Spatio-seasonal groundwater heavy metal contamination and health risks in West Sheger city, Ethiopia: integrated APCS-MLR-PMF approach

Abstract

ABSTRACT Infographic comparing seasonal groundwater contamination in West Sheger City. In dry season, low rainfall and stable cadmium (Cd) combine with arsenic (As) to drive risk; children face higher non-carcinogenic risk than adults. In wet season, rising arsenic (Pb) from agriculture and industry exceeds WHO limits. Groundwater contamination by toxic elements poses health risks in water-limited regions, yet seasonal monitoring and source identification remain limited. This study evaluated the spatioseasonal variation of heavy metals, identified pollution sources, and assessed health risks in West Sheger City (spanning three subcities), Ethiopia. Twenty-four groundwater samples were collected during dry and wet seasons and analyzed for As, Hg, Cd, and Pb. Absolute principal component scores–multiple linear regression and positive matrix factorization (PMF) receptor models, cluster analysis, and principal component analysis were applied to resolve patterns, and with source-factor selection guided by diagnostic criteria and optimized PMF solutions. Pollution indices indicated contamination. Arsenic exceeded World Health Organization guideline values in the wet season, while Pb concentrations were higher in the dry season near identified sources; Cd remained stable under low-oxygen conditions. Mapping identified persistent contamination hotspots. Four sources: industrial, agricultural, geogenic, and atmospheric were identified, with seasonal variability. Health risk assessment indicated non-carcinogenic risks from drinking water, with greater susceptibility in children. Cd and As dominated risk during the dry season, whereas Pb predominated in the wet season. Risk estimates were evaluated using Monte Carlo simulation (10,000 iterations) to characterize uncertainty and variability. Seasonal pollutant-specific management and prioritization required to reduce exposure.