THE EFFECTS OF SIMULTANEOUS LARGE ACIDIC AND ALKALINE AIRBORNE POLLUTANTS ON FOREST SOIL

The effects of air pollutants on soil were studied in Scots pine (Pinu s sylvestris L.) forests near the boundary of Russia and Estonia. The study area is characterized by large amounts of acidic and basic pollu tants, mainly sulphur dioxide (SO2) and calcium (Ca). Several variable s were measured in different horizons of the podzolic soil polluted by emissions from local sources in areas of several thousands of square kilometres. Alkalinization dominates the processes in the soil, since sulphur is absorbed only in small quantities and Ca is much better abs orbed. Ca content in humus horizon may rise even to 100 000 mg kg(-1) and the pH of originally very acidic soil may rise to 8.3. Total alumi num (Al) content was high in the heavily polluted plots, since emissio ns contain much Al. On the other hand, the exchangeable Al was very lo w in these alkaline sires. A larger quantity of exchangeable Al occurr ed farther from the pollutant sources, even though total Al in these p lots was low. These plots had acidic soils in which Al is in exchangea ble form. Due to the neutralizing effect of acidic and basic pollutant s, forest damage in the study area was not as serious as might be supp osed. Complicated pollutant situations must be taken into consideratio n when pollution-caused environmental protection measures are planned. It is not reasonable to reduce only SO2 emissions, but necessary to l ower the basic emissions at the same time. (C) 1997 Elsevier Science L td.