1.0 Introduction
1.1 Background to the Study
Water is a finite resource that is very essential for the human existence, agriculture and industry thus, inadequate quantity and quality of water have serious impact on sustainable development. In developing countries such as Nigeria, people have little or no option but to accept water sources of doubtful quality, due to lack of better alternative sources or due to economic and technological constraints to treat the available water adequately before use (Calamari and Naeve, 1994; Aina and Adedipe, 1996). The scarcity of clean water and pollution of fresh water has therefore led to a situation in which one-fifth of the urban dwellers in developing countries and three-quarter of their rural dwelling population do not have access to reasonably safe water supplies (Lloyd and Helmer, 1992).
Water quality characteristics of aquatic environment arise from a multitude of physical, chemical and biological interactions. A regular monitoring of water bodies with required number of parameters in relation to water quality prevents the outbreak of diseases and occurrence of hazards. According to Wotton (1992), material pollution of rivers is caused by toxic pollutants (heavy metals, phenols and insecticides, among others) that have direct adverse effect on aquatic biota and by-pollutants (human and animal waste) that indirectly affect aquatic biota, which are not toxic but due to bacterial action on them, dissolved oxygen is used up which harms aquatic biota. Assessment of water is not only for suitability for human consumption but also in relation to its agricultural, industrial, recreational, commercial uses and for its ability to sustain aquatic life. Water quality monitoring is therefore a fundamental tool in the management of freshwater resources.
The biotic component of the aquatic ecosystem, which consists of fauna and flora, are indispensable economic resources. Major components of aquatic fauna are the finfish and shellfish (shrimps, prawns, crabs, lobsters, clams, scallops, periwinkles and oysters among others). Rural artisans who depend on fisheries as a means of livelihood concentrate on shallow water bodies like rivers, creeks, lakes and lagoons for their fishing expedition; this is due to their inability to explore larger water bodies because of limited capital. In Nigeria, the artisanal fisheries sector produces bulk of fish consumed by the populace; in addition, this fisheries sector provides income, employment, raw materials and foreign exchange to the Nigerian populace and the nation (Kumolu-Johnson, 2004).
However, in recent times, Nigeria inland water bodies have been subjected to various forms of degradation due to pollution arising from domestic wastes, industrial effluent, agricultural run-offs, oil spillage, mine effluents and obnoxious fishing practices (Ndimele, 2008). The result is that the associated fishery, the biota and the ecosystem upon which fishers depend for a living are destroyed and consumption of fish caught from such polluted water bodies poses severe danger to the consumers (Kumolu-Johnson et al., 2005). One of such pollutants is heavy metals.
The term “heavy metals” refers to any metallic element that has a relatively high density and is toxic or poisonous even at low concentration (Lenntech, 2004). “Heavy metals” is a general collective term, which applies to the group of metals and metalloids with atomic density greater than 4 g/cm3 or 5 times or more, greater than water (Garbarino et al., 1995; Hawkes, 1997). Heavy metals are pollutants that have been a source of concern for aquatic ecologists because most of them are non-biodegradable; once they enter the system of a biota, they persist there and bio-accumulate along the food chain (Ndimele et al., 2009). The presence of heavy metals in aquatic ecosystems is the result of two main sources of contamination; natural processes or natural occurring deposits and anthropogenic activities.
In the fresh water environment, toxic metals are potentially accumulated in water, sediments and aquatic organisms and are subsequently transferred to man through the consumption of these aquatic organisms and from consumption of water from these aquatic bodies. Studies on heavy metals in rivers, lakes, fish and sediments have been a major environmental focus especially during the last decade (Fernandes et al., 2008; Pote et al., 2008; Praveena et al., 2008). Sediments have been reported to form the major repository of heavy metals in the aquatic ecosystem while both allochthonous and autochthonous influences could make a concentration of heavy metals in the water high enough to be of biological significance (Oyewo and Don-Pedro, 2003). Water is commonly employed as a pollution indicator by heavy metals and sediments can provide a deeper insight into the long-term pollution state of the water body (Ikem et al., 2003). Heavy metal content in rivers may vary between the water column and the bed sediments. However, variation in concentration of parameters depends on concentration from processes operating within the catchments. Some heavy metals found in water and sediments include Lead, Mercury, Chromium, Manganese, Nickel, Cadmium, Copper, Cobalt, Iron and Selenium, amongst others.
This study is geared towards determining the physico-chemical parameters and concentration of heavy metals in the water and bottom sediments of Warri river, located in Warri, Delta state, Nigeria, with a view to establishing a basic data on the current pollution status of the river. The results obtained from this study would also provide information on current levels of metals in the water and sediments of the river, contributing to the effective monitoring of both environmental quality and health of the organisms inhabiting the river.
1.2 Justification
Water is important, directly or indirectly, to human and animal life and thus, requires that proper attention be given to its quality, consisting of the physical and chemical characteristics, which motivated this study. The many human activities in the last decade have increased the metal mobility in the environment, and heavy metals happen to be one of the main pollutants in aquatic systems as some metals are persistent thus becoming potentially dangerous to biota.
Over the years, some work has been done on the physico-chemical parameters of some creeks along Warri River (Peretiemo-Clarke et al., 2009; Ogunlaja and Ogunlaja, 2007), but there has been limited study on the physico-chemical parameters as well as heavy metal contaminants of the Ogbe-Ijoh waterside of the Warri river, hence the need for this study. The study will also provide baseline data for future work on the river.
1.3 Aims and Objectives
The main aim of this study is to investigate and determine the physico-chemical parameters and concentration of some selected heavy metals in the water and sediment of Ogbe-Ijoh waterside. This would be achieved by:
- Determining the physico-chemical parameters of the water
- Determining the heavy metal concentration in water and sediments of Ogbe-Ijoh waterside
- Inferring if the water from the river is safe for consumption and for the sustenance of the aquatic organisms inhabiting the biota when compared against set standards by Food and Agricultural Organisation (FAO) and World Health Organisation (WHO).
