RISK ASSESSMENT, LEVELS, SPECIATION AND SEASONAL VARIATION OF HEAVY METALS (Cd and Cu) IN WATER AND PARTICLE SIZES OF SEDIMENTS FROM HUNKI OX-BOW LAKE, AWE LGA, NASARAWA STATE-NIGERIA

This research aimed at assessment of the levels, speciation, risk indices and seasonal variation heavy metals (Cd Cu) in water sediments from Hunki Ox-bow Lake Awe L.G.A Nasarawa State, using Atomic Absorption Spectrophotometer (AAS), during dry wet seasons. The mean concentration Cd samples both seasons was higher than that Cu, but Cu on whole (raw) sediment samples. baseline levels (mg/L) were as follows: (0.354) (0.014), which revealed level WHO Guidelines for Drinking Water Quality. (mg/kg) (7.149) (8.363) showed lower Interim Sediment Quality – High (Cd: 10 Cu: 270 mg/kg). However, Low 1.5 mg/kg (65 Results Tessier five-step sequential extraction procedure indicated more first four steps (non-residual) accounted 84.64 - 94.52 % Copper dominated organic matter fraction (48.17 85.54 %) Bioavailability Index (BI) season relatively season. values Mobility Factor (MF) had irrespective mobilizable bioavailable to this aquatic ecosystem compared Cu. geo-accumulation (I-geo) practically unpolluted (sites 1, 2 5 season), moderately polluted 3 4 heavily 2, season) very (site 3of season). I-geo unpolluted. In generally, Contamination (Cf) all moderate Cf high contamination factor season, while low seasons, ecological index (Er) risk, serious Er low. study that: season; concentrations manmade sources rather natural most evaluated greater risk.