Air pollution - State and impacts (Latvia)

Exceedance of air quality limit values in urban areas

Particulate matter (PM₁₀)

Preliminary data for the centre of the capital city, Riga, from 2004 to 2008 indicate that the mean annual concentration of PM₁₀ exceeds the limit value for the protection of human health. Meanwhile, at urban and rural stations throughout Latvia limit values for human health protection were not exceeded (Figure 1).

Several of the recorded 24-hour PM₁₀ values in Riga and Liepaja were also above the limit value (Figure 2).

 Figure 1: Annual average PM₁₀ concentrations (annual limit value is 40 μg/m³)

Source: Latvian Environment, Geology and Meteorology Centre

Figure 2: Number of days on which the PM₁₀ daily limit value for human health protection (50 μg/m³) was exceeded (limit may not be exceeded more than 35 times per calendar year).

Source: Latvian Environment, Geology and Meteorology Centre

Latvia began measuring PM_2.5 in 2008 in the Riga metropolitan area, at Milgravis and Brivibas Street stations and at other stations across Latvia (Ventspils and Liepaja).

Nitrogen dioxide (NO₂)

Annual average limit values of nitrogen dioxide for human health protection in Latvia were only exceeded at one traffic station in Riga (Valdemara Street). During 2008, nitrogen dioxide concentrations reached the limit value (44 μg/m³) for the protection of human health (within the margin of tolerance) (Figure 3).

Figure 3: Nitrogen Dioxide (NO₂) annual average concentration (annual limit value is 40 μg/m³)

Source: Latvian Environment, Geology and Meteorology Centre

Exposure of ecosystems to acidification, eutrophication and ozone

Deposition from the atmosphere is a major indicator of precipitation, ambient air quality and ecosystem status. Between 2004 and 2008, there was no significant change in the total deposition of sulphur and nitrogen at Latvian rural background stations (Figure 4).

Figure 4: Total deposition (mg/m² year) of sulphur (S_tot) and nitrogen (N_tot) at the rural background stations Rucava and Zoseni

Source: Latvian Environment, Geology and Meteorology Centre

The computed area at risk of eutrophication covers all ecosystems in Latvia, but the area at risk of acidification is 16 % of the total ecosystem area (Figure 5).

  Figure 5: Damage to Latvian ecosystems as a result of acidification and eutrophication

Source: Latvian Environment, Geology and Meteorology Centre

Figure 6: AOT40 index, rural background station Rucava

Source: Latvian Environment, Geology and Meteorology Centre

Assessment of the impact of surface ozone on vegetation using the internationally-recognised AOT40 index shows that the critical level (6 000 µg/m³×h) was exceeded at the Rucava rural background station in 2006 and 2008 (Figure 6). In 2006, observations of visible ozone damage to white clover under the ICP Vegetation programme registered a medium degree of leaf damage (5–25 %). During the period 2004–2008, there was no exceedance of the target value (18 000 µg/m³×h) for the protection of vegetation[1]

[1] Air Quality Annual Report 2008 (in English and Latvian)