Air quality

Tropospheric ozone, nitrogen dioxide and fine particulate matter are the most common compounds decreasing air quality. Air pollutants are removed from the atmosphere, for example, by sedimentation, diffusion, washout or occult deposition. Dry sedimentation involves especially heavy particles. Wind and other air turbulence disperse air pollution, and rain and snow cause washout or wet deposition of particles and other air pollutants. Occult deposition is the deposition of airborne particles on the surface of vegetation.  


In Finland where air is not heavily polluted, the formation of tropospheric ozone requires the presence of nitrogen oxides and sun light. If the concentration of nitrogen oxides is low, the tropospheric ozone is oxidized and thus its concentration declines. If there are abundantly nitrogen oxides in the air, the ozone is formed in oxidation process of methane (CH4), carbon monoxide (CO) and volatile organic compounds (VOC).

Tropospheric ozone is highly phytotoxic as it is a powerful oxidizer. It damages plants, animals and human-made structures such as buildings. It is a threat to both agriculture and forestry by decreasing plant health and productivity. It has a negative effect also on human health, especially on respiratory organs. Tropospheric ozone accelerates global climate change.


Nitrogen dioxide is formed in a combustion process, most often in combustion of gas (methane), oil or coal. About 65% of nitrogen dioxide origins from energy and industry sector, 35% from traffic. In cities the significance of traffic is larger. Nitrogen dioxide impedes the function of respiratory organs. In natural environments as well as on human constructions it causes acidification and eutrophication.


Fine particulate matter ranging from sub-micron aerosols to visible dust origins from, for example, street sand and dust and combustion processes such as oil in traffic or domestic burning of wood. Particulates may be chemically non-toxic or they may contain toxins such as heavy metals and hydrocarbons. Particulate matter inflicts respiratory problems.


Other air pollutants are for example carbon monoxide, nitrogen oxides, sulphur dioxide and volatile organic compounds.


Ilmanlaatuportaali. Ilmatieteen laitos. Ympäristöministeriö. [In Finnish]

Air quality in Finland. Finnish Meteorological Institute. Ministry of Enviroment.


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