Geochemical assessment of influence of urbanization on heavy metal enrichment in stream sediments of Ondo town, south-western Nigeria

Abstract

Trace element enrichment and pollution caused by urbanization with its associated effects increasingly becoming a great threat to environmental and human health. This paper, sediments from streams that drain Ondo town were sampled to evaluate the potential effects of urbanization on trace element accumulation in stream sediments. Fifty (50) samples of stream sediments samples were collected along the main stream and other adjoining streams in the town, wet sieved, digested and analyzed by Inductively coupled plasma- Atomic emission spectrometer (ICP-AES) for trace element (Cu, Zn, Pb, Cd, Cr,).. The result of the concentration of trace elements in ppm showed in the order of distribution: Cu (1-114); Pb (3-214); Zn (8-1332); Ni (1-17); Co (1-20); Mn (26-1699); Th (3-16); Sr (5-145); Cd (0.5- 1.4); V (3-188); La (11-51); Cr(2-116); and Ba (40-337). From the result, several hot-spot areas were identified. These hot-spots were identified to be located close to areas where activities like, vehicle related workshops, road junctions, municipal waste, abattoir and farm gardens. Except for some of the elements, such as Cd, Sr and Th, which shows low concentration, the rest of the heavy metals in the stream sediments had two to three folds of magnitude of the concentration compare with the limits values of Granite, Migmatite and Average Shale samples. Principal component analyses (PCA) and geoaccumulation Index (Igeo) of the compositional data, slightly shows presence of metal contamination except Cd, Sr and Th which are ascribed to anthropogenic activities. Pb, Zn, Cu, Cr, Mn, Ni and V positively correlated with each other (R= 0.51-0.95), which indicate analogous sources of geochemistry characteristics.

KEYWORDS: Ondo town, Sediment, Geo-accumulation index, Urbanization, Hot-spot.