The release of colloids from a shallow Southeastern Coastal Plain deposit, in response to treatment with solutions that perturbed electrostatic and cementitious associations among the clay-size constituents, suggested that these constituents arepredominantly chemically bound within the interstitial matrix. Sediment-packed columns subjected to a sequence of high/low ionic strength solutions, acidic pH (2.6) solutions, and anionic surfactant solutions yielded undetectable colloid releases.Treatment with elevated pH (8.8) solutions and solutions containing phosphate resulted in mobilization of colloids only partially representative of the bulk matrix. Organic acids, which both (i) initiated dissolution of the amorphous iron oxyhydroxideintermediaries among kaolinite books and (ii) imparted negative charge to the iron oxyhydroxide surfaces to generate sufficiently repulsive forces among the juxtaposed matrix constituents, appeared to induce mobilization of colloids compositionallyrepresentative of the entire bulk matrix. These results suggest that "cross-bonding" of juxtaposed matrix constituents in this sediment may hinder colloid mobilization in response to only electrostatic perturbations, an effect that must be considered toaccurately predict colloid mobilization and concomitant facilitated transport in this and other diagenetically similar deposits.
展开▼
