A study on the impact of phosphate fertilizers on the radioactivity profile of cultivated soils in Srirangam (Tamil Nadu, India)

摘要

Phosphate fertilizers are enriched with 238 U during its production from phosphate rocks. Since, application of phosphate fertilizers in modern agriculture is ever on the increase, the present study investigated the impact of phosphate fertilizers on the radioactivity profile of cultivated (fertilized) soils as against virgin soils. Thirty soil samples each from cultivated fields and virgin fields were collected from Srirangam taluk and analyzed for the activity concentrations of 238 U, 232 Th and 40 K employing gamma ray spectrometry. Similar analysis was also undertaken in commonly used phosphate fertilizers. Among the phosphate fertilizers analyzed single super phosphate (396.3?Bq/kg) and triple super phosphate (284.2?Bq/kg) registered higher level of 238 U. The mean activity level of 238 U in cultivated soil (8.4?Bq/kg) was 25% higher than that of virgin soil (6.8?Bq/kg), while the mean 232 Th and 40 K activities in cultivated soil (98.4?Bq/kg & 436?Bq/kg) were elevated by 12.4% and 4% respectively as compared to virgin soil (87.5?Bq/kg & 419?Bq/kg). The mean radium equivalent (Ra eq ) value for virgin and cultivated soil samples was found to be 164.5?Bq/kg and 181.7?Bq/kg respectively. It is evident that the application of phosphate fertilizers elevated 238 U level of the soil. However, the mean Ra eq value for soil samples is well below the permissible limit of 370?Bq/kg and hence cultivated soils do not pose any radiological risk.