisions:

Chlorine loss of sea salt aerosol was always found in the sampling area, however, particulate chloride were not found in the chemical analysis and long term variation analysis. It was also suggested to analyze the trend variation of Criteria gaseous pollutant data.

Figure 1: The resolution of Figure 1 needs to be improved.

Lines 100-113: The authors collected blank samples as a background correction? and how were filter samples stored after collection? More information about sampling and storage should be presented in Ms.

Double “in” were found in line 178. Moreover, please recheck the English by a native Editor

Line 136: Table 1 should be revised to a trilinear table.

Line 230: “For winter PM₅, the relative importance of OM increased (up from 31% in 2008 to 40% in 2017)… as well as EC (down from 7.8% to 5.3%).” I can’t find any value of 31% in 2008 to 40% in 2017 in the wintertime figure (Figure 3).

Line 231: Valid numbers should be uniform.

Line 233: Do authors have any ideas about the decrease percentage of EC in summer was about 4 times higher than that in winter?

Figure 3: The percentage values in the chart use an art font that is unclear and needs to be modified.

Line 392: “The concentration levels of shipping emission tracers (V and Ni)… respectively”, Is this result from Table 2?

Line 418: “K+ more representative of burning crop residues high in K+ content vs. levoglucosan representative of burning of cellulose, thus all types of vegetative biomass including hill fires.” Grammar errors. The sentence components are unclear and there is no cause-and-effect relationship in this sentence.

Line 418: “The two elements are highly correlated, reflecting their common material sources and spatial origins”, are the correlation values in the literature or your results?

Line 499: Valid numbers in Table 4 should be uniform.
Citation: https://doi.org/10.5194/acp-2022-100-RC1
- AC1: 'Reply on RC1', Jian Zhen Yu, 19 Jun 2022
  
  Please refer to the supplement for a point-by-point response to the review comments.
  
  Thank you.
  
  Citation: https://doi.org/10.5194/acp-2022-100-AC1
RC2:
'Comment on acp-2022-100', Anonymous Referee #2, 22 Apr 2022
The manuscript presents a ten-year data set of PM_2.5 major components and source-specific tracers at an urban site in Hong Kong, South China. The authors investigate the trends of these compounds and evaluate the influence of emission control on their variations. They also discuss the impact of ENSO events on the abnormal change in PM_2.5 components, especially in 2011. Overall, I think the research is äººé´å°quite interesting and valuable to the community. I recommend the manuscript to be published in the journal after considering the following specifics:

Major concerns:

There should be emission inventory data in Hong Kong and the PRD. If so, the authors are suggested to compare the long-term trends of PM₅ species (tracers) with the variations of local and regional emission inventories. For example, when the authors discuss the long-term variations of SO₂ and EC, they list the major emission control measures implemented in Hong Kong (Figure 7 and 8, respectively). Are the changes in these species consistent with the variations in emission inventories in Hong Kong?

Recent studies have demonstrated that organic compounds, such as levoglucosan and hopanes, are not stable in the atmosphere as previously thought. As Table 2 shows, the levels of ozone continue to increase at the site. This implies that the atmospheric oxidation capacity is increasing. The authors should add some discussion about the influence of the increase in oxidation capacity on the decrease of organic species.

In section “3. 4 Secondary inorganic aerosol components”, the authors discuss the uneven reduction of SO₂-sulfate and NOx-nitrate. How about the temporal trends of sulfur oxidation rate (SOR) and nitrogen oxidation rate (NOR)? The changes in SOR and NOR might provide additional information about the formation chemistry of sulfate and nitrate.

Minor comments

Page 8 line 233-234. The authors state that the decrease in EC is due to local control of vehicular emissions. However, in addition to vehicular emissions, EC could be emitted from biomass burning and shipping exhaust. In fact, the tracers of the latter two sources (e.g., K⁺ and Ni) also continued to decrease (Table 2). The “%Relative change” of EC is close to that of K⁺.

Page 12 Figure 5. SO₂ had a local source in 2008 but a regional source in 2017. What is the explanation?

Page 19 Table 4. The coefficients in WINTER are not listed in Table 4.
Citation: https://doi.org/10.5194/acp-2022-100-RC2
- AC2: 'Reply on RC2', Jian Zhen Yu, 25 Jun 2022
  
  Please refer to the supplement for a point-by-point response to the review comments. Thank you.
  
  Citation: https://doi.org/10.5194/acp-2022-100-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Jian Zhen Yu on behalf of the Authors (26 Jun 2022) Author's response Author's tracked changes Manuscript

ED: Publish subject to minor revisions (review by editor) (23 Jul 2022) by Willy Maenhaut

The authors have reasonably addressed the comments of the two anonymous referees and they have modified their manuscript accordingly. However, many alterations and corrections are needed for both the Main text and Supplement before the manuscript can be published in ACP:

Main text:
Line 16: Replace "displayed significant" by "displayed a significant".
Line 37: GBA was already defined in line 34; it should not be defined again; therefore, replace "Area (GBA)" by "Area".
Line 40: Replace "in term" by "in terms".
Line 94: Abbreviations and acronyms should be defined (written full-out) when first used; therefore, replace "LOESS (STL)" by "locally estimated scatter plot smoothing (LOESS)"; note that STL is defined in line 155.
Line 125: OC and EC were already defined in line 50; they should not be defined again; therefore, replace "Organic carbon (OC) and elemental carbon (EC)" by either "Organic carbon and elemental carbon" or "OC and EC".
Line 130: Replace "al.,2008" by "al., 2008".
Line 148: HKEPD was already defined in line 72; it should not be defined again; therefore, replace "Hong Kong Environmental Department (HKEPD)" by either "Hong Kong Environmental Department" or "HKEPD".
Lines 150 and 151: Abbreviations and acronyms, here "HKUST ENVF", should be defined (written full-out) when first used.
Line 154: Replace "in supplementary" by "in the supplementary".
Line 155: Replace "with LOESS" by "with the LOESS".
Line 157: STL was already defined in line 155; it should not be defined again; therefore, replace "decomposition (STL)" by "decomposition".
Line 162: LOESS was already defined in line 94; it should not be defined again; therefore, replace "locally weighted regression (LOESS)" by "LOESS".
Line 169: Replace "of interquartile" by "of the interquartile".
Line 174: Replace "from STL" by "from the STL".
Line 177: Replace "of changing" by "of the changing".
Line 182: It should be indicated what the symbols ϕ and θ denote.
Line 187: Replace "indictors" by "indicators".
Line 189: Replace "in supporting" by "in the supporting".
Line 192: There is an inconsistency between "Wilcox, 2017" here and "Wilcox, 2018" in the Reference list.
Line 193: Replace "run Mann-Kendall" by "run a Mann-Kendall".
Line 200: Replace "of CAGR" by "of the CAGR".
Line 201: Replace "of supporting" by "of the supporting".
Line 211: Replace "summertime and bring" by "summertime bring".
Line 218: Replace "variations, therefore" by "variations and are therefore".
Line 224: Replace "in summer" by "in the summer".
Line 225: Replace ", however" by "; however".
Line 227: Replace "of 10-year" by "of the 10-year".
Line 232: Replace "computed to be" by "computed as".
Line 242: Replace "than <4%" by "than 4%".
Line 248: Replace "examined annual" by "examined the annual".
Line 255: Replace "degree of freedom" by "degrees of freedom".
Line 256: OLS was already defined in line 177; it should not be defined again; therefore, replace "squares (OLS)" by "squares".
Line 268: Replace "of STL-GLS-ARMA" by "of the STL-GLS-ARMA".
Line 279: Replace "by GLS-ARMA" by "by the GLS-ARMA".
Line 280: Replace "flatten variation" by "flattened variation".
Line 282: Replace "between two" by "between the two".
Line 289: Replace "confine trend" by "confine the trend".
Page 11, last but one line: Replace "in the bracket denote" by "in parentheses denote".
Lines 317 and 333: Replace "select components" by "selected components".
Line 323: Replace "align with" by "alignment with".
Line 324: Replace "displays comparable" by "displays a comparable".
Line 342: Replace "namely, sulfate" by "namely sulfate".
Line 343: Replace "of PM2.5" by "of the PM2.5".
Line 354: There is an inconsistency between "Zheng, 2018" here and "Zheng et al., 2018" in the Reference list.
Line 354: Replace "in Supplementary" by "in the Supplementary".
Line 389: Replace "for higher" by "for a higher".
Line 394: Replace "project, thus" by "project and are therefore".
Line 400: Replace "hese significant" by "These significant".
Line 408: Replace "in Shing" by "in the Shing".
Line 417: Replace "in the top plot" by "in the plot".
Line 422: Replace "show that" by "shows that".
Line 456: There is an inconsistency between "Yang et al., 2017" here and "Yang and Zhu, 2017" in the Reference list.
Line 466: Replace "in 205" by "in 2015".
Line 478: Replace "tropical Pacific" by "the tropical Pacific".
Line 480: Replace "of Walker" by "of the Walker".
Line 495: Replace "in 2008-2017" by "in the 2008-2017".
Line 508: Replace "δ's" by "δ1's" with the "1" in subscript.
Line 513: Replace "was observed" by "were observed".
Line 524: Replace "select source" by "selected source".
Line 525: Replace "were obtained" by "was obtained".
Line 548: Replace "sources for" by "source for".
Line 551: Replace "China as the" by "China are the".
Line 559: Replace "aerosol constitutes" by "aerosol constituents".
Line 569: The abbreviation "HKSAR" should be replaced by what it stands for.
Line 571: Replace "thank Hong" by "thank the Hong".
Lines 578-584: "Chen, Z. et al., 2019" should come after "Chen, W. et al., 2021".
Lines 684-687: "World Health Organization" should come after "Wilcox".

Supplement:
Lines 8 and 46: Replace "The meteorological" by "Meteorological".
Line 20: Replace "The changes in percentage share of emissions by sources and the variations" by "Ten-year changes in percentage share of emissions by sources and variations".
Lines 22, 40, 125, and 254: Replace "The changes" by "Changes".
Lines 23 and 127: Replace "Loess Method and the Generalized" by "Loess Method (STL) and Generalized".
Lines 34 and 238: Replace "The overall" by "Overall".
Lines 36 and 245: Replace "all the pairwise" by "all pairwise".
Lines 37 and 247: Replace "ENSO" by "El Niño-Southern Oscillation (ENSO)".
Lines 44 and 263: Replace "the PRD" by "the Pearl River Delta (PRD)".
Line 47: Replace "are summarized" by "is summarized".
Line 49: Replace "in summer" by "in the summer".
Lines 51, 56 and 58: Replace "in Shing" by "in the Shing".
Line 64: Replace "then calculated" by "then we calculated".
Line 65: Replace "in normal distribution (e.g. the" by "in the normal distribution (e.g., the".
Line 66: Replace "verse theoretical" by "versus the theoretical".
Line 67: Replace "in Q-Q" by "in the Q-Q".
Figure S3: The units in the ordinates should be indicated; furthermore, it is unclear what the # at the end of the legend in the ordinate denotes.
Lines 75 and 82: Replace "while that of the remaining is" by "while those of the remaining substances are in".
Figure S5: It is unclear what the # at the end of the legend of the ordinate in Figure S5(b) denotes.
Figure S6: It should be indicated in which units the concentrations were.
Line 103: The "2" of "SO2" should be in subscript.
Line 107: Replace "begun" by "began".
Line 112: Replace "shows that" by "show that".
Line 113: Replace "TW" by "Tsuen Wan (TW)".
Line 115: Replace "GBA" by "Greater Bay Area".
Line 120: Replace "The ten-year changes in percentage share of emissions by sources (columns) and the variations" by "Ten-year changes in percentage share of emissions by sources (columns) and variations".
Line 122: Replace "Hong Kong and Guangdong" by "Hong Kong (HK) and Guangdong (GD), HK El indicates Public Electricity Generation in Hong Kong".
Figure S9: It should be specified what the small boxes and numbers between the bars denote.
Line 138: Replace "with initially" by "with an initially".
Line 139: I presume that the "s" of "ns" should be in subscript.
Line 139: Replace "Jan is" by "January is".
Line 141: Replace "in inner" by "in the inner".
Line 153: Replace "robustness weights" by "robustness weight" and replace "respected to" by "respect to".
Line 161: Replace "square with ARMA" by "squares with the ARMA".
Line 162: Replace "of time" by "of the time" and replace "it assumes" by "it is assumed".
Line 165: Replace "Prior from directly running the model, autocorrelation issue on time series by Auto" by "Prior to directly running the model, the autocorrelation issue on the time series by the Auto".
Line 166: Replace "Figure" by "Figures".
Line 177: Replace "select by minimum AIC/AICc were" by "selected by minimum AIC/AICc was".
Line 179: Replace "were not" by "was not".
Line 192: Replace "while the rest is" by "while for the other species it is".
Line 194: Replace "denote for the significance of slope differ" by "denotes that the significance of the slope differs".
Line 197: Replace "by STL method, OLS instead of GLS-ARMA" by "by the STL method, OLS instead of the GLS-ARMA".
Line 199: Replace "from OLS" by "from the OLS".
Line 202: Replace "incorrected in" by "incorrect in".
Line 203: Replace "Concentration estimated" by "Concentrations estimated".
Line 206: Replace "were dominated" by "was dominated".
Line 208: Replace "were generally" by "was generally".
Figure S12: The units in the ordinates should be indicated.
Table S3: The units of the Concentrations should be specified.
Line 224: Replace "with STL-GLS-ARMA" by "with the STL-GLS-ARMA".
Line 227: Replace "of species" by "of the species".
Line 228: Replace "observed in" by "observed in the".
Line 229: Replace "flatten in later year" by "flattened in later years".
Line 231: Replace "started from" by "starting from".
Line 236: Replace "in bracket" by "in parentheses".
Line 240: Replace "summarize the" by "summarizes the".
Line 249: Replace "MLR" by "multiple linear regression (MLR)".
Line 260: Replace "RH" by "relative humidity (RH)".
Page 25, line 3 from bottom: Replace "labeled species" by "the labeled species" and replace "unit of the rest" by "the unit of the other".
Page 25, last line: Replace "of other" by "of the other".
Page 26, middle column: Replace "60 mins" by "60 min".
Page 27, last column: Replace "e.g." by "e.g.,".

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AR by Jian Zhen Yu on behalf of the Authors (27 Jul 2022) Author's response Author's tracked changes Manuscript

ED: Publish subject to minor revisions (review by editor) (06 Aug 2022) by Willy Maenhaut

AR by Jian Zhen Yu on behalf of the Authors (07 Aug 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (14 Aug 2022) by Willy Maenhaut

AR by Jian Zhen Yu on behalf of the Authors (18 Aug 2022)

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Short summary

Long-term monitoring data of PM_2.5 chemical composition provide essential information for evaluation and planning of control measures. Here we present a 10-year (2008–2017) time series of PM_2.5, its major components, and select source markers in an urban site in Hong Kong. The dataset verified the success of local vehicular emission control measures as well as reduction of sulfate and regional sources such as industrial and coal combustion and crop residue burning emissions over the decade.

Measurement report: The 10-year trend of PM2.5 major components and source tracers from 2008 to 2017 in an urban site of Hong Kong, China

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Interactive discussion

Peer review completion

Measurement report: The 10-year trend of PM_2.5 major components and source tracers from 2008 to 2017 in an urban site of Hong Kong, China