DEVELOPMENT OF ASSESSMENT FOR POTENTIALLY TOXIC ELEMENT CONTAMINATION INDICATOR IN CLOSED LANDFILLS AND PROSPECTIVE GEOSTATISTICAL ANALYSIS

Abstract

Post-closure management of landfill in Malaysia does not include assessment of the contaminant level in abiotic and biotic factors that inhabit the aged topsoil of closed landfills. Considering the bioaccumulation effect in the ecosystem, post-closure classification with the status of contaminant concentration below the permitted level does not promise safe closure to the ecosystem as time passes. Thus, substantial and constant qualitative analysis of contaminant concentration needs to be developed for sustainable management of landfill post-closure. In this work, heavy metals in common constituents (abiotic and biotic factors) of closed landfills were selected; that is, soil, stagnant water, and common communities of plant species in closed landfills in Selangor, both sanitary and non-sanitary, were studied. The results of the analysis demonstrated that the concentration of Cd was not detected in the soil of both landfills but the highest concentration was present in the leaves of Ageratum conyzoides compared to other plant species at both study sites. A parallel situation was discovered for the non-detection of Cd concentration in stagnant water at Ampar Tenang landfill, but the leaves of A. conyzoides contained this element. The sensitivity and affinity of A. conyzoides for accumulating heavy metals in this study were revealed particularly for Cd. Hence, this study suggests the use of A. conyzoides as a promising trace metals contamination indicator for closed urban landfills. Additionally, Guess-Field Kriging is believed to be a useful geostatistical tool to interpolate potential contamination area by utilising the abiotic and biotic factors as assistant variable to the target variable i.e. soil.