Comparative assessment of portable x-ray fluorescence and atomic absorption spectrophotometry for metal analysis in urban dumpsite soils of Ibadan, Nigeria

Abstract

Accurate measurement of metals in contaminated soils is essential for environmental assessment, yet conventional methods such as atomic absorption spectrophotometry (AAS) are often time-consuming and resource-intensive. This study appraised the comparability of portable X-ray fluorescence (p-XRF) and AAS for ascertaining metal concentrations in urban dumpsite soils in Ibadan, Nigeria. Soil samples were picked from twelve (12) dumpsites across eight Local Government Areas using a composite sampling approach. Concentrations of Ca, Cu, Zn, Cr, Pb, Ni, and Fe were analysed using both techniques in a comparative analytical design. Paired-samples t-tests, Pearson correlation, and Bland–Altman analysis were used to evaluate differences, relationships, and agreement between methods. Results showed significant differences (p < 0.05) for Ca, Cr, and Ni, while Cu, Zn, Pb, and Fe showed no substantial differences. Correlation analysis displayed a very strong positive relationship for Ca (r = 0.950, p < 0.001) and a moderate correlation for Fe (r = 0.691, p = 0.013), whereas other metals showed weak associations. Bland–Altman analysis indicated a consistent positive bias, with p-XRF generally overestimating concentrations relative to AAS, and stronger agreement observed for major elements than trace metals. The findings suggest that p-XRF is suitable for rapid, non-destructive field screening of major elements but has limited reliability for trace metal quantification. A tiered analytical approach combining p-XRF screening with AAS validation is recommended for accurate environmental assessment.