Assessment of Sri Petaling Landfill Towards Pollution in an Unconfined Aquifer

An investigation on the extent of leachate from a landfill towards the surface and groundwater pollution was carried out using resistivity imaging survey. Aquifer parameters determined were porosity, hydraulic conductivity, resistivity and the associated fonnation factor. The aquifer type was indicated to be an unconfined. It was covered with a superficial layer of hard materials ranged in thickness between 1 and 2 m with high resistivity ranged from 87 to 1726 Om. The depth to the aquifer from the surface ranged between 1 and 3 m. The aquifer materials having variable resistivity values ranged between 15 and 150 Om, and associated porosity values ranged between 18 and 35%. The aquifer thickness ranged between 14 to 47 m. The bed rock ranged in resistivity between 48.6 and >9329 Om and has irregular topography, and its depth from the surface ranged from 20 to 38 m. Resistivity values of rock samples varied between 39 and 1238 Om, while for soil samples between 9 and 74 Om. The hydraulic conductivity varied between 0.8 x 10⁻⁸ and 11x 10⁻⁸ mlsec for rock samples and between 5.2 x 10⁻⁷ and 23.1 x 10⁻⁷ mlsec for soil samples. The subsurface porosity distribution of the fonnation along each line of resistivity survey was also established. Within the landfill groundwater flow was estimated towards the downstream area. Leachate production was interpreted from the resistivity survey lines within the landfill. The leachate migrated following the ground water flow patterns from east to west and from north to south directions. The leachate movement towards the downstream as interpreted from resistivity survey lines was supported by the results of the groundwater chemistry. Chemical analysis of the groundwater revealed that the pH was slightly alkaline downstream (8.1) compared to acidic pH at the upstream bore hole. The Na, K, Ca, Cl concentrations and EC were statistically significant in the downstream area. These results supported the fact of inorganic pollution in the area. No sign of heavy metals pollution in the surface and groundwater. The resistivity survey was also used to interpret the IDS distribution within the landfill and in the regional area. The TDS distribution indicated high ion (up to 1 5435 mgll) concentration within the landfill. These high IDS amounts verified the waste decomposition, leachate production and inorganic pollution within the landfill body. Soil exchangeable bases were significantly higher in the downstream saturated zone compared to the vadose zone. With the exception of Cd, the concentration ranges of all trace elements (Cu, Zn, Cr, Pb, and Ni) of the landfill soils were below the upper limits of baseline concentrations as published from different sources.

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