HR: 0800h
AN: H21D-1039    [Abstracts]
TI: Effect of Simulated Rainfall on the Facilitated Transport of Metals in Unsaturated Soil Cores from a Flood Plain Contaminated by Mine Wastes
AU: * DeNovio, N M
EM: nicole.denovio@nv.doe.gov
AF: Stoller-Navarro Joint Venture, 7710 West Cheyenne Avenue, Building 3, Las Vegas, NV 89129 United States
AU: Ryan, J N
EM: joseph.ryan@colorado.edu
AF: University of Colorado at Boulder, UCB 428, Boulder, CO 80309 United States
AB: Facilitated transport of contaminant metals by colloids in the vadose zone may contribute to shallow groundwater contamination in some systems. Our laboratory study sought to determine the extent of metal-associated colloid transport generated by simulated rainfall in unsaturated, intact soil cores from a river flood plain contaminated by mine wastes. To do this, we tested expected interactions between metal ions and colloids by evaluating the influence of chemical factors such as pH, Ca$^{2+}$ concentration, and organic matter concentration on the extent of metal-colloid associations. We also examine the influence of water flow and colloid size on metal transport. During two rainfall simulations spaced 14 days apart, only about 20 percent of the metal present in the $<$63 $\mu$m size fraction of the soil was leached through large soil cores. On average, the colloid-bound fraction of mobile Zn was 20 percent, Mn was 35 percent, Cu was 55 percent, and Pb was 90 percent. The fraction of colloid-bound Zn and Pb tended to increase with increased colloid concentrations. Colloid-size distribution, pH, and Ca$^{2+}$ concentrations were not correlated to calculated partition coefficients (K$_{d}$) for Cu, Mn, Pb, and Zn. Further analytical work using flow flow-field-flow fractionation techniques suggests that most colloids were primarily organic matter and that the extent of metal binding was not affected by the size of the colloid or the pore-scale flow regime.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1875 Unsaturated zone
DE: 1045 Low-temperature geochemistry
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting