Influence of macromolecules on chemical transport

Abstract

Macromolecules in the pore fluid influence the mobility of hydrophobic compounds through soils. This study evaluated the significance of macromolecules in facilitating chemical transport under laboratory conditions. Partition coefficients between 14C-labeled hexachlorobenzene and three macromolecules [dextran, humic acid, and groundwater dissolved organic carbon (DOC)] were determined in a three-phase (water-macromolecule-soil) system. There were significant differences between the macro-molecu1e:water partition coefficients, which ranged from 1 X lo3 to 1 X 106. Soikwater partitioning for humic acid was demonstrated by using column breakthrough curves where the breakthrough curve for humic acid was retarded behind 3H20. Breakthrough curves for dextran and groundwater DOC demonstrated apparent size exclusion, as these compounds eluted from the soil column before the 3H20. The impact of the dextran was demonstrated under dynamic conditions by use of hexachlorobenzene, anthracene, and pyrene with and without macromolecules in replicated, biologically inhibited (sodium azide), saturated soil columns. The results may help explain the mechanism by which hydrophobic pollutants appear in deep groundwater aquifers.

Field Tracer Tests on the Mobility of Natural Organic Matter in a Sandy Aquifer

“…The rationale for studies of NOM transport often derives from concerns about its potential effect on several processes, including facilitated transport of organic or inorganic contaminants bound to the NOM [Dunnivant et al, 1992b;Enfield et al, 1989;Kan and Tomson, 1990], the stability and transport of inorganic colloids [Liang et al, 1993a;Amirbahman and Olson, 1993], or its potential effect on the chemical stability (formation and dissolution) of mineral oxides [Ryan and Gschwend, 1990;Liang et al, 1993b]. Yet different subcomponents of NOM affect these processes differently.…”

Experimental investigation of acoustically enhanced colloid transport in water-saturated packed columns

“…The large specific surface areas of these colloids cause relatively weak forces such as van der Waals forces, electric double layer forces, and electrostatic forces to have a profound effect on their transport and deposition. Experimental evidence has shown that colloids can have a faster breakthrough compared to solute tracers in packed columns (e.g., [9,[11][12][13][14]). This effect is attributed to size exclusion and electrostatic repulsive forces [15].…”

“…The downstream boundary condition (12) preserves concentration continuity for a semi-infinite system. The solution to the governing equation(6) subject to conditions (10)-(12) is obtained analytically by Laplace transform and inverse Laplace transform techniques following the methods of Lapidus and Amundson[36], Chrysikopoulos et al[31], and Sim and…”

Development of Permeable Reactive Barriers (PRB) Using Edible Oils

“…In all the sampling points, the peak emulsion concentration was observed at the same time or slightly before the peak tracer concentration. Early colloid breakthrough has been observed in a number of previous studies (Enfield et al 1989, Higgo et al 1993, Grindrod 1993, Grindrod et al 1996, James and Chyrsikopoulos 1999, Keller et al 2004) and has generally been attributed to colloid exclusion from the smaller soil pores. In the FS-7% layer (50 cm depth), the maximum emulsion concentration in sampling points closest to the injection wells were close to 100% of the injection concentration, similar to results obtained during the homogeneous test ( Figure 5).…”