Although the Indian population is largely vegetarian, not much attention has been given to the cultivation of vegetables, as compared to other crops like cereals, pulses and oil seeds. Therefore, the present study was conducted on two leafy vegetables, spinach (Spanacia oleracea L.) and methi (Trigonella foenum graecum L.) commonly grown in Aligarh, as the two popular vegetables of Indian diet. The study was conducted for two successive years and during the first year, phosphorus and fly ash interactions with a uniform dose of nitrogen and potassium on both vegetables was observed. During the second year, while keeping nitrogen and phosphorus uniform, potassium and fly ash combinations were studied again with both vegetables, to determine the optimum dose of inorganic fertilizers and fly ash combination. It was observed that fly ash applied at the rate of 15 t ha-1 along with N40P15K20, proved optimum for spinach while in the case of methi, N20P30K40 + FA10 was sufficient. Therefore, both vegetables can safely be grown with 10 to 15 t ha-1 of fly ash and a comparatively lower quantity of NPK.

We investigated the occurrence and distribution of microplastics in surface water from the Three Gorges Reservoir. Nine samples were collected via trawl sampling with a 112 μmmesh net. The abundances of microplastics were from 3407.7 × 103 to 13,617.5 × 103 items per square kilometer in the main stream of the Yangtze River and from 192.5 × 103 to 11,889.7 × 103 items per square kilometer in the estuarine areas of four tributaries. The abundance of microplastics in the main stream of the Yangtze River generally increased as moving closer to the Three Gorges Dam. The microplastics are made exclusively of polyethylene (PE), polypropylene (PP), and polystyrene (PS). Together with microplastics, high abundance of coal/fly ash was also observed in the surface water samples. Comparing with previously reported data, microplastics in the TGR were approximately one to three orders of magnitudes greater, suggesting reservoirs as potential hot spot for microplastic pollution.

To develop an efficient adsorbent for humic acid, the present study represents the first attempt to investigate the capability of zeolitic imidazole frameworks to remove humic acid from water. Zeolitic imidazole framework-8 (ZIF-8) is particularly selected as a prototype ZIF to adsorb humic acid owing to its high stability in aqueous solutions. ZIF-8 was synthesized and characterized using scanning electronic microscopy (SEM), powder X-ray diffraction pattern (PXRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analyzer (TGA) and then used to adsorb humic acid under various conditions. The structure of ZIF-8 was found to remain intact after the exposure to humic acid in water. Factors affecting the adsorption were examined, including solid-to-liquid ratio, mixing time, temperature, pH, presence of salt, and surfactants. The adsorption capacity of ZIF-8 was found to be much higher than that of activated carbon, fly ash, zeolites, graphite, etc., showing its promising potential for removal of humic acid. The adsorption mechanism could be attributed to the electrostatic interaction between the positive surface of ZIF-8 and the acidic sites of humic acid, as well as the π–π stacking interaction between imidazole of ZIF-8 and benzene rings of humic acid. The humic acid adsorption to ZIF-8 could be enhanced in the acidic conditions, and the adsorption process remained highly stable in the solutions of a wide range of NaCl concentrations. ZIF-8 can be also regenerated by simple ethanol-washing process and reused for humic acid adsorption. These features enable ZIF-8 to be an efficient and stable adsorbent to remove humic acid from water.

We investigated a peat profile from the Izery Mountains, located within the so-called Black Triangle, the border area of Poland, Czech Republic, and Germany. This peatland suffered from an extreme atmospheric pollution during the last 50 years, which created an exceptional natural experiment to examine the impact of pollution on peatland microbes. Testate amoebae (TA), Centropyxis aerophila and Phryganella acropodia, were distinguished as a proxy of atmospheric pollution caused by extensive brown coal combustion. We recorded a decline of mixotrophic TA and development of agglutinated taxa as a response for the extreme concentration of Al (30 g kg⁻¹) and Cu (96 mg kg⁻¹) as well as the extreme amount of fly ash particles determined by scanning electron microscopy (SEM) analysis, which were used by TA for shell construction. Titanium (5.9 %), aluminum (4.7 %), and chromium (4.2 %) significantly explained the highest percentage of the variance in TA data. Elements such as Al, Ti, Cr, Ni, and Cu were highly correlated (r > 0.7, p < 0.01) with pseudostome position/body size ratio and pseudostome position. Changes in the community structure, functional diversity, and mechanisms of shell construction were recognized as the indicators of dust pollution. We strengthen the importance of the TA as the bioindicators of the recent atmospheric pollution.

Surface and groundwater are often contaminated with toxic anions such as arsenic and selenium. Because of their large surface areas, selenium adsorption on carbon sorbents is considered an attractive water treatment technique. In this present work, selenium sorption on copper-impregnated activated carbon and fly ash-extracted char carbon was evaluated. Unburned carbon was extracted from fly ash using froth floatation techniques, and the carbon sorbents were modified using copper ions. Adsorption experiments confirmed the strong influence of electrostatic forces on equilibrium uptakes of selenite (Se (IV)) and selenate (Se (VI)). Selenium sorption on virgin char carbon was maximum only at acidic pH, i.e., at pH < pHₚzc (pH at point of zero charge). Upon copper modification of the carbon surface, the pHₚzc shifted towards the alkaline region, and as a result, the positive charge density on the carbon surface increased. At pH > pHₚzc, a two- to fourfold increase in sorption coverage and threefold increase in selenium percent removal was observed. Se (IV) sorption was higher compared to Se (VI) sorption. The effect of selenium concentrations and competing anions was studied to evaluate adsorbent performance. The order of maximum surface coverage followed the order: modified char carbon > modified activated carbon > char carbon. The main mechanism of selenium (Se) sorption appeared to be (1) electrostatic attraction of the Se ions to the modified carbon surface at acidic to neutral pH; (2) complexation of Se ions with the copper ions/oxides on the carbon surface; and (3) co-precipitation with copper hydroxides at alkaline pH.

With the gradual depletion of high-grade copper ore deposits, secondary wastes are gaining importance as a source for metal recovery. However, the alkalinity and low copper concentration in some of these resources underscore the need for selective leaching agents. In this work, indigenous alkaliphiles from a fly ash landfill site with inherent pH tolerance, metal tolerance and copper leaching capability were isolated and investigated. Four isolates, namely Agromyces aurantiacus TRTYP3, Alkalibacterium pelagium TRTYP5, Alkalibacterium sp. TRTYP6 and Bacillus foraminis TRTYP17, each selectively leached about 50 % copper from 1 % (w/v) of fly ash. Mixed culture of these bacteria resulted in higher leaching of copper. The optimal combination was TRTYP3, TRTYP5, TRTYP6 and TRTYP17 in the ratio 1:1:3:1, which leached 88, 81, 78, 76, 70 and 55 % Cu from 1, 2.5, 5, 10, 15 and 20 % (w/v) of fly ash. While Cu and Pb were bioleached into solution, Fe and Zn were precipitated.

The reaction of Hg²⁺with sulfite is a major identified reduction pathway in the atmosphere. UV absorption spectroscopy was used to study the kinetics of Hg²⁺reduction by sulfite (Na₂SO₃) in the presence of fly ash. Upon the addition of Cumberland and Shawnee fly ash samples, the reduction rates were 0.0071 ± 0.0008 and 0.0009 ± 0.0006 s⁻¹, respectively. This represents c.a. 40 and 90 % decreases in the homogeneous rate, 0.013 ± 0.007 s⁻¹. The reduction reaction was also observed when Cumberland was added without Na₂SO₃. Sulfur elemental analyzer and high-resolution field emission scanning microscopy with energy dispersive X-ray spectroscopy (HR-FE-SEM-EDS) characterization confirmed that Cumberland fly ash particles were rich in sulfur. Nanoparticle Tracking Analysis (NTA) determined the mean particle size in solution to be 246 ± 25 nm for Cumberland fly ash and 198 ± 14 nm for Shawnee. To obtain further insight on observed Hg²⁺homogeneous reduction rates by sulfite, the effects of several environmental variables were investigated. Hg(NO₃)₂and HgO were used as the sources of Hg²⁺. Extended pH (1–7) and temperature (1.0–45.0 °C) ranges were studied for the first time. The enthalpies of activation for the HgO reduction were 94 ± 3 kJ mol⁻¹at pH 1 and 92 ± 4 kJ mol⁻¹at pH 3, while the entropies were 33 ± 9 J mol⁻¹ K⁻¹at pH 1 and 30 ± 10 J mol⁻¹ K⁻¹at pH 3. It was determined that increasing ionic strength, especially with nitrate species, slows down the reaction at pH = 7. Significance of the results on the variability of mercury reduction by sulfite at various environmental conditions, and its implication in modelling are discussed.

Fly ash, an industrial waste from thermal power plants, was used for the adsorptive removal of 1,4-benzoquinone, one of the oxidation intermediates generated in AOPs. Effect of fly ash dosage and solution pH was investigated. The highest 1,4-benzoquinone uptake occurred at pH 7.0. Neutral and alkaline conditions were more favourable for the adsorptive removal of 1,4-benzoquinone. Isotherm data at 288, 298 and 308 K were simulated by Langmuir, Freundlich, Temkin, Redlich-Peterson, Koble-Corrigan and Dubinin-Radushkevich isotherm models. Both the Koble-Corrigan and Dubinin-Radushkevich isotherms can predict equilibrium adsorption behaviour better at different reaction temperatures. The reaction enthalpy was 29.42 kJ/mol and the entropy achieved 164.52 J/mol·K. The change of Gibbs free energy achieved -19.48 kJ/mol at 298 K. The above indicates that the sorption process was spontaneous and endothermic. This also reveals that, fly ash has the potential for the adsorptive removal of 1,4-benzoquinone.

Potential changes in the mobility and bioavailability of risk and essential macro- and micro-elements achieved by adding various ameliorative materials were evaluated in a model pot experiment. Spring wheat (Triticum aestivum L.) was cultivated under controlled condition for 60 days in two soils, uncontaminated Chernozem and multi-element contaminated Fluvisol containing 4900 ± 200 mg/kg Zn, 35.4 ± 3.6 mg/kg Cd, and 3035 ± 26 mg/kg Pb. The treatments were all contained the same amount of sulfur and were as follows: (i) digestate from the anaerobic fermentation of biowaste, (ii) fly ash from wood chip combustion, and (iii) ammonium sulfate. Macro- and micro-nutrients Ca, Mg, K, Fe, Mn, Cu, P, and S, and risk elements Cd, Cr, Pb, and Zn were assayed in soil extracts with 0.11 mol/l solution of CH₃COOH and in roots, shoots, and grain of wheat after 30 and 60 days of cultivation. Both digestate and fly ash increased levels of macro- and micro-nutrients as well as risk elements (especially Cd and Zn; the mobility of Pb decreased after 30 days of cultivation). The changes in element mobility in ammonium sulfate-treated soils appear to be due to both changes in soil pH level and inter-element interactions. Ammonium sulfate tended to be the most effective measure for increasing nutrient uptake by plants in Chernozem but with opposite pattern in Fluvisol. Changes in plant yield and element uptake in treated plants may have been associated with the higher proline content of wheat shoots cultivated in both soils compared to control. None of the treatments decreased uptake of risk elements by wheat plants in the extremely contaminated Fluvisol, and their accumulation in wheat grains significantly exceeded maximum permissible levels; these treatments cannot be used to enable cereal and other crop production in such soils. However, the combination of increased plant growth alongside unchanged element content in plant biomass in pots treated with digestate and fly ash suggests that these treatments have a beneficial impact on yield and may be effective treatments in crops grown for phytoremediation.

The objectives of this study were to determine the concentrations of Pb, Cd, As, Cr, Cu, Co, Ni, Zn, Ba, Fe, Al and Ag in Erigeron canadensis L. growing on fly ash landfill of power plant “Kolubara”, Serbia. The content of each element was determined in every part of plant separately (root, stalk and inflorescence) and correlated with the content of elements in each phase of sequential extraction of fly ash. In order to ambiguously select the factors that are able to decidedly characterize the particular part of plant, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed. The bioconcentration factors and translocation factors for each metal were calculated in order to determine the feasibility of the use of plant E. canadensis L. for phytoremediation purpose. There were strong positive correlations between metals in every part of plant samples, and metals from pseudo total form of sequential extraction indicate that the bioavailability of elements in fly ash is similarly correlated with total form. Retained Al, Fe, Cr and Co in the root indicate its suitability for phytostabilization. This plant takes up Cd and Zn from the soil (bioconcentration factors (BCFs) greater than 1), transporting them through the stalk into the inflorescence (translocation factors (TFs) higher than 1). Regarding its dominance in vegetation cover and abundance, E. canadensis L. can be considered adequate for phytoextraction of Cd and Zn from coal ash landfills at Kolubara.