Heavy Metal Pollution in Aquatic Ecosystems and its Phytoremediation using Wetland Plants: An ecosustainable approach

Abstract

This review addresses the global problem of heavymetal pollution originating from increased industrialization and urbanization and its amelioration by using wetland plants both in a microcosm as well as natural/field condition. Heavymetal contamination in aquatic ecosystems due to discharge of industrial effluents may pose a serious threat to human health. Alkaline precipitation, ion exchange columns, electrochemical removal, filtration, and membrane technologies are the currently available technologies for heavy metal removal. These conventional technologies are not economical and may produce adverse impacts on aquatic ecosystems. Phytoremediation of metals is a cost-effective "green" technology based on the use of specially selected metal-accumulating plants to remove toxic metals from soils and water. Wetland plants are important tools for heavy metal removal. The Ramsar convention, one of the earlier modern global conservation treaties, was adopted at Ramsar, Iran, in 1971 and became effective in 1975. This convention emphasized the wise use of wetlands and their resources. This review mentions salient features of wetland ecosystems, their vegetation component, and the pros and cons involved in heavy metal removal. Wetland plants are preferred over other bio-agents due to their low cost, frequent abundance in aquatic ecosystems, and easy handling. The extensive rhizosphere of wetland plants provides an enriched culture zone for the microbes involved in degradation. The wetland sediment zone provides reducing conditions that are conducive to the metal removal pathway. Constructed wetlands proved to be effective for the abatement of heavymetal pollution from acid mine drainage; landfill leachate; thermal power; and municipal, agricultural, refinery, and chlor-alkali effluent. the physicochemical properties of wetlands provide many positive attributes for remediating heavy metals. Typha, Phragmites, Eichhornia, Azolla, Lemna, and other aquatic macrophytes are some of the potent wetland plants for heavy metal removal. Biomass disposal problem and seasonal growth of aquatic macrophytes are some limitations in the transfer of phytoremediation technology from the laboratory to the field. However, the disposed biomass of macrophytes may be used for various fruitful applications. An ecosustainable model has been developed through the author's various works, which may ameliorate some of the limitations. The creation of more areas for phytoremediation may also aid in wetlands conservation. Genetic engineering and biodiversity prospecting of endangered wetland plants are important future prospects in this regard.

Constructed wetlands with light expanded clay aggregates for agricultural wastewater treatment

“…If the capacity of CWs to depurate waters from bulk pollutants and nutrients is generally recognized, recent research has been directed to the removal of other contaminants such as metals and organic micropollutants from several types of wastewaters (Matamoros et al, 2008;Rai, 2008;Imfeld et al, 2009;Park et al, 2009;Avila et al, 2010;Marchand et al, 2010;Breitholtz et al, 2012). In particular, several studies showed successful applications of CWs to remove hardly biodegradable organic xenobiotic compounds such as pesticides and pharmaceuticals (Cheng et al, 2002;Matamoros et al, 2008Matamoros et al, , 2012aDordio et al, 2009bDordio et al, , 2010Avila et al, 2010;Hijosa-Valsero et al, 2011;Agudelo et al, 2012;Warsaw et al, 2012).…”

Phytoremediation potential of Eichhornia crassipes for the treatment of<br>cadmium in relation with biochemical and water parameters

“…Physicochemical approaches have been widely used for remedying polluted soil and water. However, they experienced more difficulties for a large scale of remediation because of high initial capital cost, larger volume of chemicals, continuous maintenance, skilled technicians and even generate large amount of sludge which adds into the secondary waste generation, posing threats to aquatic life and minimizes the acceptability of the treatment technique (Rai, 2008).…”

Effects on the Photosynthetic Activity of Algae after Exposure to Various Organic and Inorganic Pollutants: Review

“…Several other large natural inputs of heavy metals into water ecosystems are from the erosion or rocks, wind-blowing dusts, volcanic activity, and forest fires [128]. In addition, several anthropogenic activities such as energy production technologies, industrial effluents, and wastes (from coal mines, thermal power plants, metallurgy, plating, chemical plant, curry and paper-making industries, and other allied industries) alter the physicochemical characteristics of water bodies and elevate the heavy metals concentration according to the nature of effluent being discharged [130,131]. Therefore, aquatic ecosystems receive inputs of different source containing a variety of metal ions (M x+ )…”