TABLE OF CONTENT

Title page    –        –         –         –         –         –         –         –         –         i

Certification           –         –         –         –         –         –         –         –         ii

Dedication   –         –         –         –         –         –         –         –         –         iii

Acknowledgement           –         –         –         –         –         –         –         iv

Table of Content              –         –         –         –         –         –         –         v-vii

CHAPTER ONE

1.0 INTRODUCTION           –         –         –         –         –         –         1-3

CHAPTER TWO

2.0    HEAVY METALS          –         –         –         –         –         –         4

2.1     Sources of heavy metal in the soil        –         –         –         –         4-7

2.2    Effect of heavy metal in the environment      –         –         –         7-8

2.2.1 Arsenic         –         –         –         –         –         –         –         –         8-9

2.2.2 Lead    –         –         –         –         –         –         –         –         –         9-10

2.2.3  Mercury       –         –         –         –         –         –         –         –         10-11

2.3     Factors Affecting the Uptake Mechanisms     –         –         –         12-16

2.4     Advantages of Phytoremediation         –         –         –         –         16-17

2.5 Limitation of Phytoremediation Technology     –         –         –         17-18

CHAPTER THREE

3.1     Remediation of Trace Metals Contaminated Soil     –         –         19-20

3.2     Mechanism of Phytoremediation         –         –         –         –         20-21

3.2.1 Phytoextraction       –         –         –         –         –         –         –         21-23

3.2.2  Phytostabilization  –         –         –         –         –         –         –         23

3.2.3  Phytovolatilization –         –         –         –         –         –         –         24

3.2.4  Rhizofiltration        –         –         –         –         –         –         –         25-26

3.3     Plant Hyperaccumulators           –         –         –         –         –         26-28

3.4     Optimization of Metal Phytoextraction –       –         –         –         28

3.4.1  Plants Selection     –         –         –         –         –         –         –         28-29

3.4.2  Genetic Engineering        –         –         –         –         –         –         29-30

3.4.3  Soil Fertilization    –         –         –         –         –         –         –         30-31

3.4.4  Enhancement of Metal Bioavailability –         –         –         –         31-32

3.5     Disposal of Plant Residues        –         –         –         –         –         32-33

CHAPTER FOUR

4.0     SUMMARY AND CONCLUSION

4.1     Summary     –         –         –         –         –         –         –         –         34

4.2     Conclusion  –         –         –         –         –         –         –         –         34

             References

CHAPTER ONE

1.0 Introduction

Environmental pollution has become a severe public health concern because it a major source of health risk and causes several serious diseases throughout the world. The most serious concern of environmental pollution is the presence of toxic metals. The severity of toxic metals on humans has been known since ages, and its exposure continues and is increasing in many areas. Heavy metals severely affect humans beings and even cause death (Jarup, 2003). Industrialization has increased the heavy metals pollution and the concentration of these heavy metals is higher in industrial areas (Jiao et al., 2015).

Naturally heavy metals are found in the earth’s crust with diversity more than 5 gcm^-3 (Alloway and Ayres, 1997) and atomic number greater than 20 As, Ni, Hg, Cd, Cr, Pb and Zn are the most common toxic metals in soil and water bodies. Trace elements are metals whose percentage in rock composition does not exceed 0.1%. Heavy metals in the soil occur naturally from the weathering of parent material as traces (<100mg kg^-1) and are not toxic (Panzanganeh et al., 2012). Anthropogenic sources such as mining. Smelting, electroplating energy and fuel production, power transmission, intensive agriculture, sludge dumping and melting operation ate the main contributor to heavy metal pollution (Ali et al., 2013).

Excessive metal accumulation in contaminated soil can result in decreased soil microbial activity, soil fertility and overall quality and reduction in yield and the entry to toxic materials into the food chain (Hann and Lubbers, 1983). Although it is necessary to clean up contaminated sites, the application of environmental remediation strategies is often very expensive and intrusive. Thus, it is important to develop low-cost and environmentally friendly strategy. Recently, the notion of using metal accumulating plants for environmental clean up has been vigorously pursued (Brown et al., 1995; Salt et al., 1995), giving birth to the philosophy of “phytoextraction” within the broader concept of “Phytoremediation” (Kumar et al., 1995).

Recent concerns regarding the environmental contamination have initiated the development of appropriate technologies to assess the presence and mobility of metals in soil water, and waste water. Presently, phytoremediation has become an effective and affordable technological solution use to extract or remove inactive metals and metals pollutants from contaminated soil. Phytoremediation is the use of plant to clean up a contamination from soils, sediments and water. This technology is environmental friendly potentially cost effective. Plant with exceptional metal accumulating capacity are known as hyperaccumulator plants. Phytoremediation takes the advantage of the unique and selective uptake capabilities of plant root systems, together with the translocation, bioaccumulation, and contaminant degradation abilities of the entire plant body. Many species of plant have been successful in absorbing contaminants such as lead, cadmium, chromium, arsenic, and various radionuclides from soils.