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Fly ash generates as the result of coal combustion in thermoelectric power stations whereas ore mining activities produce mine waste-rock and tailings worldwide. High concentrations of metal(loid)s and organic pollutants in fly ash and mine wastes are released into soil, air, and water presenting a global threat to the surrounding environment and human health. The environmentally sound management of fly ash and mine waste–rock and tailings includes monitoring stability of the dam construction and seepage flowrate, prevention of water erosion and dust spreading, reducing the footprint of the management facilities and successful restoration/revegetation. Harsh conditions prevailing on fly ash and mine deposits are unfavorable mechanical composition and pH, high concentrations of soluble salts, lack of nitrogen and phosphorous, reduced number of microorganisms and fungus, toxic concentrations of As, Au, Ag, B, Cu, Cd, Cr, Hg, Mn, Mo, Ni, Pb, Zn, and the presence of PAHs and PCBs. The review addresses phystostabilization, phytoextraction, rhizodegradation, and phytodegradation as main phytoremediation green technologies which use plants to clean up the contaminated area to safe levels. Establishment of the self–sustaining vegetative cover on fly ash and mine deposits is crucial for recovering ecosystem health, stability, and resilience. Therefore, here we have discussed the essential role of native plants in the ecorestoration process on waste deposits. Additional emphasis is given to the evaluation of plant adaptive response to pollution stress. This review presents a current knowledge in phytomanagement of fly ash deposits, mine waste-rock and tailings. Also, it provides a new frontier in restoration physiology where physiological and biochemical tools can be used to predict plant response to stressors and success of restoration projects.

Fly ash (FA) is a coal combustion by-product of thermal power plants, and has been recognized as a great environmental and health hazard worldwide. The establisment of a permanent green cover on fly ash deposits is essential and can be achieved by sowing the native plant species that should be crucial for stability and resilience of an ecosystem. Improved understanding of species’ response to unfavorable properties of fly ash provides key insight into the decision about ecorestoration practice and management. Therefore, long-term research based on the assessment of the phytoremediation potential and adaptive response of Festuca rubra L. (red fescue) sown on the fly ash deposits at the thermoelectric power plant ‘Nikola Tesla-A’ in Obrenovac (Serbia) was the main concern. Field research was carried out on the passive FA lagoons (L3—the lagoons 3 years old and L2—the lagoons 11 years old) and in the Botanical Garden ́́Jevremovać́ in Belgrade (CS—control site). The physico-chemical properties of soil and fly ash were determined by using standard soil analyses. The element concentrations in soils, fly ash and plants were determined by using ICP-OES. Chlorophyll a fluorescence parameters were measured by using the Plant Stress Meter. Pigments, phenolics and malonyldialdehide contents (MDA) in leaves were measured spectrophotometrically and the total antioxidant capacity in plant leaves was determined by using DPPH free radical. Site-dependent variations were observed for all the parameters examined. FA contains alkaline pH, high electrical conductivity (EC) and low total nitrogen (N) coupled with toxic elements i.e. As and B as well as deficiency of Mn and Zn. Improvement of the physico-chemical characteristics of FA over time is reflected in the increased values of higroscopic water (HW), silt, clay, the amount of adsorbed bases (S), total adsorption capacity (T) and the reduced concentrations of total and available As, B, Cu, Zn and Mn (except available As content) indicating favorable fly ash conditions. F. rubra is an excluder plant, it retains a larger content of As, Cu, Mn and Zn in roots than in leaves and with extensive root system it can provide good fly ash stabilization, i.e. this species has a great potential in phytoremediation of FA. Furthermore, results show that F. rubra sown on the FA deposits has a high amount of MDA and reduced values of chlorophyll a fluorescence parameters (Fm, Fv, Fv/Fm, Fm/Fo), chlorophylls (Chl a , Chl a + b ) and total carotenoids (Tot Carot) indicating high oxidative stress and lower efficiency of photosynthesis. However, in spite of toxic concentrations of As and B and low content of Cu, Mn and Zn in the leaves, this species has high potential to activate adaptive mechanisms, such as increased biosynthesis of anthocyanins, phenolics, ascorbic acid and total radical scavenging activity. Taken together, F. rubra possesses high adaptive capacity to perform functional ecorestoration on fly ash deposits. These findings indicate that F. rubra can be identified as a vital element for large-scale reclamation purpose. [ABSTRACT FROM AUTHOR]

Fly ash dump has been noticed as one of the hazardous dumpsites on the earth, which pollutes our environment. Therefore, an affordable and effective approach for the restoration of fly ash dumps is urgently required worldwide. In this direction, to find out potential plant species through the assessment of naturally colonized vegetation is a basic criterion of ecological restoration. With the above vision, the present study was performed to identify potential colonizer plants of fly ash dumps for ecological restoration. The intensive field studies were made during 2019–2020 to gather naturally occurring plants from fly ash disposal area of Koradi Thermal Power Plant, Nagpur, Maharashtra, India. Therefore, naturally colonizing plants were assessed on the basis of their dominance, ability of improving the rhizospheric FA, and ecological significance for their ecorestoration potential. Acacia nilotica L., Acmella oleracea L., Bacopa monnieri L., Cynodon dactylon (L.) Pers., Cyperus rotundus L., Dactyloctenium aegyptium L., Digitaria sanguinalis L., Trianthema portulacastrum L., Typha latifolia L. and Portulaca oleracea L. were recognized as potential plants for ecological restoration of FA dumps. Hence, the characteristics of above identified potential plant species can be used in ecological restoration of newly FA disposal areas. • Natural plant communities were assessed to have insights on ecorestoration potential. • Eco-restoration of fly ash dump via naturally colonized plant species is limited. • Both sites are not similar in features due to change in colonizing species pattern. • Restoration programs on fly ash dump should base on natural colonizer plant species. • Colonizing plant species over fly ash dumps have ecological resilience that governs the response to hash conditions. [ABSTRACT FROM AUTHOR]