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The air quality in the Helsinki city centre is affected by pollution sources and meteorology

The air quality in the Helsinki city centre is affected by pollution sources and meteorology

Meteorological parameters that affect most the air quality in the Helsinki city centre are wind speed and temperature.

Research conducted by Finnish Meteorological Institute showed that the main particle sources in the Helsinki city centre are local traffic related emissions and long-range transportation. It was found that the pollutant concentrations were mostly affected by wind speed and temperature. Air pollutants were removed more efficiently with the increasing wind speed. This was seen especially for fine particles. However, the concentration of coarse particles (PM2.5—10) increased with increasing wind speed. This is due to more efficient suspension of road dust to the surrounding air.

Highest pollutant concentrations were measured when temperature was either low or high. Removal of air pollutants was observed to be hindered during cold winter days due to temperature inversion. Inversion causes the air pollutants to trap on the boundary layer and therefore increased concentrations were observed. Removal of air pollutants was also limited also during calm summer days with high temperatures. Strong solar radiation together with high concentration of water vapour in the ambient air during these days also enhanced photochemical oxidation reactions in the atmosphere. This increased the formation of particulate organic matter from gaseous organic compounds.

Concentrations of air pollutants, PM10, PM2.5, trace gases (ozone, nitrogen oxide and nitrogen dioxide, were measured in Helsinki city centre for two years between 2013 and 2015. In addition chemical composition of fine particles (PM1) was measured continuously. Measured components were total organic, sulphate, nitrate, ammonium and black carbon. Organic material was the major component of fine particulate matter being on average 60% of its mass. The average mass fraction of sulphate was 12%, black carbon 11%, nitrate 10% and ammonium 7%.

Research was done in co-operation between Helsinki Region Environmental Services authority and University of Helsinki. The research and results presented are funded by Cluster for Energy and Environment (CLEEN Ltd), Measurement, Monitoring and Environmental Assessment (MMEA), Tekes INKA-ILMA/EAKR, NAQT and Cityzer projects and Helsinki-Uusimaa Regional Council (HAQT project).

Further information:

Senior researcher Kimmo Teinilä, Finnish Meteorological Institute,

Reference: Teinilä, K., Aurela, M., Niemi, J. V., Kousa, A., Petäjä, T., Järvi, L., Hillamo, R., Kangas, L., Saarikoski, S., Timonen, H., (2019). Concentration variation of gaseous and particulate pollutants in Helsinki city centre – observations from a two year campaign in 2013–2015. Boreal Env. Res. 24, 115–136.


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