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

✍ Scribed by Giles H. Brown; Bryn Hubbard; Andrew G. Seagren

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 133 KB
• Volume: 15
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/hyp.1039

✦ Synopsis

Abstract

Twenty five laboratory dissolution experiments have been conducted to quantify rates of solute acquisition, measured as Ca^2+^ 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 Ca^2+^ concentrations and model output, with goodness‐of‐fit, expressed as χ^2^, reducing in all cases to less than 1·7 × 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 × 10^−8^ (R^2^ = 0·88) and 1·2 × 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 © 2001 John Wiley & Sons, Ltd.