THIRTY-FIVE YEARS OF RECOVERY FROM ACIDIFICATION AT JEZERI CATCHMENT, CZECH REPUBLIC – IS THAT ENOUGH FOR SUCCESS STORY?

Jezeri catchment is located in the northern Czech Republic, formally one of the most polluted regions in the world, so called “Black triangle”. Catchment monitoring started in 1977, during the period of extremely high sulfur (S) deposition. Bulk deposition of S was measured between 20-25 kg ha^-1 yr^-1 and dry deposition was estimated to be close to 100 kg ha^-1 yr^-1. After desulphurization of lignite burning power plants in the 1990´s S deposition has declined to 5-7 kg ha^-1 yr^-1 and dry deposition to ca. 10 kg ha^-1 yr^-1. In the 1970s high airborne SO₂ concentration together with soil acidification led to the forest decline (namely Norway spruce plantations) with subsequent extensive forest deforestation.

As a result of high S deposition, stream water sulfate concentration was around 1550 μeq L^-1 in late 1970´s. Also stream water NO₃ concentration was high – around 200 ueq L^-1. Despite high concentration of strong acid anions, streamwater pH was around 4.9 and total Al around 40 μmol L^-1 as a result of relatively high weathering rates of base cations (BC=Ca+Mg+Na+K). The bedrock consists of gneiss and the total BC weathering rate was estimated to be 148 meq m^-2 yr^-1.

As a result of forest dieback in 1970´s and power plant desulfurization in 1990´s, SO₄ and NO₃ concentration declined to ca. 700 μeq L^-1 and to 60 μeq L^-1, respectively in late 2000´s. Stream water pH increased to 5.8 and total Al declined to 7 μmol L^-1.

MAGIC model was used to simulate annual stream water and soil chemistry for the period 1850-2030. Using atmospheric deposition as specified in the Gothenburg Protocol, the model predicts that streamwater SO₄ will decline to 550 μeq L^-1 and pH will decline to 5.4 in 2030; corresponding pre-industrial streamwater SO₄ was simulated to be 180 μeq L^-1 and pH=6.6.

Large antropogenic acidification in the 20^th century caused significant decline in soil base saturation – preindustrial estimate was 38%, measured was 14% in 1994 and estimate is 2% only for 2030. Thus depletion of soil cation-exchanger is reason for estimated re-acidification of stream in the near future.