Determination of Elemental Composition of Treated Sewage Compost Used as Fertilizer in Zaria Metropolis, Nigeria, Using Instrumental Neutron Activation Analysis

Abstract

The use of treated sewage compost in agriculture promotes nutrient recycling and sustainable waste management. However, the presence of potentially toxic elements (heavy metals) necessitates detailed knowledge of elemental composition before large-scale land application. In this work, we determined the elemental composition of treated sewage compost used by farmers in Zaria metropolis, Nigeria, using instrumental neutron activation analysis (INAA). Ten samples were collected from ten dump sites as well as and two reference soil samples from uncontaminated locations. The samples were analysed at the Nigeria Research Reactor-1 (NIRR-1) laboratory, located at the Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria, where they were irradiated in a thermal neutron flux of 5.0 × 10¹¹ n·cm⁻²·s⁻¹. Gamma-ray spectrometry was performed using a high-purity germanium detector. A total of 32 elements Mg, Al, Ca, Ti, V, Mn, Dy, Na, K, As, Br, La, Sm, U, Sc, Cr, Fe, Co, Zn, Rb, Sr, Cs, Ba, Nd, Eu, Tb, Yb, Lu, Hf, Ta, Sb, and Th were detected. Comparative evaluation with reference soils revealed higher concentration of elements in the compost. Although most concentrations were within internationally recommended agricultural limits, however, long-term accumulation may pose environmental risks under continuous application. The study provides baseline data for regulatory assessment in Nigeria.