Fly Ash Lagoons Research Articles

Ecophysiological response of Populus alba L. to multiple stress factors during the revitalisation of coal fly ash lagoons at different stages of weathering.

The enormous quantities of fly ash (FA) produced by thermal power plants is a global problem and safe, sustainable approaches to reduce the amount and its toxic effects are still being sought. Vegetation cover comprising long-living species can help reduce FA dump-related environmental health issues. However, the synergistic effect of multiple abiotic factors, like drought, low organic matter content, a deficit of essential nutrients, alkaline pH, and phytotoxicity due to high potentially toxic element (PTE) and soluble salt content, limits the number of species that can grow under such stressful conditions. Thus, we hypothesised that Populus alba L., which spontaneously colonised two FA disposal lagoons at the 'Nikola Tesla A' thermal power plant (Obrenovac, Serbia) 3 years (L3) and 11 years (L11) ago, has high restoration potential thanks to its stress tolerance. We analysed the basic physical and chemical properties of FA at different weathering stages, while the ecophysiological response of P. alba to multiple stresses was determined through biological indicators [the bioconcentration factor (BCF) and translocation factor (TF) for PTEs (As, B, Cr, Cu, Mn, Ni, Se, and Zn)] and by measuring the following parameters: photosynthetic efficiency and chlorophyll concentration, non-enzymatic antioxidant defence (carotenoids, anthocyanins, and phenols), oxidative stress (malondialdehyde (MDA) concentrations), and total antioxidant capacity (IC50) to neutralise DPPH free radical activity. Unlike at L3, toxic As, B, and Zn concentrations in leaves induced oxidative stress in P. alba at L11, shown by the higher MDA levels, lower vitality, and reduced synthesis of chlorophyll, carotenoids, and total antioxidant activity, suggesting its stress tolerance decreases with long-term exposure to adverse abiotic factors. Although P. alba is a fast-growing species with good metal accumulation ability and high stress tolerance, it has poor stabilisation potential for substrates with high As and B concentrations, making it highly unsuitable for revitalising such habitats.

Bioaccumulation of chemical elements at post-industrial freshwater sites varies predictably between habitats, elements and taxa: A power law approach

Elevated environmental levels of elements originating from anthropogenic activities threaten natural communities and public health, as these elements can persist and bioaccumulate in the environment. However, their environmental risks and bioaccumulation patterns are often habitat-, species- and element-specific. We studied the bioaccumulation patterns of 11 elements in seven freshwater taxa in post-mining habitats in the Czech Republic, ranging from less polluted mining ponds to highly polluted fly ash lagoons. We found nonlinear, power-law relationships between the environmental and tissue concentrations of the elements, which may explain differences in bioaccumulation factors (BAF) reported in the literature. Tissue concentrations were driven by the environmental concentrations in non-essential elements (Al, As, Co, Cr, Ni, Pb and V), but this dependence was limited in essential elements (Cu, Mn, Se and Zn). Tissue concentrations of most elements were also more closely related to substrate than to water concentrations. Bioaccumulation was habitat specific in eight elements: stronger in mining ponds for Al and Pb, and stronger in fly ash lagoons for As, Cu, Mn, Pb, Se, V and Zn, although the differences were often minor. Bioaccumulation of some elements further increased in mineral-rich localities. Proximity to substrate, rather than trophic level, drove increased bioaccumulation levels across taxa. This highlights the importance of substrate as a pollutant reservoir in standing freshwaters and suggests that benthic taxa, such as molluscs (e.g., Physella) and other macroinvertebrates (e.g., Nepa), constitute good bioindicators. Despite the higher environmental risks in fly ash lagoons than in mining ponds, the observed ability of freshwater biota to sustain pollution supports the conservation potential of post-industrial sites. The power law approach used here to quantify and disentangle the effects of various bioaccumulation drivers may be helpful in additional contexts, increasing our ability to predict the effects of other contaminants and environmental hazards on biota.

Muddying the unexplored post-industrial waters: Biodiversity and conservation potential of freshwater habitats in fly ash sedimentation lagoons

Deposits of fly ash and other coal combustion wastes are common remnants of the energy industry. Despite their environmental risks from heavy metals and trace elements, they have been revealed as refuges for threatened terrestrial biodiversity. Surprisingly, freshwater biodiversity of fly ash sedimentation lagoons remains unknown despite such lack of knowledge strongly limits the efficient restoration of fly ash deposits. We bring the first comprehensive survey of freshwater biodiversity, including nekton, benthos, zooplankton, phytoplankton, and macrophytes, in fly ash lagoons across industrial regions of the Czech Republic. To assess their conservation potential, we compared their biodiversity with abandoned post-mining ponds, the known strongholds of endangered aquatic species in the region with a shortage of natural ponds. Of 28 recorded threatened species, 15 occurred in the studied fly ash lagoons, some of which were less abundant or even absent in the post-mining ponds. These are often species of nutrient-poor, fishless waters with rich vegetation, although some are specialised extremophiles. Species richness and conservation value of most groups in the fly ash lagoons did not significantly differ from the post-mining ponds, except for species richness of benthos, zooplankton, and macrophytes, which were slightly lower in the fly ash lagoons. Although the concentrations of some heavy metals (mainly Se, V, and As) were significantly higher in the fly ash lagoons, they did not significantly affect species richness or conservation value of the local communities. The differences in species composition therefore does not seem to be caused by water chemistry. Altogether, we have shown that fly ash lagoons are refuges for threatened aquatic species, and we thus suggest maintaining water bodies during site restoration after the cessation of fly ash deposition. Based on our analyses of environmental variables, we discuss suitable restoration practices that efficiently combine biodiversity protection and environmental risk reduction.

Biodiversity variability and metal accumulation strategies in plants spontaneously inhibiting fly ash lagoon, India.

Out of 29 plant species taken into consideration for biodiversity investigations, the present study screened out Cyperus rotundus L., Calotropis procera (Aiton) W.T. Aiton, Croton bonplandianus Baill., Eclipta prostrata (L.) L., and Vernonia cinerea (L.) Less. as the most suitable metal-tolerant plant species (high relative density and frequency) which can grow on metal-laden fly ash (FA) lagoon. Total (aqua-regia), residual (HNO3) and plant available (CaCl2) metal concentrations were assessed for the clean-up of metal-contaminated FA disposal site using naturally colonized plants. The total metal concentration (in mg kg-1) in FA followed an order of Mn (229.8)>Ni (228.4)>Zn (89.4)>Cr (61.2)>Pb (56.6)>Cu (51.5)>Co (41.9)>Cd (9.7). The HNO3- and CaCl2-extracted metals were 0.57-15.68% and 0.03-7.82% of the total metal concentration, respectively. The concentration of Ni and Cr in FA in the present study was highest among the previously studied Indian and average world power plants and Cd, Ni, and Cr were above soil toxicity limit. The variation in total, residual, and plant-available metal (single extraction) concentration indicated the presence of different proportions of metals in FA lagoon which affects the metal uptake potential of the vegetation growing on it. It has been reported that plant-available metal extractant (CaCl2) is the most suitable extractant for assessment of metal transfer from soil to plant. However in the present study, Spearman's correlation showed best significant correlation between total metal concentration in FA and shoot metal concentration (r=0.840; p<0.01) which suggest aqua-regia as the best extractant for understanding the bioavailability and transfer of metal, and in calculation of BCF for moderately contaminated site. It can be stated that plant-available extractant is not always suitable for understanding the availability of metal, but total metal concentration can provide a better insight especially for moderate or low metal-contaminated sites. Principle component analysis revealed that all the plants showed positive correlation with Co and Cd which suggest its subsequent uptake in root and shoot. The biological indices (BCF, BAF, and TF) revealed that E. prostrata (10mg Cd kg-1) and C. procera (3.5mg Cd kg-1) can be utilized efficiently for the phytoextraction of Cd and phytostabilization of other potentially toxic metals (Pb, Cr, and Co) from FA lagoon. All the plants were tolerant to Pb pollution (TF>1, BAF>1, and BCF>1); hence, there was a negligible translocation of Pb to the aerial tissues of these plants which shows their suitability in phytostabilization. In addition, V. cinerea accumulated elevated concentration of potentially toxic Cr (50mg Cr kg-1) and Ni (67mg Ni kg-1) which could also help in the phytoremediation of FA lagoon.

Assessment of the phytoremediation potential and an adaptive response of Festuca rubra L. sown on fly ash deposits: Native grass has a pivotal role in ecorestoration management

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.

An Assessment of Metal in Fly Ash and Their Translocation and Bioaccumulation in Perennial Grasses Growing at the Reclaimed Opencast Mines

Rapid expansion of the industrial sector adds more effluent into the agricultural land and in the vicinity of industry, which possesses the major threat of land contamination and environmental degradation. The present study was conducted to determine toxic metal concentration in fly ash and metal accumulation potential of the Saccharum munja and Cynodon dactylon, the two main grass species growing naturally on fly ash lagoon for Fe, Ni, Zn, Cu, Mn, Pb and Cd. Accumulation of metals were found in the order of Fe > Zn > Mn > Cu > Ni > Pb and Cd. In spite of significant accumulation of Fe in the root and shoot, the BCF and BAC were found very low ( 1 for Zn and Pb) and low bioaccumulation coefficient (<1 for Fe, Mn, Ni, Cu and Cd) suggests its suitability for phytoremediation of fly ash lagoons. Findings of the study suggest that weed species may be used for the stabilization of toxic metals contaminated land and to empower the rural economy.

Ecophysiological and biochemical traits of three herbaceous plants growing on the disposed coal combustion fly ash of different weathering stage

The ecophysiological and biochemical traits of Calamagrostis epigejos (Roth.) Festuca rubra L. and Oenothera biennis L. growing on two fly ash lagoons of different weathering stage (L1-3 years and L2-11 years) of the ?Nikola Tesla- A? thermoelectric plant (Obrenovac, Serbia) were studied. Species-dependent variations were observed at the L1 lagoon; the greatest vitality (Fv/Fm and Fm/Fo) followed by higher photopigment and total phenolic contents were measured in O. biennis in relation to C. epigejos (p&lt;0.001) and F. rubra (p&lt;0.001). At the L2 site, higher vitality was found in O. biennis (p&lt;0.001) and F. rubra (p&lt;0.01) compared to C. epigejos. O. biennis had the highest photosynthetic capacity. The results obtained in this study indicate that all examined species maintained a level of photosynthesis that allowed them to survive and grow under the stressful conditions in ash lagoons, albeit with lower than optimal success.

Naturally growing Saccharum munja L. on the fly ash lagoons: A potential ecological engineer for the revegetation and stabilization

Increasing areas of coal fly ash (FA) deposit pose a serious concern for its safe disposal to maintain the environment quality. Several thousand hectares of land have been occupied for the storage of FA all over the world. FA deposits cause serious environmental pollution through wind erosion and ground water contamination through leaching process. Naturally growing Saccharum munja on the derelict FA lagoons of NTPC Unchahar, India was identified as a native perennial grass in the rehabilitation process. We tested its ecological suitability for the effective restoration of FA lagoons in terms of their abundance and stabilization. The FA contains alkaline pH, and low organic C coupled with toxic metals i.e. Fe, Cd, Cr, Cu, Mn, Ni, Pb and Zn. The concentrations of these metals in different parts of the plant fall in the average range of plants and were found within toxic limits. Natural colonization of S. munja predominate in the areas of FA deposits with fast growth and high biomass which is used by local people for making ropes, baskets, mats, huts, etc. to support their livelihood. These results suggest that S. munja would be potentially useful to rehabilitate the FA dumps more efficiently if it is introduced properly on fresh lagoons to convert barren FA deposits into ecologically and socio-economically productive habitats without any inputs or maintenance.

Natural revegetation of coal fly ash in a highly saline disposal lagoon in Hong Kong

Abstract.Question: What is the relationship of the naturally colonizing vegetation and substrate characteristics in fly ash lagoons?Location: West lagoon, Deep Bay, a 13‐ha coastal lagoon in Hong Kong in subtropical Southeast Asia.Methods: Vegetation establishment was examined in a coal fly ash lagoon two years after its abandonment to investigate the distribution of vegetation in relationship to the chemical properties of the fly ash in the lagoon. A greenhouse experiment assessed the limits imposed on plant growth in fly ash.Results: The fly ash was saline, slightly alkaline and very poor in organic matter and nitrogen. Ash from bare and vegetated areas differed significantly in their salinity and extractable concentrations of inorganic nitrogen and various metals. Bare ash had a significantly higher conductivity and extractable sodium, aluminum, manganese, potassium, and lead. In total 11 plant species that belonged to seven families were found growing on the fly ash; all species except the shrub Tamarix chinensis were herbaceous. Using discriminant analysis, the most important factors in distinguishing bare and vegetated ashes were conductivity and sodium. Cluster analysis of bare samples gave two distinct groups, one from the periphery of the lagoon, which had lower sodium, conductivity, organic carbon, potassium and copper, and the other from a second group that contained ashes from the central region of the lagoon. Results of the greenhouse experiment showed that the inhibition of plant growth was significantly correlated with the presence of soluble toxic elements in ash.Conclusion: Toxicity and salinity seem to be the major limiting factors to plant establishment in fly ash, and these factors must be ameliorated for the successful reclamation of these fly ash lagoons.

Bioaccumulation and translocation of metals in the natural vegetation growing on fly ash lagoons: a field study from Santaldih thermal power plant, West Bengal, India

A field study was conducted in the fly ash lagoons of Santandih Thermal Power Plant located in West Bengal (India) to find out total, EDTA and DTPA extractable metals in fly ash and their bioaccumulation in root and shoot portion of the naturally growing vegetation. Fly ash sample has alkaline pH and low conductivity. The concentration of total Cu, Zn, Pb and Ni were found higher than weathered fly ash and natural soil, where as Co, Cd and Cr were found traces. Five dominant vegetation namely, Typha latifolia, Fimbristylis dichotoma, Amaranthus defluxes, Saccharum spontaenum and Cynodon dactylon were collected in the winter months (November-December). Bioaccumulation of metals in root and shoot portions were found varied significantly among the species, but all concentration were found within toxic limits. Correlation between total, DTPA and EDTA extractable metals viz. root and shoot metals concentration were studied. Translocation factor (TF) for Cu, Zn and Ni were found less than unity, indicates that these metals are immobilized in the root part of the plants. Metals like Mn have TF greater than unity. The study infers that natural vegetation removed Mn by phytoextraction mechanisms (TF > 1), while other metals like Zn, Cu, Pb and Ni were removed by rhizofiltration mechanisms (TF < 1). The field study revealed that T. latifolia and S. spontaenum plants could be used for bioremediation of fly ash lagoon.

Revegetation of Waste Fly Ash Lagoons II. Seedling Transplants and Plant Nutrition

As an alternative or in addition to direct seeding, container-grown transplants provide a means of economically and rapidly revegetating waste fly ash lagoons through the expeditious establishment of vegetation islands. Survival and growth of Enchylaena tomentosa and Nitraria billardierei transplants were largely dependent on the size of the root volume at transplanting. Growth response of both species in fly ash increased significantly as transplant container size increased from 110 ml to 800 ml. Fly ash incorporated into the potting mix during the containerised stage of growth generally reduced plant growth and survival following eventual trans plantation. Gradual hardening of Enchylaena tomentosa seedlings to increasing concentrations of fly ash in the potting mix (25 to 50 to 75% fly ash), however, improved immediate survival following transplantation, into pure ash. Nitrogen deficiency in Port Augusta fly ash was a major nutritional limitation to growth of these two species. Growth and dry matter production responded optimally to application of N fertiliser (NH4NO3) at 100-150 kg N ha 1. Although bicarbonate- extractable P levels in fly ash were high (over 250 mg kg-1), a response of Enchylaena tomentosa to supplementary P application [Ca(H2PO 4)2.H2O] at 100-200 kg P ha-1 was observed. N. billardierei did not respond to supplementary P, and it was suggested that fly ash P may be selectively available to plants on a species dependent basis. No growth responses to K application (KCl) at rates of up to 400 kg K ha -1 were found. © 1997 ISWA

REVEGETATION OF WASTE FLY ASH LAGOONS II. SEEDLING TRANSPLANTS AND PLANT NUTRITION

As an alternative or in addition to direct seeding, container-grown transplants provide a means of economically and rapidly revegetating waste fly ash lagoons through the expeditious establishment of vegetation islands. Survival and growth ofEnchylaena tomentosaandNitraria billardiereitransplants were largely dependent on the size of the root volume at transplanting. Growth response of both species in fly ash increased significantly as transplant container size increased from 110 ml to 800 ml. Fly ash incorporated into the potting mix during the containerised stage of growth generally reduced plant growth and survival following eventual transplantation. Gradual hardening ofEnchylaena tomentosaseedlings to increasing concentrations of fly ash in the potting mix (25 to 50 to 75% fly ash), however, improved immediate survival following transplantation, into pure ash. Nitrogen deficiency in Port Augusta fly ash was a major nutritional limitation to growth of these two species. Growth and dry matter production responded optimally to application of N fertiliser (NH4NO3) at 100–150 kg N ha−1. Although bicarbonate-extractable P levels in fly ash were high (over 250 mg kg−1), a response ofEnchylaena tomentosato supplementary P application [Ca(H2PO4)2.H2O] at 100–200 kg P ha−1was observed.N. billardiereidid not respond to supplementary P, and it was suggested that fly ash P may be selectively available to plants on a species dependent basis. No growth responses to K application (KCl) at rates of up to 400 kg K ha−1were found.

REVEGETATION OF WASTE FLY ASH LAGOONS. I. PLANT SELECTION AND SURFACE AMELIORATION

Glasshouse and field trials were conducted to select plant species suitable for revegetation of waste fly ash lagoons. Species which demonstrated potential for growth on fly ash or ameliorated fly ash in glasshouse trials were subsequently tested by direct seedingin situat the Port Augusta power station in South Australia. Xero- and halophytes from the families Aizoaceae, Chenopodiaceae and Zygophyllaceae performed optimally in both sets of trials, and species most suited for revegetation and regeneration includedMesembryanthemum aitonis,M. nodiflorum,Atriplex holocarpa,A. lindleyi,A. vesicaria,Enchylaena tomentosa,Halosarcia halocnemoides,H. pergranulata,Scaevola collarisandNitraria billardierei. A range of surface amelioration treatments for fly ash lagoons designed to overcome the chemical and physical limitations of fly ash to plant growth, and to reduce the effects of high temperatures, strong winds and low rainfall in the region were also tested. A 50–100-mm surface cover (overlay) of either local sandy topsoil or compost, stabilized with coarse organic mulch, hydromulch or erosion control fabric supported good germination and plant growth. The soil or compost overlay provided a seed bed for initial germination away from the toxic elements of the ash, while the stabilization treatment prevented wind-blown removal of both seed and seed bed, while also conferring some protection to germinating seedlings.

Revegetation of Waste Fly Ash Lagoons. I. Plant Selection and Surface Amelioration

Glasshouse and field trials were conducted to select plant species suitable for revegetation of waste fly ash lagoons. Species which demonstrated potential for growth on fly ash or ameliorated fly ash m glasshouse trials were subsequently tested by direct seeding in situ at the Port Augusta power station in South Australia. Xero and halophytes from the families Aizoaceae, Chenopodiaceae and Zygophyllaceae performed optimally in both sets of trials, and species most suited for revegetation and regeneration included Mesembryanthemum aitonis, M. nodiflorum, Atriplex holocarpa, A. lindleyi, A. vesicaria, Enchylaena tomentosa, Halosarcia halocnemoides, H. pergranulata, Scaevola collaris and Nitraria billardierei . A range of surface amelioration treatments for fly ash lagoons designed to overcome the chemical and physical limitations of fly ash to plant growth, and to reduce the effects of high temperatures, strong winds and low rainfall in the region were also tested. A 50-100-mm surface cover (overlay) of either local sandy topsoil or compost, stabilized with coarse organic mulch, hydromulch or erosion control fabric supported good germination and plant growth. The soil or compost overlay provided a seed bed for initial germination away from the toxic elements of the ash, while the stabilization treatment prevented wind-blown removal of both seed and seed bed, while also conferring some protection to germinating seedlings. © 1997 ISWA

Observations of an ash lagoon spill on the new River, Virginia

An estimated 7 million liters of slightly alkaline water (pH = 7.7) and ash entered New River on 23 July 1973 near Pearisburg, Virginia. The rate of dispersion, 1.4 km/hr, allowed qualitative collections of fishes and macroinvertebrates to be made immediately before and after the biological impact of the spill. Diversity and relative abundance indicated that fishes and macroinvertebrates were little affected. Physicochemical parameters from the flyash lagoon, as projected from 1971–1972 data, were within the known tolerance ranges of aquatic biota common to New River.