Optimization of a Method for the Detection of Biomass-Burning Relevant VOCs in Urban Areas Using Thermal Desorption Gas Chromatography Mass Spectrometry

Round 1

Reviewer 1 Report

Review  attached

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for his/her positive general comments and appreciating that the work can be published after addressing the comments. We have individually addressed all the comments in the attached.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper reports a method for identification of biomass burning smoke using dual bed sorbent tubes followed by off-line thermal desorption – gas chromatography – mass spectrometry (TD-GC-MS) analysis for acetonitrile and several other VOCs. An automated sampler is presented that can collect 16 TD tubes sequentially. Stability of the target compounds during storage after sampling of laboratory-generated and wood burning VOCs is investigated, showing that most target compounds, except acetone, are stable upon storage for at least 15 days, while acetone can be stored for up to 9 days. Examples from application of the sampling and analytical methodology to real-life sampling is also presented.

The paper describes a fairly simple method for sampling ambient air to identify biomass burning influences and is, thus, of considerable interest for atmospheric chemistry community. The paper, however, appears to be somewhat rushed. For example, stability of the target compounds after sampling biomass burning smoke was assessed with a single experiment in which wood logs were burned in a fire pit. While this experiment does provide a more realistic matrix than a laboratory-generated compound mix, the paper conclusions and statements would have been made stronger if a similar experiment was performed with real-life wild fire samples. The effects of ozone and humidity on the accuracy of the method are not discussed, but are to “be communicated as a separate study in detail soon”. Would it be possible to include the results of that study in this paper? I have also several, relatively minor, comments that need to be addressed before the manuscript can be accepted for publication.

 

Other comments:

Please provide part numbers and manufacturers of parts used in the sampler. A procedure of coating a filter with sodium thiosulfate pentahydrate should also be described or a reference to a prior work be provided.

Please specify sample flow and duration for LOD values provided on line 156 and in Table 1.

Retention order of pentane and iso-pentane is reversed in laboratory and real-life samples (Fig.3). Is this a typo during preparation of the figure or a result of peak misidentification?

The lower lifetime of acetone in real-life samples is suspicious as no other compound appears to be prone to “surface reactions with the inner walls … or at the adsorbent sites”. This explanation is not only vague but hardly makes sense as no such deterioration was observed for the laboratory-generated mix. Could a more feasible explanation be provided?

Since several other compounds of interests, such as furfural, were detected with the method, was there an attempt made to quantify them? Were these compounds also observed during the fire pit experiment? If yes, it would be very informative and useful to assess their stability upon storage, even using peak heights or areas, if no calibration standards were available.

 

 

Author Response

We thank the reviewer for his/her positive general remarks and appreciating that the work can be published after addressing the minor comments. We have individually addressed all the concerns in the attached document

Author Response File: Author Response.docx

Reviewer 3 Report

Chandra et al. outline the procedure used for measuring six VOCs via TD-GCMS. They apply this method in Boise, Idaho and infer the influence of biomass burning. The methods are clear and the manuscript is well written. I have two major concerns outlined below.

Major comments:

1.) The title starts “Development of a simplified method…”; however, It is unclear if the procedures listed here were developed by the authors, optimized by the authors, or borrowed from elsewhere. The analysis of all of these compounds by TD-GC-MS is not new (EPA TO-17 includes acetonitrile and the other species), and the method is not compared to existing methods. It is unclear where the details of the procedure come from as well. For a specific example, the O3 trap section( page 3) needs a reference. How were desorption cycles decided upon? etc.

2.) The manuscript indicates that six OVOCs where identified, but the humidity and storage test have not been completed. The manuscript would be more complete if these six were included here, rather than performing an identical analysis in a separate paper.

Minor comments:

1.) The title should be specific to the method used (e.g., Detection of biomass-burning relevant VOCs in urban areas via TD-GC-MS).

2.) Figure 3: Iso-pentane and Pentane peaks seem to swap between panels a and b.

Author Response

We thank the reviewer for his/her positive general remarks and addressed his/her major and minor concerns in the revised manuscript. Please find the attached document with answers to comments.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The authors have thoroughly addressed all comments.

Author Response

We thank the reviewer for his/her positive general comments and appreciating that the work can be published.