Exchange of colloidal kaolinite between stream and sand bed in a laboratory flume

摘要: Experiments were conducted in a recirculating flume to study the exchange of colloids between stream and sand bed. Observations net transport kaolinite clay from bed used validate models for colloid which include hydraulics water along with particle-specific effects filtration settling. The allowed extensive control conditions (slope, depth, velocity) parameters (bed bedform height, wavelength, velocity). All experiments had steady, uniform flow well-developed bedforms. To define chemistry system, composition was controlled, reproducibly prepared, cleaned prior every experiment. Experiments involved observing both conservative lithium chloride tracer tracer. Net determined by measuring change concentration water. Vertical profiles distribution also measured. Column performed measure sediment. The pH ionic strength column controlled vary extent filtration. Two mechanisms are responsible bed--an advective pore-water driven bedform-induced pressure variations at surface (pumping), burial release due motion (turnover). Pumping causes be carried deep where it is trapped settling. Turnover continuous mixing uppermost portion hinders penetration deeper bed. Models incorporating relevant physical chemical processes controlling developed predict Model nondimensionalized so can applied problems any scale. Models solutes finite fast-moving based on solute models, but impact settling particle paths path lines. When input data taken laboratory experiments, generally predicted results well no calibration. In all sufficiently high that could assumed entered irreversibly trapped. Additional model simulations demonstrate effect major variables exchange. These cover cases not examined provide sensitivity analysis inputs.