THE SURFACE CHARGE OF PARTICULATE MATTER IN SEAWATER

Abstract

The surface charge of particulate matter in seawater from estuarine and coastal sources was investigated by microelectrophoresis. Seston consisting mostly of bacteria, small algae, and detritus exhibited a considerable range of mobilities but all were negatively charged; the mean mobility and the range of mobilities increased when the salinity of the media was reduced. The surface charge of model particles of glass, anion exchange resin, bentonite, calcium carbonate, wax, and a polysaccharide were also studied after equilibration in both natural seawater (freed of natural particulates) and an artificial seawater containing only major ions. The considerable range of mean mobilities for these particles in artificial seawater, ‒1.5 to +1.2 (µm/sec) (V/cm)‒1, converged to ‒1.1 to ‒0.1 (µm/sec) (V/cm)‒1 in seawater. The surface adsorption of minor constituents in seawater is the most likely cause of these changes. Dialysis experiments indicated that both high and low molecular weight materials were responsible. The macromolecular component could be removed from limited amounts of seawater by a column of porous glass. Adsorbable constituents of seawater which might produce the observed surface effects are considered.