160-9 Colloid-Facilitated Hg Transport In Hg-Contaminated Soils: Effect of Ionic Strength, Humic Acid and Fe Oxides.



Monday, October 17, 2011: 3:35 PM
Henry Gonzalez Convention Center, Room 210A, Concourse Level

Yingjia Zhu1, Lena Ma1, Willie Harris1, J.C Bonzongo2 and Fengxiang Han3, (1)Soil and Water Science, University of Florida, Gainesville, FL
(2)Environmental Engineer Sciences, University of Florida, Gainesville, FL
(3)Mississippi State University, Starkville, MS
Colloidal Hg release and transport in soils is of significance due to its high Hg concentration and toxicity. Recent laboratory studies have suggested colloidal HgS is important vector for Hg dispersal from Hg-contaminated mining tailing. However the contributions by organic matter and Fe oxide colloids on Hg transport are not well studied. In this study, colloid mobilization and its effect on Hg transport were investigated in three contaminated soils: MN1 and MN2 (spiked with HgS and Hg(NO3)2 and aged for 5 years) and OR1 (contaminated soil from Oak ridge). Batch experiments were used to study the composition and Hg concentrations of water-dispersible colloids. Column experiments were conducted to examine the effect of ionic strength (0.05 and 5 mmol/L) and humic acid on colloid release from Hg contaminated soils during saturated conditions. Flow interruptions were performed to study Hg association with iron oxide colloids in the effluent. Concentrations of Hg in water-dispersible colloids in three soils were 1.6, 2.1, 4.4 times higher than in whole soils (< 2mm). Lowering the ionic strength in solution resulted in release of colloidal Hg from all three soils, with more from MN1 (0.1%, 17.7µg) than MN2 soils (0.3%, 61.1 µg). The results of this study should help better understand the role of colloids in Hg transport in contaminated soils.
See more from this Division: S11 Soils & Environmental Quality
See more from this Session: Dissolved Organic Matter (DOM): Fate and Role In Soil and Environmental Processes