RADIUM AND URANIUM IN PHOSPHATE FERTILIZERS AND THEIR IMPACT ON THE RADIOACTIVITY OF WATERS

The study of radioactivity in the phosphate fertilizers and waters of the Kanovci area was performed in order to determine the influence of the application of phosphate fertilizers on the radioactivity of waters. The activity of Ra-226, Ra-228, U-235 and U-238 was measured in different types of phosphate fertilizers and waters by means of gamma-ray spectrometry. Surface water, water from drainage channels, shallow groundwater and deep groundwater samples were collected from the Kanovci agricultural and well field area in Eastern Slavonia, where phosphate fertilizers have been used for the past 15 years. Cs-137 was also measured in water samples. The typical phosphate fertilizer used in the Kanovci area contains 75 Bq kg-1 of Ra-226, 9 Bq kg-1 of Ra-228, 52 Bq kg-1 of U-235 and 1120 Bq kg-1 of U-238. The estimated annual deposition of uranium and radium in soils of the agricultural and well field area in Kanovci is: 4.5 Bq m-2 for Ra-226, 0.5 Bq m-2 for Ra-228, 3.1 Bq m-2 for U-235 and 67 Bq m-2 for U-238. The greatest concentrations of both uranium isotopes are measured in water from drainage channels with a mean value of 120 Bq m-3 for U-238 and 5.5 Bq m-3 for U-235. The concentrations of both radium isotopes generally increase with depth of water as distinct from uranium, whose concentrations in deep groundwater are much lower. The highest concentrations of Cs-137 were measured in water from drainage channels; it was not detected in deep groundwater. The U-238/Ra-226 activity ratio (AR) is the highest in water from drainage channels and the Bosut River, while in deep groundwater the ratio is only 1.6. Results indicate that high uranium concentrations in surface water, shallow groundwater and water from drainage channels are caused by phosphate fertilizer application in agriculture on the Kanovci area.