Monday, November 13, 2006
127-19

Alternative Divalent Cation Amendments for Remediation of Brine Contaminated Soils.

Benjamin McNally and Kenneth Farrish. Div of Env Science, Stephen F. Austin State Univ, Box 13073 SFA Station, Nacogdoches, TX 75962

Brine contamination of soils is a common environmental problem associated with petroleum production. Remediation techniques usually use a calcium containing amendment to provide Ca+2 ion to exchange for Na+ on cation exchange sites, allowing for the Na+ to be leached from the surface soil. Gypsum (CaSO4) has been used most commonly because of its relatively low cost and lack of effect on soil pH. However, gypsum has low solubility and is therefore rather slow acting and is not readily available in the Midsouth Region (AR, LA and east TX). On the highly leached, acid soils of the Midsouth, other calcium or possibly magnesium amendments might be advantages in the remediation of brine contaminted land. The purpose of this research was to test several alternative low cost amendments containing the divalent cations Ca+2 or Mg+2 for effectiveness in promoting Na+ exchange and improving the physico-chemical conditions of soils contaminated with brine.  The study tested the effectiveness of MgSO4, CaCl2, lime (CaCO3), and wood ash compared to gypsum and a control (no amendment). Soil from a brine contaminated site was packed to a bulk density of 1.4 Mg m-3 into 60 cm by 5 cm PVC tubes. The amendments were incorporated into the top 5 cm of soil. The soil was irrigated weekly with deionized water and drainage water from the bottom of the tubes was collected and analyzed for electrical conductivity (EC), pH, and Na+, Ca+2, and Mg+2 concentration. After 10 weeks the tubes were sectioned into 5 cm increments. The soil in each increment was analyzed for EC, pH, CEC, and sodium adsorption ratio (SAR). Results of the column study are presented.