Development of a simulation system for a continuous flow, quiescent, aqueous environment

Aggregation and sedimentation of particles in lakes, estuaries, settling ba sins and the deep ocean play a central role in biological cycles, fate and movement of contaminants, and trace element transport. Relative quiescence with continuous influx characterizes these and other aqueous environments. However, our understanding of the processes of aggregation and sedimentatio n in these vital systems is poor. Inadequate experimental systems and measu ring instrumentation are primary causes of this shortcoming. This paper det ails a laboratory experimental system which creates a continuous flow, quie scent microcosm in which particle aggregation and settling can be studied. The system's functioning and quiescence has been rigorously verified and th e conditions for successful operation defined. A model is detailed which de scribes fluid and solute movement in the experimental system. The results o f the system verification studies indicate significant fluid mixing may occ ur in experimental systems which are assumed to be quiescent, yet where no careful temperature management has been employed. This unexpected and uncon trolled fluid motion may lead to significant errors in experiments whenever particles smaller than about 20 microns with environmentally relevant dens ities are studied. (C) 2000 Elsevier Science Ltd. All rights reserved.