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

Twenty five laboratory dissolution experiments have been conducted to quantify rates of solute acquisition, measured as Ca2+ 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 (cm(2) 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 (cm(2) 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 C-0, reflecting rapid ion-exchange reactions; an ultimate steady-state concentration C-s; and a rate parameter k. Results indicate an excellent fit between the laboratory-measured Ca2+ concentrations and model output, with goodness-of-fit, expressed as chi(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 C-0 and C-s, respectively yielding straight-line slopes of 4.2 x 10(-8) (R-2 = 0.88) and 1.2 x 10(-7) (R-2 = 0.77). However, k was found to be insensitive to changes in specific surface area by water volume (R-2 = 0.00), largely reflecting the dominance of variability in C-0 and C-s in this model. Copyright (C) 2001 John Wiley Sons, Ltd.