Radiological assessment of irrigation water used in Rustenburg, South Africa

Water is an essential input in agricultural production, which is why it plays an important role in food security. According to the World Bank, water irrigated agriculture represents about 20% of the total cultivated land and 40% of the total food produced globally. This makes water a direct and indirect route of radiation exposure to humans via contact, ingestion and consumption of agricultural products. Radiological assessment of irrigation water around Rustenburg, one of the mining and industrial cities in South Africa, is investigated in this study. The activity concentrations of (238)U, (232)Th and (40)K in irrigation water samples were determined using the total mass elemental concentrations of uranium, thorium and potassium, measured using inductively coupled plasma mass spectroscopy. The activity concentrations of (238)U and (40)K range from 1.24 × 10(−04) to 1.09 × 10(−02) Bq/l, and 7.07 × 10(00) to 1.32 × 10(+01) Bq/l, with mean activity concentrations of 2.78 × 10(−03) and 1.16 × 10(+01) Bq/l, respectively. The activity concentration of (232)Th was found below the detection level in all sampled irrigation water. Estimated annual effective dose because of ingestion because of (238)U and (40)K was also found to be below 120 μSv/y for (238)U and (232)Th, 170 μSv/y for (40)K and a total of 290 μSv/y by the United Nations Scientific Committee on the Effects of Atomic Radiation. The estimated radiation dose and lifetime cancer risk indices indicate insignificant radiological risk, making the irrigation water safe for domestic and agriculture purposes.