Phytoremediation of heavy metals—Concepts and applications

Heavy metals are well-known environmental pollutants due to their toxicity, persistence in the environment, and bioaccumulative nature. Their natural sources include weathering of metal-bearing rocks and volcanic eruptions, while anthropogenic sources include mining and various industrial and agricultural activities. Mining and industrial processing for extraction of mineral resources and their subsequent applications for industrial, agricultural, and economic development has led to an increase in the mobilization of these elements in the environment and disturbance of their biogeochemical cycles. Contamination of aquatic and terrestrial ecosystems with toxic heavy metals is an environmental problem of public health concern. Being persistent pollutants, heavy metals accumulate in the environment and consequently contaminate the food chains. Accumulation of potentially toxic heavy metals in biota causes a potential health threat to their consumers including humans. This article comprehensively reviews the different aspects of heavy metals as hazardous materials with special focus on their environmental persistence, toxicity for living organisms, and bioaccumulative potential. The bioaccumulation of these elements and its implications for human health are discussed with a special coverage on fish, rice, and tobacco. The article will serve as a valuable educational resource for both undergraduate and graduate students and for researchers in environmental sciences. Environmentally relevant most hazardous heavy metals and metalloids include Cr, Ni, Cu, Zn, Cd, Pb, Hg, and As. The trophic transfer of these elements in aquatic and terrestrial food chains/webs has important implications for wildlife and human health. It is very important to assess and monitor the concentrations of potentially toxic heavy metals and metalloids in different environmental segments and in the resident biota. A comprehensive study of the environmental chemistry and ecotoxicology of hazardous heavy metals and metalloids shows that steps should be taken to minimize the impact of these elements on human health and the environment.

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Environmental Chemistry and Ecotoxicology of Hazardous Heavy Metals: Environmental Persistence, Toxicity, and Bioaccumulation

The controversy related to the environment pollution is increasing in human life and in the eco-system. Especially, the water pollution is growing rapidly due to the wastewater discharge from the industries. The only way to find the new water resource is the reuse of treated wastewater. Several remediation technologies are available which provides a convenience to reuse the reclaimed wastewater. Heavy metals like Zn, Cu, Pb, Ni, Cd, Hg, etc. contributes various environmental problems based on their toxicity. These toxic metals are exposed to human and environment, the accumulation of ions takes place which causes serious health and environmental hazards. Hence, it is a major concern in the environment. Due to this concern, the significance of developing technology for removing heavy metals has been increased. This paper contributes the outline of new literature with two objectives. First, it provides the sketch about treatment technologies followed by their heavy metal capture capacity from industrial effluent. The treatment performance, their remediation capacity and probable environmental and health impacts were deliberated in this review article. Conclusively, this review paper furnishes the information about the important methods incorporated in lab scale studies which are required to identify the feasible and convenient wastewater treatment. Moreover, attempts have been made to confer the emphasis on sequestration of heavy metals from industrial effluent and establish the scientific background for reducing the discharge of heavy metals into the environment.

Efficient techniques for the removal of toxic heavy metals from aquatic environment: A review

Persistent heavy metal pollution poses a major threat to all life forms in the environment due to its toxic effects. These metals are very reactive at low concentrations and can accumulate in the food web, causing severe public health concerns. Remediation using conventional physical and chemical methods is uneconomical and generates large volumes of chemical waste. Bioremediation of hazardous metals has received considerable and growing interest over the years. The use of microbial biosorbents is eco-friendly and cost effective; hence, it is an efficient alternative for the remediation of heavy metal contaminated environments. Microbes have various mechanisms of metal sequestration that hold greater metal biosorption capacities. The goal of microbial biosorption is to remove and/or recover metals and metalloids from solutions, using living or dead biomass and their components. This review discusses the sources of toxic heavy metals and describes the groups of microorganisms with biosorbent potential for heavy metal removal.

https://www.mdpi.com/1660-4601/14/1/94/pdf/1

A New Strategy for Heavy Metal Polluted Environments: A Review of Microbial Biosorbents

Remediation techniques for heavy metal-contaminated soils: Principles and applicability

The release and persistence of toxic heavy metals into the natural environment is a serious concern especially in urban areas. The problem of heavy metal pollution is gaining momentum from year to year as more and more amounts of heavy metals are extracted from their ores and released into the environmental segments (water, air and soil) during processing or afterwards. Heavy metals are essentially nonbiodegradable and therefore accumulate in the environment and subsequently find their way into the food chains. Contamination of food chains by toxic heavy metals is an unwanted outcome of industrialization and unsustainable development. This contamination is a risk to the health of all organisms including humans. Entrance of toxic heavy metals (through absorption, inhalation and ingestion) into the human body beyond threshold limits causes many diseases and health abnormalities. Therefore, effective remediation of heavy metal pollution is a top priority. The different physico-chemical methods used for this purpose generally suffer from serious limitations. Phytoremediation is seen as an alternative green solution to the problem. The present study reports phytoremediation of Cd, Pb, Cu, and Zn by Trifolium alexandrinum, which is a suitable candidate plant species for this purpose. T. alexandrinum was grown in a simulated heavy metal-contaminated soil. Root bioconcentration factor values of T. alexandrinum for Zn, Pb, Cu and Cd were 4.242, 1.544, 1.071, and 0.604 respectively.

Phytoremediation of heavy metals by Trifolium alexandrinum

Evaluation of chromium phytoremediation potential of some plant species of Dir Lower, Khyber Pakhtunkhwa, Pakistan

Nickel is a known hepatotoxic, haemotoxic, pulmonary toxic, nephrotoxic, reproductive toxic, carcinogenic, phytotoxic and neurotoxic agent. The adverse ecological impacts from unnecessary heavy metals include contamination of water and soil which pose serious threats to human health. This study was conducted to screen plants for the phytoremediation of nickel from sixty-one sites of the Lower Dir. Nickel-metal was analyzed in the soil, roots and shoots of plants. The total concentration of nickel in soil, roots and shoots was found to be in the range of 1.03-18.98, 12.63-540.73 and 12.00-295.86 mg kg–1 dry weight basis (DW) respectively. The highest nickel contents were present in the roots of Xanthium strumarium (540.73) and shoots of Bryophyllum daigremontianum (295.86). None of the plant species were identified as hyper accumulators for nickel but based on BCF, TF and BAC values most of the species showed feasibility for its phytoextraction and phytostabilization. Xanthium strumarium, Filago hurdwarica, Ranunculus arvensis, Medicago lupulina, Cannabis sativa, Geranium rotundifolium and Cerastium glomeratum are suggested for the phytostabilization of nickel whereas Bryophyllum daigremontianum, Rosularia adenotricha, Iris germanica, Asplenium dalhousiae and Isatis tinctoria for the phytoextraction of soil contaminated with nickel.

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Nickel phytoremediation potential of some plant species of the Lower Dir, Khyber Pakhtunkhwa, Pakistan

Bioaccumulation of Cu and Zn in Schizothorax plagiostomus and Mastacembelus armatus from River Swat, River Panjkora and River Barandu in Malakand Division, Pakistan

Muhammad Anwar Sajad

Papers

Phytoremediation of heavy metals—Concepts and applications

Phytoremediation of heavy metals by Trifolium alexandrinum

Evaluation of chromium phytoremediation potential of some plant species of Dir Lower, Khyber Pakhtunkhwa, Pakistan

Nickel phytoremediation potential of some plant species of the Lower Dir, Khyber Pakhtunkhwa, Pakistan

Bioaccumulation of Cu and Zn in Schizothorax plagiostomus and Mastacembelus armatus from River Swat, River Panjkora and River Barandu in Malakand Division, Pakistan