Assessment of the Concentrations of Some Anions in Soils and Selected Common Vegetables Grown and Consumed in Delta State, Nigeria

Abstract

The study determined the levels of some anions (NO₃⁻, NO₂⁻, SO₄²⁻, PO₄³⁻ and SO₃²⁻) in some leafy vegetables common in Delta State, Nigeria. Three farms well spread across Delta State were taken as sampling sites. There are from Agbor, which is from the northern part of the state, Abraka, from the central and Ozoro from the south. Top soil samples as well as the vegetable samples were collected from these farms. Vegetables selected were; Telfairia occidentalis, Talinum triangulare, Vernonia amygdalina, Amaranthus hybridus and Ocimum gratissimum. Samples were collected for wet and dry seasons, representing the two seasons in Nigeria. The concentrations of the anions were determined using UV-Visible Spectrophotometry. Results of the concentrations of anions for all the anions showed that Ocimum gratissimum had the highest concentration and Amaranthus hybridus had the lowest concentration. The order is as follows; O. gratissimum > T. occidentalis > T. triangulare > V. amygdalina > A. hybridus. The transfer factor from soil to vegetable also followed the order: Statistical analysis (Students t-test) shows that there is no significant difference between the concentrations of the anions in the two seasons. ANOVA analysis also showed no significant difference in the levels of the anions from the three sites, which is an indication of similar agricultural practices. The concentrations of the anions are all below the World Health Organisation (WHO) tolerable limits. It therefore implies that these vegetables do not pose any health risk to humans as a result of these anions content.