Transfer pathway of radioactivity from fertilizer to plant parts: An in-depth analysis using SSNTD

Fertilizers contain radioactivity which can be transported to crops which are grown using these fertilizers. Present work deals with the study on the transportation process of radionuclides in the pathways of fertilizer to soil and soil to paddy-plants. For this study, we have chosen five different sites spread over three districts of southern part of West Bengal state in India. For each site, there are five different agricultural fields where paddy crops are grown. Track-etch technique using CR-39 solid-state nuclear track detectors (SSNTDs) has been employed for the measurement of radioactivity in fertilizers, soil and different parts of paddy plants. All the investigated fertilizers which include organic and inorganic fertilizers show radioactivity in the range 3.8 Bq.kg^-1 (URA) to 1171.3 Bq.kg^-1 (DAP). Due to use of the fertilizers there has been increase in radioactivity of the soils of paddy fields. Enhancement varies from 19.9 Bq.kg^-1 to 86.1 Bq.kg^-1. This enhancement is found to be independent of the type of soil and fertilizers used for cultivation and dependent on the fertilizer radioactivity per decimal of field area. So far the radioactivity of paddy plant parts are concerned, this study reveals maximum radioactivity in straw part and minimum in rice part whereas the radioactivity of husk part is in between. The transfer of radioactivity from soil to paddy plant parts is most strongly correlated with the enhancement of soil radioactivity due to application of fertilizers. Consequently, the transfer factor of radioactivity from soil to paddy plant parts is also found to be maximum for straws and minimum for rice crops which may be attributed to the transportation pathway of radioactivity, accumulation time of radioactivity in different plant parts as well as surface absorption of radioactivity from the surrounding environment.