1.1 Introduction
Waste generation is an integral aspect of human existence that is unavoidable. It is a product of resource use process that has the capacity to be inconveniencing and harmful leading in extreme cases to pollution with resultant epidemics and catastrophic consequences. Waste is used to describe any item or object that is no longer suitable for use in the owner’s or user’s consideration, waste can be products or by-products of certain processes or remnants of useful items that are considered as no longer useful. Waste comes in three broad forms of solid, liquid and gaseous waste, (Jatau, 2013).
Solid waste which consists of refuse, garbage, rubbish, dead animals, construction wastes, etc., may either be biodegradable or non-biodegradable, combustible or non- combustible. Examples of solid waste are; broken glasses, plastics, metals, broken blocks, food remnants, papers, wood, cloth, etc. Solid waste from households, commercial and industrial sources are called Municipal Solid Waste (MSW), and they are generally disposed off in a landfill (Environmental Protection Department, 2011).
Biodegradable waste items will disintegrate with the passage of time even when left on their own but apart from creating health hazards, the rate of disintegration may be too slow for the rate of generation thereby making aesthetically unappealing. Owing to the multidimensional nature of waste and its attendant negative effects on humans, wildlife and the environment, its management is highly crucial and requires concerted effort. (Adewale and Litherland, 2011).
Waste management practices which essentially covers the collection, conveyance, processing, recycling and disposal of waste items is approached in different ways in different communities all with the same goal of maintaining sustainable environment conducive for healthy human and wildlife habitation. Generally, governments are responsible for the management of non-hazardous residential and institutional waste while, commercial and industrial wastes are managed by their producers under government’s supervision.
A common practice of solid waste management in Nigeria involves the collection, transportation and disposal of solid wastes at designated areas called dumpsites. Uyo metropolis dumpsite is a major repository of municipal solid waste in Akwa Ibom State. It receives domestic, industrial and institutional waste by public and private waste management operators.
According to the Organization for Economic Co-operation and Development (OECD) through a document concerning pollution in 1976, Pollution is the production or introduction by man directly or indirectly of substances or energy into the environment, resulting in deleterious effects of such nature as to endanger human health, harm other living resources in the ecosystem and impair other legitimate uses of the environment. Pollution occurs when a product added to our natural environment adversely affects nature’s ability to dispose it off. A pollutant is something which adversely interferes with the health, comfort, property or environment of the people. Generally, most pollutant are introduced into the environment as sewage, solid waste and as compounds used to protect plants and animals. Over the years solid waste has been introduced into Uyo Metropolis dumpsite and it is suspected that this must have elicited the pollution of the environment. (Misra and Alani, 1991).
Bio-indicators are species used to monitor the health of an environment or ecosystem. They are any biological species whose function, population or status can be used to determine ecosystem or environmental integrity of such organisms are monitored for changes be it biochemical, physiological or behavioral that may indicate a problem within the environment or ecosystem. A bio-indicator can tell one about the cumulative effect of different pollutant in the ecosystem and about how long such a problem may have been present which physical and chemical testing alone may not (Karr, 1993).
An example of such a group is the gastropods and other land and water organisms. The importance and relevance of bio-indicators rather than man-made equipments in ascertaining the health staged of an environment is justified by the statement; there is no better indicator of the status of a species or a system than the species or system itself. Bio monitoring entails the use of the property of the organism to obtain information on certain aspects of the biosphere, (Tingey, 1989).
Giant African Land snail; Archachatina marginata is a species within the family archantinidae, a family of unusually large African terrestrial land snails. It is native to West Africa and found in humid areas, urban areas and sub lands including farmlands. It can be found aestivating underground during drier months, having a closed aperture, sealed with a solid, calcareous, white epiphragm, (Cowie et al., 2009).
Classification
- Kingdom: Animalia
- Phylum: Mollusca
- Class: Gastropoda
- Super family: Archatinoidae
- Genus: Archachatina
- Species: Archachatina marginata
Heavy metals are metals and metalloids having atomic densities greater than 5g/cm3. They include mercury, zinc, copper, cadmium, lead and nickel among others. At some levels of exposure, and absorption, they are harmful to most living things. Heavy metals are released into the environment through man’s industrial, domestic and commercial activities, industrial effluents, pesticides and fungicides, as well as manure from poultry farms. Many of the sites contain significant amount of ashes due to dumping of ash and the burning of refuse on the dumpsite from time to time. The burning gets rid of organic materials and oxidizes the metals leaving the ash richer in metal content. The process of oxidation and corrosion makes the metals soluble and leached from where they are picked up by plants, thereby entering into the food chain. (Wild, 1993).
The toxicity of many metals depend on the chemical forms in the environment which can be greatly affected by the leachate quality especially pH. The heavy metals present in the leachates are considered hazardous to terrestrial lives because of their availability and toxicity, bioaccumulation tendency of characterized contents and their availability. Heavy metals may reach the terrestrial environment via the flow of this leachate and plants rooted in leachates contaminated soils. (John, 2002).
Macro fauna are an important part of the soil environment. Snails, being an important macro fauna is involved in many aspects in microbial activities, nutrient cycle and crumbly structures and thus, are readily exposed to the leachate and heavy metals present in the soil. (Corlex et al., 1993).
The major dumpsite solid wastes produces heavy metals continually; this is capable of migrating unto nearby farmlands and surface water. The knowledge of the composition and quality of these solid waste will give an insight into appropriate, effective and sustainable environmental protection approach. Therefore, this study will document the physical and chemical composition of heavy metals from contaminated soil in Uyo Municipal dumpsite, and measure possible effects as well as the pollution status of the dumpsite, nearby farmland and environs using African Giant Land Snail; Archachatina marginata as bio-indicator.
1.2 Significance of the study
Uyo municipal dumpsite is situated in the heart of Uyo Metropolis close to Akwa Ibom State Government House. Residential buildings, farmlands and surface water bodies are some sensitive environmental components around the dumpsite. There has been widespread concern about potential pollution emanating from the dumpsite with its attendant negative impacts on public health and the environment.
It is imperative to ascertain the actual pollution status of the dumpsite to assist in the holistic management of the dumpsite in the interest of public health, aesthetic and the general well being of the environment.
1.3 Aim and Objectives of the Study
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.
