Abstract
This study aims to understand the extension of groundwater pollution downstream of a landfill, Andralanitra–Antananarivo–Madagascar. Twenty-one samples, composed of dug well waters, spring waters, river, and lake, were measured in stable isotopes (δ2H, δ18O) and tritium. Results showed that only two dug well waters, collected at the immediate vicinity of the landfill, have high tritium activities (22.82 TU and 10.43 TU), probably of artificial origin. Both upstream and further downstream of the landfill, tritium activities represent natural source, with values varying from 0.17 TU to 1.46 TU upstream and from 0.88 TU to 1.88 TU further downstream. Stable isotope data suggest that recharge occurs through infiltration of slightly evaporated rainfall. Using the radioactive decay equation, the calculated tracer ages related to two recent ground water samples collected down gradient of the landfill lay between [8–15] years and [4–7] years, taking into account the uncertainty of tritium measurements. For the calculation, a value of 2.36 TU was taken as Ao. The latter was estimated based on similarity between stable isotope compositions of nearby spring and dug well waters as well as tritium activities of the local precipitation. Calculation of the tritium activities from the contaminated water point having 22.82 TU to further downstream using the calculated tracer ages showed values of one order of magnitude higher than the measured values. The absence of hydrological connection from the contaminated water point to further downstream the landfill would explain the lower tritium activities measured. Groundwater pollution seems to be limited to the closest proximity of the landfill.
Highlights
Landfill use as municipal solid waste management has negative impact on water resources
Tritium data are given with uncertainties, while waterstable isotope results were measured with ± 0.15‰ for δ18O and ± 2‰ for δ2H (Analysis report no. 001/12-under reference UEC-12-001 of March 1, 2012-CNESTEN)
Tritium data showed that only just down gradient of the waste deposit site that contamination occurs, where much higher tritium activities than of natural origin value were measured in groundwater samples
Summary
Landfill use as municipal solid waste management has negative impact on water resources. Water quality has been deteriorated in different parts worldwide. It has different attributes that make it distinctive among environmental tracers of groundwater pollution: it does not interact with the aquifer materials during movement through the porous media and is considered conservative geochemically (Holland and Karl 2010); its activity in water sample can be measured at low level (IAEA et al 2001) through electrolytic enrichment prior to quantification. As tritium analysis especially can identify contamination at less than 1%, the use of tritium and other isotopes can substitute large number of chemical parameters, especially in a first phase of
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