A novel and economical approach for the synthesis of short rod-shaped mesoporous silica nanoparticles from coal fly ash waste by Bacillus circulans MTCC 6811

Coal fly ash (CFA) is an industrial byproduct produced during the production of electricity in thermal power plants from the burning of pulverized coal. It is considered hazardous due to the presence of toxic heavy metals while it is also considered valuable due to the presence of value-added minerals like silicates, alumina, and iron oxides. Silica nanoparticles' demands and application have increased drastically in the last decade due to their mesoporous nature, high surface area to volume ratio, etc. Here in the present research work, short rod-shaped, mesoporous silica nanoparticles (MSN) have been synthesized from coal fly ash by using Bacillus circulans MTCC 6811 in two steps. Firstly, CFA was kept with the bacterial culture for bioleaching for 25 days in an incubator shaker at 120 rpm. Secondly, the dissolved silica in the medium was precipitated with the 4 M sodium hydroxide to obtain a short rod-shaped MSN. The purification of the synthesized silica particle was done by treating them with 1 M HCl at 120 °C, for 90 min. The synthesized short rod-shaped MSN were characterized by UV-vis spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Particle size analyzer (PSA), Field emission scanning electron microscopy (FESEM), and transmission electron microscope. The microscopic techniques revealed the short rod-shaped mesoporous silica nanoparticles (MSN) for the final nano-silica, whose size varies from 40 to 80 nm, with an average size of 36 ± 5 nm. The XRD shows the crystalline nature of the synthesized MSN having a crystallite size of 36 nm. The FTIR showed the three characteristic bands in the range of 400-1100 cm-1, indicating the purity of the sample. The energy dispersive X-ray (EDX) showed 53.04 wt% oxygen and 43.42% Si along with 3.54% carbon in the final MSN. The particle size analyzer revealed that the average particle size is 368.7 nm in radius and the polydispersity index (PDI) is 0.667. Such a novel and economical approach could be helpful in the synthesis of silica in high yield with high purity from coal fly ash and other similar waste.

Growth, biochemical, and antioxidant response of pot marigold (Calendula officinalis L.) grown in fly ash amended soil

The present study was carried out to determine the impact of FA application on growth performance, biochemical parameters, and antioxidant defense activity of Calendula officinalis. The results revealed that under a low dose of FA (40%) amended soil, the plant growth performance and metal tolerance index (MTI) were increased compared to control plants and further decreased with increased FA application (60%, 80%, and 100% FA). In addition, the incorporation of 40% FA in soil not only improved the physicochemical properties of soil but also increased the biochemical parameters in the Calendula plant, however, these parameters declined under high FA applications. It was also observed that antioxidant enzyme activity (SOD, CAT, POD, and APX) in leaves of Calendula officinalis increased at high FA application (100% FA) to combat heavy metal stress from FA. The overall study suggests that 40% FA amended soil is the best suitable dose for growing Calendula officinalis and can be considered as metal tolerant species for phytoremediation of 40% FA amended soil.Novelty statement: Fly ash (FA) management is a major problem nowadays. The present study was carried out for FA utilization and to determine the impact of FA amended soil on growth performance, antioxidant properties, and biochemical attributes of Calendula officinalis. This is a sustainable approach in which waste (FA) utilization was done simultaneously with the enhancement in response of the medicinally potent Calendula species. The novelty of this study also suggests that Calendula has phytoremediation potential for remediation of heavy metal polluted soil. Further, the relationship between the growth, biochemical parameters, and antioxidant defense mechanism of Calendula grown on FA amended soil was studied which has not been studied so far. It was found that Calendula is a hyperaccumulator that can adapt to heavy metal stress from FA due to its ability to mitigate oxidative damage. Statistical analysis (ANOVA, Duncan's multiple range test, and PCA) was done for the results obtained using SPSS (11.5) and Origin 8 Pro software.

The Effect of Dietary Exposure to Coal Ash Contaminants within Food Ration on Growth and Reproduction in Daphnia magna

Coal ash contains numerous contaminants and is the focus of regulatory actions and risk assessments due to environmental spills. We exposed Daphnia magna to a gradient of coal ash contamination under high and low food rations to assess the sublethal effects of dietary exposures. Whereas exposure to contaminants resulted in significant reductions in growth and reproduction in daphnids, low, environmentally relevant food rations had a much greater effect on these endpoints. Environ Toxicol Chem 2020;39:1998-2007. © 2020 SETAC.

Adverse effects of fly ashes used as immobilizing agents for highly metal-contaminated soils on Xenopus laevis oocytes survival and maturation-a study performed in the north of France with field soil extracts

Amphibians are now recognized as the most endangered group. One of this decline causes is the degradation of their habitat through direct contamination of water, soil leaching, or runoff from surrounding contaminated soils and environments. In the North of France, the extensive industrial activities resulted in massive soil contamination by metal compounds. Mineral amendments were added to soils to decrease trace metal mobility. Because of the large areas to be treated, the use of inexpensive industrial by-products was favored. Two types of fly ashes were both tested in an experimental site with the plantation of trees in 2000. Aim of the present work was to investigate the effects of extracts from metal-contaminated soils treated or not for 10 years with fly ashes on Xenopus laevis oocyte using cell biology approaches. Indeed, our previous studies have shown that the Xenopus oocyte is a relevant model to study the metal ion toxicity. Survival and maturation of oocyte exposed to the soil extracts were evaluated by phenotypic approaches and electrophysiological recordings. An extract derived from a metal-contaminated soil treated for 10 years with sulfo-calcic ashes induced the largest effects. Membrane integrity appeared affected and ion fluxes in exposed oocytes were changed. Thus, it appeared that extracted elements from certain mineral amendments used to prevent the mobility of metals in the case of highly metal-contaminated soils could have a negative impact on X. laevis oocytes.

Potential of Chlorella fusca LEB 111 cultivated with thermoelectric fly ashes, carbon dioxide and reduced supply of nitrogen to produce macromolecules

Fly ashes present several minerals that along with carbon dioxide (CO₂) represent a promising nutrient source and an alternative to reduce environmental problems. Thus, the objective of this study was to investigate if CO₂, thermoelectric fly ashes and reduction in nitrogen supply alters the production of macromolecules in Chlorella fusca LEB 111. For this purpose, 1.5 or 0.75 g L^-1 of NaNO₃, injection of 10% (v v^-1) of CO₂ as well as 0, 40 and 120 ppm of fly ashes were studied. The protein content was not impaired in cultivations with 0.75 g L^-1 of NaNO₃ since nitrogen was not fully consumed. Nevertheless, this cultivation strategy increased carbohydrate content by up to 25%, which could be fermented to produce bioethanol. Therefore, Chlorella fusca presented not only potential for CO₂ biofixation and assimilation of nutrients from fly ashes but also for enhancement of carbohydrates accumulation when the nitrogen supply was reduced.

Arsenic Bioremediation by Indigenous Heavy Metal Resistant Bacteria of Fly Ash Pond

Fly ash (FA), the major by-product of coal-fired thermal power plants, causes significant environmental degradation owing to its injurious heavy metal contents. Leaching of arsenic (As) from ash ponds is especially significant as As released from FA can increase As concentration of drinking water above maximum contaminant level of 10 ppb. The aim of this paper was demonstration of As bioremediation potential of indigenous As resistant bacteria present in the weathered pond ash sample. Ten isolates belonging to Bacillus, Micrococcus, Kytococcus and Staphylococcus genera were characterized. Biochemical tests showed reduction of relatively non toxic arsenate to more toxic arsenite by two strains while four strains showed oxidation of arsenite to arsenate. Two exoplolysaccharide producing strains were shown to absorb As within their biomass. Total heterotrophs versus As resistant heterotrophs counting performed showed that FA was enriched with As resistant heterotrophs. Column leaching based microcosm study revealed overall As detoxification potential of the isolated microbes.

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 (10 mg Cd kg^-1) and C. procera (3.5 mg 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 (50 mg Cr kg^-1) and Ni (67 mg Ni kg^-1) which could also help in the phytoremediation of FA lagoon.

Effects of different treatments of fly ash and mining soil on growth and antioxidant protection of Indian wild rice

The aim of the present study was investigation of the effects of fly ash and mining soil on growth and antioxidant protection of two cultivars of Indian wild rice (Oryza nivara and Oryza rufipogon) for possible phytoremediation and restoration of metal-contaminated site. In this study, Indian wild rice showed significant changes in germination, growth, and biochemical parameters after exposure to different ratio of fly ash and mining soil with garden soil. There was significant reduction of germination, fresh weight, dry weight, leaf chlorophyll content, leaf area, Special Analysis Device Chlorophyll (SPAD) Index, proteins, and activities of antioxidant enzymes in both cultivars of the wild rice grown in 100% fly ash and mining soil compared to the plants grown in 100% garden soil. Results from this study showed that in both cultivars of wild rice, all growth and antioxidant parameters increased when grown in 50% fly ash and mining soil. Taken together, Indian wild rice has the capacity to tolerate 50% of fly ash and mining soil, and can be considered as a good candidate for possible phytoremediation of contaminated soils.

Spatial differences in trace element bioaccumulation in turtles exposed to a partially remediated coal fly ash spill

Large-scale releases of environmental contaminants from industrial facilities can cause considerable damage to surrounding ecosystems and require remediation. The expense and/or undesirable environmental side effects of physical removal may constrain remediation efforts. In 2008, approximately 4.1 million m³ of fly ash were released into the Emory River at a coal-burning power plant in Kingston, Tennessee, USA. Approximately 390 000 m³ of fly ash were not removed (hereafter "residual ash"), to avoid disturbing underlying legacy contamination from unrelated historical industrial activity. In 2011 and 2012, the authors measured trace element concentrations in an assemblage of freshwater turtles in 2 rivers impacted by the spill and in a third river that was unaffected. Concentrations of arsenic, copper, iron, mercury, manganese, selenium, and zinc were higher in turtles from rivers affected by the spill but low relative to concentrations known to be toxic to other vertebrates. Concentrations of some trace elements decreased with distance from the original spill site but were not strongly affected by nearby volumes of residual ash. Among-species differences in trace element bioaccumulation and/or the relatively low spatial resolution of available data on residual ash volumes may have obscured this effect. The results suggest that the spill influenced turtle bioaccumulation of trace elements but that distance from the spill site may be a more important factor than residual ash in influencing postremediation bioaccumulation. Environ Toxicol Chem 2017;36:201-211. © 2016 SETAC.

Impacts of coal ash on methylmercury production and the methylating microbial community in anaerobic sediment slurries

Mercury (Hg) associated with coal ash is an environmental concern, particularly if the release of coal ash to the environment is associated with the conversion of inorganic Hg to methylmercury (MeHg), a bioaccumulative form of Hg that is produced by anaerobic microorganisms. In this study, sediment slurry microcosm experiments were performed to understand how spilled coal ash might influence MeHg production in anaerobic sediments of an aquatic ecosystem. Two coal ash types were used: (1) a weathered coal ash; and (2) a freshly collected, unweathered fly ash that was relatively enriched in sulfate and Hg compared to the weathered ash. These ash samples were added to anaerobic sediment slurries constructed with a relatively pristine sediment (containing 0.03 mg kg^-1 Hg) and a Hg-contaminated sediment (containing 0.29 mg kg^-1 Hg). The results of these experiments showed negligible net production of MeHg in microcosms with no ash and in microcosms amended with the low sulfate/low Hg ash. In contrast, slurry microcosms amended with high sulfate/high Hg ash showed increases in total MeHg content that was 2 to 3 times greater than control microcosms without ash (p < 0.001). 16S amplicon sequencing of microbial communities in the slurries indicated that the coal ash addition generally increased the relative abundance of the methylating microbial community, including sulfate-reducing bacteria and iron-reducing bacteria species that are known to be efficient methylators of Hg. The stimulation of these microorganisms was likely caused by the release of substrates (sulfate and Fe) originating from the ash. Overall, the results highlight the need to incorporate both environmental parameters and coal ash characteristics into risk assessments that guide coal ash management and disposal.

Chronic Ingestion of Coal Fly-Ash Contaminated Prey and Its Effects on Health and Immune Parameters in Juvenile American Alligators (Alligator mississippiensis)

Coal-burning power plants supply approximately 37 % of the electricity in the United States. However, incomplete combustion produces ash wastes enriched with toxic trace elements that have historically been disposed of in aquatic basins. Organisms inhabiting such habitats may accumulate these trace elements; however, studies investigating the effects on biota have been primarily restricted to shorter-lived, lower-trophic organisms. The American alligator (Alligator mississippiensis), a long-lived, top-trophic carnivore, has been observed inhabiting these basins, yet the health or immune effects of chronic exposure and possible accumulation remains unknown. In this study, we investigated how chronic dietary ingestion of prey contaminated with coal combustion wastes (CCWs) for 25 months, and subsequent accumulation of trace elements present in CCWs, affected juvenile alligator immune function and health. Alligators were assigned to one of four dietary-treatment groups including controls and those fed prey contaminated with CCWs for one, two, or three times a week. However, no effect of Dietary Treatment (p > 0.05) was observed on any immune parameter or hematological or plasma analyte we tested. Our results suggest that neither exposure to nor accumulation of low doses of CCWs had a negative effect on certain aspects of the immune and hematological system. However, future studies are required to elucidate this further.

Ammonia Nitrogen Transformations in a Reactor with Aggregate made of Sewage Sludge Combustion Fly Ash

The influence of light weight aggregate made of fly ash from sewage sludge thermal treatment (FASSTT LWA) on ammonia nitrogen metabolism, and on quantitative and qualitative changes of microorganisms colonizing the filling, was investigated. Two reactors were used in the experiment. The first was filled with gravel, the other with FASSTT LWA. The reactors were operated with a wastewater hydraulic loading rate of 5 mm(3) mm(-2) d(-1). During the eleven-week experiment, high efficiency of ammonia removal was observed. The lower concentrations of nitrites and nitrates in the effluent indicate that ammonia nitrogen removal resulted not just from nitrification. Nitrate concentration increase was reflected in a decrease in nitrogen removal efficiency. One possible explanation for this phenomenon is that in the period when ammonia nitrogen and nitrites were present in the reactor's FASSTT LWA filling, facilitating conditions occurred for the deammonification process.

Influence of metal(loid) bioaccumulation and maternal transfer on embryo-larval development in fish exposed to a major coal ash spill

In December 2008, an earthen retaining wall at the Tennessee Valley Authority (TVA) Kingston Fossil Fuel Plant failed and released 4.1 millionm(3) of coal ash to rivers flowing into Watts Bar Reservoir in east Tennessee, United States (U.S.). As part of a comprehensive effort to evaluate the risks to aquatic resources from this spill - the largest in U.S. history - we compared bioaccumulation and maternal transfer of selenium (Se), arsenic (As), and mercury (Hg) in adult redear sunfish (Lepomis macrolophus), collected two years after the spill from both coal-ash exposed and non-exposed areas of the Emory and Clinch Rivers, with the success of embryo-larval development in their offspring. Whole body and ovary concentrations of Se in female sunfish at three study sites downstream of the spill were significantly elevated (site means=4.9-5.3 and 6.7-9.0mg/kg d.w. whole body and ovary concentrations, respectively) compared with concentrations in fish from reference sites upstream of the spill site (2.2-3.2mg/kg d.w. for whole bodies and 3.6-4.8mg/kg d.w. for ovaries). However, Se concentrations in coal ash-exposed areas remain below proposed U.S. Environmental Protection Agency (USEPA) criteria for the protection of aquatic life. Site-to-site variation in fish concentrations of As and Hg were not well-correlated with ash-exposure, reflecting the multiple sources of these metal(loid)s in the affected watersheds. In 7-day laboratory tests of embryos and larvae derived from in vitro crosses of eggs and sperm from these field-collected sunfish, fertilization success, hatching success, embryo-larval survival, and incidences of developmental abnormalities did not differ significantly between ash-exposed and non-exposed fish. Furthermore, these developmental endpoints were not correlated with whole body or ovary concentrations of Se, As, or Hg in the maternal fish, or with fish size, ovary weight, or gonadal-somatic indices. Results from this and related studies associated with the Kingston coal ash spill are consistent with proposed USEPA fish-based water quality criteria for Se, and to date continue to suggest that long-term exposures to sediment containing residual ash may not present a significant chronic risk to fish populations exposed to this major coal ash release.

Metal phytoremediation potential of naturally growing plants on fly ash dumpsite of Patratu thermal power station, Jharkhand, India

Three naturally growing plants Ipomoea carnea, Lantana camara, and Solanum surattense were found in fly ash dumpsite of Patratu thermal power station, Jharkhand, India. They were assessed for their metal uptake potential. The fly ash was slightly alkaline with very less nitrogen and organic carbon but enriched with phosphorus and heavy metals. Lantana camara and Ipomoea carnea showed good translocation from root to shoot for most of the metals except Mn and Pb. The order of metal accumulation in stem of both the plants were Fe(205mg/kg)>Mn(65mg/kg)>Cu(22.35mg/kg)>Pb(6.6mg/kg)>Cr(3.05mg/kg)>Ni(1 mg/kg)>Cd(0.5 mg/kg) and Fe(741 mg/kg)>Mn(154.05 mg/kg)>Cu(20.75 mg/kg)>Pb(6.75 mg/kg)>Ni(4.0 mg/kg)>Cr(3.3mg/kg)>Cd(0.05mg/kg), respectively. But Solanum surattense accumulated most of the metals in roots. The order was in the following order, Mn (382.2mg/kg) >Fe (264.1mg/kg) > Cu (25.35mg/kg) >Pb (5.95 mg/kg) > Ni (1.9 mg/kg) > Cr (1.8mg/kg) > Cd (0.55 mg/kg). The order of Bioconcentration factor (BCF) in root and shoot followed almost the same order as, Mn>Fe>Ni>Pb>Cu>Cr≈ Cd in all the three species. ANOVA showed significant variation in metal accumulation by root and stem between the species. Finally, it can be concluded that Solanum surattense can be used as phytostabilizer and other two species as phytoextractor of metal for fly ash dumpsite reclamation.

Phytoremediation efficiency of Eichhornia crassipes in fly ash pond

The present study was focused on field research to examine the phytoremediation potential of naturally grown Eichhornia crassipes in fly ash (FA) pond. Field results indicate the efficiency of E. crassipes for remediation of heavy metals from FA pond. The bioconcentration factor trend was Cr (3.75) > Cu (2.62) > Cd (1.05), and Cu (1.35) in root and stem, respectively. The survival and abundance growth of E. crassipes in the circumstance of heavy metal enriched FA pond is another highlight of the present research that reveals its toxitolerant characteristics. Thus, this lesson on phytoremediation proved that E. crassipes is a potential accumulator of Cu, Cr, and Cd from FA ponds and is a promising species for FA pond's remediation globally.

Residual organic matter and microbial respiration in bottom ash: Effects on metal leaching and eco-toxicity

A common assumption regarding the residual organic matter, in bottom ash, is that it does not represent a significant pool of organic carbon and, beyond metal-ion complexation process, it is of little consequence to evolution of ash/leachate chemistry. This article evaluates the effect of residual organic matter and associated microbial respiratory processes on leaching of toxic metals (i.e. arsenic, copper, chromium, molybdenum, nickel, lead, antimony and zinc), eco-toxicity of ash leachates. Microbial respiration was quantified with help of a respirometric test equipment OXITOP control system. The effect of microbial respiration on metal/residual organic matter leaching and eco-toxicity was quantified with the help of batch leaching tests and an eco-toxicity assay - Daphnia magna. In general, the microbial respiration process decreased the leachate pH and eco-toxicity, indicating modification of bioavailability of metal species. Furthermore, the leaching of critical metals, such as copper and chromium, decreased after the respiration in both ash types (fresh and weathered). It was concluded that microbial respiration, if harnessed properly, could enhance the stability of fresh bottom ash and may promote its reuse.

Improving growth rate of microalgae in a 1191m(2) raceway pond to fix CO2 from flue gas in a coal-fired power plant

CO2 fixation between microalgal biomass and culture solution and the weight ratio of biomass consumption at nighttime to biomass growth at daytime were compared in an open raceway pond aerated with flue gas from a coal-fired power plant. Average daytime sunlight intensity and solution temperature were optimized to improve microalgal growth rate and to enhance the efficiency of CO2 fixation. When the average daytime solution temperature increased from 12 to 26°C, the rate of biomass consumption due to microalgal respiration at nighttime increased from 6.0 to 7.9g/m(2)/d, which was approximately 25% of the biomass growth rate at daytime. Furthermore, when the average daytime sunlight intensity increased from 39,900 to 88,300lux, CO2 fixation rate in the microalgal biomass increased from 18.4 to 40.7g/m(2)/d, which was approximately 1/3 of CO2 removal rate from flue gas by the microalgal culture system.

[Leaching of Rare Earth Elements from Coal Ashes Using Acidophilic Chemolithotrophic Microbial Communities]

A method for leaching rare earth elements from coal ash in the presence of elemental sulfur using communities of acidophilic chemolithotrophic microorganisms was proposed. The optimal parameters determined for rare element leaching in reactors were as follows: temperature, 45 degrees C; initial pH, 2.0; pulp density, 10%; and the coal ash to elemental sulfur ratio, 10 : 1. After ten days of leaching, 52.0, 52.6, and 59.5% of scandium, yttrium, and lanthanum, respectively, were recovered.

Selenium bioaccumulation in fish exposed to coal ash at the Tennessee Valley Authority Kingston spill site

In December 2008, 4.1 million cubic meters of coal ash were released into the Emory and Clinch Rivers by the Tennessee Valley Authority Kingston Fossil Plant. Coal ash contains several contaminants, including the bioaccumulative metalloid selenium (Se). Because Se is predominantly accumulated in aquatic organisms through dietary rather than aqueous exposure, tissue-based toxicity thresholds for Se are currently being considered. The proposed threshold concentrations range between 4 μg/g and 9 μg/g Se (dry wt.) in whole body fish, with a proposed fillet threshold of 11.8 μg/g. In the present study, the authors examined the spatial and temporal trends in Se bioaccumulation and examined the relationship between the Se content in fillets and in whole bodies of fish collected around the Kingston spill site to determine whether Se bioaccumulation was a significant concern at the ash spill site. Whereas Se concentrations in fish (whole bodies and fillets) were elevated at sampling locations affected by the Kingston ash spill relative to reference locations, concentrations do not appear to be above risk thresholds and have not been increasing over the 5-yr period since the spill. These findings are not only relevant to guiding the human health and ecological risk assessments at the Kingston ash spill site, but because of current national discussions on appropriate guidelines for Se in fish as well for the disposal of coal combustion wastes, the results are also relevant to the general understanding of Se bioaccumulation in contaminated water bodies.

Vermicomposting of Tea Factory Coal Ash: metal accumulation and metallothionein response in Eisenia fetida (Savigny) and Lampito mauritii (Kinberg)

Earthworms can accumulate heavy metals in their intestines to a great extent. Impact of feed materials and duration of metal exposure on natural activity of earthworms are rather unclear; this investigation therefore addresses the impact of metal rich Tea Factory Coal Ash (TFCA) on reproduction, composting and metal accumulation ability of Eisenia fetida and Lampito mauritii. Earthworm count and cocoon production increased significantly during vermicomposting. pH of the vermicomposted mixtures shifted toward neutrality, total organic C decreased substantially and total N enhanced significantly compared to composting. High heavy metal (Mn, Zn, Cu, As) accumulation was recorded in the intestine of both the earthworm species. Moreover, gradual increase in the metal-inducible metallothionein concentration indicated the causal mechanism of metal accumulation in these species. TFCA+cow dung (CD) (1:1) were most favorable feed mixture for E. fetida and TFCA+CD (1:2) were good for L. mauritii in regard to metal accumulation and compost quality.

Combined ultrasonic and bioleaching treatment of hospital waste incinerator bottom ash with simultaneous extraction of selected metals

The mineralogy, as well as elemental composition, of the incinerated hospital waste (HW) ashes are not well known and need to be investigated for the safe handling and disposal of such ash. A study was conducted to investigate the chemical composition, mineralogy and bioleaching of selected metals from incinerated HW bottom ash using Aspergillus niger under the combined effect ofultrasonic radiation. Different techniques were utilized to determine the elemental composition (Electron Dispersive X-ray Spectroscopy [EDX], atomic absorption spectrophotometry, inductively coupled plasma-optical emission spectroscopy, ultraviolet-visible light spectrophotometer) and mineralogy (X-ray Diffraction) of the raw sample, as well as the bioleached samples. Chemical leaching tests were performed to determine the effect of different organic acids on metals dissolution. Microbes were tested for acid production and leaching capabilities of selected metals from medical waste (MW) bottom ash. Wet chemical and EDX analyses showed that the ash was enriched with metallic elements like Na, K, Ca, Fe and Al with a concentration range of 22-115 (g/kg). Furthermore, the ash contained heavy metals such as Cu, Cr, Ni, Sn and Ti in the range of 0.51-21.74 (mg/kg). Citric and oxalic acids generated by fungi could be important leaching agents acting to dissolve these metals. Under ultrasonic treatment, metals dissolution by the acidic metabolites was at its maximum after just 9 d of leaching. The results showed that the dissolution of metals was much higher in citric and oxalic acid than with other acids. Extraction of metals from incinerated MW ash indicated that this ash may be a potential source of metals in the future.

Spatial and temporal variation in the diet of tree swallows: implications for trace-element exposure after habitat remediation

Emerging aquatic insects play a key role in transporting aquatic contaminants into terrestrial ecosystems. Tree swallows are frequently the focus of studies examining this movement because they are thought to forage heavily on emerging aquatic insects when breeding in riparian areas. We examined the tree swallow diet to determine if trace elements from a recently remediated coal fly ash spill were moving into the terrestrial ecosystem. We collected bolus samples from adult tree swallows as they entered the nest box to feed their young. Despite strategically locating boxes in riparian areas, we found that the consumption of insects with an aquatic larval stage ranged from 28 to 75% of insects among colonies. We also found significant differences among colonies in the taxa found in bolus samples. Chironomidae (midges) were the primary emerging aquatic insects consumed by tree swallows, whereas Ephemeroptera were brought to nestlings infrequently. The consumption of insects with an aquatic larval stage, Chironomidae in particular, was positively correlated with exposure to trace elements from the spill. Bolus samples from the spill site contained greater concentrations of many trace elements compared with reference locations, but concentrations of most elements were lower than levels thought to cause reproductive impairment. These results support the hypothesis that emerging aquatic insects transport trace elements to terrestrial consumers and that Chironomidae play an important role in this movement. Our results also indicate that it is important to assess the composition of the diet and to not infer exposure to trace elements based on nesting location.

Hazard remediation and recycling of tea industry and paper mill bottom ash through vermiconversion

Considerable amount of bottom ash (BA) is produced by tea and paper factories in Northeast India. This significantly deteriorates soil and surface water quality through rapid acidification, releasing sulfur compounds and heavy metals. The present investigation endeavoured to convert this waste to organic manure through vermicomposting by Eisenia fetida. Substantial increment in bioavailability of N, P, K, Fe, Mn and Zn along with remarkable decline in toxic metal like Cr due to vermicomposting was noteworthy. Furthermore, vermicomposted mixtures of Tea Factory BA (TFBA) or Paper Mill BA (PMBA) with organic matter (OM) attributed profuse pod yield of French Bean (Phaseolus vulgaris L.). Hence, bioconversion of TFBA and PMBA is highly feasible through vermicomposting and the converted materials can be utilized as potential organic fertilizer.

Differential growth and yield by canola (Brassica napus L.) and wheat (Triticum aestivum L.) arising from alterations in chemical properties of sandy soils due to additions of fly ash

BACKGROUND

There is a need for field trials on testing agronomic potential of coal fly ash to engender routine use of this technology. Two field trials were undertaken with alkaline and acidic fly ashes supplied at between 3 and 6 Mg ha⁻¹ to acidic soils and sown to wheat and canola at Richmond (Eastern Australia) and to wheat only at Merredin (Western Australia).

RESULTS

Ash addition marginally (P< 0.10) raised the pH in the top soil layers at both sites. The exceptionally dry season at both sites constrained yields and thwarted any likelihood of gaining yield benefits from ash-induced improvements in soil conditions. Yield improvements due to ash addition were absent at Merredin and only marginal at Richmond, where no elevated accumulation of B, Mo, Se, P or S in either the straw or seeds of wheat was observed; canola increased accumulation of Mo and Se in its shoot with acidic fly ash, but it was well below phyto toxic levels. Simulations of wheat using APSIM at Richmond over a 100-year period (1909-2008) predicted yield increases in 52% of years with addition of ash at 3.0 Mg ha⁻¹ compared with 24% of years with addition of ash at 6.0 Mg ha⁻¹. The simulated yield increases did not exceed 40% over the control with addition of 6 Mg ha⁻¹ ash, but was between 40% and 50% with an addition rate of 3 Mg ha⁻¹.

CONCLUSION

We found no evidence of phytotoxicity in either crop in this unusually dry year and there is still a need for further field assessment in years with favourable rainfall to enable development of clear recommendations on fly ash rates for optimum yield benefits.

Removal of phosphorus from wastewaters by biomass ashes

Removal batch assays of phosphates from a synthetic wastewater (SWW) and a pulp and paper mill wastewater (PPWW) with two forestry biomass ashes were performed. The supernatants were not only chemically characterized but also the ecotoxicity was determined using two organisms: Vibrio fischeri and Artemia franciscana. The addition of fly ash and bottom ash to the SWW in solid/liquid (S/L) ratios of 3.35 and 9.05 g L(-1), respectively, achieved removal percentages of phosphates >97% for both ashes. The addition of fly ash and bottom ash to the PPWW in S/L ratios of 34.45 and 46.59 g L(-1), respectively, yield removal percentages of phosphates >90% for both ashes. According to the results of the Langmuir and Freundlich isotherms, the removal of phosphates from the SWW was mainly explained by surface removal mechanisms, while the removal from the PPWW was partially explained by multi-layer mechanisms. The supernatants resulting from the treatment of SWW and PPWW with both biomass ashes did not present acute ecotoxicity.

Effects of different SRT on anaerobic digestion of MSW dosed with various MSWI ashes

This study investigated different solid retention time (SRT) on municipal solid waste (MSW) anaerobic digestion with various MSW incinerator fly ash (FA) and bottom ash (BA) addition. Results showed that biogas production rates (BPRs, ≈ 200 to ≈ 400 mL/gVS) with organic loading rate of ≈ 0.053 gVS/gVS(reactor) (Day 1-435, SRT 20 days, SRT20) at FA 1g/d (FA1), BA 12 g/d (BA12) and BA 24 g/d (BA24) dosed bioreactors increased after adaptation. BPRs with SRT10 and SRT5 decreased while BPRs with SRT40 showed to increase compared to initial BPRs (≈ 200 mL/gVS) with SRT20. SRT5 operation reduced the BPRs (≈ 10 - ≈ 90 mL/gVS) significantly and only BA12 and BA24 dosed bioreactors could recover the BPRs (≈ 100 - ≈ 200 mL/gVS) after SRT20 operation (Day 613-617) compared to FA1 and FA3 and control. Released levels of Co, Mo and W at BA12 and BA24 dosed bioreactors showed most potential to improve MSW anaerobic digestion.

Trophic status and metal bioaccumulation differences in multiple fish species exposed to coal ash-associated metals

On December 22, 2008 a dike containing coal fly ash from the Tennessee Valley Authority Kingston Fossil Plant near Kingston Tennessee USA failed and resulted in the largest coal ash spill in U.S. history. Coal ash, a by-product of coal combustion, is known to contain multiple contaminants of concern, including arsenic and selenium. The purpose of this study was to investigate species differences in the bioaccumulation of arsenic and selenium and potential factors contributing to these differences (i.e., trophic dynamics and gut pH) in the vicinity of the Kingston coal ash spill. Elevated levels of arsenic and selenium were observed in various tissues of largemouth bass, white crappie, bluegill and redear sunfish from sites associated with the Kingston coal ash spill. Highest concentrations of selenium were found in redear sunfish with liver concentrations as high as 24.83mg/kg dry weight and ovary concentrations up to 10.40mg/kg dry weight at coal ash-associated sites. Investigations into the gut pH and trophic dynamics of redear sunfish and bluegill demonstrated a large difference in the gut physiology between these two species. Redear sunfish stomach and intestinal pH was found to be 1.1 and 0.16 pH units higher than in bluegill, respectively. In addition, fish from coal ash-associated sites showed enrichment differences ((15)N and (13)C) compared to no ash sites, indicating differences in food web dynamics between sites. These results imply the incorporation of coal ash-associated compounds into local food webs and/or a shift in diet at ash sites compared to the no ash reference sites. Based on these results, further investigation into a broader food web at ash-associated sites is warranted.

Phytoremediation of heavy metals from fly ash pond by Azolla caroliniana

Abundance of naturally growing Azolla caroliniana (water fern) on the surface of metal enriched fly ash (FA) pond reflects its toxitolerant characteristics. Results indicate the efficiency of A. caroliniana for phytoremediation of FA pond because of its higher bioconcentration factor. The metal concentration ranged from 175 to 538 and 86 to 753mgkg(-1) in roots and fronds, respectively. Bioconcentration factor (BCF) values of all metals in root and frond ranged from 1.7 to18.6 and 1.8 to 11.0, respectively, which were greater than one and indicates the metal accumulation potential of A. caroliniana. Translocation factor (TF) ranged from 0.37 to 1.4 for various heavy metals. The field result proved that A. caroliniana is a potential accumulator for the examined heavy metals and can be used for phytoremediation of FA pond.

Kinetic analysis of constructed systems for the recovery of contaminated areas by acid mine drainage

INTRODUCTION

Flowing of the acid mine drainage may contaminate the adjacent water bodies causing substantial changes in the aquatic ecosystem. This aspect is the most relevant problem in the southern of Santa Catarina once the contaminated areas are inserted in the watershed of the Araranguá, Urussanga, and Tubarão rivers, increasing the need for recovery studies. These areas are between Criciúma, Içara, Urussanga, Siderópolis, Lauro Müller, Orleans, and Alfredo Wagner towns where a conservation unit exist called the Environmental Preservation Area of Baleia Franca. Aiming to compare the kinetics of the ash derived from burning coal and to neutralize acid mine drainage, different neutralizer, limestone, fly, and bottom ash, was mounted on a pilot scale experiment.

DISCUSSION

The transport parameters showed the same order of infiltration and dispersion: fly ash < bottom ash < limestone. The order of measured alkalinity was: limestone < fly ash < bottom ash, with pH values of 9.34, 12.07, and 12.25, respectively. The limestone kinetics of acidic drainage neutralization was first order with reaction rate constant k = 0.0963 min(-1), bottom ash was 3/4 with k = 0.0723 mol(1/4) L(-1/4) min(-1), and the fly ash had higher order kinetics, 4/3, with reaction rate constant k = 27.122 L(1/3) mol(-1/3) min(-1). However, by mathematical modeling, it was found that due to a combination of transport and kinetics, only limestone treatment reached a pH above 6 within 5 years, corresponding to the ideal as planned.

Effects of micro-nano and non micro-nano MSWI ashes addition on MSW anaerobic digestion

This study aims at investigating the effects of micro-nano municipal solid waste (MSW) incinerator (MSWI) fly ash (FA) and bottom ash (BA) on the MSW anaerobic digestion. Results showed that suitable micro-nano and non micro-nano MSWI ashes addition (FA/MSW 3, 6, 18 and 30 g g(-1) VS and BA/MSW 12, 36, 60 and 120 g g(-1) VS) could enhance the biogas production compared to the control. It was particularly found to have the highest biogas production at the micro-nano MSWI BA/MSW ratio of 36 g g(-1) VS (∼193 mL g(-1) VS MSW, ∼3.5 times to the control). Micro-nano MSWI FA and BA added bioreactors had the higher biogas production than the corresponding non micro-nano MSWI FA and BA added ones. Suitable MSWI ashes addition could improve the biogas production due to the released metals levels suitable for the MSW anaerobic digestion particularly found in the micro-nano added bioreactors.

Wood pellet fly ash and bottom ash as an effective liming agent and nutrient source for rye grass (Lolium perenne L.) and oats (Avena sativa)

Fly ash (FA) and bottom ash (BA) from a softwood pellet boiler were characterized and evaluated as soil amendments. In a greenhouse study, two plant species (rye grass, Lolium perenne L. and oats, Avena sativa) were grown in three different treatments (1% FA, 1% BA, non-amended control) of a silty loam soil. Total concentrations of plant nutrients Ca, K, Mg, P and Zn in both ashes were elevated compared to conventional wood ash. Concentrations of Cd, Cr, Pb, Se and Zn were found to be elevated in the FA relative to BA and the non-amended soil. At 28 d, oat above-ground biomass was found to be significantly greater in soil amended with FA. Potassium and Mo plant tissue concentrations were significantly increased by addition of either ash, and FA significantly increased Zn tissue concentrations. Cadmium and Hg tissue concentrations were elevated in some cases. As soil amendments, either pellet ash is an effective liming agent and nutrient source, but high concentrations of Cd and Zn in FA may preclude its use as an agricultural soil amendment in some jurisdictions. Lower ash application rates than those used in this study (i.e. <1%) may still provide sufficient nutrients and effective neutralization of soil acidity.

Assessment of fly ash-aided phytostabilisation of highly contaminated soils after an 8-year field trial Part 2. Influence on plants

Aided phytostabilisation is a cost-efficient technique to manage metal-contaminated areas, particularly in the presence of extensive pollution. Plant establishment and survival in highly metal-contaminated soils are crucial for phytostabilisation success, as metal toxicity for plants is widely reported. A relevant phytostabilisation solution must limit metal transfer through the food chain. Therefore, this study aimed at evaluating the long-term efficiency of aided phytostabilisation on former agricultural soils highly contaminated by cadmium, lead, and zinc. The influence of afforestation and fly ash amendments on reducing metal phytoavailability was investigated as were their effects on plant development. Before being planted with a tree mix, the site was divided into three plots: a reference plot with no amendment, a plot amended with silico-aluminous fly ash and one with sulfo-calcic fly ash. Unlike Salix alba and Quercus robur, Alnus glutinosa, Acer pseudoplatanus and Robinia pseudoacacia grew well on the site and accumulated, overall, quite low concentrations of metals in their leaves and young twigs. This suggests that these three species have an excluder phenotype for Cd, Zn and Pb. After 8 years, metal availability to A. glutinosa, A. pseudoplatanus and R. pseudoacacia, and translocation to their above-ground parts, strongly decreased in fly ash-amended soils. Such decreases fit well together with the depletion of CaCl(2)-extractable metals in amended soils. Although both fly ashes were effective to decrease Cd, Pb and Zn concentrations in above-ground parts of trees, the sulfo-calcic ash was more efficient.

Amendments promote the development of Lolium perenne in soils affected by historical copper smelting operations

The Puchuncaví valley, central Chile, has been exposed to aerial emissions from a copper smelter. Nowadays, soils in the surroundings are sparsely-vegetated, acidic, and metal-contaminated, and their remediation is needed to reduce environmental risks. We assessed effectiveness of lime, fly ash, compost, and iron grit as amendments to immobilize Cu in soils and promote plant growth. Amended soils were cultivated with Lolium perenne for 60 days under controlled conditions. Total dissolved Cu and Cu2+ activity in the soil solution, ryegrass biomass, and Cu accumulation in plant tissues were measured. Addition of lime and fly ash decreased Cu concentrations and Cu2+ activity in the soil solution, increased plant biomass, and reduced shoot Cu concentration below 22 mg kg(-1) (the phytotoxicity threshold for the species). The most effective amendment with respect to the shoot biomass yield was a combination of lime and compost. Water content of the substrate and the K accumulation were positively correlated with the compost application rate. Compost combined with iron grit decreased dissolved Cu concentrations during the period of highest solubility, i.e., during the first 60 days after the compost application. However, iron grit incorporation into soils amended with lime and compost decreased the shoot biomass of ryegrass.