Suspended particulate matters (PM10)
Suspended particulate matters of size up to 10 micrometers are particles able to pass through an opening conducting selection by size, with 50% loss in efficiency at aerodynamic diameter of size less than ten micrometers (10 μm). These particles of size not exceeding 10 micrometers are the so called fine particles or aerosols. Their retention time in the air is long and they originate from natural and anthropogenic sources. Among natural sources, the more prominent include yellow rains, present also with us, forest fires and chemical reactions going on in nature. Combustion of coal, wood and oil, industrial processes, transport and waste burning are the most significant anthropogenic sources.
Increased concentrations of suspended particulate matters can be recorded in urban areas, especially in autumn-winter seasons, which is most probably due to increased frequency in traffic, fossil fuels combustion and meteorological conditions.
Based on data processed for the period 2004-2017, we may conclude that throughout the period, the population was exposed at concentrations of suspended particulate matters exceeding limit values (mean limit value of 50 mg/m3 which should not be exceeded in more than 35 days during a calendar year and annual limit value of 40 mg/m3). Highest concentrations of this pollutant were recorded in Skopje, which was most probably due to human lifestyle, dense population, intensive use of solid fuel for households heating during winter, as well as impacts of industry.
Nitrogen dioxide (NO2)
Investigations have testified the presence of several nitrogen oxides in the air, but the most significant among them are nitrogen dioxide and nitrogen monoxide. These pollutants most often originate from natural sources. However, in urban environments, the main source is the traffic, and industry is minor source. The most toxic of all nitrogen oxides is the nitrogen dioxide, the concentrations of which are dependent on season and meteorological conditions. Namely, concentration of NO is higher in morning hours when the traffic is more frequent, while the intensification of solar radiation during the day leads to transformation of NO into NO2 resulting in increased concentration of NO2. Nitrogen oxides influence the content of ozone and other photochemical oxidants in the air. During the spring-summer period, the concentration of NO2 is higher, while in autumn-winter period, the concentration of NO is higher. The quantity of NOx increases in winter period due to the higher frequency of traffic.
Data processed indicate that the mean annual concentration of nitrogen dioxide was exceeded only in Skopje, which was most probably due to high frequency of traffic and operation of industrial facilities.
Sulphur dioxide (SO2)
Sulphur dioxide in the air most frequently originates from major thermal power plants, as well as from small and medium size boilers for coal combustion in urban environments. The main anthropogenic sources include coal and oil combustion. This pollutant is also released in the air from industrial processes (production of cellulose and paper, sulphuric acid, lead and zinc ores smelting).
In the period 2004 to 2017, there was no exceeding of the mean daily limit value for sulphur dioxide, i.e. population was not exceeded at concentrations of sulphur dioxide above the limit value at all analyzed measuring points.
Ozone – O3
Ozone layer is positioned at height of 10 km to 15 km from Earth and it plays the role of a filter for UV radiation and climate stabilizer.
Automatic monitoring stations measure the ground-level ozone formed as a result of photochemical reactions involving nitrogen oxides, volatile organic compounds (most frequently hydrocarbons), etc. However, its content is also dependent on solar radiation and annual seasons. Thus, higher ozone concentrations are observed in warmer days, especially during summer.
In the period 2004 to 2017, the highest concentrations of ozone were recorded in Bitola, due to the fact that the city is situated in southwestern part of the country with higher number of sunny days during the year. Ozone concentrations measured in Skopje throughout the analyzed period were significantly lower compared to ozone concentrations measured in Bitola and Veles.
