Air quality

The Finnish Meteorological Institute investigated the air quality effects caused by car traffic, energy production and industry in Riihimäki using diffusion models commissioned by the city in a just-completed study. The effects of household wood burning on air quality were also investigated. According to the study, the air quality in Riihimäki is mostly good, but there are regional and temporal variations in the concentrations. The air quality is particularly good in rural areas further from the center and busy traffic routes. From time to time, the air quality can deteriorate along Riihimäki's busiest thoroughfares and in densely built small house areas.

Air quality is most significantly affected by emissions from car traffic, street dust, wood burning in residential buildings and long-range transport of small particles.

• The most significant effect on Riihimäki's nitrogen dioxide concentrations is the emissions from car traffic.
• Concentrations of respirable particles increase especially in the street dust season in the vicinity of busy thoroughfares. The formation of high concentrations of respirable particles can be significantly affected by winter street maintenance and timely sand removal and dust binding.
• Long-range transport and background concentrations cause most of the small particle concentrations.
• Among the emission sources, household wood burning and car traffic cause a significant increase in fine particle concentrations in areas of small houses and in the area affected by traffic lanes.
• On the other hand, the impact of energy production and industrial emissions on air quality at breathing height is small, because the emissions are mainly released from tall chimneys, where they spread and dilute effectively.

The concentrations of nitrogen dioxide, small particles and respirable particles in Riihimäki fall below the limit values ​​for air quality. The daily limit value of respirable particles is not exceeded, but daily concentrations may exceed the limit value level several times during the year. The World Health Organization WHO guideline values ​​for small particle concentrations are exceeded, which is mainly due to the long-distance transport of small particles. Limit values ​​aim to reduce or prevent harmful effects on health and the environment.

The Finnish Meteorological Institute measured the air quality in the center of Riihimäki in May-October 2016. According to the measurement results, the air quality was generally good in terms of particle concentrations.

The outdoor air particle concentrations measured in the center of Riihimäki were typical for a city the size of Riihimäki. The measured concentrations of respirable particles clearly fell below the air quality guideline value and limit value level given for particle concentrations during the review period.

Car traffic exhaust emissions and street dust raised by traffic had the greatest influence on the concentrations of respirable particles measured in Kolmiopuisto. In the measurements, no influence of energy production and industrial facilities on particle concentrations could be observed. On average, the highest concentrations of respirable particles were observed in calm weather, when the dilution of exhaust gas emissions and particulate emissions caused by dusting is weak near the ground surface and concentrations can rise to higher than normal levels.

An air quality index was calculated from the concentrations of respirable particles measured in Riihimäki Kolmiopuisto, which describes the prevailing air quality situation on a five-point verbal scale: good, satisfactory, avoidable, bad and very bad. As described by the index, the air quality in Riihimäki was good or satisfactory during almost the entire measurement period. The air quality was bad only on one day, and no very bad air quality situations were observed in May-October. The poor air quality situation was probably caused by local dusting caused by the demolition site of a nearby building.

The Finnish Meteorological Institute measured the concentrations of so-called respirable particles with a diameter of less than 1 micrometers on Hämeenkatu from 2005 March 30 to 2006 May 10 using a continuous particle concentration analyzer. A report on the measurements, Respirable particle concentration measurements, has been published.

According to the results, the air quality in the center of Riihimäki on Hämeenkatu was bad or even very bad every day in March-April 2005. The guideline value for the daily concentration of respirable particles, 70 µg/m³, was exceeded in both of the above-mentioned months. In summer - October 2005, the hourly and daily concentrations of respirable particles remained at a relatively low level for most of the time. In December 2005, the base level representative of the concentration of inhaled particles through snow was measured on Hämeenkatu under conditions where the dusting of the streets had little effect on the measurement results. Particle concentrations in March-April 2006 were significantly lower than in the spring season of 2005 and in the early days of May slightly higher than in 2005. The air quality in the center of Riihimäki was clearly better in terms of particle concentrations in the spring of 2006 than the previous year. The improved result was influenced by the more efficient removal of sandblasting sand.

The particle concentrations in the central area of ​​Riihimäki are most significantly affected by street dust lifted from the ground by traffic and wind, and the cleaning of the streets from winter sandblasting, which was timed around the same time as the clear rise and peak concentrations observed in the vicinity of the measurement point. The study showed that the influence of particle emission sources other than street dust and traffic exhaust emissions on the concentration of respirable particles in the center of Riihimäki is mostly marginal during the spring dust season. Emissions from local energy production and industry, as well as long-range particulate emissions originating from other parts of Finland and abroad, caused only a very small background concentration to the particle concentrations in the city center.

The effects of air pollutants on the state of the environment were studied in Kanta- and Päijät-Hämee with the help of bioindicators in 304 research areas, of which 13 were in Riihimäki. Pine trunk lichens, pine crown condition, elemental concentrations of mosses, needles and humus, as well as dioxin and furan concentrations in humus were used as indicators. The study was financed by the municipalities and regional associations of the region, as well as the facilities that cause air emissions. The study was coordinated by the Häme ELY Center and Nab Labs Oy was responsible for the implementation of the study.

The effects of air pollutants were most evident in the bioindicators in the most heavily loaded areas. In scattered areas, the effects were mild. The condition of the lichens deteriorated and the number of lichen species decreased due to industrial activities, energy production, waste treatment and wastewater treatment plants in the area. The strength of the effect depended significantly on the emission height: emissions spreading through tall chimneys are strongly diluted in the air and do not cause as strong a local load as emissions from low ones.

Based on the study, the air quality in the area was on average the same as elsewhere in Finland. In Kanta-Häme, e.g. the degree of damage to ringworm increased, while the occurrence of algae decreased compared to 2002. The mercury content of the moss and the cadmium and lead content of the humus decreased, but the copper content increased. The emission load of the area was best described by the metal concentrations of moss and humus. High metal concentrations were observed especially in the Heinola Myllyoja research area and Riihimäki. The lead and chromium concentrations measured in the moss were higher in the area than in reference materials elsewhere in Finland, higher average concentrations were observed for chromium, copper, lead, vanadium and nickel than in the humus reference materials. The metal load in the Riihimäki area was reflected in the metal concentrations of humus and moss, which were the highest for several metals in the Haapahuhta area.

In a study completed in early 2011, the Finnish Meteorological Institute analyzed the air quality effects caused by car traffic, energy production and industry in Riihimäki using diffusion models. The study did not take into account possible interference emissions from facilities, which can locally cause high short-term concentrations.

According to the study, the air quality in the area is generally good, but air pollution concentrations can occasionally rise along the busiest traffic routes;

• Car traffic and long-distance transportation cause most of the concentrations of nitrogen dioxide and respirable particles in the outdoor air in Riihimäki.
• Particle concentrations caused by car traffic are high, especially during the dry spring dust season in March–April, when, in addition to exhaust gas emissions, particle concentrations are strongly affected by dust rising from the road surface.
• The highest concentrations of nitrogen dioxide and respirable particles occur along the highway (vt 3), in its intersections and along the main streets of the city center.
• The concentrations clearly decrease as the distance from the busiest traffic routes and from the center of Riihimäki increases.
• With their current emissions, energy production and industry cause only a very small increase in the concentrations of nitrogen dioxide and respirable particles in the outdoor air, as emissions released from high altitudes are effectively diluted.

The concentrations of nitrogen dioxide and respirable particles fall below the limit values ​​set to protect health in areas where people live or stay. However, in parts of Riihimäki's downtown area and along the busiest traffic routes, air pollution concentrations may exceed the air quality guidelines. Guideline values ​​are used to prevent harm to health and nature.