Abstract
The Tunisian coast is suffering from several active or abandoned polluted sites, suspected to have released high concentrations of various contaminants infiltrating the environment and probably causing groundwater degradation. Within this scope, this study comes to assess and model the Sfax-Agareb aquifer contamination by fluoride released through phosphogypsum leachate percolation. For that, a spatial-temporal monitoring of fluoride contents was achieved for the period between October 2013 and October 2014. Observed data show that hazardous water contamination is occurring especially close to the phosphogypsum leachate collection basins. At this level, groundwater fluoride concentrations may reach up to 29 mg/L. Flow and transport modeling to evaluate fluoride contamination plume expansion in 2030 was achieved using MODFLOW and MT3DMS software packages based on a homogeneous and isotropic aquifer conceptual model. Flow and transport model calibrations were assessed by varying hydraulic conductivity, effective porosity, and dispersivity and then validated through observed data for two reference dates (October 2013 and October 2014). Based on the Tunisian NT 106-002 liquid discharge norms, fluoride contamination front was set at 3 mg/L. Numerical simulation shows that, in 2014, plume contamination by fluoride in the saturated zone extended over 250 m from the contamination source. In 2030, the spatial extent of this contamination will extend over a distance of 900 m towards the sea, following the aquifer flow direction. At the control piezometer, fluoride concentrations will increase from 29 mg/L in 2014 to 86 mg/L in 2030. This study, using numerical modeling, gives new insights for short- and medium-term prediction of eventual fluoride concentrations in the saturated zone of the Sfax-Agareb aquifer.
Highlights
Industrialization progress during the last century has led to a significant growth of industrial waste, of various toxic products, thrown in the natural environment, escalating the risk of its contamination [1, 2]
The present study is a first attempt to model and predict, using the Visual MODFLOW Classic, eventual fluoride concentrations in the saturated zone of the Sfax-Agareb aquifer and the extent of the area affected by the element pollution on short and medium terms. e outcome of this modeling will help to define the adequate means to reduce and eventually remove undesirable effects
A bimonthly spatial-temporal monitoring of fluoride contents in the Sfax-Agareb aquifer waters was achieved for one year (October 2013-2014)
Summary
Industrialization progress during the last century has led to a significant growth of industrial waste, of various toxic products, thrown in the natural environment, escalating the risk of its contamination [1, 2]. The present study is a first attempt to model and predict, using the Visual MODFLOW Classic, eventual fluoride concentrations in the saturated zone of the Sfax-Agareb aquifer and the extent of the area affected by the element pollution on short and medium terms.
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