SOME PHYSICOCHEMICAL CHARACTERISTICS AND SPATIAL DISTRIBUTION OF HEAVY METALS AND POLY AROMATIC HYDROCARBONS IN THREE RIVERS IN AHOADA WEST, RIVERS STATE OF NIGERIA

ABSTRACT

Environmental pollution/contamination has led to world-wide issues of source identification and abatement practices of pollutants. In this study, water and sediment samples collected from Taylor Creek, Kolo Creek and Orashi River (all in Ahoada West Local Government Area of Rivers State) were examined for physicochemical characteristics, heavy metals and polycyclic aromatic hydrocarbons. Water physicochemical parameters indicated that all the parameters were within acceptable range for drinking water except biochemical oxygen demand (BOD), turbidity and dissolved oxygen (DO) in some instances. The result of heavy metals in water from all the sampled rivers indicated that Nickel (Ni) was the most concentrated metal, which was followed by that of iron (Fe). All the examined metals were within acceptable limits in the water except Ni and Fe (in some case). Contamination factor (Cf) analysis of the heavy metals indicated the rivers were generally contaminated with the examined metal except Ni that fall within the region of pollution. Pollution index (PI) determination gave values which indicated that the rivers were not polluted with the heavy metals. Contamination degree (Cd) assessment of the water samples indicated that the rivers showed values between low contamination to moderate contamination with heavy metals. Modified contamination degree (mCd) analysis showed that the rivers were within the range of non-contamination to very low contamination degree. The concentrations of polycyclic aromatic hydrocarbons in the rivers were in the order; Kolo Creek > Orashi River > Taylor Creek. There was the predominance of higher molecular weight (HMW) PAHs over lower molecular weight (LMW) PAHs in Kolo Creek and Orashi River, while in Taylor Creek, no particular group predominated. The concentrations of the heavy metals in sediment in all the rivers were in the order: Fe > Zn > Cu > Pb > Mn > Ni > Cr > Cd > Hg. The general order of metals concentrations in the rivers was Kolo Creek > Orashi River > Taylor Creek. Contamination factor analysis of sediment samples showed that the sediments were not contaminated with heavy metals. Pollution index examination indicated sediments free from heavy metals pollution. Contamination degree and modified contamination degree assessment indicated sediments with zero contamination with heavy metals. Geo-accumulation Index assessment showed sediments practically uncontaminated with heavy metals.  The values obtained in ecological risk assessments in the sediments showed that the environment is free from heavy metals associated risk. However, the values obtained for enrichment factor analysis, showed some form of anthropogenic enrichment of heavy metals, especially Zn and Cu. All the PAHs compounds were detected in the sediments of the rivers except naphthalene in Taylor Creek. The HMW PAHs were predominant over the LMW PAHs in all the sediments of the rivers. Source and diagnostic ratio assessment of PAHs gave both pyrogenic and petrogenic sources of PAHs thus implicating different input sources. The results obtained for all the parameters examined in both water and sediment showed that the aquatic environment generally may have health implications on human users and therefore adequate measures be taken to curb or abate the input sources.

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

    CHAPTER 1

INTRODUCTION

1.1 Background of the Study

Pollution is a well-known phenomenon all over the world. The content of water, land and air are consistently interfered with by man while searching for a better alternative to life. Pollution can be defined as damage to the physical, chemical and biological properties of the environment, which may be water, air or land (Etim and Onianwa, 2013). When an environment is polluted, the use or applicability of that environment becomes difficult and harmful due to change in quality of the constituents of the environment (Uzoekwe and Oghosanine, 2011). Pollution constitutes stress to bio-organisms within the environment (Omoregie et al., 1997), hence the need to put the environment under constant check and evaluation.

Water pollution has been on the increase due to population growth, urbanization, and industrialization (Egborge, 1995; Ekaete et al., 2015). Increase in agricultural activities and other forms of production have also contributed immensely to water pollution (William et al., 2010). Water transports waste materials such as organic and inorganic chemicals through runoffs, river flows (current) and precipitation, which may have originated from agricultural farms, industries and in some cases, natural factors (Popoola et al., 2014).

Water sources need protection from degradation and devastation from agricultural, industrial and other forms of contamination or pollution which continually impact negatively on both terrestrial and aquatic environment (Iyama et al., 2014; Brraich and Jangu, 2015). The negative impact imposed on the water environment and the ecosystem resulted from its exposure to unwanted substances in the form of waste discharged into it. These wastes (which in most cases are not treated) are composed of different chemical components which possess the capacity to affect the environment (Adewuyi and Olowu, 2012). Both human and natural sources are known to introduce numerous unwanted pollutants and contaminants such as organic and inorganic constituents into the environment in the form of heavy metals, poly aromatic hydrocarbons (PAHs) (Baran and Oleszczuk, 2002; Obiakor et al., 2014). BTEX, aliphatic and alicyclic hydrocarbons (Ahmed et al., 2015; Edokpayi et al., 2016), polychlorobiphenyls (PCBs), phenols, pesticides, biocides, suspended and dissolved solids are notable water pollutants (Suleimanov, 1995). The presence of these substances react and alter the natural state or chemical composition and the use of water, which eventually become harmful and toxic to aquatic plants and animals and man (the end user) (Ajiboye et al., 2011).

Heavy metals and other organic pollutants such as poly aromatic hydrocarbons are toxic and are persistent in the environment (Hajisamoh, 2013). Among the rural dwellers, there is complete absence of potable water, whereas it is very irregular in town and city settlements in Nigeria (Eneh, 2007). The pollution of the aquatic environment has led to its toxicity and therefore constitute a threat to aquatic biota which man depends on for food and water. This has driven man to search for alternative sources of drinking water such as digging of well and drilling of boreholes, which themselves are not altogether safe from heavy metals, hydrocarbons and other pollutants and contaminants (Bay et al., 2003; Uzoekwe and Oghosanine, 2011). Even the organisms which inhabit the aquatic environment have also been found to bio-accumulate heavy metals, Poly aromatic hydrocarbons and other hydrocarbons (Ashraj, 2005).

It is well documented (Baran and Oleszczuk, 2002; Obiakor et al., 2014) that heavy metals and poly aromatic hydrocarbons pose health challenges to consumers (animals and man). They possess carcinogenic, mutagenic and teratogenic effects to animals and man that got contact with them because of occupation (Ajiboye et al., 2011; Hajisamoh, 2013). Due to the health implication of heavy metals and hydrocarbons, the environment must be constantly examined so as to curb or avert the effects of these chemical constituents which are consistently discharged into the environment (Ajiboye et al., 2011).

Heavy metals belong to a group of metals and metalloids which have densities greater than 5g/cm³. They all fall into the group of transition elements. The presence of heavy metals in water, food, soil and air at some concentrations is considered dangerous to health and are considered as toxicants and pollutants, yet some of them are known as micronutrients at trace concentrations (Hogstand and Haux, 2011). The most unwanted metals in the environment are lead, mercury, cadmium and arsenic. This is due to the fact that even at very low concentrations, they are human poisons or toxicants which cause a lot of physiological problems in biological systems (Damek-Proprawa and Sawicka-Kapusta, 2003). Others, such as copper, zinc, iron, manganese, selenium and others are required by man and animals for proper growth and functions of cell system at trace or very small concentrations (Edori and Marcus, 2017). Sources through which heavy metals contaminate the aquatic environment are divers, but generally classified into natural and anthropogenic sources (Tajam and Kamal, 2013; Bhateria and Abdullah, 2015).

Poly aromatic hydrocarbons (PAHs) which consist of hydrogen and carbon are large group of compounds containing two or more fused aromatic (benzene) rings which differ from one another by the number of rings or substituents on the basic ring system (Mzoughi and Chouba, 2011). The arrangement may be linear, angular or clustered. Environmentally classified as pollutants among this large group of hydrocarbons are the following: naphthalene (Naph), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Fl), phenanthrene (Phe), anthracene (An), fluoranthene (Flu), pyrene (Py), benzo [a] anthracene (BaA), chrysene (Ch), benzo [b] fluoranthene (BbF), benzo [K] fluoranthene (BkF), benzo [a] pyrene (BaP), indeno [1,2,3 – cd] pyrene (IP), dibenzo [ah] anthracene (DA) and benzo [g,h,i] perylene (BP) (Hajisamoh, 2011). 

Due to human explorative activities, heavy metals and poly aromatic hydrocarbons are very common and have almost become a natural component of the ecological environment. They are introduced into lakes, rivers, streams, seas and oceans on daily basis from rock weathering, runoffs, precipitation, industrial and domestic effluents, oil exploration and exploitation, oil spills and vandalization, illegal discharge and allowable or permissible discharges and flares (Alloway, 1990; Ogbonna et al., 2009).

Aquatic animals which inhabit the water system feed from the environment and therefore got heavy metals and hydrocarbons entrained into their systems (tissues and organs). These pollutants in the tissues of fishes bioaccumulate and bioconcentrate and are subsequently transferred to humans, which consume them for food (Mansour and Sidky, 2002; Vosyliene and Jankaite, 2006).

Many environmental (physico-chemical) factors are responsible for the association, dissociation, dissolution, mobility and toxicity of heavy metals in the aquatic environment. These factors include temperature, pH, salinity, pressure, organic content, hardness of water, nutrient levels of the water and sediment and redox potential (Iyama and Edori, 2016).

Sediment or soil is the final sink of pollutants. When pollutants (heavy metals or PAHs) get into any aquatic environment, they finally sink down to the sediment and therefore, the sediment becomes more polluted when compared to the water part of the environment (Bakan and Buyukgungor, 2000).

1.2 Statement of the Problem

It is a well-known fact that both industrial and agricultural activities by man are the major contributors of pollution or contamination of the environment with heavy metals and organic pollutants (William and Benson, 2010; Popoola et al., 2014). Different water bodies (rivers, lakes, reservoirs, creeks, streams and rain) are polluted by flared gases (Uzoekwe and Achudume, 2011), precipitation, discharged effluents from companies and residential quarters and runoffs (Abam, 1999). Uncontrolled waste discharges, bunkering activities, illegal refining of petroleum products, pesticides application and discarding of agricultural wastes are consistently increasing proportionally to population growth (Ghosh and Singh, 2005; Wokoma, 2014). Also, oils spill from old ruptured pipes due to age and vandalization (Abii and Nwosu, 2009), faecal deposition directly into the rivers are well known practices in the Niger Delta (Iyama and Edori, 2014).

Before the advent of drilling of boreholes in private homes by individual, creeks and rivers had been the only sources of water (except rainwater) for domestic uses, discharge of wastes, public toilet (defecation) and fishing, for consumption and commercial purposes (Iyama et al., 2014). The constant degradation of the water quality of these water bodies by man’s activities is becoming unbearable (Ekpenyong and Udofia, 2015) and also constitute a major problem to the community dwellers. Therefore, it becomes necessary to determine the extent of pollution/ contamination of these water bodies and the aquatic organisms in them, so that the effect of pollution or contamination on man could be avoided, minimized or controlled, since man directly depends on water and fish for livelihood.

1.3 Aim and Objectives of the Research

This research work is aimed at determining the pollution levels of Taylor Creek, Kolo Creek and Orashi River within the Engenni axis of the Ahoada West Local Government Area. The specific objectives were to:

(i)     Determine the concentrations of heavy metals in water and sediment samples from these rivers (creeks)

(ii)   Determine the concentrations of poly aromatic hydrocarbons (PAHs) in water and sediment samples from these rivers (creeks)

(iii)  Evaluate the enrichment factor (EF), ecological risk index (ERI), potential ecological risk index (PERI), geo-accumulation index (I-geo), contamination factor (CF), pollution load index (PLI), contamination degree (CD) and modified contamination degree (mCD) resulting from the concentration of heavy metals in the sediment

(iv)  Examine the levels of some physico-chemical parameters of the different river waters and,

(v)   Compare the results obtained with set standards for water and sediment by regulatory agencies.

1.4 Purpose of the Study

The purpose of this work is to determine the concentrations of heavy metals, poly aromatic hydrocarbons and total hydrocarbon content in these water bodies. The study will be able to ascertain the sources of the pollutants, whether anthropogenic or natural, the levels of pollution or contamination of these water bodies and possible health implications associated with these pollutants. Again, the concentrations of the different pollutants in the different rivers will be of importance to the rural dwellers, who can be advised on the proper use of these rivers and also attract the attention of the government and multi-national oil companies operating within the area.

1.5 Significance of the Study

At present, there is no documented comprehensive study conducted on the concentrations of heavy metals, poly aromatic hydrocarbons (PAHs) and other pollutants in the three water bodies (Taylor and Kolo Creeks and Orash River) in the Engenni axis in Ahoada West L. G. A of these rivers. The area where this research was carried out hosts two multinational oil companies (Shell and AGIP) whose exploration and exploitation activities are associated with spills and transportation of heavy equipment. Also, the people in the area under study are involved in intensive subsistence farming and fishing activities of which the proceeds attract large markets on weekly basis. This study will therefore, provide

a)      a baseline data on heavy metals and poly aromatic hydrocarbons and total hydrocarbon content in sediment and water in the study area

b)      the data generated will be used to assess the impact of heavy metals, PAHs and total hydrocarbon content on the consuming population

c)      the result obtained could be used by the Rivers State and Nigerian government in legislation as regard waste disposal, waste management and regulation of the activities of multi-national oil companies

d)     suggest proper clean-up process for the companies and government

e)      the result can be useful to health practitioners in disease diagnosis among the dwellers

      1.6 Scope of the Study

The study was designed to examine the extent of contamination / pollution of the water and sediments of three rivers/creeks (Taylor Creek, Kolo Creek and Orashi River) in Engenni, Ahoada West, Rivers State, Nigeria with respect to heavy metals, poly aromatic hydrocarbons (PAHs) and total hydrocarbons. The atomic absorption spectrophotometer was used for analysis of heavy metals, while gas chromatography coupled with mass spectrometry (GC/MS) technics was used to determine the concentrations of the different PAHs,. The physico-chemical characteristics of the water were measured using appropriate methods. The physico-chemical properties are contributory factors for absorption, mobility and bioavailability of pollutants in the environment. The work was limited to seasonal sampling for twelve months for all the indices with sampling rate of once in two months in the chosen river/creeks within the study area.

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