Distribution of Selected Heavy Metals and Other Water Quality Parameters in Thuruwila Wewa Reservoir

Abstract

Water is a valuable natural resource and many anthropogenic activities including population growth,
agricultural, and industrial development have deteriorated the quality leading to water pollution.
Accumulation of heavy metals in water and sediments in reservoirs is a major environmental issue
and the consequences are much worse if the reservoirs are used for domestic use especially for
drinking purposes. The main objective of this study is to investigate spatial distribution and the
concentration of selected heavy metals and other water quality parameters in Thuruwila wewa
drinking water supply reservoir. Fifteen (15) surface water samples and ten (10) sediment samples
were collected in July 2020 and analyzed using internationally accepted standard procedures. Water
samples were analyzed for pH, conductivity, metals: Fe, Mn, Cd, Pb, Cu, Ni, Cr, Na, K, Ca, and Mg,
and anions: F-
, Cl-
, NO3
-
and SO4
2-
. The sediments were analyzed for the metals Mn, Fe, Cd, Pb, and
Ni. The concentration of heavy metals and other water quality parameters tested in this study were
within permissible limits given by World Health Organization except for Cd and Fconcentration.
The average Cd concentration was 9.19 µgL-1 which exceeded the guideline value of 3.0 µgL-1
and
the average Fconcentration is 0.486 mgL-1 which is below the guideline value of 0.5-1.5 mgL-1
.
According to the spatial distribution of heavy metals, higher concentrations for Fe, Ni, Cd, Cu, and
Mn metals were observed at the inlet compared to other areas of the reservoir. The concentrations of
heavy metals (mgkg-1
) in surface sediments ranged from 53 to 1,716 for Mn, 22 to 637 for Fe, 0.213
to 1.995 for Cd, 0.262 to 0.777 for Pb, and from 1 to 33 for Ni. The high concentrations of Fe, Mn,
and Ni in sediments were observed in the middle, south, and west parts of the reservoir. Since
Thuruwila is suitable as a drinking water reservoir, it is crucial to constantly monitor Cd levels. More
experimental data is required to properly assess the water quality in the reservoir.

Keywords: Heavy metals, Water quality, Sediment, Drinking water