Spatial Variation and Sources of Heavy Metals in Soils Near Waste Disposal Points on University Farms in Rivers State, Nigeria

The study assed the spatial variation and sources of heavy metal in soils around waste disposal points on university farms in Rivers tate University. Each university farm in Rivers State, Nigeria, the study adopted quasi experimental design. Forty-eight composite topsoil samples 0–20 cm was collected from April to June 2026 at four farms, from stations within 10 m ST1 and 150–200 m ST2 of each waste disposal point. Lead (Pb), cadmium (Cd), arsenic (As), chromium (Cr), cobalt (Co), zinc (Zn), potassium (K) and magnesium (Mg) were measured by atomic absorption spectrophotometry, compared with Nigerian soil target values, and analysed by three-factor ANOVA, correlation and principal component analysis (PCA). Zn, Pb, As, Cr and Co were far below their target values, but Cd mean of 0.72 mg/kg approached its 0.8 mg/kg target, which 18 of 48 samples exceeded, 15 of them at ST1. All eight elements were significantly higher at ST1 than at ST2 p ≤ 0.001 and varied between months p ≤ 0.027, with most lowly in May. PC1 (45.6% of variance) loaded on all eight elements and separated ST1 from ST2 samples. Waste disposal points are therefore localised hotspots of joint metal enrichment where Cd already exceeds the national target, and soil levels change within a single season. The study recommends waste segregation at source, relocation of disposal points away from cultivated beds, and seasonal monitoring of Cd near disposal points.