The vegetable cover of the cities usually is almost completely presented by "cultural plantings" – parks, squares, lawns, flower beds, avenues. The structure of anthropogenous fitotsenoz does not correspond to zone and regional types of natural vegetation. Therefore development of green plantings of the cities proceeds in artificial conditions, is constantly supported by the person. Perennial plants in the cities develop in the conditions of strong oppression.
Characterizing pollution of the air basin of the city, to mention that it is subject noticeable , caused both the weather conditions, and the mode of a of the enterprise and motor transport.
As a rule, the atmosphere gas contamination is more in the afternoon, than at night, it is more in the winter, than in the summer, but also the connected, for example, with a photochemical smog in summertime or education over the city of stagnant mass of air at night meet here. For the cities located in climatic zones and which are in specific landscape conditions various types of critical during which the gas contamination of the atmosphere can critical values are characteristic, but in all cases they contact long windless weather.
Of course, in comparison with power global pollution by means of chemical industry is small, but it too rather notable local influence. The majority of organic semi-products and the end products applied or made in branches of chemical industry is made of limited number of the main petrochemical products. When processing crude oil or natural gas at various stages of process, for example, distillation, catalytic cracking, removal of sulfur and alkylation, arise both the gaseous, and dissolved in water and dumped in the sewerage waste. The remains and waste of technological processes which are not giving in to further processing concern to them.
Pollution of atmospheric air is the most serious environmental problem of the modern city, it causes damage to health of citizens, to the material objects located in the city (buildings, objects,, the industrial and transport equipment,, an industrial output, raw materials and semi-finished products) and green plantings.
In Ancient Rome built aqueducts for supply with fresh water and "Cloaca maxima" - a sewer network, the pool of a settler and by that prevention of a contamination of the sewerage and formation of products of rotting ("Dortmund wells" and" emsky wells").
Besides improvement of automobiles planning actions, actions for a of management of automobile streams and actions for rationalization of transportations in the city can make a contribution to decrease in a gas contamination of the atmosphere of the cities. Creation in the cities of an automated control system for transportations can sharply reduce run of cars within the city and respectively reduce pollution of its air basin.
Existence in the cities of green plantings is one of optimum ecological factors. Green actively clear the atmosphere, condition air, the level of noise, interfere with emergence of the wind modes, besides, greens in the cities well affect an emotional condition of the person. Thus plantings have to be most approached to a residence of the person, only then they can render positive ecological effect.
Thus, pollution of the air basin becomes a real brake of scientific and technical progress in the cities which will constantly amplify in process of increase of requirements to purity of technologies, to growth of accuracy of the industrial equipment and distribution of microminiaturization.
Also the soil cover of urban areas is exposed to radical restructuring. On big squares, under highways and quarters, it is physically destroyed, and in zones of recreations – parks, squares, the yards – strongly is destroyed, becomes soiled household waste, harmful substances from the atmosphere, is enriched with heavy metals, nakedness of soils promotes a water and wind erosion.
Economic activity, planning of residential quarters, limited number of green plantings lead to that in the cities, especially large, there is the microclimate which in general worsens its ecological characteristics.