Characteristics of Real-World Gaseous Emissions from Construction Machinery

Round 1

Reviewer 1 Report

The authors carried out a particularly difficult study analyzing the air pollutants and GHGs of heavy machinery under real working conditions. Such studies are particularly difficult to implement technically, require a lot of coordination and are time-consuming.

The structure of the article is well prepared. A very good attempt was made to relate GHG and air pollutant emissions to engine load and express them in formulas (table 4).

Despite the positives, there are things that could be improved.

In the abstract, the statement "considerably improved" should be expressed as a specific number, X times or X%, or Xvalue.

In the Introduction, the statement "emission reduction technologies are at a lower level” would be good to be based on the scientific source.

In the Introduction part, it is possible to review more similar scientific studies that examined fuel consumption and their impact on the environment (engine load and GHG dependencies). Moreover, there are articles that are very suitable for the topic discussed by the authors - the dependence of fuel consumption, air pollutants and GHG on engine load. https://doi.org/10.3390/app11188662

If possible, Table 1 should be supplemented with additional parameters - the year of manufacture of the machine and the engine hours worked. These are very important parameters when evaluating machines. If such data is available.

Abbreviations EGR, SCR, etc. are used in Table 1., which are explained only in the following paragraph after the Table 1. Examining Table 1, it is not clear to a non-specialist what this is. All abbreviations used in the article must first be written in full text, only then shortened and only those abbreviations used later in the article. This applies to all abbreviations throughout the article.

Chapter 2. “PEMS system” talks about Ambient temperature and humidity. Do they continue to be used in the study and have they affected the results obtained? If not, then there is no need to talk about them. The same section talks about 2.5 and 3 inches. Wouldn't it be better to use mm and cm?

The Materials and methods section lacks the PEMS specification. There could be a separate table with measurement parameters. What gas is measured, what is the resolution of the device for each gas, other, specific information related to the PEMS.

The upper right image in Figure 2 is untitled. Probably missed the “Fork lift...”

Real-world is used very often when reading an article. I counted 59 times. There is a need to solve this word combination in some other way. Or to declare at the beginning of the article that "real-world" tests will be carried out and not to repeat it further. Or use some kind of abbreviation.

On pages 10-11, table 3, the authors talk about CO2 emissions. If other GHG and air pollutants can be reduced by introducing advanced engine technologies, then CO2 depends mostly on the amount of fuel used. This should be noted more clear in the article. Possibilities of reducing fuel consumption (at the same time GHG), dependence of GHG on engine load, use of telematic data are also discussed there: https://doi.org/10.3390/app11188662 and https://doi.org/10.3390/atmos12060674

In Table 4, the authors present some of the most important results of their research. It is not clearly highlighted what parameter L is. Engine load?

The formulas presented in Table 4 are a very interesting result of the authors' work. Their biggest drawback is the small sample of tested and investigated machines (14 units). The margin of error is likely to be huge. This allows future research to be carried out by increasing the sample size and refining the formulas. At this stage, I think their credibility is low. The authors, by the way, honestly admit it themselves.

The Conclusions section is too broad and long. It should be shortened and leave only the conclusions obtained during the investigation. Make it more concise and specific. There are too many elementary truths in this chapter, such as Tier3 emissions being higher than Tier4. In the conclusions, I think more attention should be paid to the developed formulas (dependence of emissions on engine load), to briefly discuss their scientific novelty and potential benefits.

In the Reference section, there is a link to the EEA Emission Inventory Guidebook 2016. Although the meanings are essentially the same, the newer 2019 version should be referred to: https://www.eea.europa.eu/publications/emep-eea-guidebook-2019

The article is relevant, taking into account the non-essential comments, I think it can be published.

Author Response

The response is enclosed as below.

Author Response File: Author Response.docx

Reviewer 2 Report

The present study describes engine operation characteristics and emissions from the 14 units of excavators, wheel loaders, and forklifts, of K-tier 3 and K-tier 4, which were selected to evaluate the gas emissions under real-world working conditions of the construction machines. The real-world gas emissions were measured with PEMS, which comprise the largest proportion among the construction machinery types in Korea. The measured real-world gas emissions have been compared with the laboratory emission limits and the conventional emission factors used in CAPSS. I recommend this manuscript for publication with some revisions.

Review comment:

1.    Subscript and superscript should be mentioned carefully and uniform in the manuscript, such as equation one “P_a or P_c”.

2.    Significance of the relationship between load factor and emission should be included before the Results and discussion section in the manuscript.

3.    The significance of the conformity factor has been mentioned in the manuscript, but the methodology for determination has not been mentioned, the author should include the determination method in the manuscript.

4.    MAW description is not sufficient for the current manuscript. The author should include the methodology and full description of MAW. How the author has applied the MAW to determine the goal?

Author Response

Please, find the attachment. Thanks.

Author Response File: Author Response.docx