HR: 10:20h
AN: H32D-01    [Abstracts]
TI: Mixing-Controlled Reactive Transport: Where do we Stand?
AU: * Cirpka, O A
EM: Olaf.Cirpka@EAWAG.CH
AF: Swiss Federal Institute of Aquatic Science and Technology (Eawag), Überlandstr. 133, Dübendorf, 8600, Switzerland
AB: Over the past years it has been widely recognized that insufficient solute mixing may cause severe limitations of chemical transformations in groundwater. In particular, natural attenuation of compounds that are continuously emitted may depend on transverse mixing, which is a very slow process. For homogeneous systems, it can be shown that the length of steady-state plumes is inversely proportional to the transverse dispersivity. Transverse pore-scale dispersion also controls the transfer from longitudinal spreading to longitudinal mixing. Thus, accurate estimation of transverse dispersion coefficients is of primary importance in mixing studies. Recently, several groups have developed techniques of mapping conservative-transport results to reactive systems. If the relationship between the concentrations of reactive compounds is algebraic, these concentrations can directly be computed from the mixing ratio. Such techniques are extremely helpful in uncertainty estimation, either via error propagation or by applying Monte Carlo techniques. Past studies on conservative solute transport in heterogeneous systems have led to conceptual confusions. Typically, these studies addressed the spatial distribution of ensemble-averaged concentrations. By averaging over an ensemble of possible realizations, the uncertainty of the plume position is transferred to intermediate concentration values. The single plume, however, may be much less smoothed at its boundaries. A particular approach of transferring the transport of conservative compounds to mixing-controlled reactive transport considers the expected width in breakthrough curves of point-like observations and the uncertainty in mean travel time. Other approaches require mean mixing ratios and their variance. The presentation gives an overview about timely issues of mixing-controlled reactive transport in heterogeneous media.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: 2007 Fall Meeting