NILU - The Norwegian Institute for Air Research

Better air quality in Norway

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Courtesy of Courtesy of NILU - The Norwegian Institute for Air Research

The air over Norway has become better and cleaner past the last ten years, shows a report that The Norwegian Institute for Air Quality (NILU) has worked out for The Norwegian Pollution Control Authority (SFT). The concentration of persistent pollutants and metals in air and precipitation from other countries has been reduced. There is also less acid rain over Norway than before.

The report, ”Overvåkning av langtransportert forurenset luft og nedbør (Atomosfærisk tilførsel, 2003)” (TA-2033/2004), presented in Norwegian, shows the 2003 monitoring results from the rural air- and precipitation chemistry monitoring network in Norway.

The measurement sites

In 2003, main components in precipitation were measured at 20 sites. Trace elements were determined at 7 sites. Air concentrations of sulphur and nitrogen compounds were measured at 9 sites, and ozone concentrations at 12 sites.

Persistent organic pollutants and heavy metals in air are determined at two sites. Particle measurements of PM10 and PM2.5 are determined at Birkenes, where mass and organic and elemental carbon (OC and EC) is determined.

Better air quality in Norway
The highest mean volume weighted concentrations of sulphate, nitrate, ammonium and strong acid (H+) in precipitation were found along the southern Norwegian coast. The highest wet deposition loads (weighted mean concentrations multiplied by the respective precipitation amounts) of sulphate, nitrogen components and strong acid occurred along the coast from Aust-Agder to Hordaland county.

Sulphur dioxide and sulphate in air

The annual mean concentrations of sulphur dioxide and sulphate in air are highest along the south west coast and in Finnmark. The high concentrations of SO2 in Finnmark are partly due to emissions from nickel smelters in Russia. The highest values of oxidised nitrogen species are found in south of Norway.

In all counties except Finnmark dry deposition of sulphur compounds in 2002 was assessed to be 6-20% of the total deposition during winter and 15-30% during the growing season. In Finnmark county, the contribution of sulphur dry deposition to total deposition was calculated to be 51% in winter and 49% in summer. These high numbers are caused by high air concentrations and low precipitation amounts.

Better air quality in Norway

Since 1980 the content of sulphate in precipitation at the various sites decreased by 62-76%. Similar reductions in airborne concentrations were between 82%-93% and 64-73% for sulphur dioxide and sulphate, respectively. The observed reductions in concentration levels are in agreement with reported downwards trends in pollutant emissions in Europe.

There are not those significant trends for the nitrogen species. For ammonium one can observe both positive and negative trends at different sites, probably due to local influence of ammonia. However, there is a clear decrease in the NO2 concentration that last 10 years.

Health guidelines

The highest hourly mean value of ground level ozone (162 µg/m3) was observed at Osen and Kårvatn. The air quality guidelines for protection of human health given by SFT of 80 µg/m3 as 8-hourly mean were exceeded frequently at all the monitoring sites in Norway. The guideline set by WHO of 120 µg/m3 (8-hourly mean) were only exceeded a few times in 2003.

Regarding the effects on vegetation, the critical level of 50 µg/m3 (7-hourly mean) during the growing season (April-Sept.) was exceeded at all sites. Furthermore, SFT’s critical level of 60 µg/m3 (8-hourly mean) for protection of vegetation and EU’s guideline of 65 µg/m3 (daily mean) were exceeded throughout the country. ECE’s critical level for accumulated ozone exposure above the threshold of 80 µg/m3 (40 ppb) (termed AOT40) of 10.000 ppb hours for forests was not exceeded at any of the stations in 2003. The threshold limit for accumulated ozone exposure of crops (3000 ppb hours) was exceeded at two sites.

Heavy metals

The highest annual mean concentrations of most of the heavy metals in precipitation were measured in Sør-Varanger (Svanvik) due to emissions in Russia. The heavy metal concentrations have generally decreased by about 60-80% from the late seventies, but after 1990 the concentration level has been relatively constant, except at Svanvik where there has been a slight increase in the lead concentrations the last couple of years.

In contrast to precipitation, the air concentrations of heavy metals don’t show any trend, the same is true for the average concentrations of mercury in air and precipitation. However there were observed a number of episodes with decomposition of elemental mercury to more reactive species at Zeppelin in the spring 2002. The episodes correlate well with the decomposition of ground level ozone in the three months period of polar sunrise.

The concentrations of alpha- and gamma-hexachlorocyclohexane (alpha- and gamma-HCH) in both air and precipitation at Lista were the lowest observed since the measurements started in 1992.

Better air quality in Norway
The concentrations of PM10 at Birkenes is typically between 5 and 8 µg m-3, but during episodes the concentration may raise up to 20-30 µg m-3. The PM2.5 concentration is highly correlated with PM10, and an average of 67% of the PM10 mass is PM2.5. The sum of inorganic ions contributes with 35–77% of PM10. The marine contribution is between 3-32%. Total carbon contributes with 11-24% of PM10. The main fraction of the total carbon is organic carbon (OC), contributing to about 80-90% of the total carbon.

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