Increasing silicon concentrations in Bohemian Forest lakes
- 1Department of Geochemistry, Czech Geological Survey, Geologická 6, 152 00 Prague 5, Czech Republic
- 2Hydrobiological Institute AS CR and Faculty of Biological Sciences USB, Na Sádkách 7, 370 05 Ceské Budejovice, Czech Republic
- 3Geophysical Institute AS CR, Bocní II, 14 000 Praha-Sporilov, Czech Republic
- 4Department of Earth Sciences, Bryand Global Sciences Center, University of Maine, Orono, Maine, 04469-5790, USA
Abstract. Long-term trends of dissolved silicon (Si) concentrations in five glacial lakes in the Bohemian Forest, Czech Republic, recovering from acidification show higher mobility of Si from the soil to surface waters despite lower atmospheric deposition of acids. Si increased by 0.95 to 1.95 µmol yr-1 (36 to 51%) from 1986-2004 and with increasing pH. A change in soil solution conditions because of a sharp decrease in acidic deposition has led to marked decline in Al mobility and to considerable decreases in dissolved Al, especially Al3+. The increase in Si may be related to: (1) unblocking of the inhibitory effect of dissolved Al on weathering of aluminosilicates, (2) biogenic opal (phytoliths) dissolving faster, and/or (3) lower Si precipitation as secondary aluminosilicates in soil. The change in Al speciation on the dissolution rate of biogenic silica is critical. A lack of change in Si at sites outside central Europe may be explained by small or no decline in mobility of dissolved Al. The effect of a long-term increase in temperature was probably minor.