Assessing conceptual models of peatland hydrology using natural geochemical tracers in a circumboreal mire complex.

摘要

Conceptual models of northern peatland hydrology can characterize hydrogeochemical flow systems controlling the distribution of raised bogs and fens. I hypothesize that groundwater flowpaths originating under bog crests extend laterally beneath intervening Sphagnum lawns to fens at bog flanks. Stable isotopes of water and mineral solutes display vertical zonation of geochemical gradients in a survey of peat porewater along a transect from raised bog to fen. At lawn sites, modern meteoric recharge (delta 18O = -10.80‰), with a different composition than mean bog crest porewater (delta18O = -12.21‰), has penetrated to the basal peat. The fen profile contains a mix of evaporated surface water (delta18 = -7.78‰) and deep groundwater. Ca/Mg ratios show that groundwater (Ca/Mg∼1.4) upwells locally at the fen and extends laterally beneath ovoid bog islands downgradient. Incongruities between water isotope and divalent cation mixing trends can be explained by diffusion of solutes from the dual porosity peat.;Keywords: Glacial Lake Agassiz Peatlands, peat landforms, bog, fen, ovoid islands, hydrogeology, geochemistry, oxygen-18, deuterium