A critical review of principal component analysis of groundwater contamination in Nigeria

Groundwater remains the most reliable source of potable water in Nigeria, particularly in rural and peri-urban areas. However, increasing anthropogenic activities -ranging from oil exploration and industrial effluents to agricultural practices and improper waste disposal-have intensified contamination pressures on this vital resource. Principal Component Analysis (PCA) has emerged as a powerful multivariate statistical tool for identifying pollution sources, understanding contaminant pathways, and interpreting complex hydrogeochemical datasets. This review critically examines the application of PCA in groundwater contamination studies across Nigeria, synthesizing findings from peer-reviewed literature spanning the past two decades. The review evaluates methodological approaches, identifies common limitations, and assesses the effectiveness of PCA in source apportionment. Key findings reveal that while PCA has been widely applied in the Niger Delta region for petroleum hydrocarbon contamination studies, its application in other regions and for other contaminant classes (e.g., heavy metals, nitrates, pharmaceuticals) remains limited. Common methodological shortcomings include inadequate data preprocessing, insufficient sample sizes, lack of validation, and over-interpretation of components. This review proposes standardized protocols for PCA application in Nigerian groundwater studies. It identifies priority areas for future research, including the integration of PCA with geospatial techniques and machine learning approaches. The findings underscore the need for rigorous statistical practices to enhance the reliability of source identification and support evidence-based groundwater management policies in Nigeria.