Base cation composition of pore water, peat and pool water of fifteen Ontario peatlands: Implications for peatland acidification

Base cation (Ca, Mg, Na, K) concentrations in surface waters, pore waters and surface peats were determined along a mineral-poor to mineral-rich fen gradient for 15 south-central Ontario peatlands. Surface waters of the peatlands ranged in pH and alkalinity from 4.5 to 6.3 and 0 to 181 mu eqL(-1), respectively. Both surface water and pore water Ca and Mg concentrations followed the expected decrease along the mineral-rich to poor-fen gradient. Surface water concentrations of Ca and Mg were significantly lower in the mineral-poor versus the moderately-poor and mineral-rich fens (P < 0.05, ANOVA). Pore water concentrations of base cations were 3-5 fold less in mineral-poor vs. mineral-rich fens. In contrast to surface and pore waters, peat base cation concentrations did not decrease along the mineral-rich to mineral-poor fen gradient. Surface peat base cation concentrations were also independent of pore water cation concentrations, and local bedrock geology. Relative concentrations of base cations in surface peats of all peatlands were best described by the exchangeable cation capacity of the surrounding soils.