How Helsinki’s air quality has improved over the last 30 years
How Helsinki’s air quality has improved over the last 30 years
Dust concentrations can still be a difficult challenge to overcome
Late last week Helsinki the municipality’s website proudly reported that the city has been for the past three decades significantly improved air quality profile. The capital of Finland is usually a good place to fill your lungs.
Sulfur dioxide concentrations have fallen by more than 90% and this gas is no longer a major air quality problem in the Helsinki metropolitan area. Nitrogen dioxide concentrations have also halved. In contrast, the decrease in particulate matter concentrations has not been as significant as the reduction in the other two pollutants.
Sulfur dioxide – a great success story
Sulfur dioxide (SO2) comes mainly from energy production and partly from ship emissions. Sulfur dioxide levels fell, especially in the 1980s and 1990s, when emissions from energy production and industry were curtailed.
Sulfur emissions from road transport decreased e.g. switching to low-sulfur and sulfur-free fuelsl. Today, road transport accounts for less than 1% of sulfur dioxide emissions in the Helsinki metropolitan area.
Sulfur dioxide concentrations have also fallen in ports, especially in the 2010s. These concentrations have been reduced by tightening emission standards for shipping in the Baltic Sea in 2010 and 2015.
Nitric oxide – NOx old cars
Oxides of nitrogen (NOx) airborne emissions from transport, especially diesel cars and heavy vehicles. Nitrogen dioxide concentrations have fallen significantly at metering stations in the Helsinki Metropolitan Area over the past nearly 30 years. NO concentrations in the busiest placesx Exhaust emissions have roughly halved from what they were at the start of measurements in the late 1980s.
The decline in nitrogen dioxide concentrations has contributed fleet renewal and emission reduction techniques, as well as reducing emissions from the city’s HSL bus fleet. The annual limit value for nitrogen dioxide was still exceeded in 2015. Today, the concentrations are below the annual limit value, and the limit value is not expected to be exceeded in the future.
Fine particles, not yet in very good condition
Respirable particles are mainly street dust in traffic environments. The most significant local the sources of small particles are emissions from transport and wood burningand the latter varies greatly according to weather conditions.
Particulate matter concentrations in the region have decreased over the years, but the decrease in concentrations has not been as significant as the reduction in sulfur dioxide and nitrogen dioxide.
Concentrations of respirable particles have dropped to about a third of what they were when measurements began in the mid-1990s. The amount of street dust has been reduced by e.g. enhanced street cleaning and dusting with dilute calcium chloride solution, use of a sand screen and reduction of driving speeds.
The street dust season of spring 2021 in the Helsinki Metropolitan Area was heavier than in the previous year, which is partly due to the fact that the winter of 2021 was colder and the streets still had to be polished at the end of February. Another reason, of course, was the reduced traffic during the first COVID closures. Street dust was highest in March, but concentrations of respirable particles were also high in early April.