Heavy Metal Contamination of Groundwater Resources in a Nigerian Urban Settlement
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African Journal of Environmental Science and Technology Vol. 4(4), pp. 201-214, April 2010 Available online at http://www.academicjournals.org/AJEST DOI: 10.5897/AJEST09.098 ISSN 1991-637X © 2010 Academic Journals Full Length Research Paper Heavy metal contamination of groundwater resources in a Nigerian urban settlement O. T. Oyeku1 and A. O. Eludoyin2* 1African Regional Centre for Space Science and Technology Education-English,Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria. 2Department of Geography, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria. Accepted 7 February, 2010 The aim of the study was to create awareness on the effect of dumpsite on groundwater in developing countries, especially Nigeria. In order to achieve this, water samples were obtained from 20 randomly selected hand dug wells and boreholes in the area, in February and August, 2006. 10 leachates samples were also obtained from the dumpsite. From these samples, pH and conductivity were determined using a pH/conductivity meter (Jenway model), while the concentrations of the heavy metals (Co, Fe, Pb and Cu) were determined using atomic absorption spectrophotometer (AAS). The trend of dispersion of each variable was demonstrated on Landsat ETM+ (2006) imagery using Erdas Imagine and ArcView GIS software. The study showed that the groundwater in the study area were generally alkaline (8.3 ± 2.77) and contained Cu (0.02 ± 0.04 mg/l), Fe (4.23 ± 6.4 mg/l), Pb (2.4 ± 3.3 mg/l) and Co (1.03 ± 1.1 mg/l) concentrations that are higher than the permissible limits recommended by the World Health Organization (0.5, 0.1, 0.01 and 0.0002 mg/l, respectively; p > 0.05). The study concluded that the groundwater sources within 2 km radius of a major landfill will be vulnerable to the effect of landfill, if they are not adequately protected. Key words: Groundwater, landfill, Landsat imageries, heavy metals contamination. INTRODUCTION Pollution of groundwater sources by leachate from disease, clogging drains and creating a myriad of related landfills have been recognized for a long time (Hem, health and infrastructural problems. 1989; Butow et al., 1989; Alloway and Ayres, 1997). The practice of landfill system as a method of waste Clark (2006) described landfill practices as the disposal disposal in many developing countries is usually far from of solid wastes by infilling depressions on land. The standard recommendations (Mull, 2005; Adewole, 2009). depressions into which solid wastes are often dumped A standardised landfill system involves carefully selected include valleys, (abandoned) sites of quarries, excava- location, and are usually constructed and maintained by tions, or sometimes a selected portion within the means of engineering techniques, ensuring minimized residential and commercial areas in many urban settle- pollution of air, water and soil and risks to man and ments where the capacity to collect, process, dispose of, animals. Landfilling involves ‘placing’ wastes in lined pit or re-use solid waste in a cost-efficient, safe manner is or a mound (sanitary landfills) with appropriate means of often limited (www.makingcitieswork.org, 2009) by leachate and landfill gas control (Alloway and Ayres, available technological and managerial capacities. In 1997). In most cases however, ‘landfill’ in developing most developing countries such as Nigeria, several tons countries’ context is usually an unlined shallow hollow of garbage are left uncollected on the streets each day, (often not deeper than 50 cm). Zurbrugg et al. (2003) acting as a feeding ground for pests that spread referred to it as ‘dumps’ which receive solid wastes in a more or less uncontrolled manner, making a very uneconomical use of the available space and that which allows free access to waste pickers, animals and flies, *Corresponding author. E-mail: [email protected]. Tel: and often produce unpleasant and hazardous smoke +2348067281611. from slow-burning fires. Besides, instances have been 202 Afr. J. Environ. Sci. Technol. shown that revealed that even the lined (protected) on groundwater sources of those selected areas. The landfills have been inadequate in the prevention of objectives are to map and describe the distribution of groundwater contamination (Lee and Lee, 2005). some selected heavy metals like cobalt (Co), cadmium In Nigeria, open dump is almost the verily available (Cd), lead (Pb) and copper (Cu)) in the groundwater option for solid waste disposal, even in the capital cities. around the Olusosun landfill in Ojota area of Lagos State, Sanitary landfill, however, is rare and unpopular, except Nigeria. perhaps among few institutions and few affluent people. Financial and institutional constraints are the immediate identifiable reasons for this in Nigeria and some other STUDY AREA developing countries, especially where local governments The study was carried out in Ojota area of Lagos State in Nigeria. are weak or underfinanced and rapid population growth The area covers Ikosi Ketu, Oregun industrial estates, the continues (Nnuan, 2000; Elaigwu et al., 2007). Other commercial area of Kudirat Abiola way, Ojota residential area and reasons include the issue of inappropriate guidelines for LAWMA dumpsite (Figure 1), known as Olusosun landfill (Bello, siting, design and operation of new landfills as well as 2002). The landfill is located between 6°23’N; 2°42’E and 6°41’N; missing recommendations for possible upgrading options 3°42’E. It is the largest of all the landfills in Lagos area; it has received more than 50% of the total refuse in Lagos area since of existing open dumps (Zurbrugg et al., 2003). Often the 1989. As at the period when the dumpsite was created, the area available guidelines for landfills available are those from (Ojota) was almost a vacant land (Bello, 2002). The area is high-income countries, and they are based on technolo- however a flourishing commercial central district in Lagos State. gical standards and practices suited to the conditions and Figure 2 shows some views of the landfill as at 2007. regulations of the source countries, they often do not take The site of the landfill is about 10 km South East of Ikeja Local Government Area (LGA). Ikeja is the capital city of Lagos State. into account for the different technical, economical, social The state is the most flourishing Nigerian commercial arena, with a and institutional aspects of developing countries. In population of more than 9, 013, 534 and an annual growth rate of another case, many of the municipal officials think that 3.2% (NPC, 2006). uncontrolled waste disposal is the best that is possible The depths of hand dug wells in this region vary from 3.81 to (www.makingcitieswork.org, 2009). In the case of Lagos 30.37 m above the mean sea level (a.s.l), and boreholes are State, Nigeria, Adewole (2009), exemplifies the unaccep- generally between 21 and 58.86 m deep. Most of the hand dug wells are neither lined nor have properly constructed base or table view that dumpsite has been adopted for use in the covers. Some are simply covered with planks and rusted metal State because more refined methods are technically and sheets. The geology of the area is generally characterized by financially expensive. This equally revealed a general coastal plain sands which form the low lying, gently sloping ignorance of the deleterious effects of dumpsites on the uplands, and the coastal deposits forming extensive red earths, and groundwater sources on which a number of city dwellers loose poorly sorted sands that are mixed with an abundance of depend (Foster, 1986; Ako et al., 1990). According to clays (World Bank, 2002). The topography is generally low, ranging from 18 to 52 m above the mean sea level (Figure 3) Zurbrugg et al. (2003), one out of four people in cities, in The climate of Lagos area is characterized by two main seasons: developing countries, lives in ‘absolute poverty’ while wet (April - October) and dry (November - March) seasons. The another one in four is classified as ‘relatively poor’ (see peaks of rainfall occur in July and September/October, and they are also, Human Development Report, 2009). It has also often characterized by floods, which effects are usually aggravated been revealed that municipal authorities in these by the poor surface drainage systems. Mean annual rainfall in Lagos area varies from 1567.2 mm at the North West to 1750 mm countries tend to allocate their limited financial resources at the mainland (Oyeku, 2007). to the richer areas of higher tax yields where citizens with more political pressure reside (Onakerhoraye and Omuta, 1994; Akinbode et al., 2008). MATERIALS AND METHODS Furthermore, acidification and nitrification of ground- water have been linked to dumpsite around their outlets 20 groundwater points (10 each of boreholes and hand dug wells) were randomly selected for this study. Water samples were (Bacud et al., 1994) while a number of dumpsites have collected between February, 2006 and August, 2007 in the selected been implicated for bacterial contamination of drinking groundwater points. The locations of the groundwater points were water (Torres et al, 1991) in some cases, causing obtained with a hand held Global Positioning System (GPS, Germin poisoning, cancer, heart diseases and teratogenic 72 model) with position accuracy of less than 10 m (Table 1). abnormalities (Sia Su, 2008). Although there have been The choice of the sampling stations considered location, accessibility, proximity to residential areas and the topography of no in-depth studies yet concerning groundwater quality the study area. 12 sample stations were within the 2 residential around the Olusosun or Lagos State Waste Management areas (in the 2 km radius), 5 in the commercial area and 3 in the Authority (LAWMA) dumpsite in Nigeria, it will be in industrial section of the study area. Water samples were obtained interest of the future of Lagos State, Nigeria and for both dry and wet seasons in February and August 2006, development agencies in other developing cities to be respectively.