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Air quality in Latvian cities and towns is assessed based on the information on air pollution level in 6 biggest cities and in Olaine. The air quality in cities and towns is influenced by traffic and the pollution from local industries and energy production. The increasing traffic causes increase of toxic emissions and contribute to the generation of photochemical smog.
The measurements executed by the State Hydrometeorological Agency in the time period from 1993 until 1997, indicate that the highest pollution level of nitrogen dioxide has been observed in Riga. The mean annual concentration in the observation period in Riga was 70-80 mkg/m3. This pollution level exceeds the current EU guide value which is 50 mkg/m3.
The highest pollution of ammonia has been observed in Ventspils where its mean annual concentration is being monitored, and it is 120 mkg/m3. Nearly in all cities and towns, the maximum allowable concentration (M.A.C.) of formaldehyde (the normative for formaldehyde will be altered in future) is being exceeded. The mean annual concentrations of sulphur dioxide are low, in average 3 mkg/m3 in all cities and towns, and it does not reach the limit value in EU. The mean annual level of dust in Riga, Ventspils, Valmiera, Liepaja and Daugavpils is 100 mkg/m3, so exceeding the EU limit value which is 40 - 60 mkg/m3.
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Air Quality in the Capital
Air quality in Riga is monitored by three DOAS (Differential Optical Absorption Spectroscopy) system monitoring stations. This report includes information for the year 1997 from the Riga City Council monitoring station located in the Central Railway Station Square.
The concentration of sulphur dioxide (SO2) in Riga does not exceed the mean daily M.A.C. of 50 mkg/m3 even during the heating season and is several times lower that the EU limit value. The mean daily and mean annual amounts of sulphur dioxide are significantly lower than in the biggest European cities. The mean annual concentration of nitrogen dioxide (NO2) was 43.2 mkg/m3.
The mean daily M.A.C. of NO2 was exceeded in 53% of days during the year. It has been lower in summer (July) but in spring, autumn and winter - significantly higher.
The pollution with NOx gases from traffic and unfavourable weather conditions form smog. For example, in November the heavy breathing of population has been observed in several parts of Riga.
The formation of the tropospheric (near the Earth) ozone (O3) occurs under the influence of exhaust fumes emissions which contain nitrogen oxides and hydrocarbons. The tropospheric ozone is a harmful oxidant for flora, fauna and human health. In spring and summer 1997, in the Central Railway Station Square the concentration of the tropospheric ozone exceeded the EU limit concentration for vegetation in 10 days but during the whole year the Latvian daily M.A.C. which is 30 mkg/m3, was exceeded in nearly all days (93%).
In polluted air, formaldehyde is formed in photochemical reactions. In the Central Railway Station Square in Riga, the pollution with formaldehyde exceeded the daily M.A.C. which is 3 mkg/m3 (the normative will be altered in future), during the whole year nearly (98.7 %).
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Heavy Metals
The concentration of lead in air in Latvia is quite low in comparison to other European cities. Also the average concentrations of cadmium and zinc correspond to the pollution observed in other European cities. Generally, the air pollution with heavy metals does not exceed the Latvian normatives. Comparatively highest concentrations of zinc have been observed in Olaine, of cadmium - in Olaine and Riga, and of lead and copper - in Liepaja and Riga.
Near the steel production around Liepaja the level of heavy metals (lead, zinc and vanadium) in mosses and soil is comparable with the highest polluted areas in Europe.
In the south-west of Latvia, the increase of concentrations of heavy metals is caused also by transboundary pollution. Generally, the background level of heavy metals in Latvia is much lower than in the industrialised areas of Central Europe.
Transboundary Pollution of Sulphur and Nitrogen
The calculations of import - export balance for sulphur and nitrogen indicate that the pollution import is typical for Latvia. The source states for the transmission of air pollutants are Germany, Poland, Lithuania. Together these states export 40% of oxidised sulphur, 35% of oxidised nitrogen, 24% of reduced nitrogen from the total deposits in Latvia. However, since 1993 the amount of deposits of oxidised sulphur and nitrogen and reduced nitrogen from the transboundary transmissions has decreased 1.3 times. The amount of emissions originating from Latvia and polluting neighbouring countries is from 1 to 4%.
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