Evaluation of the Pollution Status in Uyo Dump Site Metropolis Using African Giant Land Snail; Archachatina Marginata
Chapter One
AIM AND OBJECTIVES
The study was aimed at evaluating the current pollution status of Uyo Metropolis dumpsite using African giant land snail Archachatina marginata as a bio-indicator.
The specific objectives of the study were:
- To assess the levels of heavy metals composition in the African giant land snail Archachatina marginata pick from dumpsite Uyo Metropolis.
- To ascertain the heavy metals content of soil at Uyo Metropolis dumpsite
- To provide scientific information on the pollution status of Uyo Metropolis dumpsite and create necessary public awareness as a prelude to the management of the dumpsite.
CHAPTER TWO
REVIEW OF RELATED LITERATURE
INTRODUCTION
This chapter presents the review of related literature on evaluation of the pollution status in Uyo dump site metropolis using African giant land snail; Archachatina marginata. Views and opinions of other authors will be presented as follows.
HEAVY METALS COMPOSITION IN THE AFRICAN GIANT LAND SNAIL
Trace metals are natural components of the earth crust and cannot be degraded. The systematic release of these metals from both natural sources and human activities into the environment is of great concern (Adholeya, 2004). Some of these metals pose a risk to environmental and human health via the food chain and other sources of human exposure as a result of their toxicity (Malik, 2004). These contaminants are accumulated by living organisms in their bodies and subsequently biomagnified as they pass from one trophic level to the next. Contamination of terrestrial environment by trace elements leads to an increasing uptake of metals by soil invertebrates, including land snails. Since man is at the top of food chain, he is vulnerable to metal pollution (Fulekar, 2006).
The African giant land snail feeds on the debris from the soil surface which may be contaminated with trace metals which may have accumulated to harmful levels. Snails are abundant in many terrestrial and aquatic ecosystems, being easily available for collection. They are highly tolerant to many pollutants and exhibit high accumulations of them, particularly heavy metals (Bordean, et al 2012). Trace metals such as Cu, Zn, Pb, Hg, Al, Cr and Cd are normal constituents of marine environment, and traces are always found in marine organisms. The African giant land snail feeds on the debris from the soil surface which may be contaminated with trace metals which may have accumulated to harmful levels. Snails are abundant in many terrestrial and aquatic ecosystems, being easily available for collection. They are highly tolerant to many pollutants and exhibit high accumulations of them, particularly heavy metals (Bordean, et al 2012). Trace metals such as Cu, Zn, Pb, Hg, Al, Cr and Cd are normal constituents of marine environment, and traces are always found in marine organisms. (Johnston, 1990).
Metal uptake through food is regarded as the main route of contamination in terrestrial invertebrates (Bordean, et al 2012). Metal uptake via epithelial tissues cannot be ignored because terrestrial pulmonates spend their entire lives on or in the upper soil horizons and therefore, the snail tegument comes frequently in direct contact with polluted substrates (Sturzenbaum, et al 2000). However, in natural environments, metal uptake is a cumulative process that occurs via mixed air, soil and food exposures (Badot, 2006). Most ingested metals are metabolically regulated in the snail body either by cellular compartmentalization or by complexation to specific metallothioneins (Dallinger, 2000). Such processes of bioaccumulation in organisms may be associated with significant interactions between these trace metals and macro metallic elements such as K, Ca, Na and Mg. Thus, people who eat snails from estuarine or coastal areas from oil polluted soils are at risk of trace metal poisoning (Mahmood, et al 1995). Very little information is known of metal levels in the African giant snail as consumed in the Southern part of Nigeria. This work was tailored towards assessing the levels of toxic trace metals in African giant snail commonly consumed by majority of populace in Southern Nigeria.
HEAVY METAL POLLUTED SOILS
Heavy metals are elements that exhibit metallic properties such as ductility, malleability, conductivity, cation stability, and ligand specificity. They are characterized by relatively high density and high relative atomic weight with an atomic number greater than 20 (Kumar, 1994). Some heavy metals such as Co, Cu, Fe, Mn, Mo, Ni, V, and Zn are required in minute quantities by organisms. However, excessive amounts of these elements can become harmful to organisms. Other heavy metals such as Pb, Cd, Hg, and As (a metalloid but generally referred to as a heavy metal) do not have any beneficial effect on organisms and are thus regarded as the “main threats” since they are very harmful to both plants and animals.
Metals exist either as separate entities or in combination with other soil components. These components may include exchangeable ions sorbed on the surfaces of inorganic solids, nonexchangeable ions and insoluble inorganic metal compounds such as carbonates and phosphates, soluble metal compound or free metal ions in the soil solution, metal complex of organic materials, and metals attached to silicate minerals (Marques, 2009) Metals bound to silicate minerals represent the background soil metal concentration and they do not cause contamination/pollution problems compared with metals that exist as separate entities or those present in high concentration in the other 4 components (Gonzalez, 1994).
CHAPTER THREE
MATERIALS AND METHODS
DESCRIPTION OF STUDY AREA
Uyo, the capital city of Akwa Ibom State is located on the north west of the State. It extends from latitude 7o 471 to 8o 031 North and longitude 4o 521 to 5o 071 East. By 1991, the population of Uyo Urban was 118, 250. The mean annual temperature in Uyo Urban is 27o C. The relative humidity varies through the year from 70 – 80%. The mean annual rainfall is 2484mm. The city has two distinct seasons, namely; dry and rainy seasons. The dry season usually starts in November and ends in March. The rainy season starts usually in April and end in October. The prevailing wind blows from south west in the wet season and from north east in the dry season. Uyo is within the modified rainforest zone now called oil palm bush. This type of vegetation is however disappearing due to urban development. The topography of the area is generally undulating, except in the north eastern part that is occupied by Valley of Ikpa River which runs in a North West southwest direction. Parts of the valley are so steep that they are described as ravines. This topography poses a major limitation to physical development of the city; attention has been given to the stabilisation of the slope to protect the city from further encroachment by ravines. These areas have been turned into conservation areas and utilised for purposes that do not require buildings.
SAMPLE COLLECTION AND SAMPLE TREATMENT
Twenty soil samples were collected from five waste dumpsites. In each dumpsite, four soil samples were collected at a depth of between 0-15cm and 15-30cm. Six samples were also collected from three locations away from the dumpsites, at depth of between 0-15cm, and 15-30cm plant samples: cocoa yam (colocasia) were also collected at dumpsites and some distances away from the dumpsites. Both plant and soil samples were packed in separate bags and taken to the laboratory for analysis.
(1) Soil Samples: At the laboratory; the sample soils were air dried and ground to powdery form using a pestle and mortar. The sample was sieved with a 2mm sieve. The soil sample (1g) was weighed into a digestion flask. Concentrated nitric acid (20ml) was added and the mixture was digested using hot plate. After digestion it was allowed to cool and 30 ml of distilled water was added and filtered with Whatman filter paper. The digest was made up to 50 ml solution with distilled water. Then, the digest was sent to Aluminum smelting company of Nigeria (ALSCON) for the determination of heavy metals using Unicam 939 model of atomic absorption spectrometer (AAS).
CHAPTER FOUR
RESULTS AND DISCUSSION
PHYSICOCHEMICAL PROPERTIES OF STUDY AREA
Table 1a: Physicochemical Properties of Study Area
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
Introduction
This chapter presents the conclusion and recommendations based on the findings of this study.
CONCLUSION
Based on major findings, heavy metal concentration is generally higher at the surface than the subsurface soil Therefore, if deep rooted crops are cultivated there, the rate at which the plants will take up these heavy metals may take place more slowly than shallow rooted crops. Also, the waste dumpsites and plants around it had higher concentrations of heavy metals than on the control sites.
RECOMMENDATIONS
Based on the findings of this study, the researcher made the following recommendations:
- Efforts should be intensified to discourage the practice of cultivating on dumpsites soils. Hence the use of dumpsite soils as a source of manure for plants and vegetables which is a common practice in Nigeria should be noted as devastating tradition and should be discouraged.
- Proper education and legislations on handling of wastes in the society should be intensified to forestall waste related problems along the food chain.
- The wastes dumpsites should be upgraded to a modern waste deposition (sanitary landfill). Waste sorting into biodegradable and non-biodegradable ones before deposition should be encouraged.
- Education and legislation on management of dumpsite should be intensified to forestall other causes of contamination problems.
REFERENCES
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