Multivariate and Correlation Analysis of Soil Quality Parameters in Traffic-Impacted and Control Sites in Ilorin Metropolis

Abstract

Vehicular emissions are a major source of urban pollution, releasing heavy metals and other toxicants that impair soil quality and threaten food safety. This study evaluated the impact of traffic-derived pollutants on soil physicochemical properties, heavy metal accumulation, and non-enzymatic antioxidant responses of Celosia argentea, a common leafy vegetable in Nigeria. Soil and plant samples were collected from three roadside stations with varying traffic densities and a rural control site in Ilorin, North-Central Nigeria. Soil pH, electrical conductivity (EC), organic carbon, nitrogen, phosphorus, exchangeable cations, and heavy metals were determined using standard procedures, while non-enzymatic antioxidants (ascorbic acid, phenolics, flavonoids, and carotenoids) were quantified spectrophotometrically. Results revealed significant spatial variation (p ≤ 0.05) in soil quality and heavy metal content. Station 1 (high traffic) recorded the lowest pH (6.08 ± 0.02), highest EC (275.67± 18.09 dS/m), and elevated Pb (3.01 ± 0.01 mg/kg), Cd (0.49 ± 0.01 mg/kg), Cu (2.73 ± 0.02 mg/kg), and Zn (3.60 ± 0.02 mg/kg), relative to other sites. C. argentea from polluted stations accumulated higher levels of these metals, accompanied by increased non-enzymatic antioxidant activities, suggesting an adaptive response to vehicular stress. Interestingly, carotenoid levels remained stable across all sites, highlighting their inherent resilience and essential role in photosynthetic protection. These findings underscore the risks of heavy metal transfer into edible vegetables and the implications for food safety and urban environmental health.