ASSESSMENT OF LEAD (PB) AND MERCURY (HG) CONCENTRATION IN SOIL AND STREAM WATER AROUND INDUSTRIES IN ENUGU MUNICIPALITY, ENUGU STATE, NIGERIA

ASSESSMENT OF LEAD (PB) AND MERCURY (HG) CONCENTRATION IN SOIL AND STREAM WATER AROUND INDUSTRIES IN ENUGU MUNICIPALITY, ENUGU STATE, NIGERIA

CHAPTER ONE

INTRODUCTION

 

 

1.1 Background of the Study

Heavy metals are toxic metallic elements with a specific gravity that is at least 5 times higher than that of water. The important once are arsenic, cadmium, iron, lead, mercury (Lide, 1992). Heavy metal contamination affects large areas worldwide. Hot spots of heavy metal pollution are located close to industrial sites, around large cities and in the vicinity of mining and smelting plants (Dudka and Adriano, 1997). Heavy metals become toxic when they are not metabolised by blood and accumulate in soft tissues of fishes or animals which will be consumed by humans.

Increase in poverty and hunger, lack of formal employment opportunities, demand for food, proximity to markets and availability of cheap resources such as urban organic wastes and wastewater have stimulated the development of diverse agricultural system in and around cities (D’mello, 2003). The most common urban agricultural activities are community gardens (formal and informal), home gardens, institutional gardens and nurseries managed by schools, hospitals, prisons and factories (Mubofu and Bahemuka, 1999). The major entry route to plants (crops and vegetables) reported is through roots and leaves which absorb the chemicals from contaminated soil, water and air (Zurera et al., 1989). Industrial exposure accounts for a common route of exposure for adults and workers while ingestion of food, water and inhalation of contaminated air is the most common route of exposure in humans and animals (Robert, 1999).Absorption through the skin has been reported when the effluents come in contact with humans in industrial settings.

Children may develop toxic signs of heavy metal from the normal hand to mouth habit practices of small children who come in contact with contaminated soil by eating objects that are not food (dirt or paint chips) (Dupler, 2001). Animals grazing on pasture or vegetables at the effluent pathways have been shown to ingest large quantity of heavy metals. Less common route of exposure recorded was in radiological procedures or monitoring during intravenous nutrition (Smith et al., 1997). As trace elements, some heavy metals such as copper, selenium and zinc are essential to maintain the metabolism of the human body. However, at high concentration they can lead to poisoning (Cambra et al., 1999).

Since farm activities in this area of study involve irrigation water from industrial effluents, it is therefore imperative to design a study to investigate the extent of heavy metal pollution in soil, vegetable gardens or pastures and surface water along the industrial effluent pathways. This will provide information on the potential source of heavy metals and transfer to food chain. Industry—stream—soil—plants (vegetables)—animals (aquatic)—humans. Metal contamination of garden soils may be widespread in urban areas due to industrial activitiy and the use of fossil fuels (Chronopoulos et al., 1997). Vegetables are made up of chiefly cellulose, hemi-cellulose and pectin substances that give them their texture and fairness (Sobukola and Dairo, 2007). However, heavy metals rank high among the chief contaminants of vegetables and pastures (Mapanda et al., 2005).

The Vegetables take up metals by absorping them from contaminated soils, as well as from deposits on different parts of vegetables exposed to the air from polluted environments (Sobukola et al., 2010). Vegetable plants growing on heavy metal contaminated medium (effluents) can accumulate high concentrations of trace elements to cause serious health risks to consumers (Long et al., 2003). Excessive content of Pb and Cd in food has been associated with a number of diseases such as cardiovascular, kidney, nervous as well as bone diseases (WHO, 1992; 1995., Steenland and Boffetta, 2000., Jarup, 2003). The pollution load from different industrial sites has destroyed the surface water used by animals and man as source of drinking water and especially ruined fresh water used in fish communities which contributes an important share in the domestic protein (Khan 2008).  Also studies of heavy metal contents of surface waters at Ibadan showed that the levels of Pb may reach 50 ug/litre (Mombeshora et al., 1983). It is important that this study be carried out to test and analyse the industrial effluents, vegetables/pastures and surface water along industrial effluent pathways in the study area to determine the levels of heavy metal concentrations. The findings will be compared with the international permissible limits for the discussion on the public health implications.

 

1.2 Statement of the Problem

Due to unrestricted discharge of industrial waste, the soil and water environment have been contaminated by waste which are demonstrated by accumulation of heavy metals in surface soils. Heavy metals from industrial processes can accumulate in nearby lakes and rivers. They are toxic to marine life such as fish and shell fish, and subsequently to humans who eat them. The metals have been shown not to be toxic as condensed free elements but are dangerous in the form of cations and when bonded to short chains of carbon atoms (Bairds, 1995). Heavy metals can slow development, result in birth defects and some are carcinogenic. They can cause immune suppression as well. Heavy metal contamination has caused serious environmental and health-related problems around the world (Alloway and Ayres, 1997). The toxic elements accumulate in organic matter in soils and are taken up by growing plants (Dara, 1993). It has been recognized that food crops can be an important source of heavy metals for humans and animals (Dudka and Miller 1999). Vegetable plants growing on heavy metal contaminated medium can accumulate high concentrations of trace elements to cause serious health risks to consumers (Long et al., 2003).

Excessive content of lead and cadmium metals in food is associated with aetiology of a number of diseases especially with cardiovascular, kidney, nervous as well as bone diseases (WHO, 1992, 1995., Steenland and Boffetta, 2000., Jarup, 2003). Lead is very toxic and has very chronic health implications even at very low concentration (Meiltinien, 1975; Bryan, 1976). Ingestion of lead could cause mental retardation in children (Huges et al., 1980), colic anaemia and renal diseases (Fisherhbein, 1992). Cultivation of crops and vegetables for human or livestock consumption along industrial effluent discharge pathway or using such effluents for irrigation can potentially lead to the uptake and accumulation of these heavy metals in edible plants parts with a resulting risk to human and animal health (Gupta and Gupta, 1998, Lim et al., 2008). Serious systemic health problems can develop as a result of excessive dietary accumulation of heavy metals such as cadmium and lead in the human body (Oliver, 1997). Carrying out this study will provide information on the levels of contamination and bioaccumulation of heavy metals in the environment from industrial effluents in the study area.

 

 

1.3 Aim and Objectives of the Study

The aim of this study is to determine the levels of heavy metal concentration in effluents, soil, and surface water along the pathways of effluents from industries in Enugu municipality.

The specific objectives include:

1. To determine the presence of lead and mercury in stream water and soil around the selected industries.
2. To determine the level of concentration of lead and mercury from point source to distances along the pathway down to the receiving stream water.
3. To determine if there is seasonal variation in the levels of occurence of lead and mercury in the effluents from industries in the study area.
4. To compare the levels of heavy metals in the water and soil with the international permissible standards
5. To determine if the stream water receiving the effluents from the industries could be toxic to Artenia salina, ( brine shrimp).

1.4 Significance of the Study

In order to find solution to environmental and public  health problems arising from poor waste management in industries situated in Enugu state, this study becomes imperative to provide baseline information on the possible source of heavy metal contamination of soil and water around industrial sites and most importantly the dangers associated with it. The study will provide baseline information on the possible sources of heavy metal contamination of soil and stream water around industrial sites and their public health implications.

Information generated will be used to create awareness to the public health authorities and other stakeholders on the inherent danger posed by heavy metals to humans, animals and marine life and the need for industries to provide proper waste disposal system to reduce the concentration of heavy metals in the environment.

This study will also buttress the need for government to enforce rules for proper monitoring and auditing industries to effectively manage their wastes.

 

1.5. Scope of the Study

The study covered major industries (paint, aluminium, and plastic etc)  in Enugu state that are located within Enugu municipality covering up to  3 local government areas (Enugu West, Enugu East, and Enugu South).

 

1.6. Null Hypotheses

The following hypotheses were used to guide this study and were tested at 0.05 level of significance.

1. Lead and mercury are not present in stream water and soil around industrial sites
2. The level of lead and mercury concentrations are not significantly different along the distance and seasons.
3. The values of Pb and Hg obtained do not exceed the WHO International Permissible Standard
4. Waste water from industries in Enugu State is not toxic to aquatic life

 

ASSESSMENT OF LEAD (PB) AND MERCURY (HG) CONCENTRATION IN SOIL AND STREAM WATER AROUND INDUSTRIES IN ENUGU MUNICIPALITY, ENUGU STATE, NIGERIA

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