High Contribution of Biomass Combustion to PM_2.5 in the City Centre of Naples (Italy)

Round 1

Reviewer 1 Report

The revised version of the manuscript is much improved and I will recommend publication with the following minor amendments. 

The uncertainties described in the new section 3.3 should be referenced in the conclusion and the order of priority of sample merging described in the response to reviewer should be explicitly stated in the methods section. The description of the processing of blanks also suggests that the blank filters were exposed to ambient vocs for much longer than the collected sample filters and the reason for this should be clarified/explained.

Author Response

The minor amendments suggested by the reviewer have been all implemented and they are highlighted in light blue in the revised version of the manuscript.

Reviewer 2 Report

The Authors have addressed all my comments and the structure of the paper now is much better.

Author Response

No further feedback by the reviewer has required changes to the previous version of the manuscript, which underwent just to few minor language style, grammar, spelling and misprint amendments.

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 manuscript describes investigations using radiocarbon analysis to determine the fossil fraction of carbon. This is a valid and interesting approach to the question of where the carbonaceous aerosol originates and provides a measure independent of other commonly employed approaches, such as the aethalometer model. Overall, an interesting study, but there are some issues that should be addressed.

The sample collection was a byproduct of online PM mass monitoring by a SWAM, an automated PM monitor rather than a dedicated sample collector. As a consequence the authors had inadequate amount of sample to analyse both EC and OC on the sunset thermo-optical OCEC analyser. Instead, only EC was analysed and OC was estimated on the basis of a pre-determined ratio between OC values from the Sunset and the AMS. It would have been advisable to ensure that enough sample was collected, but this shortcoming is understandable in view of the fact that the study did not receive external funding, as pointed out in the acknowledgements.

The chain of calculations that lead to the final values of fossil fuel and biomass fractions involves a series of assumptions of empirically determined fixed ratios between parameters, by the authors or from the literature, in equations 1, 3, 5, 7 and 8.

This is a valid approach to extracting potential information from the available data, but it warrants a longer discussion on the inherent uncertainties in the end result.

The extraction procedure involves a temperature ramp to separate OC and EC in the AMS. They exclude the intermediate part of the EC because it is hard to separate the more refractory OC and the less refractory EC. There should be some more discussion on the quantitative implications of this step. How much was excluded?

The procedure of using water extraction of samples used for EC determination to avoid charring of OC. This procedure should be discussed and explained in more detail, and the quantitative implications should be explained, how much was lost to extraction?

It is not clear why only EC was determined by the sunset instrument. If the eusaar-2 protocol was used, that will include both OC and EC stages of temperature and gas. This should be explained better.

The field blank OC reported is very high. (1.9% - 7%). This warrants some discussion, presumably this reflects the VOC content in the Naples atmosphere. How does  it compare with other European cities?

The samples have been pooled according to air mass trajectories obtained by hysplit. Table 1 shows the dates, air mass origins and wind directions. It is noticeable that the wind direction varies only between the northern sectors, NE to NW throughout the entire period. The fact that samples are pooled according to air mass trajectories rather than local wind directions implies an assumption that the transported air mass has more influence on the sample than the local sources. this choice has to be better justified. For example, the discussion mentions local pizza restaurants as possible contributors. So it is not clear why the air mass trajectories are prioritised over local sources. Figure 4 is good, because it allows the reader to compare both local wind direction and air mass origins with results.

It is true that local wind direction shows little variation, for the 24hr averages. However, some analysis of wind speed changes throughout the day could be interesting. Presumably there would be some sun breeze in the middle of the day, so on low wind speed days it is possible that the port air did have some influence on the sample. 

A minor question not addressed is the averaging procedure for wind speeds over the 24 hours, or 48 hrs for combined samples. 

The results involve several different OC and EC values as discussed in equations 1 through to 9, but it is not clear which ones are listed in table 2.

In fact, there should be a table where all the measured and calculated parameters are listed (OCff ECff ECbb OCbb SOCff, etc.). The manuscript mentions both SOCff and SOC, but it is not clear if SOC refers to something different from SOCff and if so, how it is estimated.

Figure 6 shows OCff vs ECff in absolute values, but it would probably be more interesting to see the relationship between OFff/OC  and ECff/EC, which are the fractions also shown in Figure 5.

There appears to be an issue with the rendition of the graphics, because figures 3, 5, 6 and 7 contain a number of symbols that have been replaced by a ?

In the conclusion, there should be no room for confusion as to whether the results refer to fraction of C or fraction of Organic Matter. For example, in the sentence "TC accounts for 48 % ot total PM2.5", that this refers to C, not organic matter.

The conclusion that 70% of TC is from non-fossil sources is interesting and important. But as referred to above, this figure depends on a series of empirical ratios and there should be an acknowledgement of the uncertainty inherent. The conclusion could benefit from being a bit more concise and succinct highlighting the actual findings more. It is unsual to end the conclusion with a reference to other studies.

Author Response

Please, see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper entitled “ High contribution of biomass combustion to PM2.5 in the 2 city centre of Naples (Italy)” which really good study and experiment and the authors tried to write a good paper. However, the paper is lacking of design the paper structure. The dataset looks great, but it needs to apply PMF or CMP to the dataset give more information and address some scientific questions .Very low quality presenting figures and tables. Please re-structure the paper in order to make it easy to reader.

Abstract:

Line 17: I don’t think the “first time” right, this is should be removed. There are many studies have already been carried out in Naples.

Add KEY CONCLUSION FROM EACH OF SECTIONs of results. I can’t find the clear aim of the study, please state a clear objectives in the abstract.

Abstract should be clearly stated these parts, background, methodology, results and conclusion. Please you should revise the abstract as above.

Introduction:

Here the authors should write clear four to five paragraphs about background PM2.5 pollution in Italy and Naples, second , talk about the sources and challenges of pollution of PM2.5, and one paragraph for source apportionment methods, such as PMF, Factor, PCA and so on, the last one, should state previous studies in Naples, research gap and objective of the study. Please re-write the introduction as above structure.

Methodology:

The methodology are not clear at the present form.

There are missing many things such as, sampling info , more detail about Naples and the monitoring site, instrumentation, I don’t know which instrument was used to collect filter samples in this study, and QA/QC is very important and I can’t see much about the quality control of the study. The authors need to address very cleary and state in the paper. Since the QA/QC is a key for the study like this.

Please re-write methodology and experimental part, and write down some sub section to make a better structure.

Section 2.4 source apportionment. It’s very strange methodology. Did you use PMF or any other receptor model to quantity and identify sources?

Result and discussion:

Line 224-228: You don’t need to write procedure here. Please write those information in the Experimental part.

Table 1 and 2 are  very confusing and needed to be changed and presented in proper way.

All figures look very bad and please modify them and show high quality figure. Discussion on the figures are very low quality.

It would be great if authors re-write this section and show them in scientific way.

Conclusions:

Please re-write and change the structure to bulling points. You can write brief conclusion for each section of results and discussion.

Please write a future work and implication your work.

Author Response

Please, see the attachment.

Author Response File: Author Response.pdf