ASSESSMENT OF HEAVY METALS IN GROUNDWATER FROM HAND-DUG WELLS IN THE ALLUVIUM, COASTAL PLAIN SANDS AND ILARO FORMATION OF OGUN STATE, SOUTHWESTERN NIGERIA

This study assessed the levels of heavy metal in groundwater drawn from hand-dug wells in selected communities underlain by alluvium deposits, coastal plain sands and Ilaro formation in western part of Ogun State, Southwest Nigeria including Yewa North, Yewa South and Ipokia Local Government Area of Ogun State. Water samples were collected from fifty-two hand-dug wells at wet and dry seasons. The samples were analysed for metals using Inductively Coupled Plasma – Mass Spectrometry. The acquired data were analysed for descriptive namely mean to determine the significant difference between the individual heavy metals while inferential statistics namely correlation analysis, principal component analysis were carried out to characterize and determine the relationship and contribution of the parameters to the variation within a group of entries while seasonal variation effect were analyzed with bar charts using SPSS statistical package. Results indicated that Aluminium (134.5±25.52 µg/L for wet season and 93.5±15.06 µg/L for dry season) was higher than the World Health Organisation (WHO) and the National Industrial Standard (NIS) permissible limits at both dry and wet season. The concentrations of As, Mn, Cr, Ni, V, Hg, Li and Sn were higher during the dry season than wet season; continuous consumption water containing elevated concentration of these heavy metals without adequate treatment could result to greater health impact.