Seasonal Variability in the Composition of Particulate Matter and the Microclimate in Cultural Heritage Areas

Round 1

Reviewer 1 Report

Could you provide some comparisons to other studies? Describe the context and the general aim of the study?

Is there anything different in this study? Some specific issues which appeared?

Port activities could be one source of the problem, however, road traffic can’t be neglected either in this location. Can you discuss it?

How do your results translate to the outer world?

Author Response

Reviewer 1

Could you provide some comparisons to other studies? Describe the context and the general aim of the study? Is there anything different in this study? Some specific issues which appeared?

Thanks to the reviewer for the comments. The article was improved by comparison to another study which made similar measurements (i.e., temperature and relative humidity determined indoor, 12 months, in four exhibition halls in the museum building located in a big city in Upper Silesia, Poland – reference [35]). The article was improved (Introduction Section) by the sentence “The novelty of this study is highlighted by the multitude of reported data (indoor and outdoor) with direct correlations between climatic factors and PM chemical composition with direct influence on artwork museum and on visitor’s health”.

Port activities could be one source of the problem, however, road traffic can’t be neglected either in this location. Can you discuss it?

Thanks to the reviewer for the comments. It is truth; Constanta is the main port in the Black Sea and also the most important one in Romania and the fourth one in Europe. Annually, few touristic vessels transit the Constanta Port, more being commercial vessels. This preliminary study will be the first complex research achieved in Romania referring to the influence of climatic and microclimatic factors, correlated with PM chemical composition and sea earthquakes on original archaeological components degradation according with the objectives of the project 51PCCDI/2018 “New diagnosis and treatment technologies for the preservation and revitalization of the archaeological components of the national cultural heritage”. The first campaign (summer 2018 – spring 2019) was focused on the climatic and microclimatic monitoring parameters (i.e. temperature, relative and absolute humidity, pressure, wind direction and speed, dew-point, noise level, solar irradiance, luminance), on sea earthquakes and PM chemical composition in well-established points from historical sites of Constanta, Dobrogea Region, Romania. The multitude of obtained data during of one year of campaign, statistically analyzed, were reported already in the First Scientific Report of the project, available just for Romanian National Authority for Scientific Research, UEFISCDI (according with Romanian regulation). In the second campaign (summer 2019 – spring 2020) the anthropic, traffic and industrial pollution will be monitored and briefly correlated with the obtained data, evaluating the influence of the port activity on the investigated archaeological monument and so on.

How do your results translate to the outer world?

Thanks to the reviewer for the comments. The final objective of the project 51PCCDI/2018 will be the achievement of a new polymeric hybrid material (an EPO patent with the procedure of this material already was request in May 2019) for preservation and revitalization of the archaeological components of the national cultural heritage.

Author Response File: Author Response.docx

Reviewer 2 Report

The seasonal variability of particulate matter composition and the microclimate in cultural heritage areas

Summary:

This study adopted FTIR and ICP-MS techniques to characterize PM composition indoors and outdoors of the Roman Mosaic Edifice Museum. The authors conducted gravimetric sampling from summer 2018 until Spring of 2019, thereby nicely accounting for all four season. The authors also accounted for microclimate parameters such as temperature and RH. This is a very impressive study and a great step in the right direction for assessing exposures in environments of cultural heritage importance.

That said, I have some comments and suggestions to improve the overall readability of the current write up.

Comments:

Page 1, line 41: “long-term exposure to a high or even low concentration” Can authors give a range, how high and how low? This is because there are international limits and this can give a reader an idea of the levels of concentrations in question. This part of the introduction is key because later on, the authors provide concentrations of the airborne metals detected yet, we have no idea what the levels mean for health. Secondly, although this was not the focus of the study, since the authors conducted gravimetric sampling, are they able to provide the mass concentrations of the PM measured? Thirdly, why was PM2.5-10 measured (I believe this is course PM) as opposed to PM2.5 or PM10 or TSP? Just providing this information up front is key to ensuring the readability and clarity of the manuscript. Again the authors need to recall that they are moving into new horizons with their study and so it is always important to orient readers on the ‘normal’ information that the air pollution camp currently know, then gently ease into the new method presented. Lastly, why is PM the primary/only focus, why not others e.g. VOCs from off gassing of the displays, etc since this can also be a source of indoor air pollution in this setting?

Page 1 line 27-28: Please rewrite this sentence. The authors mention “high concentrations of metals (i.e. Al, Fe, Zn, Mn and Pb)”: I think they want to add “heavy metals” to differentiate from trace metals.

Page 2 line 53: “According to several researches” are the authors referring to researchers?

Page 2 line 71: “corroborated” are the authors referring to correlated or along with?

Page 3 line 111: The authors refer the reader to a seaport. Can they discuss briefly whether how this may affect air pollution since there will be some combustion products from the fuels of the ocean going vessels? This is an important nugget since the authors allude to it again in the Conclusions (line 328).

Page 3 line 133 – downwards. Please revise. I think the research presented herein provided results that seek to inform future solutions, it did not provide solutions on improving environmental conditions at the Edifice. Again, in the Conclusion (line 330) the authors state that “several solutions can be proposed in order to reduce the impact of the external climatic risk”…Unless my understanding of the work was incomplete, I did not see any solutions such as changes to ventilation or closing down the place during season with highest metal composition levels etc.

Page 7 line 218: Very detail tables. Can authors create a table, or better still a figure, where they explore the relationship between outdoor and indoor levels? For example, the authors stated that the anthropogenic activities at the port was contributing to indoor levels, they can do a ratio or even simple subtraction of indoor levels from outdoor levels and graph that to show that some metals were from outdoor sources, others were from indoors, or there was no change, nothing fancy (see ref: https://www.sciencedirect.com/science/article/pii/S0160412016300162)

Page 11 line 263: I am unclear what the authors are referring to by stating that PM is spatially homogeneous. I believe the Lippmann et al results were referring to the fact that their results suggested that “spatially homogeneous pollution indices show higher associations” with the health outcomes that they had considered. On the contrary a lot of studies report that air pollutants are not spatially homogeneous. E.g. when person A is by the roadside, the PM levels may be highest, but person B who is 300m away, has less exposure to the same pollution that is being emitted by the car on the road. Please review and revise these thoughts.

General comment: What are the health implications of the levels measured in Table 3? And will the authors recommend that visitors continue to come to this edifice to view the artwork, is it worth the health risk (I am assuming tourists/visitors come in for about an hour or more? (See Conclusion section, line 332).

General minor comment: In most parts of the manuscript, the authors place citations in the middle of the sentence or close to the beginning but in a few places, they place citations at the end. It makes it a hard read for an otherwise interesting piece of work.

Example with citation close to beginning

E.g. Page 2 line 55: “Along the years, researchers [12, 16‐18] have reported different results…”

Example with citation at the end

Page 2 line 73-74: “Further free radicals such as SO2· and irritant peroxyacetyl nitrates (PAN) are dangerous to people’s health and to materials [24].”

​

Author Response

Reviewer 2

Page 1, line 41: “long-term exposure to a high or even low concentration” Can authors give a range, how high and how low? This is because there are international limits and this can give a reader an idea of the levels of concentrations in question. This part of the introduction is key because later on, the authors provide concentrations of the airborne metals detected yet, we have no idea what the levels mean for health.

Thanks to the reviewer for the comments. PM_2.5 are the greatest risks to health. It has been reported that a long-term exposure to PM_2.5 is associated with an increase in cardiopulmonary mortality by 6–13% per 10 μg/m³ of PM_2.5 [7, 8] and the sentence was completed as follow: “Long-term exposure to a high or even low concentration of particulate matter (PM) and soot particles can cause cancer and premature death, according to the World Health Organization (WHO) Air quality guidelines (AQGs), in which are recommended a possible concentration of PM2.5 as 10 µg / m³ annual mean and 25 µg / m³ 24-hour mean, as well as for PM10 a value of 20 µg / m³ annual mean and 50 µg / m³ 24-hour mean” [6].

Secondly, although this was not the focus of the study, since the authors conducted gravimetric sampling, are they able to provide the mass concentrations of the PM measured?

Thanks to the reviewer for the comments. The PM mass concentration determining was not the goal of this study, but these data were centralized after each monitoring campaign, and are the subject of other article which is already in evaluation in order to be published. Hence, for reviewer, the authors will give the mean values of PM_2.5-10: summer – 35 µg / m³ 24 hour; autumn – 17 µg / m³ 24 hour; winter – 18 µg / m³ 24 hour; spring – 22 µg / m³ 24 hour, with an annual mean of PM2.5-10 23 µg / m³.

Thirdly, why was PM2.5-10 measured (I believe this is course PM) as opposed to PM_2.5 or PM₁₀ or TSP? Just providing this information up front is key to ensuring the readability and clarity of the manuscript. Again the authors need to recall that they are moving into new horizons with their study and so it is always important to orient readers on the ‘normal’ information that the air pollution camp currently know, then gently ease into the new method presented.

According with general definition “Total suspended particles (TSP) is an archaic regulatory measure of the mass concentration of particulate matter (PM) in community air”. In this respect, TPS was defined by the (unintended) size-selectivity of the inlet to the filter that collected the particles. Unfortunately, the size cut varied with wind speed and direction and was from 20 to 50 µm in aerodynamic diameter. Under windy conditions the mass tended to be dominated by large wind-blown soil particles of relatively low toxicity. The terms "fine" and "coarse" were originally intended to apply to the two major atmospheric particle distributions which overlap in the size range between 1 and 3 µm. Now, “fine” has been defined by EPA as PM_2.5 and "coarse" as PM_10–2.5. However, PM_2.5 may contain, in addition to the fine-particle mode, some of the smaller sized "coarse" particles. Conversely, under high relative humidity conditions, the larger particles in the accumulation mode extend into the 1 to 3 µm range.

Lastly, why is PM the primary/only focus, why not others e.g. VOCs from off gassing of the displays, etc. since this can also be a source of indoor air pollution in this setting?

Thanks to the reviewer for the comments. Inside of exhibition space (built entirely of glass and aluminium profiles), with natural ventilation and without heating systems, no VOCs measurements were made. Even if VOCs were not the goal of this study, in the future monitoring campaigns (i.e. the project is carried out during three complete seasons cycles), taking into account the reviewer's observations, these organic compounds will be determined, evaluating their influence on the general chemical composition of PM.

Page 1 line 27-28: Please rewrite this sentence. The authors mention “high concentrations of metals (i.e. Al, Fe, Zn, Mn and Pb)”: I think they want to add “heavy metals” to differentiate from trace metals.

Thanks to the reviewer for the comments. The sentence “In this respect, the chemical measurements of the PM_2.5-10 mass highlighted high concentrations of metals (i.e. Al, Fe, Zn, Mn and Pb) and low concentrations of trace metals (Cr, Ni, Cu and Cd)” is now changed based on the reviewer’s comments as follow “In this respect, the chemical measurements of the PM_2.5-10 mass highlighted high concentrations of heavy metals (i.e. Al, Fe, Zn, Mn and Pb) and low concentrations of trace metals (Cr, Ni, Cu and Cd)”.

Page 2 line 53: “According to several researches” are the authors referring to researchers?

Thanks to the reviewer for the comments. The “researches” word was replaced with “studies”.

Page 2 line 71: “corroborated” are the authors referring to correlated or along with?

Thanks to the reviewer for the comments. The “corroborated” word was replaced with “correlated”.

Page 3 line 111: The authors refer the reader to a seaport. Can they discuss briefly whether how this may affect air pollution since there will be some combustion products from the fuels of the ocean going vessels? This is an important nugget since the authors allude to it again in the Conclusions (line 328).

Thanks to the reviewer for the comments. It is truth; Constanta is the main port in the Black Sea and also the most important one in Romania and the fourth one in Europe. Annually, few touristic vessels transit the Constanta Port, more being commercial vessels. As reviewer remark, in the sentence “This is a very impressive study and a great step in the right direction for assessing exposures in environments of cultural heritage importance”, this preliminary study will be the first complex research achieved in Romania referring to the influence of climatic and microclimatic factors, correlated with PM chemical composition and sea earthquakes on original archaeological components degradation according with the objectives of the project 51PCCDI/2018 “New diagnosis and treatment technologies for the preservation and revitalization of the archaeological components of the national cultural heritage”. The first campaign (summer 2018 – spring 2019) was focused on the climatic and microclimatic monitoring parameters (i.e. temperature, relative and absolute humidity, pressure, wind direction and speed, dew-point, noise level, solar irradiance, luminance), on sea earthquakes and PM chemical composition in well-established points from historical sites of Constanta, Dobrogea Region, Romania. The multitude of obtained data during of one year of campaign, statistically analyzed, were reported already in the First Scientific Report of the project, available just for Romanian National Authority for Scientific Research, UEFISCDI (according with Romanian regulation). In the second campaign (summer 2019 – spring 2020) the anthropic and industrial pollution will be monitored and briefly correlated with the obtained data, evaluating the influence of the port activity on the investigated archaeological monument and so on. 

Page 3 line 133 – downwards. Please revise. I think the research presented herein provided results that seek to inform future solutions, it did not provide solutions on improving environmental conditions at the Edifice. Again, in the Conclusion (line 330) the authors state that “several solutions can be proposed in order to reduce the impact of the external climatic risk”…Unless my understanding of the work was incomplete, I did not see any solutions such as changes to ventilation or closing down the place during season with highest metal composition levels etc.

Thank the reviewer for the comments. The sentence “several solutions can be proposed in order to reduce the impact of the external climatic risk” was rewritten as “several solutions will be proposed in the future, at the end of the project, in order to reduce the impact of the external climatic risk”. The final objective of the project will be the achievement of a new polymeric hybrid material (an EPO patent with the procedure of this material already was request in May 2019) for preservation and revitalization of the archaeological components of the national cultural heritage.

Page 7 line 218: Very detail tables. Can authors create a table, or better still a figure, where they explore the relationship between outdoor and indoor levels? For example, the authors stated that the anthropogenic activities at the port was contributing to indoor levels, they can do a ratio or even simple subtraction of indoor levels from outdoor levels and graph that to show that some metals were from outdoor sources, others were from indoors, or there was no change, nothing fancy (see ref: https://www.sciencedirect.com/science/article/pii/S0160412016300162).

Thank the reviewer for the comments. It is truth; Constanta is the main port in the Black Sea and also the most important one in Romania and the fourth one in Europe. Annually, few touristic vessels transit the Constanta Port, more being commercial vessels. As reviewer remark, in the sentence “This is a very impressive study and a great step in the right direction for assessing exposures in environments of cultural heritage importance”, this preliminary study will be the first complex research achieved in Romania referring to the influence of climatic and microclimatic factors, correlated with PM chemical composition and sea earthquakes on original archaeological components degradation according with the objectives of the project 51PCCDI/2018 “New diagnosis and treatment technologies for the preservation and revitalization of the archaeological components of the national cultural heritage”. The first campaign (summer 2018 – spring 2019) was focused on the climatic and microclimatic monitoring parameters (i.e. temperature, relative and absolute humidity, pressure, wind direction and speed, dew-point, noise level, solar irradiance, luminance), on sea earthquakes and PM chemical composition in well-established points from historical sites of Constanta, Dobrogea Region, Romania. The multitude of obtained data during of one year of campaign, statistically analyzed, were reported already in the First Scientific Report of the project, available just for Romanian National Authority for Scientific Research, UEFISCDI (according with Romanian regulation). In the second campaign (summer 2019 – spring 2020) the anthropic and industrial pollution will be monitored and briefly correlated with the obtained data, evaluating the influence of the port activity on the investigated archaeological monument and so on.

Page 11 line 263: I am unclear what the authors are referring to by stating that PM is spatially homogeneous. I believe the Lippmann et al results were referring to the fact that their results suggested that “spatially homogeneous pollution indices show higher associations” with the health outcomes that they had considered. On the contrary a lot of studies report that air pollutants are not spatially homogeneous. E.g. when person A is by the roadside, the PM levels may be highest, but person B who is 300m away, has less exposure to the same pollution that is being emitted by the car on the road. Please review and revise these thoughts.

Thank the reviewer for the comments. The sentences “According to data reported by Lippmann et al. [35], particulate matters are considered spatially homogeneous pollutants, but the exact extent of homogeneity has not been confirmed. This can be an important issue when it is necessary that we have air-quality data which are accurate enough as far as the museum premises are concerned, so that we can assess the effects on visitors’ health as well as on the exhibits” were removed from the article.

General comment: What are the health implications of the levels measured in Table 3? And will the authors recommend that visitors continue to come to this edifice to view the artwork, is it worth the health risk (I am assuming tourists/visitors come in for about an hour or more? (See Conclusion section, line 332).

Thank the reviewer for the comments. Only Pb levels exceeded the maximum concentration according to Romanian regulation, both indoor and outdoor of exhibition space. A health risk for visitors can be through the exceeded Pb concentrations in spring and summer, but the risk can be for all the peoples which are living in the neighbor areas of exhibition place. Assuming the fact that the visiting time is less than one hour we agree that the Pb levels not affect the health of visitors. These data are preliminary results which will be taken in consideration by Romanian authorities in rehabilitation and conservation procedures of historical objects/monuments.    

General minor comment: In most parts of the manuscript, the authors place citations in the middle of the sentence or close to the beginning but in a few places, they place citations at the end. It makes it a hard read for an otherwise interesting piece of work.

Example with citation close to beginning

E.g. Page 2 line 55: “Along the years, researchers [12, 16‐18] have reported different results…”

Example with citation at the end

Page 2 line 73-74: “Further free radicals such as SO2· and irritant peroxyacetyl nitrates (PAN) are dangerous to people’s health and to materials [24].”

Thanks to the reviewer for the comments. The citations were placed at the end of the sentences.

Author Response File: Author Response.docx

Reviewer 3 Report

The author presented the indoor and outdoor PM composition variation in cultural heritage areas. These data are unique and important for us in identifying seasonal pollutant patterns. However, the presentation of the work needs to be improved, together with the data analysis section. General and specific comments are listed below.

General comments:

Indoor and outdoor PM mass concentrations are critical, and the author should include this information in the manuscript. The metal concentrations measured by ICP-MS, with a unit of “mg/kg”, needs to be explained in detail. The practical meaning of this unit is not very clear. The result section is not organized well and can be improved with more detailed descriptions.

Specific comments

Line 89-111 can be shortened. Too many descriptions here. Line 153, the author needs to briefly explain what the apparent temperature means. Why the author calculated it other than simply report temperature and humidity. In Table 2, it is a little bit confusing why the outdoor temperature in autumn is lower than that in winter? The author tried to explain in Line 198-199, however, not very convincing. For Figure 1, please add the unit to the y-axis. Also, using a 20C interval on the y-axis will be better. The equation for calculating MTHI should be equation (2) For Table 3 and Table 4, a figure instead of a table will be more straightforward. The author can put these tables in supplementary materials. Please put the definition of the coefficient of variation in method section with an equation. Line 298, “cm-1” typo. The word “perfect” may not be a good adjective for relationship

Author Response

Reviewer 3

The author presented the indoor and outdoor PM composition variation in cultural heritage areas. These data are unique and important for us in identifying seasonal pollutant patterns. However, the presentation of the work needs to be improved, together with the data analysis section. General and specific comments are listed below.

General comments:

Indoor and outdoor PM mass concentrations are critical, and the author should include this information in the manuscript.

Thanks to the reviewer for the comments. The PM mass concentration determining was not the goal of this study, but these data were centralized after each monitoring campaign, and are the subject of other article which is already in evaluation in order to be published. Hence, for reviewer, the authors will give the mean values of PM_2.5-10: summer – 35 µg / m³ 24 hour; autumn – 17 µg / m³ 24 hour; winter – 18 µg / m³ 24 hour; spring – 22 µg / m³ 24 hour, with an annual mean of PM2.5-10 23 µg / m³, but these values were not been inserted in the article due to the explanations were not been made by mass concentration of PM, only by chemical composition of PM.

The metal concentrations measured by ICP-MS, with a unit of “mg/kg”, needs to be explained in detail. The practical meaning of this unit is not very clear. The result section is not organized well and can be improved with more detailed descriptions.

Thanks to the reviewer for the comments. The measurement unit for metals concentration is “mg/kg”, according with International System of Units. Authors have determined the metals concentration in dry mass of PM powder samples, obtained in accordance with Sample Preparation Subsection.

Specific comments:

Line 89-111 can be shortened. Too many descriptions here.

Thanks to the reviewer for the comments. The mentioned paragraph was shortened according with reviewer’s suggestion.

Line 153, the author needs to briefly explain what the apparent temperature means. Why the author calculated it other than simply report temperature and humidity.

Thanks to the reviewer for the comments. The apparent temperature, the temperature felt by people, was calculated with equation (1).

In Table 2, it is a little bit confusing why the outdoor temperature in autumn is lower than that in winter? The author tried to explain in Line 198-199, however, not very convincing.

Thanks to the reviewer for the comments. Due to the global climatic changes, in the autumn 2018 were recorded very low temperatures, comparative with the mean values of the last 15 years (in the monitored area and period).

For Figure 1, please add the unit to the y-axis. Also, using a 20C interval on the y-axis will be better.

Thanks to the reviewer for the comments. Figures 1 and 2 were replaced according with the reviewer suggestions.

The equation for calculating MTHI should be equation (2)

Thanks to the reviewer for the comments. This remark was replaced.

For Table 3 and Table 4, a figure instead of a table will be more straightforward. The author can put these tables in supplementary materials.

Thanks to the reviewer for the comments. The authors consider that the tables 3 and 4 are necessary for better explanations. More than that, a new representative figure was inserted. The figures in text were renumbered. The explanation of this figure was inserted in text: “From data reported in Tables 3 and 4 the indoor and outdoor (I/O) ratio was calculated and the obtained results are presented more clearly in the following graph (figure 3). In this respect, can be reported two types of observations: the first group of metals (i.e., Al, Cu, Cd, and Pb) show high ratios in summer and spring seasons, while the second group of metals (i.e., Cr, Mn, Fe, and Zn) show high ratios in autumn and winter seasons. This can be explained by the high level of metals pollution in warm seasons, while in cold seasons the metals content in PM (outdoor) decrease. The Ni is a singular case and the I/O ratio is constant along the entirely monitoring campaign”.

Please put the definition of the coefficient of variation in method section with an equation.

Thanks to the reviewer for the comments. The definition of CV was inserted in text. 

Line 298, “cm^-1” typo. The word “perfect” may not be a good adjective for relationship

Thanks to the reviewer for the comments. The measurement unit “cm-1” was replaced. The word “perfect” was replaced with “strong”.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for addressing my concerns.

Reviewer 3 Report

The author addressed the majority of the comments. The structure and the content are improved compared to the last version. Therefore, the reviewer would recommend accepting this manuscript.  

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The study on “Seasonal variability of particulate matter composition and microclimate in cultural heritage area” seems to point to understand the “effect” of PM composition on tourist’s health and historical objects like mosaics. Indoor and outdoor measurements of PM_2.5-10 and selected metals together with temperature and humidity have been carried out in some detail.

As a matter of fact, the potential risk for tourists and the cultural heritage is not clearly connected with the measurements, the study resulting just “an attempt to decipher” (abstract, l.18 and introduction l.122). Promised suggestion and indication pointing to the health safety of visitors seems not to be based on the in-field measurements campaign, being the latter the main subject of the study.

In my opinion, the study is weak to be published in the present version. A number of Major Issues (MI) and minor changes (mc) should be considered by authors to review the manuscript. Mandatory MIs are intended to put the campaign results as the focus of the work (as the title already states), with some further analyses required.

MI-1 Introduction.

The discussion about the health and environment damages posed by PM does not support some authors’ choices.

MI-1a Why have they selected PM_2.5-10 and neglected PM_2.5? Most of cited papers focussed on smaller particles [see 5]. The rather unique case discussing result on PM_2.5-10 referred is Pascal et al. (2014) [15], comparable with another Swedish study related to sources with local specific characteristics. Authors should explain much better the choice.

MI-1b I have not found in the cited references [13-14] details on tourists health risks, even as perception [15]. The intended “attempt to decipher” the effects of PM composition in indoor and outdoor environmental air is not reached by the presented work.

MI-2 Methodology.

The time strategy to collect the 84 PM samples during the year is not clear. I found the seasonal analyses, not any daily monitoring output or analysis (as promised in line 19 and 123). Also T and RH measurements strategy should be better described, to evaluate if they can be considered or not representative of the season. By definition, AT depends on RH and T: the use of AT seemed pointless.

MI-3 Results and discussion

MI-3a Meteorology parameters. Rather obvious seasonal results have been obtained. Lower outdoor temperature in autumn rather than in winter may suggest bad seasonal representativeness of measurements (what about rain days?). Threshold defining exceeding values reported at ll. 190, 198 and 200 are not reported. Besides the correlation shown in Fig.2, other correlated sub-patterns (seasonal?) seemed evident. They should suggest different (seasonal?) indoor-outdoor air exchange patterns whose investigation should enhance the study.

MI-3b Metal composition.

This is the weakest paper section.

The seasonal variability of the order of the metals abundance has not a clear explanation in terms of source/meteorology conditions.

None attempt is done on measurements analysis in terms of the indoor-outdoor air exchange (seasonal dependent?), limiting the analysis to infra-indoor and infra-outdoor correlations (tab.5 and 6).

Metal abundance is considered as ppm (mg/kg), with none information on concentration in air, information that would add important pieces of analyses.

Pb exceedance is relevant, but some data to corroborate the marine traffic as possible explanation should be found and added.

The mere detection of ions and organic carbons seemed pointless.

The last sentence (l.291-1.293) is rather generic and weakly corroborated by what foregoing.

MI-4 Conclusions

After reviewing the article as described in the previous MIs, Conclusions should be changed accordingly, stressing how temperature and relative humidity, PM local sourced and indoor-outdoor exchanges may influence PM composition and metal concentration values. Potential effect on health and cultural heritage might by better suggested, with reference to the results.

Minor changes

mc-1 Introduction

l.41 COx (carbon oxides) should not been referenced as “first category of pollutants” (CO should be instead), anyeay they are not quoted in [7]

mc-2 Introduction

Check for non English words like “d’art” or false friend like “antic” instead of “ancient”

mc-3 Introduction

Consider to reduce the paragraph from l.85 to l.102

mc-4 Methodology

Eq. 1 formulation differs from that found in [28]. Indeed, the formulation should come from another work cited in [28].

mc-5 Results and discussion

Eq.2 (erroneously reported as 1) formulation cannot be found in [34].

mc-6 Results and discussion

The Mn indoor summer value could be 1.79 (tab3).

mc-7 Results and discussion

Matrices in tab..5 and 6 should be triangular; check Ni-Mn in tab.5 and Cd-Cu in tab.6.