Wednesday, 18 January 2012

Radiation threat in Nagarjunasagar dam: Radionuclides and heavy metals present in the reservoir sediment and water make their way into the fish meat

By Syed Akbar
Hyderabad: In a major health concern for people, teams of
scientists funded by the Bhabha Atomic Research Centre (Barc) have
noticed that the fish, caught from Nagarjunasagar dam and downstream
in the river Krishna, contain harmful radionuclides and heavy metals.

Nagarjunasagar reservoir produces as much as 90 tonnes of fish every
year and the catch is sold in Guntur, Nalgonda, Mahbubnagar, Ranga
Reddy, Hyderabad and Krishna districts.

The area abutting the reservoir contains long-lived radionuclides like uranium (U-238), thorium (Th-232) and Potassium (K-40), and heavy metals including zinc, cadmium and cobalt. The researchers found that the radionuclides and heavy metals present in the reservoir sediment and water have made their way into the fish meat.

Two different teams from the Centre for Environmental Nuclear
Research, SRM University, Chennai, Environmental Assessment Division,
Barc, Mumbai, and Environmental Survey Laboratory, Health Physics Division, Barc,
Kalpakkam, collected samples of fish sold in the markets around the
reservoir, and analysed them for presence of radionuclides and heavy

As part of the research, they selected commercially popular fish
species like Anguilla rostrata (eel), Cirrhinus mrigala (Indian carp),
Labeo rohita (rohu), and Labeo calbasu (a carp variety). “The
concentration of zinc in all the fish species was above the
permissible levels, while cadmium and cobalt were below detectable
level,” the researchers pointed out in their presentation at the just
concluded 99th session of the Indian Science Congress in Bhubaneswar.

Labeo rohita and Anguilla rostrata showed higher accumulation of cadmium than cobalt, while Labeo calbasu showed more quantities of cobalt than cadmium. The results showed that the heavy metal concentration was higher in the reservoir sediment, followed by fish and reservoir water.

Anguilla rostrata and Cirrhinus mrigala showed the presence of
radionuclides, which made their way into the reservoir from the
adjoining uranium deposits-enriched areas of Lambapur and Peddagattu.

The researchers evaluated the distribution pattern of environmental
pollution of uranium and thorium by determining their concentrations
in Nagarjunasagar sediment and water and from the two commercial
species of fish. The average uranium concentrations found in the
sediment sample was 281 Bq/Kg, whereas the concentration of the
uranium found in the water sample is of 2-3 micrograms per litre.
Based on them, they arrived at the bio-concentration factor and
distribution coefficient of the fishes in the dam.

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