Integrated Hydrogeochemical and Probabilistic Health Risk Assessment of Groundwater Contamination from Brewery Effluent in Aba, Southeastern Nigeria

Purpose. This study evaluates groundwater contamination and associated human health risks arising from brewery effluent discharge in Aba, southeastern Nigeria, with emphasis on hydrogeochemical processes and probabilistic risk characterization. Design / Method / Approach. Fifteen groundwater samples from wells and boreholes were analysed for arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb) using atomic absorption spectrometry under strict quality control. Hydrogeochemical facies were determined, while multivariate statistical techniques (Pearson correlation, principal component analysis, and hierarchical cluster analysis) were applied to identify contamination sources. Spatial distribution was assessed using inverse distance weighting. Health risks were evaluated using deterministic models and Monte Carlo simulation (10,000 iterations), including sensitivity analysis. Findings. Results revealed a hydrogeochemical shift from Ca–HCO₃ to Na–Cl facies near the effluent zone, indicating anthropogenic influence. Arsenic concentrations exceeded permissible limits in several locations. Deterministic risk assessment showed hazard index (HI) values above unity, particularly in children. Probabilistic analysis indicated elevated non-carcinogenic and carcinogenic risks, with a 95th percentile HI of 6.20 and cancer risk up to 9.8 × 10⁻⁴. Sensitivity analysis identified arsenic as the dominant risk contributor. Theoretical Implications. The study advances understanding of contaminant transport mechanisms and risk variability in groundwater systems impacted by industrial effluents in developing urban environments. Practical Implications. Findings highlight the urgent need for effective effluent treatment, groundwater monitoring, and public health interventions in industrialized regions. Originality / Value. This research integrates hydrogeochemical analysis with probabilistic health risk modelling, providing a comprehensive framework for assessing industrial groundwater contamination in sub-Saharan Africa. Research Limitations / Future Research. The study is limited by sample size and spatial coverage. Future research should incorporate seasonal variations, larger datasets, and advanced predictive modelling approaches. Article Type. Empirical Paper.