Brown, G. H. and Hubbard, B. and Seagren, A.G. (2001)

Kinetics of solute acquisition from the dissolution of suspended sediment in subglacial channels

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Hydrological Processes
DOI: 10.1002/hyp.1039
Twenty five laboratory dissolution experiments have been conducted to quantify rates of solute acquisition, measured as Ca2C concentration against time, from glacigenic sediments suspended in cold, dilute waters. Suspended sediment character was constrained by field-calibrated ranges of both concentration in meltwater (g cm-3) and specific surface area by sediment mass (cm2 g-1). This constraint yielded, for the first time in a glacier hydrochemical study, dissolution rate data as a function of the specific sediment surface area by water volume (cm2 cm-3). The resulting experimental data are used to calibrate a kinetic dissolution model, where the rate of solute acquisition is considered in terms of three parameters: an initial concentration C0, reflecting rapid ion-exchange reactions; an ultimate steady-state concentration Cs ; and a rate parameter k. Results indicate an excellent fit between the laboratory-measured Ca2C concentrations and model output, with goodness-of-fit, expressed as 2, reducing in all cases to less than 1.7 x 10-14 following iterative curve fitting for each experiment. Plotting the resulting best-fit equation parameters against specific surface area by water volume reveals a strong positive relationship for both C0 and Cs, respectively yielding straight-line slopes of 4.2 x 10-8 (R2 = 0.88) and 1.2 x 10-7 (R2 = 0.77). However, k was found to be insensitive to changes in specific surface area by water volume (R2 = 0.00), largely reflecting the dominance of variability in C0 and Cs in this model.