Gasoline Vehicle Emissions at High Altitude: An Exploratory STATIS Study in Guaranda, Ecuador
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn their paper the authors provide a statistical analysis of emissions found for gasoline powered vehicles in a high altitude location. Although the topic of vehicles operated in challenging conditions is interesting, the current state of this study has only limited value and needs a general overhaul before it should be published. Reasons for this are:
* Especially in section 1 (Introduction) but also later in the text, emission of CO and CO2 in a way that is confusing. The introductions gives figures for CO emissions, while later a key indicator "CD" is defined as CO2. Do the authors report carbon dioxide or carbon monoxide emissions?
* If actually CO2 is the pollutant of interest: What about carbon monoxide emissions and NOx emissions? Usually these are also regulated in emission standards and contribute to SMOG. These should be even more harmful in locations where the human respiration is pushed to the limits.
* Line 85: the number of vehicles evaluated is missing. Only "xxx" is given, Based on which criteria were models considered for exhaust gas testing and others not? This is a critical factor for interpreting the study.
* Table 1: Please translate the table header to English. What does column "Frecuencia" show? The fraction of vehicles evaluated or the fraction of vehicles that were actually tested? Do both frequencies (vehicle of a given brand in the pool of all observed vehicles and vehicle of a given brand in the - hopefully much smaller pool - of actually tested vehicles) correlate? Apparently only 79 vehicles were analysed. Is this representative enough for a statistical analysis?
* Since 1.27% looks suspiciously like 1/79, does this actually mean that for most of the models only a single vehicle was evaluated? Does this justify the use of multivariate statistical analyses?
* Is vehicle brand actually an explanatory variable for the observed phenomena? Did the authors pool e.g. by variables like engine power, engine displacement, engine aspiration (naturally aspired engines should be more sensitive for changes in atmospheric pressure i.e. altitude than charged engines).
* Did the authors check, which systems for regulating the air intake were used by different vendors?
* In the current evaluation, the number of analysed vehicles is too small to analyse the effect of 30 vehicles.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsYou presented the wonderful manuscript, that is aimed at solving an environmental task. It will undoubtedly be useful not only for highmountain areas, but also for flat regions. The literature review covers the subject area sufficiently. The results are presented logically and transparently, their reliability is beyond doubt.
I would like to add some comments.
The most dangerous emissions (nitrogen oxides) for the environmental situation are produced by diesel-powered equipment.
The cars is represented by different environmental classes. Please add this.
It is not obvious to me what fuel the cars were refueled with. What was the octane number of the fuel and its environmental class? The cars were refueled at the same network of gas stations.
Good luck
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe modified version improved the quality of the manuscript and the motivation for the study as such and the study design are better described.
Especially the newly introduced section 5 discussing the benefits and limitations justifies the publication.
It would be great if a follow-up study could separate effects like accelerated aging/increased wear of engine or components of the exhaust purification system in the local environment at high altitude from the effect of poorer or better adjustment of vehicles by certain vendors right from the start.
