Results of Monitoring at Olkiluoto in 2006 - Environment (pdf) - Posiva

31706050Percolation waterStand throughfallmm4030201020052006019.7-5.85.8-22.822.8-6.96.9-13.923.5-19.619.6-17.717.7-14.814.8-11.911.9-10.1010.10-7.11Figure 21. The amount of percolation water passing down to a depth of 5 cm duringthe snow-free period in 2005-2006 in FIP10. The amount of stand throughfall is alsoshown.The chemical composition of the soil solution during the snow-free period in both plotswas compared with corresponding values in a Scots pine (FIP4) or Norway spruce(FIP10) stand growing on a site of similar fertility (Tammela, period 1998-2000, depthsof 5, 20 and 40 cm). Since the monitoring in FIP4 began earlier, the values could alsobe compared with those from 2004.In FIP4, the acidity of the soil solution was relatively similar at all depths in all threeyears, apart from a sharp drop at 10 cm in 2006 (Fig. 22, Table F-3). However, this wasdue to relatively low values (average 4.0) on the three sampling occasions in autumn.Otherwise the pH values at all depths were fully comparable to a site of similar fertilityat Tammela. In FIP10 the pH of the soil solution at all depths in both years was considerablyhigher than that in the reference spruce stand at Tammela, growing on similarsite type (Fig. 23, Table F-4). The main reason for this is that the soil at Olkiluoto isconsiderably younger than that at Tammela, and therefore contains much higher concentrationsof base cations (Ca, Mg, K) (see Tables F-11 to F-14). Soil solution pH andbase cation concentrations are strongly negatively correlated in forest soils.