**Abstract**

Over use of chemical inputs and exploitation of natural resources have degraded our ecosystem to a large extent. Our water bodies are drastically affected, especially due to the impact of heavy metal loading. The biomagnification that results from these difficult to degrade metals is naturally affecting the human health. The physical and chemical methods commonly employed for water purification are not only highly expensive but also further aggravate the pollution problem. Hence, all efforts must be taken to exploit the emerging green technology approach in pollution remediation. Several aquatic plants have specific affinity towards heavy metals and they flourish well in this contaminated environment. The common mechanisms of phytoremediation and varied type of aquatic plants with high remediation potential are reviewed in this chapter.

**Keywords:** pollution, aquatic macrophytes, phytoremediation, hyperaccumulators

## **1. Introduction**

Industrialization, urbanization and over exploitation of precious natural resources have resulted in much degradation of our environment. The dire need for promotion of intensive cultivation to satisfy primary human needs led to over dependence on chemical resources. This in turn, caused much degradation to our ecosystem mainly through environmental pollution. Among the natural resources, the worst affected are water resources. 97% of hydrosphere is covered by saltwater, leaving only mere 3% fresh water, of which hardly 1.5% is available for ready use [1]. The entire world is relying on this meager resource for daily consumption, irrigation, industrial purposes, power and other diverse uses. Injudicious human activities including disposal of sewage and wastes have caused great impact on water bodies all over the world. Wetlands act as sink for contaminants and thereby reduce the impact of point and non-point sources of pollution [2]. But drastic reduction in water inflow has been resulted due to fragmentation of water bodies and irreversible conversion to satisfy human needs.

Heavy metal pollution in water bodies is a serious environmental problem, threatening not only the aquatic ecosystems, but also human health. Over the years, the main sources of metal pollution have shifted from mining and manufacturing to rock weathering and waste discharge [3]. There are several reports on the deleterious effects of biomagnification of heavy metals within aquatic organisms and its impact on human nervous, reproductive and cardio vascular systems [4]. Disposal of plastic wastes, batteries, fertilizer materials, untreated industrial effluents etc. releases heavy metals including Cd into the aquatic environment which causes several causalities like osteoporosis, kidney failure, infertility and improper brain development. Globally, majority of surface water bodies are highly polluted with heavy metals like As, Co, Cr and Ni, with levels exceeding WHO and USEPA guideines and have evoked much concern among the government agencies and public [5].

As heavy metals are non-biodegradable, removal of these metals from the aquatic system is the only remedy available for decontamination [6]. The conventional methods usually employed to remove the metals from a polluted system like coagulation, flocculation, osmosis, stabilization etc. are highly expensive. In addition, they further aggravate deterioration with the release of chemicals being used and hence these methods are not at all environmentally safe [7, 8]. But, a new method of decontamination employing green plants is fast emerging, referred as phytoremediation, which is specifically suited for wetland restoration. The plants growing in the contaminated areas will absorb the elements from the sediment/soil/ water by roots. The absorbed elements travel from root through cell sap and finally get precipitated in vacuole or cell membrane, thereby reduces the level of contaminants in sediment/soil/water [9]. Such aquatic plant species and adsorbents can be included in land management plans to reduce human risks. This method is relatively cheap and very successful over other methods [10].
