Organic solute‐mineral surface interactions: A new method for the determination of groundwater velocities

Abstract

When the adsorption processes affecting the migration rates of organic solutes in groundwater systems are considered in detail, it can be shown that the use of multiple tracers should allow accurate calculation of the groundwater velocity even when all the tracers are retarded to some extent by interactions with mineral surfaces in the aquifer and even when the extent of that retardation is not known beforehand. It should be required only that the tracers be members of a series of compounds whose surface interaction energies vary regularly, this condition being met, for example, by compounds in the series C2ClnF6−n Experimental studies aimed at testing this concept show that two series of tracers behave as expected on laboratory columns (limestone and sand), thus indicating the fundamental validity of the approach. Further, the nature of the interactions between the mineral surfaces and the tracer molecules can be shown in these cases, at least, to be nonspecific, the strength of the interaction depending only on the polarizability of the tracer molecule. It seems likely that other satisfactory tracers can be selected using this criterion and that the approach should be applicable even to systems involving many different mineral surface types.

Transport and degradation of chlorofluorocarbons (CFCs) in the pyritic Rabis Creek aquifer, Denmark

“…The mechanisms of CFC sorption and degradation are not precisely known. Ciccioli et al [1980] and Russell and Thompson [1983] found negligible sorption of CFC‐12 and CFC‐113, although the organic‐carbon sorption coefficient (K oc ) values for these two gases are higher than for CFC‐11, suggesting higher sorption affinity. Cook et al [1995] found low (K d < 0.03) and moderate (K d = 0.09 − 0.14) sorption for CFC‐12 and CFC‐113, respectively.…”

Chlorofluorocarbons as Tracers of Groundwater Transport Processes in a Shallow, Silty Sand Aquifer

“…The sorption of CFCs on the solid phase of soils has been studied in column experiments by Ciccioli et al [1980], Brown [1980], and Jackson et al [1992]. Ciccioli et al [1980] found negligible retardation of any of CFC-11, CFC-12, or CFC-113 during passage through a column of ground Ottawa sand.…”

“…Differences in sorption characteristics for Ottawa sand in the two studies may be due in part to differences in flow velocity. In the study of Brown [1980] the water velocity was 2.9 cm min -•, while in the study of Ciccioli et al [1980] it was 21 cm min-•, suggesting that in the latter case, equilibrium partitioning between the liquid and solid phases may not have occurred. Other possible explanations for differences in the sorption behavior hre discussed by Brown [1980].…”

Trichlorofluoromethane in groundwater—A Possible tracer and indicator of groundwater age

“…Although information about the long-term stability of F-11 in the subsurface is scarce, and the possibility cannot be eliminated that it has been permanently sorbed on the aquifer material, the only available data suggests that this should not have happened. Laboratory column studies by Ciccioli et al [1978], and field tracing tests with F-11 conducted by the University of Arizona indicate that it is not strongly sorbed on silicates or inorganic materials in general. Although some sorption is usually apparent on natural silicates, it appears to be reversible.…”