Ai. Packman et al., EXPERIMENTAL-TECHNIQUES FOR LABORATORY INVESTIGATION OF CLAY COLLOID TRANSPORT AND FILTRATION IN A STREAM WITH A SAND-BED, Water, air and soil pollution, 99(1-4), 1997, pp. 113-122
The exchange of kaolinite clay between a stream and its associated san
d bed was investigated in a recirculating flume. Bedforms at the sedim
ent-water interface result in two bed-exchange mechanisms: the bedform
shape induces an advective flow through the bed ('pumping'), and dune
propagation causes the trapping and release of pore water ('turnover'
). Chemical and electrostatic interactions then result in filtration o
f clay by the bed. In order to allow modeling of chemical effects, all
flume materials must have defined chemical parameters. This required
improvements in the flume water supply, construction of sand-washing e
quipment, and the use of defined clay and sand preparation procedures.
Flume experimental results indicate that clay is extensively trapped
by the bed. Advective pumping tends to carry clay to the deep bed wher
e it can be permanently trapped, while turnover tends to continuously
mix the upper layers of the bed, hindering penetration to the deep bed
.