Abstract
The monitoring of pollution plumes from municipal landfills is essential in order to control and, where necessary, remediate aquifer contamination. The Atlantis historical landfill was established in 1975 and was unlined as it preceded the promulgation of the Minimum Requirements by the Department of Water and Sanitation. As the underlying, unconfined sandy aquifer serves as a water supply source to the town of Atlantis, regular quarterly hydrochemical monitoring was carried out from 1989 to 1997, at irregular intervals until 2003, and resumed in 2015 when new, deep boreholes were drilled. Groundwater monitoring over nearly three decades provided valuable information on the nature of the chemical reactions that take place in the subsurface and the extent of transport of chemical constituents. Ammonium and organic carbon, which are subject to redox reactions, were lagging compared to chloride and sodium, which are transported advectively. The most recent data indicated the plume consisted mainly of salinity (electrical conductivity (EC) > 200 mS m−1) in the form of sodium, calcium, chloride and bicarbonate ions 350–400 m down-gradient of the landfill, and it is still expanding at a maximum rate of about 25 m a−1, with local deviations from the regional flow pattern. It also became evident that the plume migrated to greater depth as it was transported further from the waste pile. The breakthrough of contaminants being observed at different depths highlights the importance of suitably designed monitoring networks.
Highlights
Introduction and BackgroundMunicipal landfills are a potential source of pollution for underlying groundwater, where release of contaminants may occur for decades and longer, and contamination may spread in the form of pollution plumes down-gradient of the source
According to the 1:250,000 Land Type Survey map, the soils in the vicinity of the Atlantis historical landfill are dominated by the homogenous Fernwood and Langebaan soil series [32] or Arenosols according to the United Nations Food and Agriculture Organization (FAO) classification [33]
We present first the groundwater monitoring network, we interpret and discuss chronologically data of geophysical surveys, groundwater level and water-quality monitoring obtained over nearly three decades in order to describe the development of the pollution plume from the Atlantis historical waste site
Summary
Municipal landfills are a potential source of pollution for underlying groundwater, where release of contaminants may occur for decades and longer, and contamination may spread in the form of pollution plumes down-gradient of the source. We attempt to characterize the leachate plume originating from the historical landfill in Atlantis (South Africa) over time, space and depth using long-term geophysical and hydrochemistry measurements. This investigation was required because groundwater is used extensively in the study area for water supply to urban users. Using the geophysical and hydrochemical data collected over some three decades, this paper thedevelopment geophysical and and breakthrough hydrochemicalcurves data collected over some three decades, this paper tracksUsing plume of the various parameters and discusses its tracks plume development and breakthrough curves of the various parameters and discusses its relevance in terms of groundwater monitoring at waste disposal sites. The study demonstrates measurements at different depths (e.g., shallow and deep boreholes) demonstrates how measurements at different aquifer depths provided novel insights into the mechanisms of plume transport
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