Assessment of naturally occurring radionuclides in irrigation water from selected vegetable farms in Lagos, Nigeria

Abstract

This study aims at evaluating the radiological impact of industrial activities on untreated surface and well water used for irrigation on different farms in Lagos, Nigeria. The concentrations of naturally occurring radioactive materials (NORM) in water used for irrigation on different farms have been determined using Sodium Iodide activated with Thallium NaI (Tl) detector. The concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K ranged from below detectable limit (BDL) to 5.71±0.41, BDL to 6.76±0.28 Bq/l and BDL to 14.93±1.06 Bq/l respectively. The mean overall activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K are 4.14± 0.16 Bq/l, 2.68 ±0.05 Bq/l and 9.10±0.15 Bq/l respectively. Mean activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in surface water are 4.25±0.13 Bq/l, 2.96±0.02 Bq/l and 9.68±0.13 Bq/l respectively. For deep well water, activity concentrations are 3.69±0.29 Bq/l, 1.57±0.05 Bq/land 6.83±0.11 Bq/l respectively. Concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K from deep well are 40 87%, 53% and 71% of the concentrations from the surface water respectively. The values obtained for ⁴⁰K are comparable to those in the literature but the values obtained for ²²⁶Ra and ²³²Th in surface and deep well water are above the recommended safe limits. The overall mean values obtained for ²²⁶Ra and ²³²Th are about 300% and 1680% times higher than the World Health Organization (WHO) reference values for each. The long-term use of these water sources for irrigation on vegetables farms in Lagos poses potential radiological health risks to consumers of the vegetables.

Keywords: Naturally Occurring Radioactive Materials (NORM); Activity Concentration; Irrigation Water; Gamma Spectrometer