COMPARATIVE ANALYSIS OF HEAVY METALS IN CARICA PAPAYA (PAWPAW) FRUIT AND SOIL IN SELECTED URBAN, RURAL AND FORESTLAND IN OWERRI, IMO STATE

In most developing coun tries like Nigeria, the quest for rapid economic growth through urbanization, industrialization and modern agriculture have resulted in concomitant inflow of several contaminants (such as heavy metals) into the environment. This study assessed the comparative levels of heavy metals in pawpaw fruits and soils of urban, rural and forest land in Owerri Imo State, Southeastern Nigeria. Randomly, soil samples (0-30 cm depth) and partially ripe pawpaw fruits were collected each from urban, rural and forest land. Heavy metals (Pb, Cd, Ni, Zn, Cu, Cr, Co and Fe) were analyzed using standard methods. Data were subjected to Analysis of Variance (ANOVA) and correlation using Genstat Statistical Package Version 18. The heavy metals in the soil samples were low and varied significantly (P<0.05) apart from Cr, Co and Fe. With the exception of Cu, heavy metals were generally more concentrated in urban soils followed by rural and forest soils where decreasing pattern of urban (1.534 mgkg-1) > forest (1.534 mgkg-1) > rural (1.426 mgkg-1) was recorded. Heavy metal concentrations of the pawpaw fruit also differed significantly (P<0.05) apart from Co and Fe. Similar pattern of decreasing trend (urban > rural > forest) like for the soil, was observed for pawpaw fruits apart from Cu and Cr contents that followed decreasing trend of urban > forest > rural. In addition, metal transfer factor was not uniform for the heavy metals across the sites. However, least values of metal transfer factor for Co (0.51-0.21) and Fe (0.44-0.32) suggested that Co and Fe are not easily mobilized in pawpaw tree. Positive significant relationship that Pb, Cd, Ni, Zn, Cu, Cr and Fe had with pawpaw Pb, Cd, Ni, Zn and Fe indicated strong influence of these metals on each other. There is need for occasional monitoring of these heavy metals in the soil and pawpaw fruit to prevent excessive build up of these heavy metals in the human food chain.