Groundwater flow and dissolved carbon movement in a boreal peatland

Measurement of the groundwater flux and the consequent advection of dissolved carbon (DOC (dissolved organic carbon), CH4 and CO2) were made in a boreal peatland in northern Sweden in summer 1993. The early summer gradients in hydraulic head indicated a downward flux of water in the peatland, but after a persistent mid-summer dry period the gradients changed to produce an outward radial flow from the centre to the margins of the peatland. This shift in gradients corresponded to the removal of some of CH4 and CO2 dissolved in groundwater. The concentrations of dissolved CH4 and CO2 were spatially variable, with the highest observed in the centre of the peatland. In contrast, DOC concentrations were relatively constant near the centre of the peatland, and switched in the margin from being the highest during dry periods to lowest during wet periods. The changes in concentration of CH4, CO2, and DOC are a function of the seasonal patterns of production and consumption, but groundwater flow is significant in the redistribution of dissolved carbon and the spatial patterns of concentration. The calculated mass flux of dissolved carbon was significant: it was approximately 20% of annual CO2 fixation.