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Assisted phytoremediation of fly ash dumps through naturally colonized plants
Ecological Engineering 82 (2015) 1–5
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Assisted phytoremediation of fly ash dumps through naturally colonized plants Vimal Chandra Pandey * Eco-Auditing Group, CSIR-National Botanical Research Institute, Lucknow 226001, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 8 October 2014 Received in revised form 1 March 2015 Accepted 5 April 2015 Available online xxx
The present article briefly describes a strategy regarding the remediation and management of fly ash (FA) dumps to mitigate all environmental problems of FA hazards. The onsite remediation of FA dumps through phytoremediation is still a critical challenge due to unfavorable conditions of ash deposit which inhibit plant establishment and growth. However, some naturally growing plant species colonize FA dumps as sparse cover, and rest areas of FA dumps are still naked in absence of vegetation. The entire FA dumps can be covered by “assisted phytoremediation” through naturally colonized plant species on ash disposal sites for FA dumps’ management. ã 2015 Elsevier B.V. All rights reserved.
Keywords: Assisted phytoremediation Naturally colonized vegetation Carbon sequestration Ecosystem services Heavy metals Fly ash dumps’ management
1. The challenges of fly ash dumps’ hazards Fly ash (FA) is a coal combustion residue of thermal power plants, and has been recognized as a serious global threat to environment. Safe disposal of huge generated FA is a challenging task all over the world. Globally, FA generation will increase to the amount of approximately 600 million tons year 1, which may cover up to 3235 km2 of land area for disposal by 2015 (Pandey and Singh, 2012). FA dump is a hazardous dumping site of the earth due to the presence of toxic metals i.e., Cr, Cd, Pb, Hg, As, Se etc. (Pandey and Singh, 2010; Pandey et al., 2011; Ram et al., 2015), polycyclic aromatic hydrocarbons (Ruwei et al., 2013; Ribeiro et al., 2014) and several other pollutants that pollute air, soil and water nearby ash deposits. Thus, FA contaminates both aquatic and terrestrial ecosystems, creating both historic and present-day cases of ecological damage (Skorupa, 1998; Lemly, 2002; Rowe et al., 2002; Ruhl et al., 2009; Bryan et al., 2012). FA pollution also causes several diseases like skin, cardiac, cancer, genetic and respiratory nearby residents of ash dumpsites (US EPA, 2007). Besides the presence of contaminants, FA has been recommended in agricultural and forestry areas as a soil ameliorant in lower dose due to readily available plant micro-and macronutrients (Pandey and Singh, 2010; Pandey et al., 2009a,b, 2010;
* Tel.: +91 9454287575. E-mail addresses: [email protected], [email protected] (V.C. Pandey). http://dx.doi.org/10.1016/j.ecoleng.2015.04.002 0925-8574/ ã 2015 Elsevier B.V. All rights reserved.
Ram and Masto, 2014; Ram et al., 2007; Singh et al., 2011; Singh and Pandey, 2013; Singh et al., 2013; Tripathi et al., 2009). FA (10%) amended sand has been suggested as an appropriate rooting media for macro-propagation of Leucaena leucocephala for nursery stock production (Pandey and Kumar, 2013). Furthermore, FA has been utilized in the improvement of degraded lands (Srivastava et al., 2014; Ram et al., 2006; Pandey and Singh, 2010). Therefore, it is the need of hour to use sustainable and holistic approach for remediation and management of FA dumps. Furthermore, it is of great interest to search how abandoned FA dumpsite can be rehabilitated most expeditiously to green environments. 2. Sparse naturally colonized vegetation on fly ash dumps Vegetation succession proceeds on abandoned FA dumps, when seeds of almost every plant species growing in close areas are transported via wind and biological agencies. The seeds of many plant species germinate in their respective seasons, whereas seeds of other species fail to germinate on FA dumps in appropriate regimes (Pandey et al., 2014a). After germination only some plant species having tolerance against the hostile conditions of FA substrate survive on FA dumps. The key challenges of FA dumps for plant establishment and growth are high pH, heavy metals toxicity, lack of nitrogen and organic matter (Pandey and Singh, 2010; Pandey et al., 2012), which inhibit succession. As a consequence, sparse vegetation covers come in existence on FA dumps as an early succession. In Indian scenario, most of the naturally colonizing plant species as sparse vegetation cover on FA dumps
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have been assessed and found suitable for their phytostabilization, phytoremediation and revegetation potential with special reference to raising rural livelihoods and maintaining ecosystem services (Pandey et al., 2012; Pandey 2012a,b; Pandey 2013; Kumari et al., 2013). Although some areas of FA dumps have sparse cover (sometimes dense cover) by naturally colonized vegetation, still rest areas are completely devoid of vegetation. These naked areas of FA dumps can be covered by assisted phytoremediation through naturally colonized plants. Additionally, we have been proposed the use of aromatic grasses (i.e., Vetiver (Vetiveria zizanioides), Lemon grass (Cymbopogon flexuosus), Palmarosa (Cymbopogon martinii) and Citronella (Cymbopogon winterianus)) for better in-situ remediation of FA landfill hazards and to get multiple benefits from environmental to socio-economical without any significant risk (Verma et al., 2014). In some countries like Serbia (Kostic et al., 2012), the Czech Republic (Tropek et al., 2013), the Kosovo Republic (Mustafa et al., 2012), Hong Kong (Chu, 2008), England (Shaw, 1994) and India (Pandey et al., 2014), naturally colonizing species on FA dumps have been assessed. But deep research towards “assisted phytoremediation of FA dumps" through naturally colonized potential plants is needed in detail for sustainability of ecosystems around the FA basins. 3. Assisted phytoremediation of fly ash dumps for dense green cover development Sparse vegetation of naturally colonized plant species is not effective to check completely dust air pollution and leaching of toxic metals from abandoned FA dumps. I am proposing here “assisted phytoremediation of FA dumps" through naturally colonizing vegetation for better in-situ management. Naturally colonized plants are an effective ecological asset for FA dumps’
restoration because they response better and can survive easily in comparison to introduced plant species on FA dumps (Pandey and Singh, 2011; Pandey et al., 2014a). In this direction, we studied phytodiversity on FA dumps and identified some potential plant species to be utilized for the phytorestoration of new FA dumps (Pandey et al., 2014a). Recently, a safe and viable strategy is proposed for sustainable phytoremediation based on naturally colonizing and economically valuable plants (Pandey et al., 2015a, b). In this strategy, using plant species should be natural colonizers, perennial in nature, unpalatable by livestock and socio-economical. Naturally colonized vegetation on FA dumps take place slowly due to unfavorable substrate and local conditions (Pandey and Singh, 2012). These conditions of FA dumps inhibit most of the vegetation establishment and growth. However, some naturally growing species mostly grasses colonize FA dumps due to their unusual character profile such as perennial nature, extensive root system, self-propagation, unpalatable, tolerance to high pH, FAtoxic metals and the local adverse conditions (Pandey and Singh, 2011). Ecological succession takes a long time (30–50 years) for converting FA towards soil in England and to create a birch and willow scrub woodland (Shaw, 1992). Naturally colonized FA dumps have been considered as a valuable conservation sites for some plant species like dense birch/willow woodland with glades of orchids in the UK (Greenwood and Gemmill, 1978; Shaw, 1994). Recently, it has been also proved that FA dumps have conservation potential for colonizing by vanishing some insects and arthropod groups (Tropek et al., 2013, 2014). Thus, FA dumps have strong potential for conservation of both floral and faunal diversity. The long-time of ecological succession of new FA dumps may be reduced by assisted phytoremediation through naturally growing plant species using ecological engineering, and can be achieved
Table 1 An indicative list of naturally colonized potential plant species on fly ash dumps can be used for assisted phytoremediation of FA dumps in India. Botanical name
Family
Local name
Habit
Calotropis procera (Aiton) Dryand.
Asclepiadaceae
Madaar
Shrub Bind fly ash particles to reduce erosion
Ipomoea carnea Jacq. Lantana camera L.
Convolvulaceae Behaya
Shrub Pulp and paper making
Saccharum ravennae L. Saccharum spontaneum L.
Verbenaceae Poaceae Poaceae
Uses
Raimuniya Shrub Making of furniture like chairs and tables Dholu Tall Stabilizing soil to prevent grass erosion Kans Tall Hut construction, grass Stabilizing soil to prevent erosion Goam Tall Building material (rafts, grass boats, mats and huts), paper, fibers, biofuel, etc.
Fly ash dumps
State
References
Chandrapura Thermal Power Plant, NTPC Unchahar NTPC Unchahar
Jharkand; Uttar Pradesh Uttar Pradesh Jharkhand
Maiti et al., 2005; Pandey et al., 2014a
Chandrapura Thermal Power Plant Indraprastha FA dump, Badarpur FA dump Santaldih Thermal Power Plant Santaldih Thermal Power Plant, NTPC Unchahar
Pandey, 2012b Maiti et al., 2005
Delhi region West Bengal
Rau et al., 2009
West Bengal; Uttar Pradesh Uttar Pradesh
Maiti and Jaiswal, 2008; Babcock et al., 1983; Tiwari et al., 2008; Pandey et al., 2014b
Maiti and Jaiswal, 2008
Typha latifolia L.
Typhaceae
Saccharum bengalense Retz. syn. Saccharum munja Phragmites karka (Retz.) Trin. ex Steud. Cynodon dactylon (L.) Pers.
Poaceae
Munj
Tall grass
making ropes, baskets, mats, NTPC Unchahar huts, etc.
Poaceae
Narkul
Tall grass
baskets, mats,
NTPC Unchahar
Uttar Pradesh
Pandey et al., 2014a
Poaceae
Dhoob
grass
Stabilizing soil to prevent erosion and dust pollution
Tree
Fuel wood
Bignoniaceae
Vilati babool Katsagon
Tree
–
NTPC Unchahar
Jharkhand; West Bengal Uttar Pradesh Uttar Pradesh
Maiti et al., 2005; Maiti and Jaiswal, 2008
Fabaceae
Chandrapura Thermal Power Plant, Santaldih Thermal Power Plant NTPC Unchahar
Pontederiaceae
Jalkunbhi
Herb
Biogas production
NTPC Unchahar
Uttar Pradesh
Pandey et al., 2014a
Prosopis juliflora (Sw.) DC. Fernandoa adenophylla (Wall. ex G. Don) Steenis Eichhornia crassipes (Mart.) Solms
Pandey et al., 2012
Pandey et al., 2014a Pandey et al., 2014a
V.C. Pandey / Ecological Engineering 82 (2015) 1–5
within short-time (10–15 years) by implementing my proposed strategy in action. The assisted phytoremediation of FA dumps through ecological engineering will be described in the next paragraphs. Rehabilitation of FA dumps is one of the most ecological challenges and could be achieved by enhancing the resilience through ecological engineering with the help of integrated biotechnological approach (Pandey and Singh, 2012). Some scientific efforts have been targeted for the phytoremediation of FA dumps using introduced plant species through biological interventions (Babu and Reddy, 2011; Hrynkiewiez et al., 2009; Juwarkar and Jambhulkar, 2008; Jambhulkar and Juwarkar, 2009; Ram et al., 2008; Krzaklewski et al., 2012). In this regards, fast revegetation or assisted phytoremediation of FA dumps is desirable and this challenging task can be achieved easily by adding organic matter, site-specific’s native microbes in FA deposits and using naturally colonized plants. Selection of a suitable organic matter is a key criterion to success of self-sustainable vegetative cover on these abandoned ash dumpsites. Furthermore, the low-cost and easy availability of organic amendments i.e., press mud, paper factory sludge, pig manure, sewage sludge, etc., in that area is also a success factor of restoration. Organic amendment helps in lowering the metal toxicity of substrate and provides primary nutrients (N, P, and K) to support plant growth (Wong, 2003; Chiu et al., 2006). Babu and Reddy (2011) observed that plant growth and uptake of nutrients with reducing metal translocation on FA deposits were increased by using the inoculation of native arbuscular mycorrhizal fungi and phosphate solubilizing fungus Aspergillus tubingensis of FA deposit. Furthermore, Ray and Adholeya (2009) also revealed that metal uptake ability by ectomycorrhizal fungi is substrate specific and this ability influences fungi’s organic acid exudation. Furthermore, Pandey et al. (2014a) explored phytodiversity of FA deposits to evaluate naturally colonized species for sustainable phytorestoration and identified some potential plant species like Saccharum spontaneum L., Saccharum bengalense Retz. (syn. Saccharum munja), Prosopis juliflora (Sw.) DC., Typha latifolia L., Cynodon dactylon (L.) Pers., Ipomoea carnea Jacq. and Acacia nilotica L. on the basis of their ecological importance, dominance at the study sites and socioeconomic importance for rural livelihoods for FA deposits’ restoration. The above screened species are ecologically very important as they reduce erosion by binding FA particles, add organic matter and make the site suitable for the germination of forthcoming seeds of other species. There are two naturally developed habitats (i.e., wetland and dry region) on FA disposal site because of FA is being disposed in slurry form which convert in two region. These two zones of FA dump is a source of leaching or seepage of toxic metals and FA dust particles in the surrounding ecosystems and villages (Pandey et al., 2011). A suggestive list of naturally colonized potential plant species on FA dumps is given in Table 1 and should be used for assisted phytoremediation of FA dump in Indian perspective. Two plant species like Goam (Typha latifolia L.) and Jalkunbhi (Eichhornia crassipes (Mart.) Solms) should be spread manually to cover the whole area for phytoremediation of wetland of FA dump, while rest of the plant species like Calotropis procera (Aiton) Dryand., Ipomoea carnea Jacq., Lantana camera L., Saccharum ravennae L., Saccharum spontaneum L., Saccharum bengalense Retz. (syn. Saccharum munja), Phragmites karka (Retz.) Trin. ex Steud., Cynodon dactylon (L.) Pers., Prosopis juliflora (Sw.) DC. and Fernandoa adenophylla (Wall. ex G. Don) Steenis should be exploited in assisted phytoremediation of dry land of FA dump for fast green capping to mitigate FA pollution including dust pollution because of their high tolerance nature against unfavorable conditions. Several grass species and other species have been reported in succession of FA deposits. Therefore, selected naturally colonized plant species for assisted
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phytoremediation of FA dumps should be perennial, invader and economical species. A conceptual diagram shows a strategy to introduce the “assisted phytoremediation of fly ash dumps" through naturally grown plants having three viewpoints (perennial, invader and economic value) for fast and dense green cover development (Fig. 1). Furthermore, cost-effective, dense and fast green capping of FA dumps is a desirable task to countries that are facing FA disposal problems. However, it may be achieved by assisted phytoremediation of FA dumps through naturally growing plants. It would be better, if naturally growing plants fall in nurse species category, because nurse plants play important role in the success of the ecological restoration project (Padilla and Pugnaire, 2006). Most importantly, in hostile conditions of FA dumps, the best nurse plants would be the native species that offer microhabitat for commercial plant recruitment for raising livelihoods of local residents and to develop sustainable FA ecosystem. Likewise, naturally growing exotic plant species may be used for assisted phytoremediation of FA dumps; such possibilities should be analyzed carefully because of the risk of biological invasions. For this, Doren et al. (2009) suggested a comprehensive ecological model to control spreading of invasive species. Thus, we can follow this model to stop the spreading of exotic species during assisted phytoremediation of FA dumps and to allow native species to become established. Finally, three main factors like locally available organic amendment with low-cost, site-specific’s native microbes and potential naturally colonized plant species are accountable to success “assisted phytoremediation of FA dumps". Rehabilitation of barren FA dumps offer multiple benefits from ecologically to socioeconomically such as the phytostabilization of toxic metals, binding of fine FA-dust particles, aesthetic landscape for local residents, the generation of useful bio-resource to villagers, biodiversity conservation and carbon sequestration in the substrate-plant system of FA dumps (Pandey and Singh, 2012). Thus, for quick rehabilitation, assisted phytoremediation should be implemented by using identified naturally colonized potential plant species or by making artificial supply of their seeds on FA dumping sites. The hydro-seeding technique may be used for this
Perennial
Assisted phytoremediation Economic value
Invader
Fig. 1. A conceptual diagram showing to introduce the assisted phytoremediation through naturally colonized plants having three viewpoints (perennial, invader and economic value) for speedy and dense green cover development of the entire fly ash dumps.
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Fig. 2. A schematic illustration showing to introduce “assisted phytoremediation of fly ash dump" using naturally colonized grass species for dense green cover development through ecological engineering to mitigate fly ash dust particles during summer season and leaching of toxic metals in rainy season.
purpose due to cost-effectiveness. This is the easiest, cost effective and natural way for speedy and dense green capping to entire FA dumps. In an insightful research article, Pandey and Singh (2014) demonstrated the possibilities of introducing tall grass on FA deposits without any top-soiling (organic substrate) for fast green capping development on FA dump because of the good adaptive abilities of S. spontaneum tall grass. Furthermore, Pandey et al. (2015) identified S. spontaneum as an underutilized tall grass for revegetation and restoration programs, and the field results (grass vegetation study + analytical study) showed that S. spontaneum has great ability to colonize naturally on bare FA dumps and thus can be used as a valuable genetic resource for rehabilitation of new FA dumps. A graphical diagram shows to introduce the “assisted phytoremediation of FA dumps" (Fig. 2). Thus, we can exploit the prepared substrate by assisted naturally colonized vegetation for the afforestation and next generation of target species (commercial plants) in view of revenue generation from FA dumps. 4. Concluding remarks and future prospects FA dump has been recognized as a hazardous site on the earth and a source of air, soil and water pollution to the ecosystems and residents near coal-based thermal power plants. Many researchers across the world proposed phytoremediation for the remediation of FA hazards as a holistic approach either introduced plant species or spontaneous vegetation, but these approaches have limited scope due to two reasons i.e. lengthy process and lack of economic return. I proposed here “assisted phytoremediation of FA disposal sites" through naturally grown potential plants for fast green capping development in view of FA dumps’ management. Thus, the challenging task of onsite remediation of FA dumps can be achieved easily through assisted phytoremediation with limited inputs using naturally colonized plants. Furthermore, if we could add economical plant species for assisted phytoremediation, then a more sustainable phytoremediation can be derived, that will help to restore our ecosystems nearby coal-based thermal power stations. Thus, the assisted phytoremediation of FA dumps through naturally colonized plants with multipurpose species will provide economic benefits and other ecosystem services. Finally, the assisted phytoremediation of FA dumps through naturally colonized plants is the best strategy for the solution of both problems such as increasing FA disposal areas and mitigating carbon-dioxide released by coal-based thermal power stations, and should be considered as adaptive FA management. I believe that my proposed strategy has world-wide importance from the perspective of remediation and management of FA dumps, particularly in countries that are facing serious FA disposal problems. The knowledge and insights provided here can be linked to action on the ground by practitioners for FA dumps’ remediation and management.
Acknowledgements Financial support given by Science and Engineering Research Board (No. SR/FTP/ES-96/2012), Govt. of India is gratefully acknowledged. Author is also thankful to Director, CSIR-National Botanical Research Institute, Lucknow for his kind support. Author sincerely apologies to all other fly ash dump’s phytoremediation researchers whose work could not be cited due to space limit. References Babcock, M.F., Evans, D.W., Albert, J.J., 1983. Comparative uptake and translocation of trace elements from coal ash by Typha latifolia. Sci. Total Environ. 28, 203–214. Babu, A.G., Reddy, M.S., 2011. Dual inoculation of Arbuscular mycorrhizal and phosphate solubilizing fungi contributes in sustainable maintenance of plant health in fly ash ponds. Water Air Soil Pollut. 219, 3–10. Bryan Jr., A.L., Hopkins, W.A., Parikh, J.H., Jackson, B.P., Unrine, J.M., 2012. Coal fly ash basins as an attractive nuisance to birds: parental provisioning exposes nestlings to harmful trace elements. Environ. Pollut. 161, 170–177. Chiu, K.K., Ye, Z.H., Wong, M.H., 2006. Growth of Veteveria zizanoides and Phragmites australis on Pb/Zn and Cu mine tailings amendment with manure compost and sewage sludge: a green house study. Bioresour. Technol. 97, 158–170. Chu, L.M., 2008. Natural revegetation of coal fly ash in a highly saline disposal lagoon in Hong Kong. Appl. Veg. Sci. 11, 297–306. Doren, R.E., Richards, J.H., Volin, J.C., 2009. A conceptual ecological model to facilitate understanding the role of invasive species in large-scale ecosystem restoration. Ecol. Indic. 9, 150–160. Greenwood, E.F., Gemmill, R.P., 1978. Derelict industrial land as a habitat for rare plants in S. Lancs. (vc 59) and W. Lancs. (vc 60). Watsonia 12, 33–40. Hrynkiewiez, K., Baum, C., Niedojadlo, J., Dahm, H., 2009. Promotion of mycorrhiza formation and growth of willows by the bacterial strain Sphingomonas sp. 23L on fly ash. Biol. Fertil. Soils 45, 385–394. Jambhulkar, H.P., Juwarkar, A.A., 2009. Assessment of bioaccumulation of heavy metals by different plant species grown on fly ash dump. Ecotoxicol. Environ. Saf. 72, 1122–1128. Juwarkar, A.A., Jambhulkar, H.P., 2008. Restoration of fly ash dumps through biological interventions. Environ. Monit. Assess. 139, 355–365. Kostic, O., Mitrovi c, M., Kneževi c, M., Jari c, S., Gaji c, G., Djurdj, L., Evi c Pavlovi c, P., 2012. The potential of four woody species for the revegetation of fly ash deposits from the ‘Nikola Tesla – A’ thermoelectric plant (Obrenovac, Serbia). Arch. Biol. Sci. 64 (1), 145–158. Krzaklewski, W., Pietrzykowski, M., Wos, B., 2012. Survival and growth of alders (Alnus glutinosa (L.) Gaertn. and Alnus incana (L.) Moench) on fly ash technosolsat different substrate improvement. Ecol. Eng. 49, 35–40. Kumari, A., Pandey, V.C., Rai, U.N., 2013. Feasibility of fern Thelypteris dentata for revegetation of coal fly ash landfills. J. Geochem. Explor. 128, 147–152. Lemly, D.A., 2002. Symptoms and implications of selenium toxicity in fish: the Belews Lake case example. Aquat. Toxicity 57, 39–49. Maiti, S.K., Jaiswal, S., 2008. Bioaccumulation and translocation of metals in the natural vegetation growing on fly ash deposits: a field study from Santaldih thermal power plant, West Bengal, India. Environ. Monit. Assess. 136, 355–370. Maiti, S.K., Singh, G., Srivastava, S.B., 2005. Study of the possibility of utilizing fly ash for back filling and reclamation of opencast mines: plot and pot scale experiments with Chandrapura FA. International Congress on Fly Ash TIFAC 4– 7th December 2005, New Delhi. Mustafa, B., Hajdari, A., Krasniqi, F., Morina, I., Riesbeck, F., Sokoli, A., 2012. Vegetation of the ash dump of the Kosova a power plant and the slag dump of the Ferronikeli Smelter in Kosovo. Res. J. Environ. Earth Sci. 4 (9), 823–834. Padilla, F.M., Pugnaire, F.I., 2006. The role of nurse plants in the restoration of degraded environments. Front. Ecol. Environ. 4 (4), 196–202. Pandey, V.C., Kumar, A., 2013. Leucaena leucocephala: an underutilized plant for pulp and paper production. Genet. Resour. Crop Evol. 60, 1165–1171.
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(Saccharum ravennae) colonizing abandoned fly ash dumps in Delhi urban ecosystem. Soil Biol. Biochem. 41, 813–821. Ray, P., Adholeya, A., 2009. Correlation between organic acid exudation and metal uptake by ectomycorrhizal fungi grown on pond ash in vitro. Biometals 22, 275–281. Ribeiro, J., Silva, T.F., Mendonça Filho, J.G., Flores, D., 2014. Fly ash from coal combustion – an environmental source of organic compounds. Appl. Geochem. 44, 103–110. Rowe, C.L., Hopkins, W.A., Congdon, J.D., 2002. Ecotoxicological implications of aquatic disposal of coal combustion residues in the United States: a review. Environ. Monit. Assess. 80, 207–276. Ruhl, L., Vengosh, A., Dwyer, G.S., Hsu-Kim, H., Deonarine, A., Bergin, M., Kravchenko, J., 2009. Survey of environmental and health impacts in the immediate aftermath of the coal ash spill in Kingston, Tennessee. Environ. Sci. Technol. 43, 6326–6333. Ruwei, W., Jiamei, Z., Jingjing, L., Liu, G., 2013. Levels and patterns of polycyclic aromatic hydrocarbons in coal-fired power plant bottom ash and fly ash from Huainan, China. Arch. Environ. Contam. Toxicol. 65, 193–202. Shaw, P.J.A., 1992. A preliminary study of successional changes in vegetation and soil development on unamended fly ash (PFA) in southern England. J. Appl. Ecol. 29, 728–736. Shaw, P.J.A., 1994. Orchid woods and floating islands – the ecology of fly ash. Br. Wildl. 5, 149–157. Singh, J.S., Pandey, V.C., 2013. Fly ash application in nutrient poor agriculture soils: impact on methanotrophs population dynamics and paddy yields. Ecotoxicol. Environ. Saf. 89, 43–51. Singh, J.S., Pandey, V.C., Singh, D.P., 2011. Coal fly ash and farmyard manure amendments in dry-land paddy agriculture field: effect on N-dynamics and paddy productivity. Appl. Soil Ecol. 47, 133–140. Singh, K., Pandey, V.C., Singh, B., Patra, D.D., Singh, R.P., 2013. Effect of fly ash on crop yield and physico-chemical, microbial and enzyme activities of sodic soils. Environ. Eng. Manage. J.. http://omicron.ch.tuiasi.ro/EEMJ/pdfs/accepted/ 266_716_Singh_12.pdf. Skorupa, J.P., 1998. Selenium poisoning of fish and wildlife in nature: lessons from twelve real- world examples. In: Frankenberger, W.T., Engberg, R.A. (Eds.), Environmental ChemistryofSelenium.Marcel Dekker, Inc., NewYork, pp. 315–354. Srivastava, N.K., Ram, L.C., Masto, R.E., 2014. Reclamation of overburden and lowland in coal mining area with fly ash and selective plantation: a sustainable ecological approach. Ecol. Eng. 71, 479–489. Tiwari, S., Kumari, B., Singh, S.N., 2008. Evaluation of metal mobility/immobility in fly ash induced by bacterial strains isolated from the rhizospheric zone of Typha latifolia growing on fly ash dumps. Bioresour. Technol. 99, 1305–1310. Tripathi, R.C., Masto, R.E., Ram, L.C., 2009. Bulk use of pond ash for cultivation of wheat–maize–eggplant crops in sequence on a fallow land. Resour. Conserv. Recycl. 54, 134–139. Tropek, R., Cerna, I., Straka, J., Cizek, O., Konvicka, M., 2013. Is coal combustion the last chance for vanishing insects of inland drift sand dunes in Europe? Biol. Conser. 162, 60–64. Tropek, R., Cerna, I., Straka, J., Kadlec, T., Pech, P., Tichanek, F., Sebek, P., 2014. Restoration management of fly ash deposits crucially influence their conservation potential for terrestrial arthropods. Ecol. Eng. 73, 45–52. US EPA. (2007) Human and ecological risk assessment of coal combustion wastes. US EPA (draft). Verma, S.K., Singh, K., Gupta, A.K., Pandey, V.C., Trevedi, P., Verma, S.K., Patra, D.D., 2014. Aromatic grasses for phytomanagement of coal fly ash hazards. Ecol. Eng. 73, 425–428. Wong, M.H., 2003. Ecological restoration of mine degraded soils with emphasis on metal contaminated soils. Chemosphere 50, 775–780.
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Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng
Assisted phytoremediation of fly ash dumps through naturally colonized plants Vimal Chandra Pandey * Eco-Auditing Group, CSIR-National Botanical Research Institute, Lucknow 226001, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 8 October 2014 Received in revised form 1 March 2015 Accepted 5 April 2015 Available online xxx
The present article briefly describes a strategy regarding the remediation and management of fly ash (FA) dumps to mitigate all environmental problems of FA hazards. The onsite remediation of FA dumps through phytoremediation is still a critical challenge due to unfavorable conditions of ash deposit which inhibit plant establishment and growth. However, some naturally growing plant species colonize FA dumps as sparse cover, and rest areas of FA dumps are still naked in absence of vegetation. The entire FA dumps can be covered by “assisted phytoremediation” through naturally colonized plant species on ash disposal sites for FA dumps’ management. ã 2015 Elsevier B.V. All rights reserved.
Keywords: Assisted phytoremediation Naturally colonized vegetation Carbon sequestration Ecosystem services Heavy metals Fly ash dumps’ management
1. The challenges of fly ash dumps’ hazards Fly ash (FA) is a coal combustion residue of thermal power plants, and has been recognized as a serious global threat to environment. Safe disposal of huge generated FA is a challenging task all over the world. Globally, FA generation will increase to the amount of approximately 600 million tons year 1, which may cover up to 3235 km2 of land area for disposal by 2015 (Pandey and Singh, 2012). FA dump is a hazardous dumping site of the earth due to the presence of toxic metals i.e., Cr, Cd, Pb, Hg, As, Se etc. (Pandey and Singh, 2010; Pandey et al., 2011; Ram et al., 2015), polycyclic aromatic hydrocarbons (Ruwei et al., 2013; Ribeiro et al., 2014) and several other pollutants that pollute air, soil and water nearby ash deposits. Thus, FA contaminates both aquatic and terrestrial ecosystems, creating both historic and present-day cases of ecological damage (Skorupa, 1998; Lemly, 2002; Rowe et al., 2002; Ruhl et al., 2009; Bryan et al., 2012). FA pollution also causes several diseases like skin, cardiac, cancer, genetic and respiratory nearby residents of ash dumpsites (US EPA, 2007). Besides the presence of contaminants, FA has been recommended in agricultural and forestry areas as a soil ameliorant in lower dose due to readily available plant micro-and macronutrients (Pandey and Singh, 2010; Pandey et al., 2009a,b, 2010;
* Tel.: +91 9454287575. E-mail addresses: [email protected], [email protected] (V.C. Pandey). http://dx.doi.org/10.1016/j.ecoleng.2015.04.002 0925-8574/ ã 2015 Elsevier B.V. All rights reserved.
Ram and Masto, 2014; Ram et al., 2007; Singh et al., 2011; Singh and Pandey, 2013; Singh et al., 2013; Tripathi et al., 2009). FA (10%) amended sand has been suggested as an appropriate rooting media for macro-propagation of Leucaena leucocephala for nursery stock production (Pandey and Kumar, 2013). Furthermore, FA has been utilized in the improvement of degraded lands (Srivastava et al., 2014; Ram et al., 2006; Pandey and Singh, 2010). Therefore, it is the need of hour to use sustainable and holistic approach for remediation and management of FA dumps. Furthermore, it is of great interest to search how abandoned FA dumpsite can be rehabilitated most expeditiously to green environments. 2. Sparse naturally colonized vegetation on fly ash dumps Vegetation succession proceeds on abandoned FA dumps, when seeds of almost every plant species growing in close areas are transported via wind and biological agencies. The seeds of many plant species germinate in their respective seasons, whereas seeds of other species fail to germinate on FA dumps in appropriate regimes (Pandey et al., 2014a). After germination only some plant species having tolerance against the hostile conditions of FA substrate survive on FA dumps. The key challenges of FA dumps for plant establishment and growth are high pH, heavy metals toxicity, lack of nitrogen and organic matter (Pandey and Singh, 2010; Pandey et al., 2012), which inhibit succession. As a consequence, sparse vegetation covers come in existence on FA dumps as an early succession. In Indian scenario, most of the naturally colonizing plant species as sparse vegetation cover on FA dumps
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have been assessed and found suitable for their phytostabilization, phytoremediation and revegetation potential with special reference to raising rural livelihoods and maintaining ecosystem services (Pandey et al., 2012; Pandey 2012a,b; Pandey 2013; Kumari et al., 2013). Although some areas of FA dumps have sparse cover (sometimes dense cover) by naturally colonized vegetation, still rest areas are completely devoid of vegetation. These naked areas of FA dumps can be covered by assisted phytoremediation through naturally colonized plants. Additionally, we have been proposed the use of aromatic grasses (i.e., Vetiver (Vetiveria zizanioides), Lemon grass (Cymbopogon flexuosus), Palmarosa (Cymbopogon martinii) and Citronella (Cymbopogon winterianus)) for better in-situ remediation of FA landfill hazards and to get multiple benefits from environmental to socio-economical without any significant risk (Verma et al., 2014). In some countries like Serbia (Kostic et al., 2012), the Czech Republic (Tropek et al., 2013), the Kosovo Republic (Mustafa et al., 2012), Hong Kong (Chu, 2008), England (Shaw, 1994) and India (Pandey et al., 2014), naturally colonizing species on FA dumps have been assessed. But deep research towards “assisted phytoremediation of FA dumps" through naturally colonized potential plants is needed in detail for sustainability of ecosystems around the FA basins. 3. Assisted phytoremediation of fly ash dumps for dense green cover development Sparse vegetation of naturally colonized plant species is not effective to check completely dust air pollution and leaching of toxic metals from abandoned FA dumps. I am proposing here “assisted phytoremediation of FA dumps" through naturally colonizing vegetation for better in-situ management. Naturally colonized plants are an effective ecological asset for FA dumps’
restoration because they response better and can survive easily in comparison to introduced plant species on FA dumps (Pandey and Singh, 2011; Pandey et al., 2014a). In this direction, we studied phytodiversity on FA dumps and identified some potential plant species to be utilized for the phytorestoration of new FA dumps (Pandey et al., 2014a). Recently, a safe and viable strategy is proposed for sustainable phytoremediation based on naturally colonizing and economically valuable plants (Pandey et al., 2015a, b). In this strategy, using plant species should be natural colonizers, perennial in nature, unpalatable by livestock and socio-economical. Naturally colonized vegetation on FA dumps take place slowly due to unfavorable substrate and local conditions (Pandey and Singh, 2012). These conditions of FA dumps inhibit most of the vegetation establishment and growth. However, some naturally growing species mostly grasses colonize FA dumps due to their unusual character profile such as perennial nature, extensive root system, self-propagation, unpalatable, tolerance to high pH, FAtoxic metals and the local adverse conditions (Pandey and Singh, 2011). Ecological succession takes a long time (30–50 years) for converting FA towards soil in England and to create a birch and willow scrub woodland (Shaw, 1992). Naturally colonized FA dumps have been considered as a valuable conservation sites for some plant species like dense birch/willow woodland with glades of orchids in the UK (Greenwood and Gemmill, 1978; Shaw, 1994). Recently, it has been also proved that FA dumps have conservation potential for colonizing by vanishing some insects and arthropod groups (Tropek et al., 2013, 2014). Thus, FA dumps have strong potential for conservation of both floral and faunal diversity. The long-time of ecological succession of new FA dumps may be reduced by assisted phytoremediation through naturally growing plant species using ecological engineering, and can be achieved
Table 1 An indicative list of naturally colonized potential plant species on fly ash dumps can be used for assisted phytoremediation of FA dumps in India. Botanical name
Family
Local name
Habit
Calotropis procera (Aiton) Dryand.
Asclepiadaceae
Madaar
Shrub Bind fly ash particles to reduce erosion
Ipomoea carnea Jacq. Lantana camera L.
Convolvulaceae Behaya
Shrub Pulp and paper making
Saccharum ravennae L. Saccharum spontaneum L.
Verbenaceae Poaceae Poaceae
Uses
Raimuniya Shrub Making of furniture like chairs and tables Dholu Tall Stabilizing soil to prevent grass erosion Kans Tall Hut construction, grass Stabilizing soil to prevent erosion Goam Tall Building material (rafts, grass boats, mats and huts), paper, fibers, biofuel, etc.
Fly ash dumps
State
References
Chandrapura Thermal Power Plant, NTPC Unchahar NTPC Unchahar
Jharkand; Uttar Pradesh Uttar Pradesh Jharkhand
Maiti et al., 2005; Pandey et al., 2014a
Chandrapura Thermal Power Plant Indraprastha FA dump, Badarpur FA dump Santaldih Thermal Power Plant Santaldih Thermal Power Plant, NTPC Unchahar
Pandey, 2012b Maiti et al., 2005
Delhi region West Bengal
Rau et al., 2009
West Bengal; Uttar Pradesh Uttar Pradesh
Maiti and Jaiswal, 2008; Babcock et al., 1983; Tiwari et al., 2008; Pandey et al., 2014b
Maiti and Jaiswal, 2008
Typha latifolia L.
Typhaceae
Saccharum bengalense Retz. syn. Saccharum munja Phragmites karka (Retz.) Trin. ex Steud. Cynodon dactylon (L.) Pers.
Poaceae
Munj
Tall grass
making ropes, baskets, mats, NTPC Unchahar huts, etc.
Poaceae
Narkul
Tall grass
baskets, mats,
NTPC Unchahar
Uttar Pradesh
Pandey et al., 2014a
Poaceae
Dhoob
grass
Stabilizing soil to prevent erosion and dust pollution
Tree
Fuel wood
Bignoniaceae
Vilati babool Katsagon
Tree
–
NTPC Unchahar
Jharkhand; West Bengal Uttar Pradesh Uttar Pradesh
Maiti et al., 2005; Maiti and Jaiswal, 2008
Fabaceae
Chandrapura Thermal Power Plant, Santaldih Thermal Power Plant NTPC Unchahar
Pontederiaceae
Jalkunbhi
Herb
Biogas production
NTPC Unchahar
Uttar Pradesh
Pandey et al., 2014a
Prosopis juliflora (Sw.) DC. Fernandoa adenophylla (Wall. ex G. Don) Steenis Eichhornia crassipes (Mart.) Solms
Pandey et al., 2012
Pandey et al., 2014a Pandey et al., 2014a
V.C. Pandey / Ecological Engineering 82 (2015) 1–5
within short-time (10–15 years) by implementing my proposed strategy in action. The assisted phytoremediation of FA dumps through ecological engineering will be described in the next paragraphs. Rehabilitation of FA dumps is one of the most ecological challenges and could be achieved by enhancing the resilience through ecological engineering with the help of integrated biotechnological approach (Pandey and Singh, 2012). Some scientific efforts have been targeted for the phytoremediation of FA dumps using introduced plant species through biological interventions (Babu and Reddy, 2011; Hrynkiewiez et al., 2009; Juwarkar and Jambhulkar, 2008; Jambhulkar and Juwarkar, 2009; Ram et al., 2008; Krzaklewski et al., 2012). In this regards, fast revegetation or assisted phytoremediation of FA dumps is desirable and this challenging task can be achieved easily by adding organic matter, site-specific’s native microbes in FA deposits and using naturally colonized plants. Selection of a suitable organic matter is a key criterion to success of self-sustainable vegetative cover on these abandoned ash dumpsites. Furthermore, the low-cost and easy availability of organic amendments i.e., press mud, paper factory sludge, pig manure, sewage sludge, etc., in that area is also a success factor of restoration. Organic amendment helps in lowering the metal toxicity of substrate and provides primary nutrients (N, P, and K) to support plant growth (Wong, 2003; Chiu et al., 2006). Babu and Reddy (2011) observed that plant growth and uptake of nutrients with reducing metal translocation on FA deposits were increased by using the inoculation of native arbuscular mycorrhizal fungi and phosphate solubilizing fungus Aspergillus tubingensis of FA deposit. Furthermore, Ray and Adholeya (2009) also revealed that metal uptake ability by ectomycorrhizal fungi is substrate specific and this ability influences fungi’s organic acid exudation. Furthermore, Pandey et al. (2014a) explored phytodiversity of FA deposits to evaluate naturally colonized species for sustainable phytorestoration and identified some potential plant species like Saccharum spontaneum L., Saccharum bengalense Retz. (syn. Saccharum munja), Prosopis juliflora (Sw.) DC., Typha latifolia L., Cynodon dactylon (L.) Pers., Ipomoea carnea Jacq. and Acacia nilotica L. on the basis of their ecological importance, dominance at the study sites and socioeconomic importance for rural livelihoods for FA deposits’ restoration. The above screened species are ecologically very important as they reduce erosion by binding FA particles, add organic matter and make the site suitable for the germination of forthcoming seeds of other species. There are two naturally developed habitats (i.e., wetland and dry region) on FA disposal site because of FA is being disposed in slurry form which convert in two region. These two zones of FA dump is a source of leaching or seepage of toxic metals and FA dust particles in the surrounding ecosystems and villages (Pandey et al., 2011). A suggestive list of naturally colonized potential plant species on FA dumps is given in Table 1 and should be used for assisted phytoremediation of FA dump in Indian perspective. Two plant species like Goam (Typha latifolia L.) and Jalkunbhi (Eichhornia crassipes (Mart.) Solms) should be spread manually to cover the whole area for phytoremediation of wetland of FA dump, while rest of the plant species like Calotropis procera (Aiton) Dryand., Ipomoea carnea Jacq., Lantana camera L., Saccharum ravennae L., Saccharum spontaneum L., Saccharum bengalense Retz. (syn. Saccharum munja), Phragmites karka (Retz.) Trin. ex Steud., Cynodon dactylon (L.) Pers., Prosopis juliflora (Sw.) DC. and Fernandoa adenophylla (Wall. ex G. Don) Steenis should be exploited in assisted phytoremediation of dry land of FA dump for fast green capping to mitigate FA pollution including dust pollution because of their high tolerance nature against unfavorable conditions. Several grass species and other species have been reported in succession of FA deposits. Therefore, selected naturally colonized plant species for assisted
3
phytoremediation of FA dumps should be perennial, invader and economical species. A conceptual diagram shows a strategy to introduce the “assisted phytoremediation of fly ash dumps" through naturally grown plants having three viewpoints (perennial, invader and economic value) for fast and dense green cover development (Fig. 1). Furthermore, cost-effective, dense and fast green capping of FA dumps is a desirable task to countries that are facing FA disposal problems. However, it may be achieved by assisted phytoremediation of FA dumps through naturally growing plants. It would be better, if naturally growing plants fall in nurse species category, because nurse plants play important role in the success of the ecological restoration project (Padilla and Pugnaire, 2006). Most importantly, in hostile conditions of FA dumps, the best nurse plants would be the native species that offer microhabitat for commercial plant recruitment for raising livelihoods of local residents and to develop sustainable FA ecosystem. Likewise, naturally growing exotic plant species may be used for assisted phytoremediation of FA dumps; such possibilities should be analyzed carefully because of the risk of biological invasions. For this, Doren et al. (2009) suggested a comprehensive ecological model to control spreading of invasive species. Thus, we can follow this model to stop the spreading of exotic species during assisted phytoremediation of FA dumps and to allow native species to become established. Finally, three main factors like locally available organic amendment with low-cost, site-specific’s native microbes and potential naturally colonized plant species are accountable to success “assisted phytoremediation of FA dumps". Rehabilitation of barren FA dumps offer multiple benefits from ecologically to socioeconomically such as the phytostabilization of toxic metals, binding of fine FA-dust particles, aesthetic landscape for local residents, the generation of useful bio-resource to villagers, biodiversity conservation and carbon sequestration in the substrate-plant system of FA dumps (Pandey and Singh, 2012). Thus, for quick rehabilitation, assisted phytoremediation should be implemented by using identified naturally colonized potential plant species or by making artificial supply of their seeds on FA dumping sites. The hydro-seeding technique may be used for this
Perennial
Assisted phytoremediation Economic value
Invader
Fig. 1. A conceptual diagram showing to introduce the assisted phytoremediation through naturally colonized plants having three viewpoints (perennial, invader and economic value) for speedy and dense green cover development of the entire fly ash dumps.
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V.C. Pandey / Ecological Engineering 82 (2015) 1–5
Fig. 2. A schematic illustration showing to introduce “assisted phytoremediation of fly ash dump" using naturally colonized grass species for dense green cover development through ecological engineering to mitigate fly ash dust particles during summer season and leaching of toxic metals in rainy season.
purpose due to cost-effectiveness. This is the easiest, cost effective and natural way for speedy and dense green capping to entire FA dumps. In an insightful research article, Pandey and Singh (2014) demonstrated the possibilities of introducing tall grass on FA deposits without any top-soiling (organic substrate) for fast green capping development on FA dump because of the good adaptive abilities of S. spontaneum tall grass. Furthermore, Pandey et al. (2015) identified S. spontaneum as an underutilized tall grass for revegetation and restoration programs, and the field results (grass vegetation study + analytical study) showed that S. spontaneum has great ability to colonize naturally on bare FA dumps and thus can be used as a valuable genetic resource for rehabilitation of new FA dumps. A graphical diagram shows to introduce the “assisted phytoremediation of FA dumps" (Fig. 2). Thus, we can exploit the prepared substrate by assisted naturally colonized vegetation for the afforestation and next generation of target species (commercial plants) in view of revenue generation from FA dumps. 4. Concluding remarks and future prospects FA dump has been recognized as a hazardous site on the earth and a source of air, soil and water pollution to the ecosystems and residents near coal-based thermal power plants. Many researchers across the world proposed phytoremediation for the remediation of FA hazards as a holistic approach either introduced plant species or spontaneous vegetation, but these approaches have limited scope due to two reasons i.e. lengthy process and lack of economic return. I proposed here “assisted phytoremediation of FA disposal sites" through naturally grown potential plants for fast green capping development in view of FA dumps’ management. Thus, the challenging task of onsite remediation of FA dumps can be achieved easily through assisted phytoremediation with limited inputs using naturally colonized plants. Furthermore, if we could add economical plant species for assisted phytoremediation, then a more sustainable phytoremediation can be derived, that will help to restore our ecosystems nearby coal-based thermal power stations. Thus, the assisted phytoremediation of FA dumps through naturally colonized plants with multipurpose species will provide economic benefits and other ecosystem services. Finally, the assisted phytoremediation of FA dumps through naturally colonized plants is the best strategy for the solution of both problems such as increasing FA disposal areas and mitigating carbon-dioxide released by coal-based thermal power stations, and should be considered as adaptive FA management. I believe that my proposed strategy has world-wide importance from the perspective of remediation and management of FA dumps, particularly in countries that are facing serious FA disposal problems. The knowledge and insights provided here can be linked to action on the ground by practitioners for FA dumps’ remediation and management.
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