BIOAVAILABILITY AND BIOACCESSIBILITY OF TOXIC AND ESSENTIAL ELEMENTS IN URBAN WASTE DUMPSITE SOILS AND CONTROL WITHIN AKWA IBOM STATE, NIGERIA.

Studies on speciation, bioavailability and bioaccessibility of toxic and essential elements were undertaken in some urban dumpsite soils and Control within AkwaIbom State, Nigeria. Soil samples were collected from six designated urban waste dumpsites namely: Uyo (Uyo); Utu Abak (Abak); Atabong (Eket); NdoEyo (Onna); NungUdoeItak (Ikono) and IkotObongErong (IkotEkpene). While Control samples were obtained from a forest in IkotUdobia (Etinan). Samples collected were extracted sequentially using the Modified BCR speciation procedures to obtain the different fractions of toxic elements lead (Pb); cadmium (Cd); arsenic (As) and essential elements iron (Fe); copper (Cu) and zinc (Zn). Concentration of metal fractions in dumpsite soils and Control were analyzed for using atomic absorption spectrophotometer (Unicam 939/959 model). Bioavailability and bioaccessibility models were employed for the determination of bioavailability factor and bioaccessibility index of these elements in dumpsite soils and Control. Results obtained indicated that, Pb and As existed mostly in the reducible fraction, Cd in acid extractable fraction while Fe, Cu and Zn existed principally in the residual fraction. Consequently, toxic metals were more available and assessible than the essential elements in both dumpsite soils and Control. Results obtained revealed that, the availability of these metals in the environment studied was basically controlled by the form they exist in soil. [ABSTRACT FROM AUTHOR]