**1. Introduction**

Ambient air pollution is one of the main environmental problems in Europe, and some pollutants are the issue primarily in Poland. The European Union has implemented legislation that sets standards and goals for many air pollutants in the form of Directives 2008/50/EC and 2004/107/EC [1,2]. These provisions have been transposed into national law, primarily as the provisions of the Act on

Environmental Protection Law and the Regulation of the Minister of the Environment on the levels of certain substances in the air [3,4]. In addition to standards for the concentrations of selected pollutants, the provisions also regulate the methods of air quality assessment and management, e.g., through the development and implementation of recovery programs and air quality plans.

International organizations dealing with air quality issues and assessing their impact on society, health and the environment, such as the World Health Organization (WHO) and the European Environment Agency (EEA), study and analyze the impact of air pollution on health. According to EEA estimates, there were around 412,000 premature deaths attributable to ambient PM2.5 pollution in 41 European countries in 2016, of which 43,100 deaths occurred in Poland (premature deaths are deaths that occur before reaching the average age defined by life expectancy. Premature deaths are considered avoidable if their causes were eliminated) [5]. Particulate matter, both less than 2.5 μm and less than 10 μm in diameter, is the source of pollution that causes the most problems and exceeds permissible air quality standards.

Adverse health effects of air pollution, particularly regarding particulate matter, are observed as a result of both long- and short-term exposure. For this reason, WHO recommendations, as well as air quality standards introduced by the European Union legislation and transposed into the laws of individual Member States, define annual mean and daily limit values. According to Polish regulations, pursuant to Directive 2008/50/EC, the annual mean limit value concentration for PM2.5 is 25 μg/m<sup>3</sup> (since 1 January 2020, the so-called second phase of the standard is 20 μg/m3). For PM10, the annual mean is 40 μg/m<sup>3</sup> and the 24-h mean is 50 μg/m<sup>3</sup> (allowing 35 days with exceedances of the limit value in a calendar year). In addition, selected European countries have introduced information and alarm thresholds for PM10 concentration. As of 2019, these thresholds in Poland are respectively 100 μg/m<sup>3</sup> and 150 μg/m<sup>3</sup> for the daily mean concentration [6].

The results of the air quality assessments carried out annually in Poland by the Chief Inspectorate for Environmental Protection indicate a bigger problem with meeting the PM10 daily limit value. In 2018, the norm was exceeded in 39 of the 46 assessed zones in the country. Annual means were exceeded in nine zones. The limit value was exceeded during this period at 160 and 25 measuring sites in the country out of 227 included in the assessment, for both standardized averaging times, respectively [7]. Therefore, actions have been taken to improve air quality in Poland [8]. One example of these activities is restrictions and bans on the operation of fuel-burning installations, effective also in the Lower Silesian Voivodship. This is due to three so-called "anti-smog" resolutions adopted by the Lower Silesian Regional Assembly on 30 November 2017 [9–11]. One of the abovementioned resolutions covers the territory of the entire voivodship, excluding the city of Wrocław and 11 health resorts of the Lower Silesian Voivodship. The provisions introduced by this resolution are binding in Bogatynia commune and introduce restrictions and bans on the operation of fuel-burning installations. As of 1 July 2018, in Bogatynia commune, it is forbidden to use the following:


The resolution introduces a gradual withdrawal of out-of-class installations, and as of 1 July 2018, it is allowed to install only such new boilers and local air heaters (fireplaces) that meet the ecodesign requirements regarding particulate matter emissions [12]. As of 1 July 2024, the resolution introduces a ban on the use of solid fuel installations that do not meet a minimum of third class requirement according to PN-EN 303-5:2012. The deadline for the implementation of the resolution and the resulting bans is 1 July 2028. From then on, the use of solid fuel installations that do not meet the minimum emission standards of class 5 in terms of particulate matter emission limits according to PN-EN 303-5:2012 will be prohibited. Introducing these restrictions for the combustion of solid

fuels and the use of installations is expected to bring a significant improvement in air quality and thus reduce the likelihood of developing air pollution-related diseases.

In Poland, according to o fficial data, the majority of PM10 emissions to the atmosphere (approximately 47%) are generated by non-industrial combustion processes, including in the municipal and residential sector related to solid fuel biomass combustion for heating and hot water preparation [13]. The next three groups with the largest share in PM10 emissions are combustion processes in industry (approximately 14%), road transport (approximately 8%) and manufacturing (approximately 7%). These data are from 2017 and concern the entire country [14]. The situation may be di fferent in individual regions or may be considered locally, where the impact of individual sectors may vary. This may be connected with the presence of a specific source or group of industrial sources, or the density of the high-tra ffic road network, which occurs primarily in the central areas of the agglomeration and large cities. The impact of specific groups of sources is also time-varying and depends, e.g., on the season of the year (heating and non-heating period) or day (variability of household heating systems activity or the volume of tra ffic) [15].

The analysis of the reasons for high levels of particulate matter concentration, including the exceedance of daily limit values, must also consider the episode period, location of the area of exceedance in relation to emission sources and local topographic conditions a ffecting ventilation possibilities, as well as meteorological conditions conducive to the accumulation of pollution, such as low wind speed or temperature inversion phenomena. In the case of large urban centers, peripheral areas are generally more exposed to the influence of heating sources, while car transport may be of more importance in the city centers. In special meteorological situations and certain areas, the movement of pollutants (inflows) and their accumulations a ffect the range of impact of individual emission sources [16].

One of the elements of ambient air quality managemen<sup>t</sup> in a given area is its assessment and diagnosis of the conditions, taking into account possible exceedances of the limit values. In accordance with the current laws, as part of the State Environmental Monitoring coordinated by the Chief Inspectorate of Environmental Protection (CIEP), this assessment is carried out using three basic groups of methods [17,18]:


Actions connected with the following aspects are examples of the air quality managemen<sup>t</sup> process:


All of the above elements occur at various levels: international (e.g., European), national, regional (e.g., voivodship) and local (e.g., urban or a specific industrial plant or a single installation). All of them also use various air quality modeling techniques, such as chemical modeling of transport and transformation of pollutants, receptor or statistical modeling, also using, e.g., artificial neural networks [16,19,20].

Table 1 summarizes examples of the use of modeling techniques at various levels and for the purpose of achieving various main objectives of air quality management. It presents general examples and, in selected cases, references to specific projects or applied solutions. Considering the comfort of life and health of people, especially in the areas close to objects that can significantly a ffect the environment, activities aimed at minimizing the onerous impact of those objects are particularly important. Therefore, in order to analyze and evaluate the e ffectiveness of the implemented solutions in the context of improving air quality using modeling, the area selected as a case study is the commune in Poland of a nature unique to Poland and Europe, both due to its geographical location bordering with two countries—Czechia and Germany—and its characteristically diverse terrain. The selected area is an interesting case also because it contains one of the largest energy complexes in Poland, which includes an open-pit lignite mine with a large lignite-fired fuel combustion facility. In addition, ambient air quality in the analyzed area is influenced by combustion processes in household boilers. Therefore, the analysis of the distribution of pollutant concentrations and the assessment of the effectiveness of measures for reducing air pollutant emissions, including health risk assessment, are extremely important.


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\* SEM—State Environmental Monitoring; \*\* CIEP—Chief Inspectorate of Environmental Protection; \*\*\* IEP-NRI—Institute of Environmental Protection—National Research Institute; \*\*\*\* GAINS model —Greenhouse gas—Air pollution INteractions and Synergies model; \*\*\*\*\* AAQ Directives - EU Ambient Air Quality Directives

#### **2. Characteristics of the Research and Analysis Area**

The area of Bogatynia commune (Figure 1) located within three basic geographical regions: the mesoregion of the Zittau Basin, the Izera Foothills and Izera Mountains and the Nysa Łu˙zycka Valley were selected for the case study. The mesoregion of the Zittau Basin has a lower terrain in relation to the Izera Foothills and the Izera Mountains surrounding it from the northeast and the east. On the west side, the area is limited by the Nysa Łu˙zycka Valley, behind which the Zittau Valley extends into the Lusatian Foothills. Such location and character of the area mean that its diverse terrain can significantly shape air mass flows within it.

**Figure 1.** Natural topography in Bogatynia area (source: own study).

The largest cities of the studied region are Polish Bogatynia in the center and German Zittau (Zytawa) and Czech Hr ˙ ádek nad Nisou (Gródek na Nys ˛a) (Figure 2) in the southwest, already outside Poland. The other places are of a rural character.

Three low-volume voivodship roads, with a volume below 10,000 vehicles a day, run through the studied area. The DW352 road connects Zgorzelec with the state border at the Kunratice/Bogatynia crossing. The DW354 road runs from the Bogatynia–Zatonie district to the west, and further south to the town of Sieniawka, along the border with Germany, where it crosses the border. Road DW332 is a short section connecting route 178 (on the German side) and a border crossing with Germany in the town of Sieniawka, as well as a border crossing with Czechia in the direction of Hrádek nad Nisou, where on the Czech side it turns into route 35. Another regional road is route 99 running on the German side of the border along the Nysa Łu ˙zycka River. Other roads are local and have basically no influence on local air quality.

The analyzed area holds one of the largest energy production complexes in Poland, which supplies around 8% of the energy production to the national energy system. It consists of a conventional block heat and power plant (ELT) located in the north, with interstage steam superheating and a closed cooling water system, whose basic fuel is lignite. Currently, the installed capacity of the PGE GiEK S.A. Turów Power Plant Complex (ELT) is 1498.8 MW in six power units of 235 MW and 260 MW capacity. Coal is supplied directly by belt conveyors from the PGE GiEK S.A. Turów Coal Mine (KWBT) located

in the south. The surface of the open-pit excavation area with an internal backfill area currently covers around 26 km2. The open pit is directly adjacent to the town of Bogatynia (in the east) and the state border (in the west). Two districts of Bogatynia—Trzciniec Dolny and Zatonie, located between the power plant and the mine, are significantly exposed to the impact of both facilities. Currently, the bottom of the open-pit mine is around 10 m.a.s.l., and the elevations around it are at 225–300 m.a.s.l. The surrounding mountains and foothills lie at heights above 500 m.a.s.l. in the southern part and in the range 400–500 m.a.s.l. in the northern part.

By 2028, the ambient air quality in the analyzed area will have been shaped by a number of changes significantly affecting the size of emission balances in Bogatynia commune. These activities are discussed in detail in Section 3.1.3.

**Figure 2.** The analyzed area (source: own study).

#### **3. Materials and Methods**

#### *3.1. Mathematical Modeling and Available Input Data*

Model calculations were made using the WRF-CALMET/CALPUFF system. This system is based on the 2nd generation cloud model (CALPUFF), powered by data from the WRF meteorological model (Weather Research and Forecasting Model) [21,22]. Meteorological data for calculations are prepared by the CALMET preprocessor, which determines the time and space variables of meteorological parameters with the grid resolution specified by the user. The conducted analyses defined three scenarios of emission changes: (1) scenario (scenario 1) related to changes in emissions in the studied mine resulting from the minimizing measures indicated in the report on the mine's environmental impact [23], (2) scenario resulting from the anti-smog resolution in force in the Lower Silesian Voivodship [11] (scenario 2) and (3) scenario compiling the abovementioned scenarios (scenario 3).

For calculations on a local scale, smaller mesh sizes with detailed information about the terrain and land use are applied, as these parameters can significantly affect the shape of the pollution field, especially in mountainous areas. For the purposes of this study, a system of nested grids with resolution sizes of 0.25–1 km was used. The domain in which the meteorological parameter fields were calculated covered the area within 10 km of the border of Bogatynia commune. Meteorological data from 2018

were used, which were adapted to two nested grids with a resolution of 0.5 km in Bogatynia commune and 1 km in the rest of the computational domain (Figure 3a). Information about the terrain (as the average in a grid) and land use (as the prevailing value) was implemented into the model with the same resolution [24,25].

**Figure 3.** Parametrization of grids and receptors in the model: (**a**) meteorological grid; (**b**) discrete receptors (source: own study; map background: https://www.google.pl/maps).

Calculations of pollution concentrations were carried out based on grids in two resolutions: 0.25 km in the area of Bogatynia commune and 1 km in the rest of the computational domain (Figure 3b). The obtained results were visualized using inverse distance weighting (IDW). According to this method, the value for each interpolated cell is calculated based on the values of neighboring points weighed by the inverse of their distance. For such a dense receptor network, this is the most optimum interpolation method [26].

In the air quality modeling, the influx of pollutants from outside the examined area was also taken into account as boundary conditions varying in time and space derived from chemistry transport model (CTM) calculations. Data from the Copernicus project were used [27].
