Specifics and temporal changes in air pollution in areas affected by emissions from oil shale industry, Estonia

摘要

Atmospheric air pollution levels and long-term effects on the environment caused by simultaneous presence of SO{sub}2 and oil shale alkaline fly ash during the last five decades (since 1950) were investigated. The annual critical value of SO{sub}2 for forest (20μg m{sup}(-3)) was surpassed in 1% (～35 km{sup}2) of the study area where the load was 30-40μg m{sup}(-3). No effect of long-term SO{sub}2 concentrations of up to 10-11μg m{sup}(-3) (0.5-h max up to 270μg m{sup}(-3)) and simultaneous fly ash loads of up to 95μg m{sup}(-3) (1000μg m{sup}(-3)) on the growth and needle longevity of Pinus sylvestns was established. The yearly deposition (average load up to 20-100 kg S ha{sup}(-1)) was alkaline rather than acidic due to an elevated base cation deposition in 1960-1989. Since 1990, the proportion of SO{sub}2 in the balance of components increased: about 7O-85% of the total area was affected while the ratio of annual average concentrations of SO{sub}2 to fly ash was over 1. The limit values of fly ash for Sphagnum mosses and conifers in the presence of SO{sub}2 are recommended.