Phytoremediation: role of terrestrial plants and aquatic macrophytes in the remediation of radionuclides and heavy metal contaminated soil and water

Abstract

Nuclear power reactors are operating in 31 countries around the world. Along with reactor operations, activities like mining, fuel fabrication, fuel reprocessing and military operations are the major contributors to the nuclear waste. The presence of a large number of fission products along with multiple oxidation state long-lived radionuclides such as neptunium ((237)Np), plutonium ((239)Pu), americium ((241/243)Am) and curium ((245)Cm) make the waste streams a potential radiological threat to the environment. Commonly high concentrations of cesium ((137)Cs) and strontium ((90)Sr) are found in a nuclear waste. These radionuclides are capable enough to produce potential health threat due to their long half-lives and effortless translocation into the human body. Besides the radionuclides, heavy metal contamination is also a serious issue. Heavy metals occur naturally in the earth crust and in low concentration, are also essential for the metabolism of living beings. Bioaccumulation of these heavy metals causes hazardous effects. These pollutants enter the human body directly via contaminated drinking water or through the food chain. This issue has drawn the attention of scientists throughout the world to device eco-friendly treatments to remediate the soil and water resources. Various physical and chemical treatments are being applied to clean the waste, but these techniques are quite expensive, complicated and comprise various side effects. One of the promising techniques, which has been pursued vigorously to overcome these demerits, is phytoremediation. The process is very effective, eco-friendly, easy and affordable. This technique utilizes the plants and its associated microbes to decontaminate the low and moderately contaminated sites efficiently. Many plant species are successfully used for remediation of contaminated soil and water systems. Remediation of these systems turns into a serious problem due to various anthropogenic activities that have significantly raised the amount of heavy metals and radionuclides in it. Also, these activities are continuously increasing the area of the contaminated sites. In this context, an attempt has been made to review different modes of the phytoremediation and various terrestrial and aquatic plants which are being used to remediate the heavy metals and radionuclide-contaminated soil and aquatic systems. Natural and synthetic enhancers, those hasten the process of metal adsorption/absorption by plants, are also discussed. The article includes 216 references.

Trace metal concentrations and their transfer from sediment to leaves of four common aquatic macrophytes

“…All species studied except of G. maxima were found to be accumulators of several metals. Such ability is an advantage in phytoremediation, because it means that one species can absorb the maximum number of pollutants simultaneously (Sharma et al 2015). …”

Accumulation and distribution of lead (Pb) in plant tissues of guar (Cyamopsis tetragonolobaL.) and sesame (Sesamum indicumL.): profitable phytoremediation with biofuel crops

“…The capacities of heavy metal uptake and accumulation, mechanisms of metal concentration, exclusion and compartmentation vary among different plant species and also between various parts of plants (Lone, He, Stoffella, & Xe, 2008;Sharma, Singh, & Manchanda, 2014). Various plant species belongs to botanical families, in particular the Brassicaceae, Asteraceae, Fabaceae, Poaceae, and Chenopodiaceae showing phytoremediation potential, are well documented in the literature (Stanislaw & Gawronski, 2007;Anjum, Umar, & Iqbal, 2014) but few or less work has been reported on Cyamopsis tetragonoloba L. and Sesamum indicum L.…”

Comparative study of Zn-phytoextraction potential in guar (Cyamopsis tetragonolobaL.) and sesame (Sesamum indicumL.): tolerance and accumulation

“…The heavy metal uptake, accumulation, mechanism of metal concentration, exclusion and compartmentation vary among different plant species and also between various plant parts (Sharma, Singh, & Manchanda, 2014;Singh & Agrawal, 2010). However, the use of field crop plants for the management of long-term pollutant dispersion has been given much emphasis in this perspective to crop plants from Brassicaceae followed by Fabaceae, Asteraceae and Poaceae (Zaidi, Wani, & Khan, 2012).…”