Brown, G. H. and Hubbard, B. and Seagren, A.G. (2001)
Kinetics of solute acquisition from the dissolution of suspended sediment in subglacial channels
- Cite key
- 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.