Evaluation of the groundwater quality along coastal stretch between ...
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JOURNAL OF COASTAL SCIENCES Journal homepage: www.jcsonline.co.nr ISSN: 2348 – 6740
Volume 1 Issue No. 1 - 2014
Pages 22-26
Evaluation of the groundwater quality along coastal stretch between Vembar and Taruvaikulam, Tamil Nadu, India: a statistical approach S. Selvakumar*, N. Chandrasekar, Y. Srinivas, T. Simon Peter, N.S. Magesh Centre for Geotechnology, Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu 627 012, India
`A B S T R A C T
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The present study investigates the groundwater quality from Vembar to Taruvaikulam coastal area to provide an overview of the relationship and sources of physicochemical parameters. A total of 23 groundwater samples were collected and analyzed for various physico-chemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), bicarbonate (HCO32-) , chloride (Cl-) and sulphate (SO42-). The ionic concentrations confirm most of the groundwater samples belong to order of (Na+) > (Mg2+) > (Ca2+) > (K+) and (Cl-) > (SO42-) > (HCO32-). Spearman’s correlation matrix, principal component analysis (PCA) was used to distinguish the main contamination sources in the study area. The significant correlation (r=>0.5) of EC, TDS, sodium, magnesium and chloride indicates saline intrusion, insignificant correlation (r=+1) reflect areas highly affected and extreme negative scores (0.19 is very weak, 0.20 to 0.39 is weak, 0.40 to 0.59 is moderate, 0.60 to 0.79 is strong and 0.80 to 1.0 the very stronger. The monotonic Fig. 2 Groundwater Chemistry (Ternary plot) relationship or the r2 value has >1.0 is perfect correlation, 0 to 1 is the two variables tend to increase or decrease together, 0.0 is the two Therefore, the higher concentration of chloride and sodium ions variables do not very together at all, -1 to 0 is one variable increases in the coastal groundwater attribute to significant effect of saltwater as the other decreases and Mg > Ca > K. In sodium, 70% of the samples exceeded the desirable limit of 200 mg/l, magnesium 61% of the samples exceeded the permissible limit of 150 mg/l and calcium, potassium was mostly found within the desirable limit. The abundance of the major anions is Cl > SO4> HCO3 and almost 87% of the samples exceeded the desirable limit of Cl (600 mg/l), but the sulfate and bicarbonate concentrations are all below WHO guidelines (WHO, 2004). 24
4.2. Principal Component Analysis (PCA) The PCA was applied on the water quality dataset to identify the spatial sources of pollution within the southern coastal aquifer. With reference to the eigenvalues (>1) four components were extracted and explained 91% of the total variance (Table 2) In table 2, PC 1 accounted for 55% of the total variance. This component showed high loading of EC, TDS, Cl, Mg, Ca, Na and SO4. The electrical conductivity and total dissolved solids are generally regarded as indicator for the presence of dissolved ions; these two concentrations increases at the same dissolved ions will also increase. Salinity will also increase at the time of increase in dissolved salt concentration (Elder 1988). This statement is also supported by the strong positive component loadings for EC and TDS. The high absolute loadings for the major ions such as Cl, Mg, Ca, Na and SO4 probably shows the result of mineral water reactions and it indicates that the seawater intrusion still influence the hydrochemistry of the study area. It may also be explained by the mixing condition between freshwater and seawater (Aris et al. 2012), and occurrence of dolomitic and evaporite minerals in the aquifer. PC 2, which accounts for 19.20% of the total variance, contains high loadings for pH, K, and HCO3. Its represents the major geochemical processes taking place in the study area, which is most probably ORIGINAL
ARTICLE
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C O A S T A L
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due to the presence and dissolution of some carbonate, activities. Insignificant correlation (r=
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C O A S T A L
S C I E N C E S
JOURNAL OF COASTAL SCIENCES Journal homepage: www.jcsonline.co.nr ISSN: 2348 – 6740
Volume 1 Issue No. 1 - 2014
Pages 22-26
Evaluation of the groundwater quality along coastal stretch between Vembar and Taruvaikulam, Tamil Nadu, India: a statistical approach S. Selvakumar*, N. Chandrasekar, Y. Srinivas, T. Simon Peter, N.S. Magesh Centre for Geotechnology, Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu 627 012, India
`A B S T R A C T
ARTICLE INFO
The present study investigates the groundwater quality from Vembar to Taruvaikulam coastal area to provide an overview of the relationship and sources of physicochemical parameters. A total of 23 groundwater samples were collected and analyzed for various physico-chemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), bicarbonate (HCO32-) , chloride (Cl-) and sulphate (SO42-). The ionic concentrations confirm most of the groundwater samples belong to order of (Na+) > (Mg2+) > (Ca2+) > (K+) and (Cl-) > (SO42-) > (HCO32-). Spearman’s correlation matrix, principal component analysis (PCA) was used to distinguish the main contamination sources in the study area. The significant correlation (r=>0.5) of EC, TDS, sodium, magnesium and chloride indicates saline intrusion, insignificant correlation (r=+1) reflect areas highly affected and extreme negative scores (0.19 is very weak, 0.20 to 0.39 is weak, 0.40 to 0.59 is moderate, 0.60 to 0.79 is strong and 0.80 to 1.0 the very stronger. The monotonic Fig. 2 Groundwater Chemistry (Ternary plot) relationship or the r2 value has >1.0 is perfect correlation, 0 to 1 is the two variables tend to increase or decrease together, 0.0 is the two Therefore, the higher concentration of chloride and sodium ions variables do not very together at all, -1 to 0 is one variable increases in the coastal groundwater attribute to significant effect of saltwater as the other decreases and Mg > Ca > K. In sodium, 70% of the samples exceeded the desirable limit of 200 mg/l, magnesium 61% of the samples exceeded the permissible limit of 150 mg/l and calcium, potassium was mostly found within the desirable limit. The abundance of the major anions is Cl > SO4> HCO3 and almost 87% of the samples exceeded the desirable limit of Cl (600 mg/l), but the sulfate and bicarbonate concentrations are all below WHO guidelines (WHO, 2004). 24
4.2. Principal Component Analysis (PCA) The PCA was applied on the water quality dataset to identify the spatial sources of pollution within the southern coastal aquifer. With reference to the eigenvalues (>1) four components were extracted and explained 91% of the total variance (Table 2) In table 2, PC 1 accounted for 55% of the total variance. This component showed high loading of EC, TDS, Cl, Mg, Ca, Na and SO4. The electrical conductivity and total dissolved solids are generally regarded as indicator for the presence of dissolved ions; these two concentrations increases at the same dissolved ions will also increase. Salinity will also increase at the time of increase in dissolved salt concentration (Elder 1988). This statement is also supported by the strong positive component loadings for EC and TDS. The high absolute loadings for the major ions such as Cl, Mg, Ca, Na and SO4 probably shows the result of mineral water reactions and it indicates that the seawater intrusion still influence the hydrochemistry of the study area. It may also be explained by the mixing condition between freshwater and seawater (Aris et al. 2012), and occurrence of dolomitic and evaporite minerals in the aquifer. PC 2, which accounts for 19.20% of the total variance, contains high loadings for pH, K, and HCO3. Its represents the major geochemical processes taking place in the study area, which is most probably ORIGINAL
ARTICLE
J O U R N A L
O F
C O A S T A L
S C I E N C E S
due to the presence and dissolution of some carbonate, activities. Insignificant correlation (r=
