Abstract:
The objectives of this study were to assess the levels of water quality and heavy metals of the water,
sediments and fish tissues in the Negombo estuaries. For this study, samples were collected from
sixteen sampling locations during the one year study period from January to December 2014. The
results revealed that the average concentrations of ammonia, nitrate, pH, electrical conductivity, total
suspended solids of 0.215±0.4mg/l, 1.08±0.98mg/l, 7.8±0.28, 29.6±1.56ms/cm, 29.2±0.35mg/l, levels
were below the maximum permissible limits. Biochemical Oxygen Demand 24.8±1.3mg/l and Chemical
Oxygen Demand 469.0±36.5mg/l levels were much higher than the permissible threshold limits of
industrial wastewater quality standards for CEA,(2001) Sri Lanka. The results indicated that the
concentrations (ppm) of heavy metals in water were Pb,0.01±0.0003; Cd,0.015±0.003;
Hg,0.013±0.001; Zn,0.695±0.06; Cu,0.03±0.02; Cr,0.055±0.004 and Fe,0.485±0.04 respectively. The
sediments concentrations (mg/kg) were Pb,7.95±0.95; Cd,1.06±0.23; Hg,0.001±0.52; Cu,0.042±3.2;
Cr,14.30±1.5, Zn,154.25±3.2 and Fe,78.6±101.2 respectively. The concentrations (mg/kg) of metals
in the fish tissues were Pb,0.57±0.48; Cd,1.045±0.28; Hg,0.05±0.046; Zn,119.2±111.3; Cu,4.60±1.64;
Cr,5.22±2.49 and Fe,32.8±59.3 respectively. The highest concentrations of pollution status were
recorded in the Northern region of the estuary.
