ABSTRACT
Cohesive effects between sediment particles affects the river flow dynamics. Many studies have observed a qualitative difference in settling dynamics between clays in freshwater and in saltwater, but no simple theory exists to predict the critical coagulation concentration (CCC) of salt that separates the two regimes, even though the CCC appears to be crucial for the aggregation in estuaries. We perform systematic experiments that determine the CCC, by measuring transmitted light intensity through clay suspensions. For kaolin clay, our results show a CCC that is lower than commonly observed in nature, kaolin clay should flocculate in nearly all aquatic environments. In addition, we derive a simple theoretical approach to estimate the CCC for a kaolin clay suspension. Consequently, our theory predicts that flocculation occurs at extremely low salt concentrations.
