Appelo and Postma (2005) have described when
saline/saltwater encroaches into fresh coastal
aquifers, and so an exchange of cations occurs. It
is indicated by the relationship between Na
+ and
Ca
2+ , particularly in samples with negative
Na change . Such a process is highly influenced by
the seawater signature whereas when more seawater intrudes into the aquifer, the negative value
of Na change increases. In order to interpret the
dynamic characteristics of saltwater encroachment, some bivariate diagrams and the relationship between EC with Ca
2+ , Mg
2+ , and Cl
− are
assessed. The EC versus Mg
2+ and Cl
− shows a
relatively linear correlation (Fig. 14.6). It reveals
that admixture with seawater intrusion is one of
the potential processes responsible for the
groundwater salinization. The relationship
between EC versus Ca
2+ and SO 4
2− indicates that
concentration of SO 4
2− is generally determined by
the presence of saltwater encroachment into coastal
aquifers and is also associated with redox conditions along the seawater/freshwater interface.
14.1.3.3 Statistical Screening
of Groundwater Data
for Correlation Analysis
To understand the relation between different
ionic concentrations, inter-elemental correlation
was made. Table 14.2 presents the correlation of
coefficient matrix for all physicochemical
Fig. 14.3 Spatial distribution
map of sodium
190
S. Selvakumar and N. Chandrasekar