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.
