Natural volcanic tuff was used for the synthesis of geopolymer and then for the removal of Zn⁺². The characteristics of the natural volcanic tuff and the synthesized geopolymer were determined by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). Results referred that the synthesized geopolymer had a higher efficiency uptake of 97.7 % as against 78.5 % for the natural volcanic tuff. The uptake capacity of geopolymer for Zn⁺² adsorption increased with increasing temperature in the studied range of 25–45 °C, contact time up to 30 min, pH up to 7, and initial concentration up to 160 ppm, while it decreased with an increase in geopolymer dosage. The isotherm study showed best fit on Langmuir and Radlich-Peterson models. The maximum uptake capacity obtained from Langmuir model increased from 14.7 to 17.63 mg/g as the temperature increased from 25 to 45 °C. The pseudo-second-order model showed the best fitness for the experimental data followed by intraparticle diffusion model. The adsorption process can be characterized as endothermic, homogeneous, spontaneous, irreversible, physical, and a high adhesion of the ions to the geopolymer surface. The results obtained buttressed the feasibility and applicability of producing geopolymer from natural volcanic tuff for the removal of heavy metals.

This paper first time reports the geochemical processes that are controlling fluoride enrichment in the groundwater of western Kumamoto area, Japan. Fifty (50) groundwater samples were collected and analyzed for the study where fluoride (F⁻) concentration ranges from 0.1 to 1.57 mg/L. About 58 % of the shallow groundwater and 26 % of the deep groundwater samples contain fluoride concentration beyond the Japanese drinking water permissible limit (0.8 mg/L). High F⁻ is largely accumulated in the stagnant zone of the Kumamoto Plain area and associated with Na-HCO₃-type groundwater. High pH, high HCO₃, low Ca²⁺, and high Na⁺ are the major characteristics of high-F⁻ groundwater. Hydrolysis of F⁻-bearing minerals and desorption of F⁻ from hydrous metal oxides are considered to be the primary sources of fluoride in groundwater. A positive correlation between F⁻ and Na⁺/Ca²⁺ ratio (r ² = 0.53) indicates that major ion chemistry plays a significant role in fluoride mobilization. Weakly alkaline nature of groundwater with high pH (7.05–9.45) expedites the leaching process of exchangeable F⁻ from F⁻-bearing minerals as well as favors desorption of F⁻ from metal oxide surfaces. High HCO₃ ⁻ and high PO₄ ³⁻ in the groundwater facilitate desorption process as competing anions, while high Na⁺/Ca²⁺ ratio largely control this process by decreasing positive-charge density of the metal-oxide surfaces. High Na⁺/Ca²⁺ ratio is attributed due to the cation-exchange process, while high pH and HCO₃ ⁻ are the result of both silicate hydrolysis and microbial reduction processes. In addition, calcite and fluorite seem to have a control on groundwater fluoride geochemistry.

Biochar (BC) as a soil amendment has found considerable interest in global agriculture and food production. However, BC application to agricultural soils requires knowledge about side-effects on leachate composition potentially affecting deeper soil layers and groundwater. We investigated the effects of BC application on leachate water characteristics in a greenhouse pot experiment with two crops cultivated in series, mustard (Sinapis alba L., cv. Serval) and barley (Hordeum vulgare L., cv. Xanadu). The experiment was set up with three agricultural soils (Planosol, Cambisol, Chernozem), four different BC types, derived from three different feedstocks (wheat straw, woodchips, and vineyard pruning), added at two application rates of 1 % (w/w) and 3 % (w/w). Leachate sampling was performed five times from November 2010 to May 2011 by excess watering. The leachates were analyzed for their pH, electrical conductivity (EC), as well as their nitrate (NO₃ ⁻), dissolved phosphorus (PDISS), potassium (K⁺), and dissolved organic carbon (DOC) concentrations. The application of all BCs caused a significant pH increase in the leachates; EC increased most noticeably in the straw biochar treatment. All BC types significantly decreased leachate NO₃ ⁻ loads (by up to 80 % for woodchip-derived BC) compared to the control, while PDᵢₛₛ and K⁺ loads most significantly increased in the straw-derived BC treatment. The results show that BC may be suitable as soil amendment in soils prone to NO₃ ⁻ leaching; moreover, whereas straw-derived BC in particular may support soil nutrient status by introducing P and K.

Foundry sands from the iron foundry industry were employed as a support source for photocatalysts. TiCl₄ was used as the titanium precursor in the preparation of the supported photocatalysts. The solids were characterized by scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, diffuse reflectance spectroscopy in the ultraviolet range, small-angle X-ray scattering, nitrogen porosimetry, and zeta potential measurements. The prepared catalyst systems contained Ti, Al, Fe, K, Na, or Cu. All systems were also found to contain carbon. The systems were evaluated in the photodegradation of rhodamine B. For comparative reasons, P25 (Degussa) was also employed as a catalyst. Among the tested systems, the greatest percent dye degradation occurred with ultraviolet (65 %) and visible (38 %) radiation, whereas under the same conditions, the commercial P25 catalyst achieved 93 and 14 % degradation, respectively, for the ultraviolet and visible radiation.

The higher areal productivity and lipid content of microalgae and aquatic weed makes them the best alternative feedstocks for biodiesel production. Hence, an efficient and economic method of extracting lipid or oil from aquatic weed, Salvinia molesta is an important step towards biodiesel production. Since Salvinia molesta is an unexplored feedstock, its total lipid content was first measured as 16 % using Bligh and Dyer’s method which was quite sufficient for further investigation. For extracting more amount of lipid from Salvinia molesta, methanol: chloroform in the ratio 2:1 v/v was identified as the most suitable solvent system using Soxhlet apparatus. Based on the literature and the preliminary experimentations, parameters such as solvent to biomass ratio, temperature, and time were identified as significant for lipid extraction. These parameters were then optimized using response surface methodology with central composite design, where experiments were performed using twenty combinations of these extraction parameters with Minitab-17 software. A lipid yield of 92.4 % from Salvinia molesta was obtained with Soxhlet apparatus using methanol and chloroform (2:1 v/v) as solvent system, at the optimized conditions of temperature (85 °C), solvent to biomass ratio (20:1), and time (137 min), whereas a predicted lipid yield of 93.5 % with regression model. Fatty acid methyl ester (FAME) analysis of S. molesta lipid using gas chromatograph mass spectroscopy (GCMS) with flame ionization detector showed that fatty acids such as C16:0, C16:1, C18:1, and C18:2 contributed more than 9 % weight of total fatty acids. FAME consisted of 56.32, 28.08, and 15.59 % weight of monounsaturated, saturated, and polyunsaturated fatty acids, respectively. Higher cetane number and superior oxidation stability of S. molesta FAME could be attributed to its higher monounsaturated content and lower polyunsaturated content as compared to biodiesels produced from C. vulgaris, Sunflower, and Jatropha.

Indoor air pollution significantly influences personal exposure to air pollution and increases health risks. Nitrogen dioxide (NO₂) is one of the major air pollutants, and therefore it is important to properly determine indoor concentration of this pollutant considering the fact that people spend most of their time inside. The aim of this study was to assess indoor and outdoor concentration of NO₂ during each season; for this purpose, passive sampling was applied. We analyzed homes with gas and electric stoves to determine and compare the concentrations of NO₂ in kitchen, living room, and bedroom microenvironments (MEs). The accuracy of passive sampling was evaluated by comparing the sampling results with the data from air quality monitoring stations. The highest indoor concentration of NO₂ was observed in kitchen ME during the winter period, the median concentration being 28.4 μg m⁻³. Indoor NO₂ levels in homes with gas stoves were higher than outdoor levels during all seasons. The concentration of NO₂ was by 2.5 times higher in kitchen MEs with gas stoves than with electric stoves. This study showed that the concentration of NO₂ in indoor MEs mainly depended on the stove type used in the kitchen. Homes with gas stoves had significantly higher levels of NO₂ in all indoor MEs compared with homes where electric stoves were used.

An endophytic isolate identified as Diaporthe sp. was explored for its biosorption and biodegradation potential on triphenylmethane (TPM) dyes. Treatment with live cells demonstrated strong decolorization activities towards methyl violet (MV, 100 mg L⁻¹), crystal violet (CV, 100 mg L⁻¹), and malachite green (MG, 50 mg L⁻¹), with 84.87, 78.81, and 87.80 %, respectively. These values are far greater than decolorization by dead cells via biosorption (DE% of 18.82–48.32 %). The absence of peaks in the UV-vis spectra after 14 days further suggested degradation of dye chromophores. Results revealed that Diaporthe sp. removed TPM dyes through biodegradation and biosorption, with the former as a more desirable mechanism due to its ability to degrade most dye chromophore and enhance decolorization efficiency, and as a mechanism to tolerate toxic MG. As such, application of live cells of Diaporthe sp. is advantageous as it allows biodegradation to occur.

Dairy cows are responsible for significant emissions of enteric methane (CH₄) and produce nitrous oxide (N₂O) and ammonia (NH₃) gas from manure. As an abatement strategy, we explored the effects of long-term condensed tannin (Quebracho and chestnut extracts) addition to dairy cow diets. Previous studies have demonstrated that tannins in cow diets reduce methane and ammonia efflux, but none have done so over a >1-month time period. A modified stanchion barn equipped with gas analysis instrumentation measured CH₄, N₂O, and NH₃ fluxes into and from the barn, at the onset of the experiment, and 45 and 90 days after feeding groups of lactating dairy cows a control diet or two levels of tannin extract at 0.45 and 1.8 % of dietary dry matter. Few statistical differences among treatments were observed, likely a consequence of high variability and low sample size necessary for conducting a study of this duration. However, on a per-cow basis, low and high tannin diets lowered CH₄ emissions by 56 g cow⁻¹ day⁻¹ and by 48 g cow day⁻¹, respectively. Diet tannin additions lowered CH₄ (33 %), NH₃ (23 %), and N₂O (70 %) per unit milk corrected emissions in the high tannin treatment compared to the control at the end of the experiment, without significant loss in milk production. These results suggest that relatively low concentrations of diet tannin additions can reduce ruminant CH₄ and gaseous N emissions from manure. The tannin effect observed after 90 days is a starting point for considering tannin additions as a potential long-term strategy for improving the environmental footprint of milk production.

This study evaluated the resistance to wind erosion of a consolidated soil layer (CSL) using an indoor wind tunnel under simulated wind erosion conditions. The CSL consisted of the experimental soil (classified as a sandy soil), fly ash (FA) at two addition rates (10 and 20 % (w/w) soil), and polyacrylamide (PAM) at two addition rates (0.05 and 0.1 % (w/w) soil). Prior to the wind tunnel experiments, according to the different addition rates of FA and PAM, the sandy soil, FA, and PAM were homogeneously mixed by spraying an appropriate amount of deionized water to form different CSLs. The moisture content of the CSL was balanced to that of the sandy soil in the field. The threshold wind speeds and wind erosion amounts of different CSLs at two wind speeds of 8 and 14 m/s were measured, respectively. The results showed that the threshold wind speed of the sandy soil was significantly increased due to the formation of CSL by FA and PAM, exhibiting an increasing trend with increasing addition rate of FA and PAM. The wind erosion amounts of different CSLs were all decreased when compared with that of the sandy soil. The resistance to wind erosion of the CSL consisting of 10 % FA and 0.1 % PAM was strongest at a wind speed of 8 m/s, while only slight wind erosion occurred after 30-min exposure to the wind with a speed of 14 m/s.

Lignite (PK), bituminous (FI) and biomass (SE) fly ashes (FAs) were mineralogically and geochemically characterised, and their element leachability was studied with batch leaching tests. The potential for acid neutralisation (ANP) was quantified by their buffering capacity, reflecting their potential for neutralisation of acid mine drainage. Quartz was the common mineral in FAs detected by XRD with iron oxide, anhydrite, and magnesioferrite in PK, mullite and lime in FI, and calcite and anorthite in SE. All the FAs had high contents of major elements such as Fe, Si, Al and Ca. The Ca content in SE was six and eight times higher compared to PK and FI, respectively. Sulphur content in PK and SE was one magnitude higher than FI. Iron concentrations were higher in PK. The trace element concentrations varied between the FAs. SE had the highest ANP (corresponding to 275 kg CaCO₃ tonne⁻¹) which was 15 and 10 times higher than PK and FI, respectively. The concentrations of Ca²⁺, SO₄²⁻, Na⁺ and Cl⁻ in the leachates were much higher compared to other elements from all FA samples. Iron, Cu and Hg were not detected in any of the FA leachates because of their mild to strong alkaline nature with pH ranging from 9 to 13. Potassium leached in much higher quantity from SE than from the other ashes. Arsenic, Mn and Ni leached from PK only, while Co and Pb from SE only. The concentrations of Zn were higher in the leachates from SE. The FAs used in this study have strong potential for the neutralisation of AMD due to their alkaline nature. However, on the other hand, FAs must be further investigated, with scaled-up experiments before full-scale application, because they might leach pronounced concentrations of elements of concern with decreasing pH while neutralising AMD.