About Us | Help Videos | Contact Us | Subscriptions
 

Abstract

 

This article in JEQ

  1. Vol. 32 No. 6, p. 2354-2363
     
    Received: Jan 3, 2003


    * Corresponding author(s): nik.qafoku@pnl.gov
 View
 Download
 Alerts
 Permissions
 Share

doi:10.2134/jeq2003.2354

Aluminum Effect on Dissolution and Precipitation under Hyperalkaline Conditions

  1. Nikolla P. Qafoku *,
  2. Calvin C. Ainsworth,
  3. James E. Szecsody and
  4. Odeta S. Qafoku
  1. O.S. Qafoku, Pacific Northwest National Lab., Interfacial Geochemistry Group, 902 Battelle Blvd., P.O. Box 999, MSIN: K3-61, Richland, WA 99352

Abstract

Substantial amounts of self-boiling, Al-rich, hyperalkaline, and saline high-level waste fluids (HLWF) were deposited to the vadose zone at the Hanford Site, in Washington State. The objective of this study was to investigate the effects of similar fluids on the extent of dissolution and precipitation in the sediments. Metal- and glass-free systems were used to conduct batch experiments at 323 K under CO2 and O2 free conditions. Base-induced dissolution of the soil minerals was rapid in the first 48 h as indicated by immediate releases of Si and Fe into the soil solution. Potassium release lagged behind and dissolution of K-bearing minerals (mica and K-feldspar) proceeded faster only after 2 to 3 d of the experiment. Silicon and Fe release exhibited high dependence on aqueous [Al] (rate orders <−1), because Al decreased free OH concentration in the contact solution and probably inhibited soil mineral dissolution. Initial K release exhibited low dependence on [Al] (fractional rate orders). Initial dissolution rates calculated based on Si release varied with aqueous [Al] from 29.47 to 4.35 × 10−12 mol m−2 s−1 Aluminum participated in the formation of the secondary phases (precipitation rates of 10−8 mol s−1) but the overall precipitation rate of alumino-silicate secondary phases was probably controlled by aqueous [Si] (rates of 10−9, and rate constants between 0.0054 and 0.0084 h−1). The changes in the soil solution chemistry (release of K, Si, Fe, and other elements) may play a significant role in the fate of radionuclides and contaminants like Cs, Sr, Cr, and U in the Hanford sediments.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © 2003. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyASA, CSSA, SSSA