Geochemical Assessment of Sediment Heavy Metal(loid) Concentrations in Lofa County, Northwestern Liberia: A Comparative Analysis of Average Shale and Upper Continental Crust Background Values.

Source: PubMed, NCBI / U.S. National Library of Medicine

Despite the proliferation of mining and industrial activities within the Mano River Union member states, sediment quality assessment remains limited due to the lack of a comprehensive geochemical dataset. To narrow this knowledge gap, we evaluated heavy metal(loid) concentrations in stream sediments from Lofa County, Liberia. A total of 313 samples were collected and analyzed for eight metal(loid)s (Cu, Pb, Zn, Cr, Cd, Ni, As, and Hg). The contamination factor (CF), enrichment factor (EF), geoaccumulation index (Igeo), and potential ecological risk index (PERI) were calculated independently against two background values: the average shale and upper continental crust (UCC) values. The UCC background values proved more appropriate than average shale for Liberia's geographic location and geological setting, providing results that align with the empirical data. The results show that zinc concentrations were consistently low across all sampling sites, indicating regional depletion of the micronutrient. Despite variations in the methodological approaches, assessment results from all four indices identified mercury and arsenic as the contaminants of primary concern. The varying degrees of metal(loid) enrichment and depletion necessitate further research in the study area. This study should guide policymakers in devising a sustainable plan for tackling site-based contamination and delivering on the United Nations Sustainable Development Goal 6.3.