5 Assessment of Groundwater Quality in Sri Lanka …
133
nitrate, sulphate, sodium, magnesium, calcium, chromium, nickel, arsenic and cadmium were significantly higher in cluster 1 compared to cluster 2. Other metal ions
such as aluminium, iron, copper, zinc and lead showed a higher average value in
cluster 2. Regarding fluoride and magnesium, average concentrations in cluster 1
exceeded permissible level for drinking water (SLS 2013). Average concentrations
satisfied Sri Lankan standard for drinking water regarding the other parameters (SLS
2013). Groundwater wells located in dry and intermediate zones, which were rich in
mineral ions due to rock–water interactions and lower recharge rates, were clustered
into cluster 1. Shallow aquifers in wet zone and coastal areas and wells located on
alluvial aquifers were clustered into cluster 2, and they were located in all three climatic zones of the country. Shallow wells in the country, specifically wells located
in wet zone, were found to be liable to pollute by anthropogenic pollutants (heavy
metals). Nitrate pollution and liability to nitrate pollution are high in agricultural
areas, especially dry and intermediate zones are at high risk, because they receive
low precipitation, hence recharge rate is low. Shallow wells located in karstic aquifer
in Jaffna peninsula and coastal aquifers in Kalpitiya peninsula are some examples.
Discriminant analysis (backward stepwise mode) reduced the number of discriminating parameters into ten, but they were a mixture of ions dissolved in groundwater
by anthropogenic activities and natural interactions. Since several types of aquifers
are available in adjacent areas, clear boundaries with different groundwater quality
controlled by soil distribution or climatic condition are not identifiable in Sri Lanka.
Further, factor analysis resulted in six factors, which may influence on groundwater quality of Sri Lanka. Factors analysis was able to explain >69% of variability
in measured groundwater quality parameters. Factor 1 was accounted for natural
rock–water interactions, while factor 2 and 3 were identified as dissolution of heavy
metals due to natural processes and anthropogenic activities both. VF4 was occupied
by fluoride and pH. Fluoride is encountered in minerals and geochemical deposits.
Fluoride removal efficiency depends on the pH where the value is getting decreased
from acidic soil to basic soils. VF5 had a moderate positive loading on nitrate and
arsenic, chromium and fertilizer, and agrochemical usage may govern this factor. VF6
was occupied by lead only and hypothesized that it may due to dissolution of vehicle
emission in runoff and entering into shallow aquifers. Finally, it can be concluded
that anthropogenic activities such as agrochemical usage, fertilizer usage and industrialization have an influence on Sri Lankan groundwater already though have not
exceeded beyond the acceptable levels. However, it is noteworthy that discriminant
analysis resulted in a mixture of ten parameters to discriminate groundwater quality
in two clusters, hence the influence of anthropogenic pollutants on groundwater is
not negligible, and continuous assessment of groundwater quality is a necessity to
avoid groundwater contamination in Sri Lanka.
Acknowledgements Toyama Prefectural University, Japan, is thankfully appreciated for providing
the research fund. Eng. Ayuri Motoyama and Eng. Shiori Nagasawa are gratefully acknowledged
for their support in laboratory work. Mr. Upul Tharanga, Mr. Asanka Surawimala and Mr. Ruwan
Dissanayaka from Department of Civil and Environmental Engineering, Faculty of Engineering,
University of Ruhuna, are sincerely appreciated for their invaluable help in sampling and analysis.
133
nitrate, sulphate, sodium, magnesium, calcium, chromium, nickel, arsenic and cadmium were significantly higher in cluster 1 compared to cluster 2. Other metal ions
such as aluminium, iron, copper, zinc and lead showed a higher average value in
cluster 2. Regarding fluoride and magnesium, average concentrations in cluster 1
exceeded permissible level for drinking water (SLS 2013). Average concentrations
satisfied Sri Lankan standard for drinking water regarding the other parameters (SLS
2013). Groundwater wells located in dry and intermediate zones, which were rich in
mineral ions due to rock–water interactions and lower recharge rates, were clustered
into cluster 1. Shallow aquifers in wet zone and coastal areas and wells located on
alluvial aquifers were clustered into cluster 2, and they were located in all three climatic zones of the country. Shallow wells in the country, specifically wells located
in wet zone, were found to be liable to pollute by anthropogenic pollutants (heavy
metals). Nitrate pollution and liability to nitrate pollution are high in agricultural
areas, especially dry and intermediate zones are at high risk, because they receive
low precipitation, hence recharge rate is low. Shallow wells located in karstic aquifer
in Jaffna peninsula and coastal aquifers in Kalpitiya peninsula are some examples.
Discriminant analysis (backward stepwise mode) reduced the number of discriminating parameters into ten, but they were a mixture of ions dissolved in groundwater
by anthropogenic activities and natural interactions. Since several types of aquifers
are available in adjacent areas, clear boundaries with different groundwater quality
controlled by soil distribution or climatic condition are not identifiable in Sri Lanka.
Further, factor analysis resulted in six factors, which may influence on groundwater quality of Sri Lanka. Factors analysis was able to explain >69% of variability
in measured groundwater quality parameters. Factor 1 was accounted for natural
rock–water interactions, while factor 2 and 3 were identified as dissolution of heavy
metals due to natural processes and anthropogenic activities both. VF4 was occupied
by fluoride and pH. Fluoride is encountered in minerals and geochemical deposits.
Fluoride removal efficiency depends on the pH where the value is getting decreased
from acidic soil to basic soils. VF5 had a moderate positive loading on nitrate and
arsenic, chromium and fertilizer, and agrochemical usage may govern this factor. VF6
was occupied by lead only and hypothesized that it may due to dissolution of vehicle
emission in runoff and entering into shallow aquifers. Finally, it can be concluded
that anthropogenic activities such as agrochemical usage, fertilizer usage and industrialization have an influence on Sri Lankan groundwater already though have not
exceeded beyond the acceptable levels. However, it is noteworthy that discriminant
analysis resulted in a mixture of ten parameters to discriminate groundwater quality
in two clusters, hence the influence of anthropogenic pollutants on groundwater is
not negligible, and continuous assessment of groundwater quality is a necessity to
avoid groundwater contamination in Sri Lanka.
Acknowledgements Toyama Prefectural University, Japan, is thankfully appreciated for providing
the research fund. Eng. Ayuri Motoyama and Eng. Shiori Nagasawa are gratefully acknowledged
for their support in laboratory work. Mr. Upul Tharanga, Mr. Asanka Surawimala and Mr. Ruwan
Dissanayaka from Department of Civil and Environmental Engineering, Faculty of Engineering,
University of Ruhuna, are sincerely appreciated for their invaluable help in sampling and analysis.