Efficiency and feasibility of Acacia mangium in extracting heavy metals from contaminated soil

Contamination of soil by heavy metals commonly occurs and remediation is required before the soil is suitable for normal use. Phytoremediation is a low cost and reliable technique to remediate contaminated soil but this technique is not yet commonly used in Malaysia. In addition, phytoremediation using timber species are rarely reported. This study aims to evaluate the efficiency and feasibility of Acacia mangium, a renowned timber species in Malaysia to remediate heavy metals namely Zn, Cu and Cd contaminated soil. A pilot study was conducted in which over 200 saplings of A. mangium were planted in rows on a sewage sludge disposal site with distance of 2m apart. The growth of the trees planted was recorded for 12 months and total aboveground biomass was determined at the end of the experiment period. Results show that A. mangium accumulates 200mg/kg of Zn, 40mg/kg of Cu and 2.0mg/kg of Cd in their aboveground biomass. Thus it can be estimated that 339t/ha of biomass would be required to remove 79.8kg/ha of Zn; 1173t/ha and 1165t/ha of biomass to remove 46.9kg/ha and 2.33kg/ha for Cu and Cd, respectively. This study shows that a hectare of A. mangium plantation could generate aboveground biomass over 2,044t/ha within just 3 years, which is above the requirement needed to remove Zn, Cu and Cd of the amount stated above. Furthermore, if the biomass estimation was set to a 10-year period, over 31,000t/ha could be produced with over 25,300m3 of timber which could generate a substantial income for the remediation project and have high potential for this soil remediation technique to be commercialized.

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