Assessment of Heavy Metal Attenuation and Mobility in Compacted Soil Columns

Abstract

Groundwater pollution from unlined landfill is a worrying problem nowadays. In order to reduce the pollution, a good soil liner is very important. Natural compacted soil is used to prevent leachate from reaching the groundwater. The soil column study was performed to investigate the retention capability of three soil types in Malaysia, namely marine clay (SBMC), weathered metasediments (HMS) and river alluvium soil (ARA). All soil columns were tested against four types of heavy metals, i.e. lead (Pb), copper (Cu), nickel (Ni) and zinc (Zn). The breakthrough curves show that the SBMC has better retention capability on heavy metals compared to other soils; indicating less migration of heavy metals through SBMC soil column. The affinity of heavy metals for adsorption were also varied with soil types and can be ranked as follow: SBMC (Pb>Cu>Ni ≈ Zn) and HMS/ARA: Zn ≈ Cu>Pb>N. Soil SBMC showed very high resistance to acidic test solution (i.e. high buffering capacity), where the pH values throughout the test were in an alkaline region with the values of pH 8 to 7. The study also discovered that heavy metals entered the soil columns were retained predominantly at the top 30 mm. Engineering applications of these findings show that soil SBMC has a very good potential to function as soil liner material compared to two other soils (ARA and HMS).