STUDIES ON THE BACTERIA AND HEAVY METAL PROFILE OF RICE FIELD

CHAPTER ONE

INTRODUCTION

Background to the Study

Heavy metals are generally referred to as those metals which possess a specific density of more than 5 g/cm³ and adversely affect the environment and living organisms (Järup, 2003). They, without doubt, are important constituents for plants and humans, when present only in small amount. Some micronutrient elements may also be toxic to both animals and plants at high concentrations. For instance, copper (Cu), chromium (Cr), fluorine (F), molybdenum (Mo), nickel (Ni), selenium (Se) or zinc (Zn). Other trace elements such as arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) are toxic even at small concentrations (Divrikli et al., 2006). Heavy metals, being persistent and non-biodegradable, can neither be removed by normal cropping nor easily leached by rain water (Khadeeja et al., 2013). They might be transported from soil to ground waters or may be taken up by plants, including agricultural crops. For this reason, the knowledge of metal plant interactions is also important for the safety of the environment (Divrikli et al., 2006).

There has been increasing interest in determining heavy metal levels in public food supplied. However, their concentration in bio-available form is not necessarily proportional to the total concentration of the metal (Opaluwa et al., 2012; Nwachukwu et al., 2010).

The quality of ecosystem becomes altered, when heavy metals find their way, somehow, into it through human and natural activities. These activities are one of the most pressing concerns of urbanization in developing countries like Nigeria, which result in the problem of solid, liquid and toxic waste management. Such waste may be toxic or radioactive (Onibokun and Kumuyi, 1996; UNDP, 2006). Such waste management problems include heaps of uncontrolled garbage, roadsides littered with refuse, streams blocked with rubbish, prevalence of automobile workshops and service stations, inappropriately disposed toxic waste and disposal sites that constitute a health hazard to residential areas (Adewole and Uchegbu, 2005; Rotich et al., 2006; Ebong et al., 2008).

Occurrence of uncontrolled urban sewage farming is a common site in African cities which exposes consumers of such produce to poisoning from heavy metals (Ebong et al., 2008). Open dumps are a source of various environmental and health hazards. The decomposition of organic materials produces methane, which may cause explosions and produce leachates, which pollute surface and ground water. It ruins the aesthetic quality of the land (Oyelola et al., 2009). Automobile wastes include solvents, paints, hydraulic fluids, lubricants and stripped oil sludge; all results of activities such as battery charging, welding and soldering,  automobile body works engine servicing and combustion processes (Adewole and Uchegbu, 2005; Utang et al., 2013).

Soil is the most important component of the environment, but it is the most undervalued, misused and abused one of the earth‟s resources (Gokulakrishnan and Balamurugan, 2010). Soil contamination has become a serious problem in all industrialized areas of the country. Soil is equally regarded as the ultimate sink for the pollutants discharged into the environment (Shokoohi et al., 2009).

Most plants and animals depend on soil as a growth substrate for their sustained growth and development. In many instances the sustenance of life in the soil matrix is adversely affected by the presence of deleterious substances or contaminants. The entry of the organic and inorganic form of contaminants results from disposal of industrial effluents (Gowd et al., 2010). The source of the organic and inorganic elements of the soil of contaminated area was mainly from unmindful release of untreated effluent on the ground (Shetty and Rajkumar, 2009). The contamination of soils with heavy metals or micronutrients in phytotoxic concentrations generates adverse effects not only on plants but also poses risks to human health (Murugesan et al., 2008).

Afterwards, the consumption of contaminated bacterial rice constitutes an important route of heavy metal exposure to animals and humans (Sajjad et al., 2009; Tsafe et al., 2012). Abandoned waste dumpsites have been used extensively as fertile grounds for cultivating rices, though research has indicated that the rices

are capable of accumulating high levels of heavy metals from contaminated and polluted soils (Cobb et al., 2000; Benson and Ebong, 2005).

Statement of the Problem

Heavy metal contamination is one of the serious environmental problems limiting plant productivity and threatening human health (Luptaka et al 2002; Verma and Dubey,2003; Kadukova et al 2006 ). Inputs of heavy metals to agricultural soils can occur from a variety of sources. These include the application of biosolids, fertilisers, livestock manure, agrochemicals, irrigation water and from atmospheric deposition. Some of the concerns about accumulation of heavy metals in agricultural soils stem from their possible negative impacts on soil fertility and in some cases their potential to accumulate in the human chain (McLaugh et al.,1999; Gray et al., 2003). Among the substances that contribute anthropogenically to pollution of the biosphere, trace elements are the most toxic. Lead and Cadmium are toxic metals of increasing environmental concern as they enter the food chain in significant amounts (Luptaka et al 2002; Verma and Dubey, 2003; Kadukova et al 2006).

                        JUSTIFICATION

World Health Organization (WHO) estimates that about a quarter of the diseases facing mankind today occur due to prolonged exposure to environmental pollution (Prüss-Üstün and Corvalán, 2006; Kimani, 2007).

Heavy metal pollution of the environment, even at low levels, and their resulting long-term cumulative health effects are among the leading health concerns all over the world. Heavy metals are known as non-biodegradable, and persist for long durations in aquatic as well as terrestrial environments. They might be transported from soil to ground waters or may be taken up by plants, including agricultural crops including rice (Oluyemi et al., 2008).

It is well known that high industrial and traffic activities contribute high levels of heavy metals to the environments. Plants grown around such areas are likely to absorb these metals either from the soil through the roots or from atmospheric contaminants through the leaves (Fifield and Haina, 1997).

The soil contamination by heavy metals can transfer to food and ultimately to consumers. For instance, plants accumulate heavy metals from contaminated soil without physical changes or visible indication, which could cause a potential risk for human and animal (Osma et al., 2012).

Based on its persistent and cumulative nature, as well as the probability of potential toxicity effects of heavy metals as a result of consumption of leafy rices and fruits, there is a need to test and analyse this food item to ensure that the levels of these trace elements meet the agreed international requirements. It is on this basis that this study was designed to Study on the bacteria and heavy metal profile of rice field.

                        AIM AND OBJECTIVES

The aim of this project work is to ascertain the level of bacteria and heavy metal profile of rice field

The specific objectives of this project work are to:

1. prepare soil samples from selected rice field;
2. prepare plant samples from selected rice grains from the field
3. determine the concentration levels of heavy metals in the soil obtained from the rice field using x-ray fluorescence (XRF) spectrometer;
4. determine the concentration levels of heavy metals in the rice grains samples obtained from the rice field using x-ray fluorescence (XRF) spectrometer;
5. compare the levels of concentration of heavy metals in the soil and plant samples obtained from the field; and
6. suggest the possible measures to manage the bacterial contamination to ensure safety to humans and

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