5 Assessment of Groundwater Quality in Sri Lanka …
131
others mineral ions are supposed to enter into groundwater through natural phenomena. Hence, discrimination of clusters had based on dissolved constituents enter into
groundwater by anthropogenic and natural phenomena both.
Regarding the factor analysis, VF1 had strong positive loadings on EC, chloride, sulphate, sodium, magnesium and calcium. Gathering of above ions in one
factor usually reflects the effect of natural processes such as dissolution of carbonate, dolomitic and evaporative minerals in the groundwater (Bencer et al. 2016;
Noshardi and Ghafourian 2016). Jiang et al. (2009) also hypothesize that high positive loadings on EC, calcium and magnesium together due to water–rock interactions.
Further, dissolution of sulphide bearing minerals and chloride bearing minerals may
add those ions into water. Although sodium, chloride and sulphate are liable to enter
into groundwater through sewage effluents and chemical fertilizers, then they should
show a correlation with nitrate (Jiang et al. 2009). In our analysis, nitrate occupies
separate factor. Hence, VF1 is assumed to reflect natural geological interactions with
groundwater.
VF2 and VF3 are occupied by two groups of metal ions; VF2 is by aluminium
and iron, and VF3 is by zinc, nickel and copper. Aluminium and iron may leach
into groundwater during mineral weathering of hard rocks such as feldspars and
granites (Braga et al. 2002; Leung and Jiao 2006), and biotite and granite occur
in hard metamorphic rocks, and regolith aquifers are associated with that (Young
et al. 2011). Further, numerous anthropogenic activities, such as industrial effluent
discharge, sewerage and landfill leachate, may also contribute to increase aluminium
and iron in groundwater (Leung and Jiao 2006). Further, storm water contains high
concentrations of aluminium, iron, zinc, copper, chromium, cadmium, nickel and lead
(if leaded petrol still in use) (Leung and Jiao 2006). In our analysis, higher average
value of all five metal ions is shown in cluster 2. Therefore, it can be assumed that
aluminium and iron in groundwater are entered through anthropogenic activities and
natural rock–water interactions both because other three common metal ions (zinc,
nickel and copper) found to enter into groundwater through industrial effluents and
runoff are occupying a separate factor. Although zinc, nickel and copper can be
entered into groundwater through natural processes, the dominant phenomenon of
their availability in groundwater in Sri Lanka may be industrial activities.
There are a lot of studies carried out regarding fluoride concentration in Sri Lankan
groundwater (Young et al. 2011). Fluoride can enter into groundwater easily from
rocks and soils, which are rich in fluoride-bearing minerals. Severe weathering of
these rocks and minerals in the tropical climate enhances the entry of fluoride into the
groundwater and is therefore leached out from the fluoride-bearing minerals (Young
et al. 2011). In the factor analysis, fluoride and pH occupy a separate factor. Wang
et al. (2002) states that ‘The adsorption of fluoride in soils decreased from humid
areas to arid areas and from acidic soils to alkaline soils’. This may explain the
positive relationship observed between pH and fluoride dissolved in groundwater
(VF4 in factor analysis). Further, easy leachability of fluoride in the wet zone may
cause lower fluoride in wet zone, while dry zone has fluoride rich groundwater
(Dissanayake and Chandrajith 2007).
131
others mineral ions are supposed to enter into groundwater through natural phenomena. Hence, discrimination of clusters had based on dissolved constituents enter into
groundwater by anthropogenic and natural phenomena both.
Regarding the factor analysis, VF1 had strong positive loadings on EC, chloride, sulphate, sodium, magnesium and calcium. Gathering of above ions in one
factor usually reflects the effect of natural processes such as dissolution of carbonate, dolomitic and evaporative minerals in the groundwater (Bencer et al. 2016;
Noshardi and Ghafourian 2016). Jiang et al. (2009) also hypothesize that high positive loadings on EC, calcium and magnesium together due to water–rock interactions.
Further, dissolution of sulphide bearing minerals and chloride bearing minerals may
add those ions into water. Although sodium, chloride and sulphate are liable to enter
into groundwater through sewage effluents and chemical fertilizers, then they should
show a correlation with nitrate (Jiang et al. 2009). In our analysis, nitrate occupies
separate factor. Hence, VF1 is assumed to reflect natural geological interactions with
groundwater.
VF2 and VF3 are occupied by two groups of metal ions; VF2 is by aluminium
and iron, and VF3 is by zinc, nickel and copper. Aluminium and iron may leach
into groundwater during mineral weathering of hard rocks such as feldspars and
granites (Braga et al. 2002; Leung and Jiao 2006), and biotite and granite occur
in hard metamorphic rocks, and regolith aquifers are associated with that (Young
et al. 2011). Further, numerous anthropogenic activities, such as industrial effluent
discharge, sewerage and landfill leachate, may also contribute to increase aluminium
and iron in groundwater (Leung and Jiao 2006). Further, storm water contains high
concentrations of aluminium, iron, zinc, copper, chromium, cadmium, nickel and lead
(if leaded petrol still in use) (Leung and Jiao 2006). In our analysis, higher average
value of all five metal ions is shown in cluster 2. Therefore, it can be assumed that
aluminium and iron in groundwater are entered through anthropogenic activities and
natural rock–water interactions both because other three common metal ions (zinc,
nickel and copper) found to enter into groundwater through industrial effluents and
runoff are occupying a separate factor. Although zinc, nickel and copper can be
entered into groundwater through natural processes, the dominant phenomenon of
their availability in groundwater in Sri Lanka may be industrial activities.
There are a lot of studies carried out regarding fluoride concentration in Sri Lankan
groundwater (Young et al. 2011). Fluoride can enter into groundwater easily from
rocks and soils, which are rich in fluoride-bearing minerals. Severe weathering of
these rocks and minerals in the tropical climate enhances the entry of fluoride into the
groundwater and is therefore leached out from the fluoride-bearing minerals (Young
et al. 2011). In the factor analysis, fluoride and pH occupy a separate factor. Wang
et al. (2002) states that ‘The adsorption of fluoride in soils decreased from humid
areas to arid areas and from acidic soils to alkaline soils’. This may explain the
positive relationship observed between pH and fluoride dissolved in groundwater
(VF4 in factor analysis). Further, easy leachability of fluoride in the wet zone may
cause lower fluoride in wet zone, while dry zone has fluoride rich groundwater
(Dissanayake and Chandrajith 2007).