Assessment of rare earth elements in Asejire Lake, Nigeria

Abstract

Abstract This study evaluated the distribution of rare earth elements (REEs) in the Asejire Reservoir, Southwest Nigeria, a region lacking comprehensive REE assessment despite the growing concern over REE contamination due to industrial and technological expansion. Using inductively coupled plasma-mass spectrometry (ICP-MS), 12 water samples were analyzed to determine REE concentrations. The total REE (∑REE) concentrations ranged from 10.35 to 13.44 μg/L. The anomalies for Cerium (Ce/Ce*), Europium (Eu/Eu*) and Gadolinium (Gd/Gd*) were 0.19–0.24, 0.18–0.24, and 0.94–1.23, respectively. These values indicate strong negative anomalies for Ce/Ce* and Eu/Eu*, while Gd/Gd* exhibited a slight positive anomaly. These results suggest that the water in the study area is relatively pristine with respect to REEs. The enrichment factor (EF) analysis showed slight enrichment/contamination (1 ≤ EF < 2) for light REEs (LREEs) and middle REEs (MREEs), while heavy REEs (HREEs) mostly showed no enrichment (EF < 1). Notably, most samples had Lanthanum (La) and Cerium (Ce) concentrations above the indicative Admissible Concentration (iAC = 2.0 μg/L) for drinking water, implying potential adverse effects from chronic ingestion. Principal component analysis (PCA) revealed that 71.2% of the variability is accounted for by the first two principal components (PC). PC1, which accounts for 61.22%, is attributed to natural inputs of REEs, while PC2, accounting for 10.51%, suggests some anthropogenic input. In conclusion, this study reveals that the Asejire Reservoir is slightly impacted by anthropogenic influences and local authorities should implement appropriate measures to prevent further deterioration.

Keywords

• Rare earth elements
• Cerium Anomaly
• Europium Anomaly
• Enrichment Factor
• Asejire Reservoir