Natural radioactivity and radiological health hazard assessment of chemical fertilizers in Viet Nam

Chemical fertilizers contain a significant amount of natural radionuclides 238 U, 226 Ra, 232 Th and 40 K, which can be dispersed into environment due to a high use of fertilizer in agriculture and increase the external and internal doses to the population. In this study, the activities of 238 U, 226 Ra, 232 Th and 40 K nuclides in DAP, potash and NPK fertilizers commonly used in Viet Nam were measured using a high-purity germanium (HPGe) detector. Experimental results showed that for DAP fertilizer, the activities of 226 Ra, 232 Th and 40 K nuclides had low values, of 3.4, 9.4 and 34.6 Bq/kg, respectively. For potash and NPK fertilizers, activities of 226 Ra and 232 Th nuclides were lower 5.5 Bq/kg for 226 Ra and 17.6 Bq/kg for 232 Th, but those of 40 K were about thousands Bq/kg. Based on the measured activities, the radiological health hazard parameters, such as Ra eq , H ex , OADR, OAED, IAED, ELCR in , were calculated. The result showed that for DAP fertilizer, these parameters were within allowed ranges, whilst most of them in potash and NPK fertilizers exceeded the permissible limits.