Assessment of Gross Alpha and Gross Beta Radiation Levels of Different Types of Commercially Available Fertilizers in Sri Lanka

Abstract

Fertilizers are compounds applied to soil to increase fertility and enhance plant growth. They have induced activities of 238U, 232Th, 40K and their decay products to be redistributed in the environment. The objective of the present study is to determine the gross alpha and gross beta radiation levels of commercially available fertilizers in Sri Lanka. In this study total of thirty fertilizer samples were examined in organic and inorganic types. The gas-free, firm wear-based, single sample, manual iSolo alpha/beta counting system, model CANBERRA (SOLO300G), with a solid-state silicon PIPS detector, was used to perform the gross alpha and gross beta measurements. Am-241 and Sr-90/ Y-90 calibration standards were used to calibrate the detector. The method used for taking the measurements is EPA 900.0 standard method. The minimum detectable activities for alpha and beta activities are 0.0201Bq and 0.1850 Bq respectively for 60 minutes counting time. The gross alpha activities were detected in only two solid fertilizer samples and the resulted values are 586.06 Bq/kg, 263.80 Bq/kg. The gross beta activity ranged from 3085.60 Bq/kg to 18995.63 Bq/kg found in thirteen solid samples. For liquid samples, beta activity observed in only five samples and values are 191.0 Bq/kg, 825.0 Bq/kg, 4690.0 Bq/kg, 2750.0 Bq/kg and 233.0 Bq/kg. The results of most samples were within the values of other countries and global average recommended by UNSCEAR. NPK fertilizers exhibit the highest gross beta activity while gross alpha activity only showed in phosphate fertilizers. This study will be continued further for environmental protection purposes and the data can be used to develop radioactivity regulations in the country for gross alpha beta levels of fertilizers when comparing with regulations of other countries.