HYDROGEOLOGIC PROPERTIES IN PEAT COLUMNS

A method is being developed to assess the hydrogeologic properties of peat cores by electrically monitoring a saline tracer as it moves through the core. Two-inch diameter half cylinders of peat have been collected with a Russian peat corer from various depth in Caribou Bog, a peatland located in central Maine. Peat cores have been encased in paraffin and subjected to a constant hydraulic head gradient. A saline tracer (NaCl) will be injected as a slug and monitored by measuring the electrical resistance between electrode pairs while a voltage potential approximately 5 volts) is applied, using a function generator, longitudinally to the core. Voltages will be recorded using an analog to digital data acquisition module. Reference voltage to determine the applied current and thus determine resistivity will be measured across a precision resistor. The amount of tracer added to the peat column will be determined subject to the condition that the volume of tracer is less than one half of the estimated active pore volume of the column in order to allow detection of the arrival and departure of the entire slug. Varying concentrations of saline tracer will be used to evaluate chemical dilation of the peat. Experimental data will be matched to one-dimensional numerical simulations in an effort to quantify dispersivity and mass transfer coefficients associated with matrix diffusion.