es050168q_si_001.pdf (164.5 kB)
Coupled Stream−Subsurface Exchange of Colloidal Hematite and Dissolved Zinc, Copper, and Phosphate†
journal contribution
posted on 2005-09-01, 00:00 authored by Jianhong Ren, Aaron I. PackmanPrevious studies have shown that stream−subsurface
exchange has important implications for both colloid and
reactive solute transport in streams because it increases the
opportunity for the interaction of stream-born substances
with bed sediments. We executed a series of laboratory
flume experiments to study the coupled stream−subsurface
exchange of hematite and the sorbing solutes zinc,
copper, and phosphate. A fundamental process-based
transport model was applied to analyze the experimental
results. We found that hematite had a significant effect on
the transport of all ions tested. In addition, hematite
mobility was substantially modified by the presence of
these solutes. Batch and column experiments showed that
the difference in hematite mobility was a direct effect of
zinc, copper, and phosphate sorption to the hematite surface.
Sorption substantially modified the hematite surface
charge and subsequently hematite filtration behavior.
These results suggest that the behavior of contaminants
cannot be analyzed separately from colloids in surface and
groundwater systems because surface-chemical processes
can cause their behavior to be coupled. In particular,
our results show that general and specific interactions
between contaminants and iron oxide particles can alter
colloid mobility, perturb natural fine particle dynamics, and
either favor or disfavor contaminant mobility.