COLLOID-ENHANCED TRANSPORT OF CHEMICALS IN SUBSURFACE ENVIRONMENTS - A REVIEW

Ample published evidence demonstrates that colloidal particles can act as carriers to enhance the transport of contaminants in subsurface en vironments. Conventionally, soil and aquifer porous media are consider ed to have two phases: an immobile solid matrix and a mobile liquid. P ublished reports indicate that biocolloids, aluminosilicate clay miner als, and organic colloids can migrate to considerable distances during water flow in soils and aquifers. In the presence of such carriers, t he system should be perceived as consisting of three phases: a station ary solid matrix phase, a carrier phase, and an aqueous phase. Particl e transport through porous media has been clearly demonstrated in filt ration studies, but a need exists to investigate the role of colloidal carriers upon contaminant transport in porous media and to model carr ier-enhanced migration of contaminants accurately. In order to assess the potential role of colloidal carriers in facilitating chemical tran sport in porous media, this review was undertaken to investigate (1) t he occurrence and stability of colloids in porous media, (2) the assoc iation and movement of colloids with chemicals in porous media, (3) mo dels for the transport of colloids in porous media, and (4) models for colloid-enhanced chemical transport in porous media. In addition, sug gested areas for future research are included.