Assessment and mapping of the spatial trend in groundwater quality in Abeokuta, Nigeria

Abstract

The growth and development of a city is no doubt one of the factors that could affect the quality of water sources. Nevertheless, the level of water contamination arising from increasing population and urbanization is expected to vary from one region to the other depending on the measures taken to prevent the pollution. This study assessed groundwater quality in Abeokuta city towards the
identification of major contaminants in nine (north, north-east, east, south-east, south, south-west, west, north-west and core-central) specific areas of the city. Available groundwater quality data for Abeokuta city over a period of fifteen years (2001- 2015) was acquired from archive and used to establish the spatial variation of groundwater quality across the highlighted categorized nine sections of
the city. The Data was analyzed using descriptive (mean and standard deviation) statistics and spatial (geo-statistical analysis) assessment. Results show that the core central part of the city are the recent bank for high values of parameters such as pH, EC, TDS, Na, SO42- and Fe. Parameters such as Ca, Mg and K are currently more pronounced in the northern areas; whereas HCO3-, Zn, and Cu have more concentrations in the southern parts of the city. Also, lately concentrations of Cl, NO3- and Pb are increasing in the southwestern section, while Cd majorly occurs in the western part of the city. Chloride – nitrate ratio shows that similar sources of chloride and nitrate introduction into groundwater only exist in the northern, southwestern and western sections. The paper concluded that there is an accumulated increase in the values of all the listed parameters within year 2006 to 2010, which can be
associated to major road rehabilitation/construction in most parts of Abeokuta city in that period.