ELEMENTAL AND RADIOLOGICAL ANALYSES OF SELECTED INORGANIC AND ORGANIC FERTILIZERS IN NIGERIA

Abstract

The research consists of investigating the possible presence and concentrations of heavy metals and the concentration of natural radionuclides in inorganic and organic fertilizers in Nigeria. The 40K activity mean concentrations of inorganic fertilizers was 566±0.36Bqkg-1 ranging from 101.45 to 1033.60 Bqkg-1. 226Ra activity concentrations range from 22.99 to 34.48Bqkg-1 with a mean of 28.36±1.96Bqkg-1, 232Th had a mean of 57.33±0.7Bqkg-1 ranging from 40.71 to 77.10 Bqkg-1. The air absorbed dose rate ranged from 53.91 to 144.90nGyh-1 with a mean of 72.31nGy h-1 which is higher than the world average 51nGyh-1. The annual effective dose rate had an average of 88.37 µSvy-1(0.088mSvy-1) ranging from 60.51 to 178.23µSvy-1. The Raeq averaged 134Bqkg-1 ranging from 106 to 207Bqkg-1wich is far below the 370 Bqkg-1 set for radiation hazard. The Hex and Hin averaged 0.48 and 0.39 with ranges from 0.398 to 0.83 and 0.29 to 0.77 respectively. The 40K average activity concentration of the organic fertilizers was 305.33±0.196Bqkg-1 with a range from 120 to 907 Bqkg-1, 232Th averaged 45.04Bqkg-1 ranging from 14.66to 60.20Bqkg-1. 226Ra averaged 24.87±0.02Bqkg-1 with a range of 12.83 to 65.69Bqkg-1. The average air absorbed dose rate was 51.59nGyh-1 it ranged from 30.33 to 101.23nGyh-1. The annual effective dose rate averaged 61.33µSvy-1(0.061) which is lower than the world average (0.07µSvy-1) it ranged from 33.39 to 124.51μSvy-1. The Raeq is 112.90Bqkg-1 which is far below the 370Bqkg-1maximum.The Hex and Hin averaged 0.31 and 0.37respectively. From Radiological point, organic fertilizers do not impart significant radiological risk, because the radiological hazard indices are low compared to world averages. For the elemental analysis of inorganic fertilizer, nine fertilizers analyzed contain Cd 3.6mg/kg, Cu 11mg/kg Fe 6,228/kg, Zn 475 mg, Mn 4.42 mg/kg and Ti 631mg/kg. Eight fertilizers contain, in addition to metals above Cr 34 mg/kg, Si 814mg/ kg and K 62,954mg/kg. All except two contain Vanadium 25mg /kg. Six contain Pb 1.2 mg/kg. All inorganic fertilizers contain at least 13 heavy metals in their composition. Nine of the organic fertilizers contain Cd 0.14 mg/kg, Cu 1.8 mg/kg, Fe136 mg/kg, Ni 1.6 mg/kg, Zn .9.9 mg/kg and Mn 22.45 mg/kg. Eight organic fertilizers in addition to the metals listed above also contain, Cr 0.7 mg/kg, As 1.1 mg/kg, Co 2.7 mg/kg, Si 8130 mg/kg and Ti 298 mg/kg. Two organic fertilizers recorded the presence of Cs 0.18 mg/kg and Sb 0.06 mg /kg. The presence of the elements in the environment does not pose any immediate hazard to the environment because the concentrations are within those found in soils. However; constant monitoring of the environment should be done to avoid the accumulation of these elements in the environment.