Natural radionuclides in phosphatic fertilizer and their behaviour of absoption and accumulation in soils and crops

The systematic data on the radioactivity of U, Th, Ra and 40K in phosphate rocks, phosphatic fertilizers and soil are given. The radioactive composition and radioactivity in phosphatic fertilizers vary with different kinds of phosphatic fertilizers. The radioactive compositions in the phosphatic fertilizers made from phosphate rock are the same as that in the original phosphate rock, but the radioactivity is only 50∼60% of the original. The natural uranium in the compound fertilizer made from phosphoric acid is several times higher than that in the phosphate rock, and the other radionuclides were separated during the process of forming phosphoric acid. In soil, the radioactivity varies with the soil types. The U content is slightly higher in the south region with red earth and the 40K is higher in the north region with black earth, but all are in normal level. Usually, the radioactivity of phosphate rock and phosphatic fertilizer is between the natural background of soil and the limitation of radioactive protection, but the radioactivity of 226Ra in some phosphate rocks and phosphatic fertilizers in Guizhou and Hunan is higher than the permitted limitation set by the government