1.0 Introduction
1.1 Background of the Study
Water, sediment and (fish) and affected rivers are direct recipients of industrial waste and municipal sewage (Amadi, 2010). Changes in water chemistry of rivers are usually anthropogenic via domestic, industrial and agricultural discharges which may in turn result to degradation of aquatic ecosystems (Ugwu and Wakam, 2012). One of the most critical problems of developing countries is improper management of vast amount of wastes generated by various anthropogenic activities. More challenging is the unsafe disposal of these wastes into the ambient environment. Water bodies especially fresh water reservoir (rivers) is the most affected. This has often rendered these natural reservoirs unsuitable for both primary and secondary usage (Fakayode, 2005).
Industrial effluent contamination of natural water bodies has emerged a major challenge in developing and densely populated countries like Nigeria.Estuaries and inland water bodies, which are major sources of drinking water, in Nigeria are often contaminated by the activities of adjoining populations and industrial establishments (Adesuji, 2016). River systems are the primary means for disposal of waste especially effluents from industries that are near them. These effluents from industries have a great deal of influence on the pollution of the water body. These effluents can alter the physical, chemical and biological nature of the receiving water bodies.
Increased industrial activities have led to pollution stress on surface water both from industrial, agricultural and domestic sources (Ajayi et al., 1981). Water pollution refers to the introduction by man directly or indirectly of substance or energy into the marine environment (including estuaries) resulting in deleterious effects such as harm to living organisms, hazards to human health, hindrance to marine activities including fishing, impairment of quality use of river water and reduction of amenities (Dan et al; 2014).Rivers drain urban, suburban and rural areas where they collect more pollutants. Rivers are by far the cheapest form of water supply compared to other sources like groundwater and sea water (Amadiet al., 2010).
Meeting water quality expectations for streams and rivers is required to protect drinking water resources, encourage recreational activities and to provide a good environment for fish and wildlife. Therefore, assessment of pollution status of water (rivers) is of ecotoxicological importance. Of the aquatic ecosystem (Aiyesanmi et al.,2012), water soluble wastes and other materials that are dumped, spilled or stored on the surface of the land or in sewage disposal pits can be dissolved by precipitation, irrigation. Water or liquid wastes can eventually seep through the well in the unsaturated zone to pollute the rivers. Thus constant monitoring of rivers quality /assessment is needed so as to record any alteration in the quality and outbreak of health disorder. Sediment sources in aquatic ecosystem include soil erosion, decomposition of plants and animals and discharge of effluents (USEPA, 2012).
Wind and water help to carry these particles to rivers. Soil disturbance due to massive road construction and demolition of structures in Imo State and Abia State could significantly increase the load of sediments of Imo River. Sediments are contaminated with different pollution from effluent discharges and run off into the Imo River. (Ogwo and Okereke, 2014). The percentage of silt and clay in river sediments can have impact on the structure of the biotic assemblage. Heavy metals are wide spread pollutants of great environmental concern as they are non-degradable, toxic and persistent with serious ecological ramifications (Jumb and Nardin, 2009). Humans have always depended in aquatic resources for food, medicines and materials as well as recreational and commercial purposes such as fishes and tourism (Chopora et al; 2009). Aquatic ecosystems are strongly influenced by long term discharge of untreated domestic and industrial wastewater, storm water runoff, accidental spill and direct solid waste dumping (Amadi, 2010).
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous anthropogenic pollutants that can be biologically amplified to high concentrations in food webs. Due to their lipophilic, persistence and high toxicity, these residues are readily accumulated in the tissues of non-target living organisms where they may cause detrimental effects. PAHs are toxic, carcinogenic and mutagenic to all organisms, including humans (Al-Kahtani, 2009).The main sources of these contaminants in the environment include forest fire, natural petroleum seeps, combustion of fossil fuels, coal burning and use of oil for cooking and heating. Other sources include domestic and industrial waste waters and sewage. As a consequence, environmental contamination by PAHs has steadily increased in recent years (Ezekweet al., 2013).
Pollution of river bodies has become major and global problem due to inadequacy of surface water protection measures. Wastes are usually discharged into the rivers. Discharge of sewage, garbage, oil spills and industrial effluents are threats to the diluting capacity of rivers (UNESCO, 2006); hence constant assessments of the water quality conditions of receiving water bodies’are very critical to effective planning and management. Pollution of water bodies (rivers) by heavy metals and polycyclic aromatic hydrocarbons (PAHs) is a major challenge facing both the developed and the developing nations. There is therefore, the need to carry out assessment of pollution status of Imo River in order to regulate this ugly tend. The three relevant parameters: physicochemical analysis, heavy metal concentration and analysis of polycyclic aromatic hydrocarbons (PAHs) will be used to assess the pollution status of upper part of Imo River, South Eastern Nigeria. Physicochemical parameters such as colour, pH temperature, dissolved oxygen turbidity, salinity, total dissolved solids, total suspended solids, biochemical oxygen demand, chemical oxygen demand, chemical oxygen demand, total hardness, alkalinity acidity, phosphate, nitrate, sulphate, bacteriological analysis are necessary to ascertain the water quality index of Imo River which gives information on quality of the Rivers. The physicochemical characteristics of Imo River are important in the determination of its productive capacity and effect on the biota (Duru and Nwanekwu, 2012).
Heavy metals and polycyclic aromatic hydrocarbons may enter the sediment and aquatic environments via industrial waste disposal, refuse, sewage, application of fertilizers and pesticides, atmospheric deposition (Amadi, 2010). Heavy metal concentrations analysis of water, sediment and fishes will be used to ascertain the mobility of the heavy metals, and the bioaccumulation and bio-magnification of these heavy metals in tilapia and cat fish and the adverse health riskthese metals may pose on communities that use water from Imo River. The Environmental Protection Agency (EPA) concentrated on the sixteen polycyclic aromatic hydrocarbons that are included in their list of 126 priority pollutants. These compounds have been chosen on the basis of frequency of occurrence at hazardous waste sites and toxicity potential for human exposure (Zhang et al., 2011). Polycyclic aromatic hydrocarbons are mostly discharged into Imo River industrial effluents, domestic sewage, agricultural run-offsand vehicular emulsion. The concern is therefore that PAHs are detrimental to human beings (can impair survival and growth by causing abnormal reproduction and development). This study was carried out to assess the pollution status upper part of Imo River using water samples, sediment and biota (fishes).
1.2 Statement of Problem
Investigation revealed that most of the available literature on the pollution status of Imo River deal more on physicochemical parameters or concentration of heavy metals in water, sediment or biota. Literature available suggest that most studies conducted so far on pollution status of Imo River have not considered the sixteen (16) priority polycyclic aromatic hydrocarbons (PAHs) that are carcinogenic, mutagenic and tetragenic.
Hence this study will be useful in assessment of human health risk of pollutants, heavy metals and polycyclic aromatic hydrocarbons in water, sediments and fish from upper part of Imo River.
1.3 Aim and Objectives of the Study
The aim of the study is to assess the pollution status of Imo River by phosphate and sulphate. In achieving this aim, the following specific objectives were laid out as follows to:
- Determine the physico-chemical parameters in water and sediment from Imo River.
- Determine concentration of heavy metals in water, sediment and fish from Imo River.
- Determine the level of some polycyclic aromatic hydrocarbons in water, sediments and fishes.
- Correlate between heavy metals and polycyclic aromatic hydrocarbons in water, sediment and fish.
- Determine the potential health and ecological risk assesment of the above contaminants and pollutants using risk assessment models.
1.4 Significance of Study
The study is relevant to both the environmentalists and researchers as it will redound to knowledge of heavy metals contamination of Imo River. The findings of this study will be of immense benefit tothe Federal Ministry of Environmentin their plan to reduce pollution.This work will provide insight on the mobility and fate of heavy metal contaminants in the study area.Analysis of biota (fish) will give information on biological availability of the contaminants, its bioaccumulation and bio magnification along the food chain.
The findings of this study will help to educate residents and those who depend largely on water and biota (fish) from the study area on dangers of heavy metals and polycyclic aromatic hydrocarbons toxicity. The inhabitants of the study area will benefit from this study, since the health risk assessment will help in predicting the level of human exposure to carcinogenic and non-carcinogenic effects. Finally, this study will serve as a future reference to health workers and researchers in the field of chemistry and environmental studies.
1.5 Scope of Study
The scope of study covered reconnaissance survey of the study area, mapping of sampling location, field sampling of water, sediment and biota (fish) from Imo River in-situ and laboratory analysis of samples. The analysis in the laboratory involved:
- Determination of physico-chemical parameters of water, sediments and fish.
- Determination of heavy metals in water, sediments and fish. iii.determination of polyaromatic hydrocarbons in water, sediments and fish.
- Statistical analysis of data generated and interpretation with application of risk assessment models.
1.6 Limitations of the Study
During the course of this study, there were some problems encountered which stood as limitations to the research work. Some of the limitations include:
- Time Constraint:
The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Financial Constraint:
Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).
- Initial Cooperation Delay from Respondents:
A particular limitation of this work came as a result of the respondent refusal to offer their cooperation at the initial time they were contacted. This contributed in making the success of this research study difficult.
