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

Chemical fertilizers contain a significant amount of natural radionuclides 238U, 226Ra, 232Th and 40K, 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 238U, 226Ra, 232Th and 40K 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 226Ra, 232Th and 40K nuclides had low values, of 3.4, 9.4 and 34.6 Bq/kg, respectively. For potash and NPK fertilizers, activities of 226Ra and 232Th nuclides were lower 5.5 Bq/kg for 226Ra and 17.6 Bq/kg for 232Th, but those of 40K were about thousands Bq/kg. Based on the measured activities, the radiological health hazard parameters, such as Raeq, Hex, OADR, OAED, IAED, ELCRin, 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.