Seasonal Appraisal of Heavy Metal Bioaccumulation in Amaranthus, Gruty-stalked Jatropha, Scent Leaf, Bitter Leaf and Water Leaf in Some Poultry Farms within the State of Osun, Southwest Nigeria

Abstract

Poultry wastes contain metals which have permissible limits in crops for safe consumption by man and animals. Seasonal contents of heavy metals in soil and edible portions of five broadly eaten vegetables in Nigeria [Amaranthus (Amaranthus viridis), Gruty-stalked jatropha (jatropha podagrica), Scent leaf (Ocimum gratissimum), Bitter leaf (Vernonia amygdalina) and Water leaf (Talinum triangulare)] were evaluated in poultry farms within the state of Osun, Nigeria. Heavy metals contents in the digested samples were determined with Flame Atomic Absorption Spectrophotometer. Quality assurance techniques included blank determination, recovery analysis and calibration of standards. Descriptive and inferential statistics were used for data interpretations. Analytical results of poultry farm soils revealed that dry and wet seasons values for Cd, Cu, Fe, Pb and Zn were within the acceptable range, but As values for dry and wet seasons (323.10 and 351.41 µg/g respectively) were higher than acceptable values of a typical agricultural soil. Highest contents of As (42.042 µg/g), Cd (0.550 µg/g) and Pb (0.618 µg/g) were recorded for Amaranthus viridis; the highest Cu level (0.998 µg/g) was present in Ocimum gratissimum; Fe had its highest content (148.031 µg/g) in Vernonia amygdalina; while Talinum triangulare had the highest Zn level (62.073 µg/g). Levels of heavy metals in vegetables were higher in the dry season than the wet season but this variation was not statistically different at p < 0.05. Similarly, the levels of As and Fe were above the safe values in plants in both seasons, while Cd, Cu, Pb and Zn were below the safe value. Enrichment factor values implied that the poultry farm soils were significantly enriched with Cu, Pb and Zn, but heavily enriched with As, Cd and Fe as a result of anthropogenic inputs. Specifically, the soils were heavily contaminated with the duo of very toxic elements, As and Cd.