Total alpha radioactivity in fertilizers used in the Indian state of West Bengal using CR-39 SSNTDs: Presentation of a comparative view for different types of fertilizers

Use of fertilizers in agriculture soils is a worldwide practice to increase the yield of agricultural products. Fertilizers may contain radioactive elements may be present along with plant's nutrients in fertilizers. Migrated radioactive elements from the fertilized soils can find their entry into the environment and human body through several ways, which may lead to induce a potential radiological risk to human health. In the present study, total alpha radioactivity concentration in 68 samples of 18 different types of organic and inorganic fertilizers which are commonly used for cultivation in West Bengal and other states of India has been measured using a track-etch technique. Calibration of the CR-39 track detectors used in this measurement has been done using a distributed alpha-radioactive reference source material of IAEA-448 soil, obtained from Reference Materials Group of International Atomic Energy Commission (IAEA). The obtained source mass dependent calibration factors of CR-39 detectors have been used to estimate the alpha radioactivity of the fertilizer samples eliminating the self-absorption of alpha-particles in the sample. The estimated alpha radioactivity values have been found to vary from 29.4 Bq.kg^-1 to 114.2 Bq.kg^-1, 2.2 Bq.kg^-1 to 13.1 Bq.kg^-1 and 485.0 Bq.kg^-1 to 1125.8 Bq.kg^-1 respectively for organic, non-phosphatic and phosphatic fertilizers. The highest alpha radioactivity is exhibited by phosphatic fertilizers and lowest alpha radioactivity is exhibited by non-phosphatic fertilizers. Alpha radioactivity is found to be strongly correlated with phosphate content of the fertilizers. The alpha radioactivity values obtained in our study are consistent with the studies reported worldwide with few exceptions. Considering radiological as well as other aspects, farmers should be encouraged to use non-phosphatic fertilizers in combination and try to avoid phosphatic fertilizers as far as practicable.