CHEMICAL CONTAMINATION AND SEDIMENT TOXICITY IN SOME PARTS OF IBADAN METROPOLIS, SOUTHWESTERN NIGERIA

Drainage system in Ibadan Metropolis had been depocenter for both industrial and domestic wastes which released toxic metals into the environment. This study examines toxic metal contents and evaluates the possible pollution status in river sediments. Thirty (30) composite samples from 120 freshly deposited sediment samples were collected along stream and river channels. These were classified as Zone-1(market), Zone-2 (residential) and Zone-3 (market/residential) while the while stream and rivers were categorized as Drainage Profile (DP)-1,2 and 3. Prepared grain size (<75um) were analysed with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) analysis at Activation Laboratory Ontario Canada. Cu range from (18.30-513.00), Pb(40.30-5140.00), Zn(80.90-2450.00), Cd(0.08-24.40), As(0.20-7.10), Ni(7.20-114.00), Cr(23.10-154.00), Co(3.80-37.60), Se(0.40-4.50ppm) and Mn(102.00-2120.00). Correlation matrix (‘r’) for the trace metals is (0.61-0.81). Zn-Cu–Ni-As-Cr-Co-Mn-Pb-Se accounts for 45.5% of the total data variance in Factor-1 while contamination indices (C.I) 1<Igeo<2 to 5<Igeo indicated contaminated sediments: These also revealed Zone-1 as the most contaminated zone. Sediment quality analysis revealed DP-1 and 3 as the most contaminated DPs. DP-3 (Araromi spare parts market) signify a remarkable and polluted hotspot for Cu, Pb, Zn, Cd, As and Se which is subjective to high level of human activities with high population density. Several pollution hotspots identified indicated polluted sediment.