Water quality studies in an aquatic environment of disused tin-mining pools and in drinking water

Abstract

Large areas of abandoned tin-mining pools have found secondary uses which provide natural habitats for aquaculture activities where most freshwater fishes are bred. Soils from tin-mining areas are rich in uranium and thorium. A study has been conducted on the status of waters and aquatic habitats in disused tin-mining pools and at water intake points for public drinking water supply to assess the presence of natural radionuclides and arsenic which are potential health hazards. The concentrations of uranium and thorium were determined by gamma spectrometry. Arsenic species were preconcentrated with ammonium pyrrolidinedithiocarbamate in chloroform and were later irradiated in a neutron flux of 5.1×1012 n cm−2 s−1 of a TRIGA Mk.II nuclear reactor to induce radioactivity due to the 76As radionuclide. The concentrations of uranium were found to be relatively lower than thorium whereas the As(III) species have almost similar concentrations with the oxidized form of As(V). The determination of radium from water samples taken from water intake points as well as treated water was done by co-precipitation separation with mixed barium carrier followed by reprecipitation using sulphuric acid. Results obtained showed that the average concentration of 226Ra for raw water is 3.34 pCi l−1 compared to about 0.89 pCi l−1 for treated water samples. These figures are well below the maximum permissible level of 5 pCi l−1 for drinking water.