5 Assessment of Groundwater Quality in Sri Lanka …
129
Table 5.5
Mean (±SD) and significant values of groundwater quality variables in two clusters obtained by cluster analysis in Sri Lanka
Variable
Cluster 1 (n
= 298)
Cluster 2 (n
= 964)
t
test value
p
value
SLS for Drinking water
Fluoride (mg/L)
1.79
±
0.161
0.349
±
0.014
8.901
0.00
1.0
EC (µS/cm)
1441
±
47.4
404
±
9.50
21.423
0.00
1500 a
pH
7.93
±
0.016
7.32
±
0.025
20.416
0.00
6.5–8.5
Chloride (mg/L)
200
±
11.7
34.6
±
1.41
14.019
0.00
250
Sulphate (mg/L)
104
±
10.2
16.9
±
0.666
8.526
0.00
250
Nitrate (mg/L)
14.42
±
2.07
5.37
±
0.299
4.326
0.00
50
Sodium (mg/L)
168
±
8.61
33.0
±
1.02
15.61
0.00
200
Magnesium (mg/L)
42.4
±
1.64
10.9
±
0.321
18.884
0.00
30
Calcium (mg/L)
79.7
±
2.89
33.5
±
0.882
15.32
0.00
100
Aluminium (µg/L)
3.99
±
1.00
25.9
±
3.67
−5.752
0.00
200
Chromium (µg/L)
0.58
±
0.06
0.250
±
0.014
4.834
0.00
50
Ferrous (µg/L)
8.45
±
0.94
17.2
±
2.01
−3.955
0.00
300
Nickel (µg/L)
1.08
±
0.09
0.942
±
0.043
1.504
0.464
20
Copper (µg/L)
1.68
±
0.18
3.07
±
0.755
−1.777
0.017
1000
Zinc (µg/L)
4.81
±
0.64
16.3
±
1.67
−6.401
0.00
3000
Arsenic (µg/L)
1.78
±
0.27
0.375
±
0.026
5.14
0.00
10
Cadmium (µg/L)
0.013
±
0.002
0.005
±
0.000
2.82
0.00
3
Lead (µg/L)
0.104
±
0.026
0.426
±
0.299
−0.599
0.287
10
n
is the number of wells in each classification cluster. Concentrations exceed SLS are highlighted in bold
a
EC as per the salinity standard