Reduction of Pb Leachability by Stabilization Using Fly Ash from Contaminated Soil of Ulaanbaatar in Mongolia

Abstract

Reduction of Pb Leachability by Stabilization Using Fly Ash from Contaminated Soil of Ulaanbaatar in Mongolia

Amarbayar Jugdernamjil Department of Civil and Environmental Engineering The Graduate School Seoul National University

The focus of this laboratory research is present the findings of a study on reduction of Pb leachability by stabilization using fly-ash from contaminated soil of Ulaanbaatar in Mongolia. Lead can be stabilized in soils based on two mechanisms which are lead precipitation and soil pH control. C-class fly-ash, Portland cement, quicklime can be used to treat trace element contaminated soil, reducing their mobility due to increased soil pH which enhances precipitation and adsorption, and also due to pozzolanic reactions and cementation. In the present study, the various additives including Portland cement and quicklime with fly-ash and their various proportions were employed to stabilize Pb contaminated soil. All the Pb-contaminated 20 soil samples were obtained from 10 different locations (5 samples from gher district, 3 samples from multistoried administrative and residential building, 2 samples from industrial area) of Ulaanbaatar field. In each sample, there were collected top and sub soil sample. The concentration of Pb immobilization and effectiveness of the treatment were evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) and maximum permissible concentration (MPC) of Pb in TCLP is 5mg/L. Additional leaching solutions, Simulated Acid Rain Solution (SARS) and deionized water were prepared with TCLP solutions to assess the leachable Pb in different leaching conditions. After leaching test, the pH measurement was performed in each sample. Also, the total Pb amount was evaluated Korean test method extraction of trace elements soluble in aqua regia. Harvard miniature compaction test was performed to estimate optimum moisture content for improving activity of chemical reaction between soil and additives. The unconfined compressive strength properties of the stabilized soils were measured to estimate the possibility of civil works and stabilization. The both of top soil and sub soil with fly-ash and cement mixture samples were showed highest amount of strength. Out of many treatments, the soil with fly-ash, Portland cement and quicklime combination was shown most effective solution in every leaching solutions.

Keywords: Lead, Fly-ash, Harvard Miniature Compaction Test, Leaching solution, Unconfined Compressive Strength Test, TCLP, etc.

Student Number: 2011-22907