A Projection of Environmental Impact of a Low Emission Zone Planned in Warsaw, Poland
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsEven though the authors have previous papers with the application of the CALPUFF model to this scale and urban environment, it is important to explain the main characteristics and specificities of the air quality model used, since this is not the most current use. Most of the applications are for stationary industrial sources. There are no considerations about the meteorology considered in the simulations or the validation procedures of the model for a certain year (maybe the base year). There is also a lack of information of current air quality data from standard/official monitoring stations that show the need to implement the measure described and evaluated. It would be relevant to know more characteristics of the assumptions of the Low Emission Zone such as – everyday? including residents? all vehicles or with exceptions? How was that considered in the model? The relationship between emissions from vehicles as NOx and NO2 in the ambiente-air must be clarified, since it is NO2 that is damaging for health and is legislated. There is no annual limit value for NOx. If it was NO2 and not NOx, the annual limit-value would be 40 μg/m3 and not 30 μg/m3 as stated in Figure 6 for NOx. There is a complex relationship of NO/NO2 with ozone that under the model functioning should be also explained, eventually stating assumptions of non-reactivity considered. In many situations the units are not correct (mg/m3 or μγ/m3 in tables and text instead of μg/m3). The structure of the paper should be improved with more separate sections, including one with conclusions.
Author Response
Comments and Suggestions for Authors
Even though the authors have previous papers with the application of the CALPUFF model to this scale and urban environment, it is important to (1) explain the main characteristics and specificities of the air quality model used, since this is not the most current use. Most of the applications are for stationary industrial sources. There are no considerations about the meteorology considered in the simulations or (2) the validation procedures of the model for a certain year (maybe the base year). There is also a lack of information of current air quality data from standard/official monitoring stations that show the need to implement the measure described and evaluated. (3) It would be relevant to know more characteristics of the assumptions of the Low Emission Zone such as – everyday? including residents? all vehicles or with exceptions? How was that considered in the model? (4) The relationship between emissions from vehicles as NOx and NO2 in the ambient-air must be clarified, since it is NO2 that is damaging for health and is legislated. There is no annual limit value for NOx. If it was NO2 and not NOx, the annual limit-value would be 40 μg/m3 and not 30 μg/m3 as stated in Figure 6 for NOx. There is a complex relationship of NO/NO2 with ozone that under the model functioning should be also explained, eventually stating assumptions of non-reactivity considered.
(5) In many situations the units are not correct (mg/m3 or μγ/m3 in tables and text instead of μg/m3). (6) The structure of the paper should be improved with more separate sections, including one with conclusions
Response to Reviewer 1
1)
Done. The relevant explanations are added in initial three paragraphs of Section 4 “Simulation results”.
The sources are divided into three basic categories, according to their emission parameters (the number of sources in brackets): (a) point sources (4073), (b) line sources of the transport networks (1806+4918), (c) area sources of the municipal sector (1452+5819). The emitters of the area and line sources are divided into two subsets: sources located within the city domain and those in the outer belt to help assessing contribution of the surrounding emission field to the total urban pollution. Fig. 2 in [52] presents example spatial maps of municipal (area) and transportation (line) emission sources. Daily and seasonal variability of emission data is taken into account. Moreover, the external inflow of pollutants that enter the study domain is also taken into account. The latter is calculated off-line by the regional scale CAMIX model, using all categories of emission sources located outside the analyzed region shown in Fig. 5. In computer simulation the Warsaw metropolitan area (about 520 km2 within administrative boundaries) was digitized with a homogeneous grid 0.5 km × 0.5 km while the aggregated resolution 1 km × 1 km is applied in majority of the surrounding belt, where the satellite cities are also discretized with fine resolution grid.. The current emission data used for calculation of the initial concentration distribution are the official data provided by the Mazovian Inspectorate of Environmental Protection.
The input dataset for the year considered includes the main meteorological fields, such as wind, pressure, cloudiness, precipitation, etc. The original data sequence is re-analyzed by the mesoscale numerical meteorological WRF model and then transformed by the CALMET preprocessor to the input data required by CALPUFF, in the proper format and resolution. Within this step, additional parameters are also considered, e.g. inversion height and atmospheric stability class. The full terrain characteristic is used to assess the aerodynamic roughness parameter and generate the final wind field which is interpolated to the grid resolution used by the main model. The data (similarly as for the emissions) are finally prepared as a sequence of one hour episodes which cover the yearly time interval.
Using emission and meteorological data for the year 2018, given in the above grid, the resulting concentrations were calculated in 2111 elementary mesh receptors inside Warsaw’s administrative area (compare Figs 5-7). The simulations are performed with 1 h time steps, and the model generates the concentrations at receptor points with the same temporal resolution. On this basis, one can calculate the average values over a specified period of time (e.g. annual mean).
The above details of the model are not included in the text to avoid repeating previously published information. Basic data on the emission field, discretization of the area and implementation of the calculations are given in Section 4, while more details can be found in the extensive list of publications [9,21,38,51,52].
2)
Done The results of the CALPUFF performance validation, applied for the Warsaw metropolitan area, are presented in [51,52] that are added to the reference list. Also, a short comment is added at the beginning of Section 4.
3)
Done. The LEZ project is currently in the consultation stage (with residents, among others) so the details of how it will work are yet to be determined. According to the findings so far, the restrictions would also cover residents (that is actually taken into account in simulations), with exemptions for service vehicle. This is now explained in Section 3, lines 273-275. Moreover, general assumptions of the project, emissivity limits for five implementation stages are included and the emission of the fleet are considered and discussed in more details in Section 3 (Fig. 4, Table 1).
4)
There are several important reasons why NOx concentrations are used as an indicator of (among other) traffic pollution: (1) Emission data for traffic sources are given as NOx (the sum of NO2 and NO converted to NO2), (2) the CALPUFF model provides output concentrations as NOx by default, (3) concentration values are recorded at monitoring stations (model validation) as NOx (compare [51,52], (4) the results of the RDE test of vehicle emissions used in this study are also given as NOx (Fig. 1 in the manuscript), (5) also the Euro Norm limits for vehicle emissions refer to NOx. Moreover, the General Inspectorate of Environmental Protection for Poland determines the admissible level of NOx yearly concentration in the air in Poland as 30 mg/m3 (The sum of nitrogen dioxide and nitrogen oxide converted to nitrogen dioxide; mainly for reasons of plant protection).
https://powietrze.gios.gov.pl/pjp/content/annual_assessment_air_acceptable_lev
That is why this value is quoted in the manuscript. An explanation is added in the caption to Fig. 6.
Ozone concentration is entered as an exogenous variable based on known values and variability in a given year (due to the insufficient CALPUFF modeling precision in this case, see Section 4, lines 304-306.
(5) Done. Units are corrected in the text.
(6) Done. Accidentally omitted section title “5. Summary and discussion” is inserted.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIntroduction, discussion and references are properly detailed. The aim of the research is clear and contextualization is done in deep. In the next lines I indicate some comments and suggestions.
Comments:
- The dispersion model used (CALPUFF) is not introduced in the paper. This model should be introduced and a discussion about if this model is appropiaded for this aim is required.
- Usually, models like CALPUFF, are not used to evaluate ZBE. Complex Eulerian models like CMAQ, CAMx, or more simples like GRAL are used to this task. Authors should to explain why CALPUFF is chosen and what advantages and disadvantages has this selection.
- To use any air quality or dispersion model to obtain representative conclusions for ZBE analysis or any other analysis these models shoud be evaluated previously. Authors should add a complete performance evaluation of its modelling system before showing ZBE effects results. To do this authors should run the modelling system during a baseline scenario and to compare with air quality measurements using statistical parameters. I recommend you to use FAIRMODE recommendations.
- Review size letters in 446-448.
- Conclusions section is not included. Authors should add a specific section for conclusions and discussion in a separate form of "Simulation results".
Suggestion:
281: To modify "Gaussian Modeling System CALPUFF, v.7.0" for "Lagrangian Gaussian Puff Model CALPUFF v7.0"
Author Response
Response to Reviewer 2
1) The comment has been considered. Details concerning the implementation of the CALPUFF model for the Warsaw metropolitan area have been thoroughly presented in the cited earlier (the list has been additionally expanded) publications [9,21,38,51,52], so in this paper, in order to minimize the volume of the work and to avoid repetition of the already published information, they are limited to basic information on the main subject of the study. Short explanation is added at the beginning of Section 4.
2) The CALPUFF model is a very useful tool in analyzing the environmental effects of mid-scale air pollution propagation. Despite its relatively simple design, it takes into account the most important parameters of emission fields (high/low sources, point sources, area sources, line sources, including their temporal variability) and the basic meteorological fields (such as wind, pressure, temperature, cloudiness, humidity, precipitation, etc). The process of pollutant atmospheric transport takes into account the process of diffusion, precipitation washout, dry and wet deposition, and basic chemical transformations (formation of the secondary pollutants, aerosols). On the other hand, the linear structure of the model allows an easily to quantify the impact of individual categories of emission sources on environmental risk (source apportionment), which is important in any scenario analysis, emission reduction strategy, etc. There are many applications in the literature (for example numerous items cited in [51,52]) of practical applications of a new generation CALMET/CALPUFF modeling system, both in urban and regional scale, to assess environmental effects of gaseous and particulate matter pollution emitted by various types of sources..
3) Taken into account. Full validation of the application of the CALPUFF model for Warsaw was carried out early on actual emission and meteorological data for 2012. The results obtained [51,52] show good agreement with the measured data and confirm the suitability of the model, among other things, for the analysis of emission reduction scenarios. These references were added in the manuscript.
4) Accidentally omitted section title “5. Summary and discussion” is inserted.
5) The sentence is modified according to the suggestion
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe most relevant suggestions made were clarified and/or included by the authors.
Reviewer 2 Report
Comments and Suggestions for AuthorsNo additional suggestions.
