Geostatistical Analysis of Heavy Metal Distribution in Agricultural Soils of Kaduna State: Implications for Food Security

Agricultural soils in the basement complex terrain of Kaduna State, North West Nigeria, are subject to geogenic and anthropogenic heavy metal inputs from mining operations, industrial discharge, and agrochemical application, with potential consequences for crop quality and food safety. This study employs geostatistical methods to characterise the spatial distribution of lead, cadmium, copper, nickel, and arsenic in agricultural soils across four local government areas of Kaduna State, examining the relative contributions of geogenic background and anthropogenic enrichment. A stratified random sampling design yielded two hundred and forty soil samples collected from topsoil and subsoil horizons. Heavy metals were determined by inductively coupled plasma mass spectrometry after aqua regia digestion. Variogram modelling and ordinary kriging were applied to produce interpolated spatial distribution maps for each element. Multivariate statistical techniques including principal component analysis and cluster analysis were used to identify geochemical associations and infer source attribution. Pollution indices including the geo-accumulation index and pollution load index were computed for each sampling unit. The study tests the hypothesis that proximity to abandoned mine workings significantly elevates soil heavy metal concentrations after controlling for lithological background effects. Findings indicate spatially limited but locally severe contamination in mining-adjacent zones, with the remainder of the study area exhibiting background-level concentrations within acceptable food safety thresholds. Recommendations for monitoring and source control are provided. Keywords: geostatistics, heavy metals, agricultural soils, Kaduna State, food security.