The acidification of the soil and percolation water at soildepths from 150 to 500 cm was studied at the Solling spruce sitefrom 1991 to 1996. NH₄Cl exchangeable cations of the fineearth and bedrock fractions were obtained from different depthsand the soil solution composition was monitored at 150, 200,300, 400 and 500 cm depths using seven suction lysimeters at each depth.In the seepage water collected from 150 and 200 cm depth, pHvalues decreased in the period 1991 to 1996, but no significantchanges were observed in solutions collected below 200 cm depth.Element budgets of Al and M_b (Na, K, Mg, Ca) cationsindicated that buffering by exchange of Al with M_b cationsoccurred mainly in surface 200 cm soil depth. High variabilities in concentrations of SO₄ (at 150 cm) andM_a (Al, Mn, H, Fe) cations (at 300 and 500 cm) wereobserved. High variabilities in M_a cations could beassigned to one of the lysimeters at each depththat extracted low pH solutions. The amount of exchangeablecations in the fine earth and the bedrock fractions indicatedthat the acidification front (exchangeable M_b cations < 80equivalent="" percent)="" had="" occurred="" to="" soil="" depth="" of="" more="" than="" 360cm,="" but="" the="" extent="" of="" acidification="" that="" might="" have="" occurred="" inthe="" preindustrial="" period="" is="" not="" known.="" in="" both="" fine="" earth="" andbedrock="" fractions,="" depthwise="" changes="" of="" exchangeable="">_a andM_b cations were quite similar, suggesting that rockfractions have contributed to proton buffering not only bysilicate weathering but also by cation exchange.