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Brno
Environmental Situation The historic centre is partly situated in the fluvial plan on the northern stretches of the Dyje-Svratka depression. The Brno Highlands surrounding the city in the north is in a shape of a horse-shoe. The Drahanská vrchovina highlands extend towards the north-eastern areas of the city, along with its southern part, Moravian Karst.
The prevailing air flow in the city is north-western, which is more favourable for the dispersion of harmful substances. During the colder time of the year, the heating season, there is unfavourable influence of prevailing calm or southern or south-eastern winds at a velocity up to 2 m.s-1. Air temperatures are affected by the concentration of built-up areas, ground relief, particularly in the northern, hillier part of the city and the tendency to inversions and ground-level fogs in the closed basins and fluvial plains of the rivers. Average annual air temperature is 8, 4 ºC, average summer temperature is 17, 8 ºC, in winter it is -1ºC.
The city as a whole is situated in a mild rain shadow of the Českomoravská vrchovina highlands. The maximum rain precipitation is outside the heating season, in June - August.
Other insignificant maxima are in October and November. During the main months of the heating season, i.e. from December to March, the rainfall in this area is 20 ? 22% on average. As the rainfall has a great influence on the removal of pollutants in the air, the rainfall distribution in the city of Brno is unfavourable from this point of view.
The area of the city is an area with deteriorated air quality defined by the MoE of the CR on a yearly basis. These are areas where the ambient air quality limit is exceeded in one or several pollutants.
In a total of 7.5% of the area of the city, the ambient air quality limit is exceeded in average 24-hour concentrations of PM10, in 1.75% of the area the ambient air quality limit of NO2 is exceeded, in 58% of the area ambient air quality limit of benzo(a)pyrene is exceeded and in 100% of the area the ambient air quality limit of ground ozone is exceeded.
The main factor causing emissions in the city is traffic (68% PM10, 83% NOx, 93% benzene and 85% VOC). Stationary sources of pollution contribute mainly to the emissions of SO2 (97%) and benzo(a)pyrene (almost 100%).
A major problem related to dust emissions is the so-called "secondary dustiness" originated by formation of dust particles whirls caused by means of transport, softstanding, non-grassed surfaces and transport from agriculturally cultivated fields in the surroundings of the city.
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