Assessment of Heavy Metal Contamination of Irrigated Vegetables Grown along the Kubanni Irrigation Site in Zaria, Nigeria

Abstract

The presence of heavy metals in vegetables is a serious health issue to consumers. This study focuses on the analysis and quantification of heavy metals in vegetables, soils and irrigation water within the Kubanni irrigation site in Zaria, Nigeria. field surveys were conducted to collect samples of vegetables, soils and irrigation water through random sampling across the study area and analyze them for heavy metal contamination. A total of 175 samples of vegetables, soils and water samples were obtained from 25 farmlands. The selected vegetables include spinach, cabbage, lettuce, onion and tomatoes. The metals analyzed include Cr, Fe, Pb and Cd. Atomic absorption spectroscopy was used to measure the levels of heavy metals in the samples. Results showed that all vegetables contained detectable levels of heavy metals beyond WHO permissible limits, with Tomatoes having the highest concentration of Cr (105.9 mg/kg), Fe was highest in lettuce (1382.4 mg/kg); spinach recorded highest concentration of Pb (169.1 mg/kg) while lettuce had the highest Cd level (16.7 mg/kg). ANOVA result shows significant difference between heavy metal contents in vegetables and those of soils and irrigation water within the study area. Correlation coefficient analysis revealed that metals like Cr, Fe and Pb found in vegetables are positively related with metals in soils (0.284, 0.185, 0.453) and also with irrigation water (0.588,0.052, 0.301) while Cd is negatively correlated in both soil (-0.290) and water (-0.120). The study recommends good farming practices to ensure safety of vegetables with the Kubanni irrigation site.