ASSESSMENT OF HEAVY METAL CONTAMINATION AND pH LEVELS OF SOIL, WATER, AND SELECTED VEGETABLES IN COMMUNITIES OF RIVERS STATE, NIGERIA

ASSESSMENT OF HEAVY METAL CONTAMINATION AND pH LEVELS OF SOIL, WATER, AND SELECTED VEGETABLES IN COMMUNITIES OF RIVERS STATE, NIGERIA

Abstract

Environmental pollution resulting from anthropogenic activities has become a major ecological and public health challenge across many developing countries, particularly in oil-producing regions. This study assessed the concentrations of selected heavy metals and the pH levels of soil, water, and edible vegetables in selected communities of Rivers State, Nigeria. Samples were collected from Mbiama, Ikodi, and Okarki communities in Ahoada West Local Government Area, an area known for agricultural activities and increasing incidences of crude oil theft and illegal refining. The concentrations of Lead (Pb), Copper (Cu), Zinc (Zn), and Chromium (Cr) in soil, water, Telfairia occidentalis (fluted pumpkin), and Amaranthus hybridus (green amaranth) were determined using Atomic Absorption Spectrophotometry (AAS), while pH values were measured using standard laboratory methods. The findings revealed varying degrees of heavy metal contamination across the study sites, with several concentrations exceeding the permissible limits recommended by the World Health Organization (WHO). Soil samples ranged from slightly acidic to alkaline, whereas water samples were predominantly acidic. Statistical analysis using one-way Analysis of Variance (ANOVA) indicated significant differences (p < 0.05) in the concentrations of some heavy metals among the sampled locations. The elevated concentrations observed in vegetables suggest possible bioaccumulation and transfer of contaminants through the food chain. The study further established that soil and water pH significantly influenced the mobility and availability of heavy metals in the environment. Findings from this research suggest that oil bunkering, crude oil spills, and related anthropogenic activities may be major contributors to environmental contamination in the study area. This study highlights the urgent need for environmental monitoring, pollution control measures, and public health awareness to reduce the risks associated with heavy metal exposure in affected communities.

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Environmental contamination by heavy metals has emerged as one of the most significant global environmental challenges due to its adverse effects on ecosystems, agricultural productivity, and human health. Heavy metals are naturally occurring elements characterized by relatively high atomic weight and density, and they exist in trace amounts within the earth’s crust. While some heavy metals such as copper, zinc, iron, and manganese are essential micronutrients required for biological functions, excessive accumulation of these metals in the environment poses serious toxicological risks to living organisms (Tchounwou et al., 2012).

Rapid industrialization, urbanization, agricultural intensification, mining, and petroleum exploration activities have significantly increased the release of heavy metals into soil and water systems. Unlike many organic pollutants, heavy metals are non-biodegradable and persist in the environment for extended periods. They accumulate in soil, sediments, water bodies, and biological tissues, thereby entering the food chain through plants and aquatic organisms (Ali et al., 2019). Exposure to toxic heavy metals has been associated with several health complications, including neurological disorders, kidney dysfunction, respiratory diseases, reproductive abnormalities, and cancer (Engwa et al., 2018).

In developing countries such as Nigeria, environmental pollution resulting from oil exploration and illegal crude oil refining activities has become increasingly alarming, particularly in the Niger Delta region. Rivers State, located within the Niger Delta, is one of the major oil-producing states in Nigeria and has experienced decades of environmental degradation due to oil spills, gas flaring, pipeline vandalism, and illegal oil bunkering. These activities introduce large quantities of hydrocarbons and heavy metals into surrounding ecosystems, thereby contaminating agricultural lands and water resources (Enegide & Chukwuma, 2018).

Heavy metals such as Lead (Pb), Chromium (Cr), Cadmium (Cd), Zinc (Zn), Copper (Cu), Nickel (Ni), and Mercury (Hg) are commonly associated with crude oil contamination and industrial pollution. Once released into the environment, these metals can alter the physicochemical properties of soil, reduce soil fertility, and negatively affect microbial populations responsible for nutrient cycling (Singh et al., 2011). Soil pH is an important environmental factor influencing the mobility, bioavailability, and toxicity of heavy metals. Acidic conditions often increase metal solubility, thereby enhancing uptake by plants and increasing the risk of bioaccumulation in edible crops.

Vegetables cultivated in contaminated soils have the capacity to absorb and accumulate heavy metals through their root systems. Consequently, consumption of contaminated vegetables constitutes a major pathway of human exposure to toxic metals. Two commonly consumed vegetables in southern Nigeria are Telfairia occidentalis (fluted pumpkin) and Amaranthus hybridus (green amaranth). These vegetables are highly valued for their nutritional, medicinal, and economic importance. Telfairia occidentalis is widely consumed due to its rich iron and antioxidant content, while Amaranthus hybridus serves as a major source of vitamins, proteins, and essential minerals (Nwangwa et al., 2007; Umakanta & Shinya, 2020).

The increasing dependence on locally cultivated vegetables in oil-producing communities raises concerns regarding food safety and public health. Communities such as Mbiama, Ikodi, and Okarki in Ahoada West Local Government Area of Rivers State are predominantly agrarian and rely heavily on farming and fishing activities for sustenance and income generation. However, the continuous occurrence of crude oil spills and illegal refining operations within the region may have contributed to elevated levels of environmental contamination.

Despite growing awareness of environmental pollution in the Niger Delta, there remains limited information regarding the extent of heavy metal contamination in soil, water, and edible vegetables within many rural communities of Rivers State. Therefore, this study seeks to evaluate the concentrations of selected heavy metals and determine the pH levels of soil and water in selected communities of Ahoada West Local Government Area. The study also aims to assess the potential environmental and public health implications associated with heavy metal accumulation in commonly consumed vegetables.

1.2 Statement of the Problem

The increasing rate of crude oil theft, pipeline vandalism, and illegal refining activities in Rivers State has contributed significantly to environmental pollution within many rural communities. These activities often result in oil spills and the release of toxic substances, including heavy metals, into surrounding soil and water systems. Contaminated agricultural soils and water sources may subsequently lead to the accumulation of toxic metals in edible crops cultivated within affected areas.

Communities such as Mbiama, Ikodi, and Okarki in Ahoada West Local Government Area depend largely on farming and fishing for livelihood and food security. However, there is insufficient scientific data regarding the level of heavy metal contamination in the soil, water, and vegetables consumed by residents of these communities. The absence of adequate environmental monitoring increases the risk of prolonged human exposure to toxic contaminants through dietary intake and water consumption.

Furthermore, soil and water pH can influence the mobility and uptake of heavy metals by plants, thereby affecting contamination levels within agricultural produce. Without proper assessment of these environmental parameters, the extent of ecological degradation and associated public health risks cannot be fully understood. Therefore, there is a need for comprehensive investigation into the concentrations of heavy metals and pH characteristics of environmental samples from these communities.

1.3 Aim of the Study

The aim of this study is to assess the concentrations of selected heavy metals and evaluate the pH levels of soil, water, and selected vegetables obtained from Mbiama, Ikodi, and Okarki communities in Ahoada West Local Government Area of Rivers State, Nigeria.

1.4 Objectives of the Study

The specific objectives of this study are to:

Determine the pH levels of soil and water samples collected from the selected communities.

Assess the concentrations of selected heavy metals in soil samples from the study areas.

Evaluate the concentrations of heavy metals in water samples obtained from the selected locations.

Determine the levels of heavy metals accumulated in Telfairia occidentalis and Amaranthus hybridus.

Compare the concentrations of heavy metals across the different environmental samples and study locations.

Examine the relationship between pH levels and heavy metal concentrations in the sampled environments.

Compare the obtained values with internationally accepted permissible limits for environmental safety.

1.5 Research Questions

What are the pH levels of soil and water in the selected communities?

What concentrations of heavy metals are present in the soil samples?

To what extent are heavy metals present in water samples from the study locations?

Do Telfairia occidentalis and Amaranthus hybridus accumulate significant levels of heavy metals?

Is there a relationship between pH and heavy metal concentrations in soil and water?

Are the concentrations of heavy metals within the permissible limits recommended by WHO and other environmental agencies?

1.6 Research Hypotheses

Null Hypothesis (H?)

There is no significant difference in the concentrations of heavy metals and pH levels among soil, water, and vegetable samples collected from the selected communities.

Alternative Hypothesis (H?)

There is a significant difference in the concentrations of heavy metals and pH levels among soil, water, and vegetable samples collected from the selected communities.

1.7 Significance of the Study

This study is significant because it provides scientific information on the extent of heavy metal contamination in soil, water, and edible vegetables within oil-producing communities of Rivers State. The findings will contribute to environmental monitoring and public health awareness by identifying potential risks associated with consumption of contaminated agricultural products and water sources.

The study will also provide baseline data useful to environmental agencies, policymakers, agricultural researchers, and public health professionals involved in pollution control and sustainable environmental management. In addition, the research may support the development of strategies aimed at reducing heavy metal contamination and protecting food security within affected communities.

Furthermore, the study contributes to existing literature on environmental toxicology and offers useful reference material for future studies related to heavy metal pollution in the Niger Delta region.

1.8 Justification of the Study

Mbiama, Ikodi, and Okarki communities are located within an area frequently affected by crude oil exploration, illegal refining, and oil bunkering activities. Residents of these communities rely heavily on agriculture and local water sources for survival. Continuous exposure to contaminated environmental resources may have serious ecological and public health implications.

Despite the environmental vulnerability of these communities, there is limited information regarding the concentration of heavy metals in soil, water, and vegetables cultivated within the area. This study is therefore justified as it seeks to fill this knowledge gap by providing empirical data on environmental contamination levels and possible health risks associated with heavy metal exposure.

1.9 Scope of the Study

This study focuses on the assessment of selected heavy metals, namely Lead (Pb), Copper (Cu), Zinc (Zn), and Chromium (Cr), in soil, water, and vegetable samples collected from Mbiama, Ikodi, and Okarki communities in Ahoada West Local Government Area of Rivers State, Nigeria. The study also examines the pH levels of soil and water samples and evaluates the potential relationship between pH and heavy metal accumulation.

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