ABSTRACT
Colloids are ubiquitous. They are, for instance, present in natural waters such as oceans, surface waters, ground waters, and aquifers. The colloids in these systems are diverse: various minerals, clays, oxides, biological cells. The colloidal particles may be (partly) covered by organic molecules. Colloidal stability, or, in other words, the rate at which particles settle, in those waters has a great environmental impact. Lakes, and to a lesser extent rivers, are settling basins for particles thus forming a sediment over the years. Pollutants as well as nutrients may bind to the sedimenting particles, which implies that colloidal stability plays an important role in regulating the biological quality of those waters. In estuaries, where rivers ¤ow into oceans, delta formation takes place through aggregation and subsequent sedimentation of river-borne colloids in an environment of increased salinity. When colloidally stable particles exist in seawater, they are often stabilized by adsorption of organic compounds, such as biopolymers.
