Distribution of Arsenic (As) in Water, Sediment and Fish from a Shallow Tropical Reservoir (Aiba Reservoir, Iwo, Nigeria)

The status of arsenic in Aiba Reservoir, Iwo, Nigeria was assessed to determine its levels and distribution in water, sediment and tissues of fish. Total arsenic was estimated by atomic absorption spectrophotometry. The mean levels detected for reservoir water (1.50 \ub1 0.22ppb) and sediment (2.00 \ub1 0.17ppb) were below the World Health Organization recommended limit of 0.01mg/L (10ppb) for drinking water. Arsenic in sediments significantly followed (r = 0.588, p = 0.002, n = 24) the level of contamination of water. The distribution of arsenic in reservoir water shows significant spatial and temporal heterogeneity; while that for sediment shows temporal homogeneity. Mean As levels for fish kidney (15.72 \ub1 4.14ppb) and liver (12.04 \ub1 2.73ppb) were significantly higher than levels for fish gills (2.03 \ub1 0.34ppb) and muscle (1.46 \ub1 0.13ppb). The first and second Canonical Variate showed 49.82% and 34.75% between-species variation respectively. This report suggests that fish at the lower level of the food web have higher levels of As compared to those at a higher trophic status. The current low levels of arsenic in the abiotic component of the reservoir suggest that contamination is mainly from anthropogenic rather than from natural sources. This report suggests seasonal, municipal and agricultural sources of arsenic contamination of Aiba Reservoir