Recent environmental changes in a naturally acidic rocky lake in southern Finland, as reflected in its sediment geochemistry and biostratigraphy |
| |
| Authors: | Juhani Virkanen Atte Korhola Matti Tikkanen Tom Blom |
| |
| Institution: | (1) Laboratory of Physical Geography. Department of Geography, University of Helsinki, P.O. Box 9, Siltavuorenpenger 20 A, FIN-00014 Helsinki, Finland |
| |
| Abstract: | Paleolimnological methods are combined with statistical multivariate analyses (PCA and CCA) to study the effects of local environmental disturbances and changes in loading of atmospheric origin on water acidity and the physiochemical properties of the sediment in a small, naturally acidic rocky lake in southern Finland. The pH of the lake as calculated from the diatom flora increased by 0.9 pH units as a consequence of a forest fire in the catchment area at the turn of the last century, and the changes in the diatom assemblages point to an increase in dys(eu)trophy and turbulence. In terms of element influx (in µg cm-2 yr-1), the effects of the fire are seen in a slight increase in the accumulation of lithophilous elements. Diatom-inferred pH values decline upwards in the sediment, but do not regain the level recorded before the fire. This is attributed to reactions between Fe3+ and S, which has partly accumulated from the air as SO2-, producing internal alkalinity. Accumulation rates of many elements increase markedly after the 1960s, an effect for Al, Mg, Na, P and Zn may be connected mainly with the enhanced accumulation of dry matter, whereas the accumulation of K, Ni, Pb, Ti and V in surface sediment are obviously related to atmospheric loading. Measured accumulation rates of Cd and Cu are lower than the calculated values especially in the surface sediment, possibly because of diagenetic changes. Accumulation of Ca and Mn decreases towards the surface on account of acidification of anthropogenic origin. |
| |
| Keywords: | acidification geochemistry atmospheric loading diatoms in situ alkalinity forest fires |
| 本文献已被 SpringerLink 等数据库收录！ |
|
