The Swedish Environmental Protection Agency, the unit for Air Quality and Climate Change, is responsible for the national air quality and precipitation monitoring in rural background areas. The report presents the results from the activities within the National monitoring progamme for air pollutants regarding measurements (performed by IVL, ITM and SLU respectively) until 2013 and modelling (performed by SMHI) under 2012.
For most of the air pollutants monitored the situation has improved significantly since the measurement started between 10 and 30 years back, regarding air concentrations as well as deposition in the rural background. The pollution load is in general decreasing the further north one goes.
For most of the components for which there are environmental quality standards and environmental objectives, the concentrations are well below the limit and target values. The ozone concentrations exceed the air quality standard for health. For O3, PM2.5 and benzene (in urban background air) there is a risk for concentration levels above the specifications of the environmental objectives.
Acidifying and eutrophicating substances
Air
A comparison made between measured concentrations of SO2-S in air in the 1980s and in the 2000s shows that the annual average concentration has fallen by about 90 % at the EMEP stations. When comparing Swedish regions it becomes clear that the concentration in the 2000s was highest on the Götaland coast and in the Skåne region and in the Svealand-Stockholm region and lowest in the western parts of northern Sweden. Annual average concentrations of SO4-S, measured at the EMEP stations, have fallen by 65-70 % from the 1980s to the 2000s.
A comparison between measured air concentrations of NO2-N in the 1980s and 2000s show that the average concentrations at the EMEP stations have decreased by 40% in the Götaland coast and Skåne region (Vavihill and Rörvik/Råö) and 70% in the western parts of northern Sweden (Bredkälen). Concentrations in Bredkälen has, however, been low (<1 μg m-3) during the entire period, except in 2003.
The comparison between Swedish regions shows that the concentrations in the 2000s were highest in the Svealand-Stockholm region and lowest in the western parts of northern Sweden. Annual average of NO3-N in air, which has been measured at the EMEP stations during 1986-2013, shows a tendency to have declined somewhat in Götaland coast and Skåne region (Vavihill). The measurements at other stations show no significant trend. For NH4-N concentration in air, the annual average has decreased by 30-35% during the same period at the stations in Götaland coast and Skåne region (Vavihill and Rörvik/Råö).
Atmospheric concentrations of Cl, Na, Mg, Ca and K have been measured at the EMEP stations during 2009-2013. Generally the annual average concentrations have been highest at Råö (the county of Halland) and lowest at Bredkälen (the county of Jämtland).
The modelling is carried out by combining observations and model data into an assessment, where measurements and model data complement each other, in order to achieve a better knowledge. With models it is also possible to quantify the air pollution concentrations into contributions by Swedish and other sources (long-range transport).
The air concentration of reduced nitrogen in 2012 is modelled to range between 0.09 μg N m-3 in the most northern part of Sweden and 1.7 μg N m-3 in the south. For oxidized nitrogen the highest concentrations are modeled in the larger urban areas and the concentration varies between 0.07 and 2.6 μg N m-3 in Sweden. The air concentration of SO2 is modelled to vary between 0.03 and 1.9 μg S m-3 in Sweden, and the highest values are seen in the larger urban areas and at the Norrland coast.
In the modelled area covering Sweden, the Swedish contribution in comparison to the total concentration was 42% for SO2, 39% for NO2 and 35% for NHx in 2012.
Deposition
The deposition for many of the analyzed substances was relatively low in 2013. This can mainly be explained by the low amount of precipitation in 2013.
Measured levels of various substances in precipitation over open field consists mainly of wet deposition, but in southern Sweden dry deposition can amount to 40% of the total deposition. The further north in Sweden the lower the dry deposition fraction. The statistical analysis for wet deposition is made for the years 2000-2013. Averages for measurements divided in three different areas in Sweden are used. The measuring stations included in the analysis in the different areas are the stations that have full data coverage during all years. No aspect of the stations representativity in the different areas have been included.
No statistical trends in any areas of Sweden are obtained for the amount of precipitation. The sulphur deposition has decreased by 49-62% during 2000-2013 in all three areas in Sweden. The sulphur deposition has decreased the most in southwestern Sweden and lowest in northern Sweden. The hydrogen deposition, which may be used as a measure of the acid load, has also declined in all regions since 2000.
Wet deposition of inorganic nitrogen (nitrate + ammonium) has decreased significantly in all three areas in Sweden during 2000-2013. The deposition of inorganic components has decreased the most in southeast Sweden (30%) and lowest in northern Sweden (25%). The deposition of ammonium, showed no statistically significant change in any of the three areas. The nitrate deposition has decreased 40% in south-western Sweden and by 33% in south-east Sweden, since 2000. In northern Sweden, there are no statistically significant changes for nitrate deposition. However, it is important to bear in mind that it is only at a few of the stations in the different areas where a statistical significant reduction of inorganic components was shown. The only exception from this is the nitrate deposition in south-western Sweden, which decreased at 5 of 6 stations.
The total deposition can be divided into wet and dry deposition all over the country with the use of models. The share of the wet to the total deposition was 73% for sulfur (sea salt not included), 77% for NH x and 80% for NOy in 2012. The deposition to different land use types can also be calculated.
The modeling shows that the deposition of oxidized nitrogen is largest in the south-western part of Sweden, and is lowest in northern Sweden. In 2012 the deposition ranges between 40 and 650 mg N m-2. A similar pattern is seen for reduced nitrogen, for which the deposition varies between 35 and 620 mg N m-2 in 2012. For sulfur (sea salt not included) the total deposition varies between 80 and 670 mg S m-2. The deposition is highest in southern Sweden and along the coast of Norrland, and lowest in the inland of Norrland. In 2012 the Swedish emissions caused on average 9% of the deposition of sulfur (sea salt not included) to Swedish land areas. The corresponding number for oxidized and reduced nitrogen was 7% and 17% respectively.
Heavy metals
The concentration of heavy metals in air and in precipitation is lower in Sweden than in some other comparable countries. This can be explained by Swedens northerly position and the relative low use of fossil fuels for electricity and heath production. The highest yearly average concentrations of lead, nickel, cadmium and arsenic in the air in southern Sweden are ten times lower than the threshold values given in the EU directives 2004/107/EC and 2008/50/EC. The situation with mercury is slightly different, since this metal predominantly occurs as an elemental gas in the atmosphere. Due to its long atmospheric residence time it is more or less evenly distributed in the northern hemisphere. Nowadays the concentration levels of mercury in air and in precipitation in southern Sweden are similar to that of many other European countries.
Persistant organic substances
The concentration of PCBs and chlorinated pesticides in background air has generally declined since the start of the measurements in 1996, the decline has however in recent years levelled off. The air concentrations of PAHs, PCBs and DDTs were generally higher in southern Sweden compared to northern Finland, while α-HCH and chlordanes were in the same level both in the south and in north. The same pattern also applies to the atmospheric deposition.
The pesticides, aldrin, heptachlor, diuron, atrazine and isoproturon, which only are measured at Råö, have been detected in few air and deposition samples. Endosulfan (α- and β-endosulfan, endosulfan sulfate) is detected in all of the air and deposition samples from both Råö and Pallas.
BDE (47, 99 and 100) has declined in both air and deposition and levels are in the same range at all stations, Råö, Aspvreten and Pallas. BDE-209 and HBCDD have only been detected occasionally.
The dioxin/furans concentrations in air were generally higher at the Swedish west coast compared to the Swedish east coast, while the levels of chlorinated paraffins (SCCPs) were higher at Aspvreten compared to Råö.
The long term monitoring program gives the possibility to follow up measures and bans. Although the use of PCBs was banned long time ago, they still occur in air from background areas. The decrease in PCB levels is slow, which shows that the PCBs are stored in the communities and ecosystems. As regards e.g. PBDEs, there is a marked decline in the levels, which shows the effect of the ban of these chemicals in the EU.
Plant protection products (pesticides)
Higher concentrations and a larger number of different pesticides were found in precipitation collected at Vavihill in the very south of Sweden, compared to precipitation collected at Aspvreten (situated just south of Stockholm). Differences in findings between the sites can be explained by the closeness of Vavihill to more intense agricultural areas, both in Sweden and on the European continent. The highest number of substances was usually detected during May and June, but at lower concentrations compared to in October when concentrations were the highest. A substantial portion (close to 50 %) of the pesticides occurring in precipitation is no longer applied within Sweden, high-lightening the importance of a trans-boundary transport, also of some modern pesticides. For some of the pesticides that are now forbidden within EU, in particular atrazine, the results demonstrate decreasing concentrations over time. Among the substances applied within Sweden, prosulfocarb was the substance most frequently detected, and in highest concentrations. Prosulfocarb is applied in large quantities also in our neighbouring countries and is quite volatile. Average deposition of pesticides at Vavihill has varied between 100 and 650 mg ha-1, month-1 (10-65 μg m-2, month-1). The deposition at Aspvreten has been one tenth of that at Vavihill. Substances found in air samples are to a large extent the same as those found in precipit
Volatile organic components (VOC)
Highest concentrations of the VOCs were measured in November to Mars, i.e. during the coldest period of the year. The seasonal variations are probably due to higher emissions from combustion processes at wintertime combined with a lower mixing layer in the lower part of the atmosphere during the same period of the year. No specific seasonal variation in the distribution of the VOCs were detected in 2009-2013 the most volatile substances accounted for the largest share in all seasons.
EQS for benzene is 5 mg m-3 as an arithmetic annual average. With the guidance of 60 weekly measurements of benzene at the background site Råö and 30 weekly average values in urban background air in Gothenburg (roof level), the EQS was not exceeded at these sites during 2009-2013.
For 1,3-butadiene and benzene there are clarifications to the national environmental objectives (butadiene 0.2 μg m-3 and benzene 1 μg m-3 as annual averages). The average concentrations of more than 5 000 hourly data during 2009-2013 in urban background air in Gothenburg, was <0.1 μg m-3 for 1,3-butadiene and 0.9 μg m-3 for benzene. These results indicate a risk that the environmental objective for benzene is exceeded on an annual basis.
Particles
The concentration of PM10 in the regional background is about 15 μg m-³ in southern Sweden (Vavihill and Råö), about 8 in central Sweden (Aspvreten) and 3 in the north (Bredkälen). The concentration of PM2.5 in the regional background is 7 -9 μg m-³ in southern Sweden (annual mean, Vavihill), 5-7 μg m-³ in central Sweden (Råö and Aspvreten) and about 2 in the northern part of the country (Bredkälen). The urban background concentrations of PM2.5 in southern Sweden (Burlöv, Stockholm)is in the same order as in the regional background, while the level is slightly higher in urban than in rural areas in northern Sweden (approximately 4 μg m-³ in Umeå). The average exposure indicator shows that Sweden achieves the requirements set by the EU at an acceptable level of exposure. In Burlöv, however, the environmental objective (maximum of 3 days > 25 μg m-³) were exceeded both 2012 (11 days) and 2013 (8 days).
At Aspvreten in central Sweden, where measurements of PM10 has been going on since 1990, the level has dropped from almost 20 to 7 μg m-³ today. At Vavihill in Skåne, where measurements began in 2000, and Råö in the Gothenburg area (start of measurement in 2007), there is no clear trend.
PM2.5 at Aspvreten since 1998 has fallen from 11 to 12 to about 6 μg m-³ today. Most of the decrease occurred in the period 2000 – 2005. The trend are similar at the other stations in Sweden.
The concentration of soot, measured as organic carbon (OC), in the PM10 fraction, was approximately 1.5 μg m-³ in the southern and middle part of Sweden (Vavihill and Aspvreten) with no clear seasonal variation. The monthly averages concentration of elemental carbon (EC) is about 0.2 to 0.5 μg m-³ during the winter and from 0.1 to 0.2 during the summer. Measurements of OC and EC have been made since April 2008. No measurements are made in Northern Sweden.
Soot has been measured with an indirect method 'black smoke' (BS) in several background stations since the early 1980s. Since then, the concentration in southern Sweden decreased from 4-7 to approximately 1.5 μg m-³ today. In northern Sweden (Bredkälen) the concentration was approximately 1.5 in the 1980s and is below 1 μg m-³ today. Most of the decrease occurred in the 1980s and early 1990s. One reason that no reduction is seen thereafter may be that the levels are often below the detection limit of the measurement method.
Ground-level ozone
The concentration of ground-level ozone is largely determined by the meteorological conditions, and for the average annual level of ozone there is neither a clear trend in time nor a geographical gradient over the country. The number of episodes of high concentrations of ozone, though, is significantly higher in the southern part of Sweden than in the north, both as regards the 8 hour mean value (limit value for health) and AOT40 (limit value for vegetation). During 2012 and 2013 no hourly values above the information threshold (180 μg m-3) were observed. However, the environmental goal for hourly means (80 μg m-3) as well as the limit value for the 8 hour mean (120 μg m-3) were exceeded at many of the monitoring sites during these years.