Recycling of iron and silicon from drinking water treatment sludge for synthesis of magnetic iron oxide@SiO<Subscript>2</Subscript> composites

More attention has been paid to the deterioration of water bodies polluted by drinking water treatment sludge (DWTS) in recent years. It is important to develop methods to effectively treat DWTS by avoiding secondary pollution. We report herein a novel investigation for recovery of Si and Fe from DWTS, which are used for the synthesis of two iron oxide@SiO₂ composites for adsorption of reactive red X-3B (RRX-3B) and NaNO₂. The results show that Fe³⁺ (acid-leaching) and Si⁴⁺ (basic-leaching) can be successfully recovered from roasted DWTS. Whether to dissolve Fe(OH)₃ precipitation is the key point for obtaining Fe₃O₄ or γ-Fe₂O₃ particles using the solvothermal method. The magnetic characteristics of Fe₃O₄@SiO₂ (390.0 m² g^?1) or Fe₂O₃@SiO₂ (220.9 m² g^?1) are slightly influenced by the coated porous SiO₂ layer. Peaks of Fe–O stretching vibration (580 cm^?1) and asymmetric Si–O–Si stretching vibrations (1080 cm^?1) of Fe₃O₄@SiO₂ indicate the successful coating of a thin silica layer (20–150 nm). The adsorption capacity of RRX-3B and NaNO₂ by Fe₃O₄@SiO₂ is better than that of Fe₂O₃@SiO₂, and both composites can be recycled through an external magnetic field. This method is an efficient and environmentally friendly method for recycling DWTS.     

Single and combined effects of aluminum (Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) and zinc (ZnO) oxide nanoparticles in a freshwater fish, <Emphasis Type="Italic">Carassius auratus</Emphasis>

The increasing use of nanoparticles (NPs) worldwide has raised some concerns about their impact on the environment. The aim of the study was to assess the toxicity of metal oxide nanoparticles, singly or combined, in a freshwater fish (Carassius auratus). The fish were exposed for 7, 14, and 21 days to different concentrations of NPs (10 μg Al₂O₃.L^?1, 10 μg ZnO.L^?1, 10 μg Al₂O₃.L^?1 plus 10 μg ZnO.L^?1, 100 μg Al₂O₃.L^?1, 100 μg ZnO.L^?1, and 100 μg Al₂O₃.L^?1 plus 100 μg ZnO.L^?1). At the end of each exposure period, antioxidant enzyme activity (catalase, glutathione-S-transferase, and superoxide dismutase), lipid peroxidation, and histopathology were assessed in the gills and livers of C. auratus. The results show an increase in catalase (CAT) and superoxide dismutase (SOD) activity in the gills and livers of fish, especially after 14 days of exposure to single and combined NPs, followed by a reduction at 21 days. An increase in glutathione S-transferase (GST) was observed in gills after 7 days for all tested NP concentrations (single and combined); while in livers, a significant increase was determined after 14 days of exposure to 100 μg.L^?1 of both single ZnO and Al₂O₃ NPs. Lipid peroxidation (LPO) significantly increased in gills after 7 days of exposure to 100 μg.L^?1 Al₂O₃ NPs (single or combined). In livers, LPO increased significantly after 7 days of exposure to all tested concentrations of both single ZnO and Al₂O₃ (except for 10 μg Al₂O₃.L^?1), and after 14 days of exposure to ZnO (10 and 100 μg.L^?1) and Al₂O₃ (100 μg.L^?1)_. The results from histological observations suggest that exposure to metal oxide NPs affected both livers and gills, presenting alterations such as gill hyperplasia and liver degeneration. However, the most pronounced effects were found in gills. In general, this study shows that the tested NPs, single or combined, are capable of causing sub-lethal effects on C. auratus, but when combined, NPs seem to be slightly more toxic than when added alone.     

Study on the removal of elemental mercury from simulated flue gas by Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-CeO<Subscript>2</Subscript>/AC at low temperature

Fe₂O₃ and CeO₂ modified activated coke (AC) synthesized by the equivalent-volume impregnation were employed to remove elemental mercury (Hg⁰) from simulated flue gas at a low temperature. Effects of the mass ratio of Fe₂O₃ and CeO₂, reaction temperature, and individual flue gas components including O₂, NO, SO₂, and H₂O (g) on Hg⁰ removal efficiency of impregnated AC were investigated. The samples were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with optimal mass percentage of 3 % Fe₂O₃ and 3 % CeO₂ on Fe3Ce3/AC, the Hg⁰ removal efficiency could reach an average of 88.29 % at 110 °C. Besides, it was observed that O₂ and NO exhibited a promotional effect on Hg⁰ removal, H₂O (g) exerted a suppressive effect, and SO₂ showed an insignificant inhibition without O₂ to some extent. The analysis of XPS indicated that the main species of mercury on used Fe3Ce3/AC was HgO, which implied that adsorption and catalytic oxidation were both included in Hg⁰ removal. Furthermore, the lattice oxygen, chemisorbed oxygen, and/or weakly bonded oxygen species made a contribution to Hg⁰ oxidation.     

Physiological characteristics of <Emphasis Type="Italic">Plantago major</Emphasis> under SO<Subscript>2</Subscript> exposure as affected by foliar iron spray

Sulfur dioxide (SO₂) is considered as a main air pollutant in industrialized areas that can damage vegetation. In the present study, we investigated how exposure to SO₂ and foliar application of iron (Fe) would affect certain physiological characteristics of Plantago major. The plant seedlings exposed or unexposed to SO₂ (3900 μg m^?3) were non-supplemented or supplemented with Fe (3 g L^?1) as foliar spray. Plants were exposed to SO₂ for 6 weeks in 100 × 70 × 70 cm chambers. Fumigation of plants with SO₂ was performed for 3 h daily for 3 days per week (alternate day). Lower leaf Fe concentration in the plants exposed to SO₂ at no added Fe treatment was accompanied with incidence of chlorosis symptoms and reduced chlorophyll concentration. No visible chlorotic symptoms were observed on the SO₂-exposed plants supplied with Fe that accumulated higher Fe in their leaves. Both at with and without added Fe treatments, catalase (CAT) and peroxidase (POD) activity was higher in the plants fumigated with SO₂ in comparison with those non-fumigated with SO₂. Foliar application of Fe was also effective in increasing activity of antioxidant enzymes CAT and POD. Exposure to SO₂ led to reduced cellulose but enhanced lignin content of plant leaf cell wall. The results obtained showed that foliar application of Fe was effective in reducing the effects of exposure to SO₂ on cell wall composition. In contrast to SO₂, application of Fe increased cellulose while decreased lignin content of the leaf cell wall. This might be due to reduced oxidative stress induced by SO₂ in plants supplied with Fe compared with those unsupplied with Fe.     

Effects of realistic concentrations of TiO<Subscript>2</Subscript> and ZnO nanoparticles in <Emphasis Type="Italic">Prochilodus lineatus</Emphasis> juvenile fish

The impact of nanoparticles on fish health is still a matter of debate, since nanotechnology is quite recent. In this study, freshwater benthonic juvenile fish Prochilodus lineatus were exposed through water to three concentrations of TiO₂ (0.1, 1, and 10 μg l^?1) and ZnO (7, 70, and 700 μg l^?1) nanoparticles, as well as to a mixture of both (TiO₂ 1 μg l^?1?+?ZnO 70 μg l^?1) for 5 and 30 days. Nanoparticle characterization revealed an increase of aggregate size in the function of concentration, but suspensions were generally stable. Fish mortality was high at subchronic exposure to 70 and 700 μg l^?1 of ZnO. Nanoparticle exposure led to decreased acetylcholinesterase activity either in the muscle or in the brain, depending on particle composition (muscle—TiO₂ 10 μg l^?1; brain—ZnO 7 and 700 μg l^?1), and protein oxidative damage increased in the brain (ZnO 70 μg l^?1) and gills (ZnO 70 μg l^?1 and mixture) but not in the liver. Exposed fish had more frequent alterations in the liver (necrosis, vascular congestion, leukocyte infiltration, and basophilic foci) and gills (hyperplasia and epithelial damages, e.g., epithelial disorganization and epithelial loss) than the control fish. Thus, predicted concentrations of TiO₂ and ZnO nanoparticles caused detectable effects on P. lineatus that may have important consequences to fish health. But, these effects are much more subtle than those usually reported in the scientific literature for high concentrations or doses of metal nanoparticles.     

Formation of indoor nitrous acid (HONO) by light-induced NO<Subscript>2</Subscript> heterogeneous reactions with white wall paint

Gaseous nitrogen dioxide (NO₂) represents an oxidant that is present in relatively high concentrations in various indoor settings. Remarkably increased NO₂ levels up to 1.5 ppm are associated with homes using gas stoves. The heterogeneous reactions of NO₂ with adsorbed water on surfaces lead to the generation of nitrous acid (HONO). Here, we present a HONO source induced by heterogeneous reactions of NO₂ with selected indoor paint surfaces in the presence of light (300 nm?<?λ?<?400 nm). We demonstrate that the formation of HONO is much more pronounced at elevated relative humidity. In the presence of light (5.5 W m^?2), an increase of HONO production rate of up to 8.6?·?10⁹ molecules cm^?2 s^?1 was observed at [NO₂]?=?60 ppb and 50 % relative humidity (RH). At higher light intensity of 10.6 (W m^?2), the HONO production rate increased to 2.1?·?10¹⁰ molecules cm^?2 s^?1. A high NO₂ to HONO conversion yield of up to 84 % was observed. This result strongly suggests that a light-driven process of indoor HONO production is operational. This work highlights the potential of paint surfaces to generate HONO within indoor environments by light-induced NO₂ heterogeneous reactions.     

The effects and the toxicity increases caused by bicarbonate,chloride, and other water components during the UV/TiO<Subscript>2</Subscript> degradation of oxazaphosphorine drugs

The influences of HCO₃ ^?, Cl^?, and other components on the UV/TiO₂ degradation of the antineoplastic agents ifosfamide (IFO) and cyclophosphamide (CP) were studied in this work. The results indicated that the presence of HCO₃ ^?, Cl^?, NO₃ ^?, and SO₄ ^2? in water bodies resulted in lower degradation efficiencies. The half-lives of IFO and CP were 1.2 and 1.1 min and increased 2.3–7.3 and 3.2–6.3 times, respectively, in the presence of the four anions (initial compound concentration = 100 μg/L, TiO₂ loading =100 mg/L, anion concentration = 1000 mg/L, and pH = 8). Although the presence of HCO₃ ^? in the UV/TiO₂/HCO₃ ^? system resulted in a lower degradation rate and less byproduct formation for IFO and CP, two newly identified byproducts, P11 (M.W. = 197) and P12 (M.W. = 101), were formed and detected, suggesting that additional pathways occurred during the reaction of ?CO₃ ^? in the system. The results also showed that ?CO₃ ^? likely induces a preferred ketonization pathway. Besides the inorganic anions HCO₃ ^?, Cl^?, NO₃ ^?, and SO₄ ^2?, the existence of dissolved organic matter in the water has a significant effect and inhibits CP degradation. Toxicity tests showed that higher toxicity occurred in the presence of HCO₃ ^? or Cl^? during UV/TiO₂ treatment and within 6 h of reaction time, implying that the effects of these two anions should not be ignored when photocatalytic treatment is applied to treat real wastewater.     

Effects of land use conversion and fertilization on CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O fluxes from typical hilly red soil

Land use conversion and fertilization have been widely reported to be important managements affecting the exchanges of greenhouse gases between soil and atmosphere. For comprehensive assessment of methane (CH₄) and nitrous oxide (N₂O) fluxes from hilly red soil induced by land use conversion and fertilization, a 14-month continuous field measurement was conducted on the newly converted citrus orchard plots with fertilization (OF) and without fertilization (ONF) and the conventional paddy plots with fertilization (PF) and without fertilization (PNF). Our results showed that land use conversion from paddy to orchard reduced the CH₄ fluxes at the expense of increasing the N₂O fluxes. Furthermore, fertilization significantly decreased the CH₄ fluxes from paddy soils in the second stage after conversion, but it failed to affect the CH₄ fluxes from orchard soils, whereas fertilizer applied to orchard and paddy increased soil N₂O emissions by 68 and 113.9 %, respectively. Thus, cumulative CH₄ emissions from the OF were 100 % lower, and N₂O emissions were 421 % higher than those from the PF. Although cumulative N₂O emissions were stimulated in the newly converted orchard, the strong reduction of CH₄ led to lower global warming potentials (GWPs) as compared to the paddy. Besides, fertilization in orchard increased GWPs but decreased GWPs of paddy soils. In addition, measurement of soil moisture, temperature, dissolved carbon contents (DOCs), and ammonia (NH₄ ⁺-N) and nitrate (NO₃ ^?-N) contents indicated a significant variation in soil properties and contributed to variations in soil CH₄ and N₂O fluxes. Results of this study suggest that land use conversion from paddy to orchard would benefit for reconciling greenhouse gas mitigation and citrus orchard cultivation would be a better agricultural system in the hilly red soils in terms of greenhouse gas emission. Moreover, selected fertilizer rate applied to paddy would lead to lower GWPs of CH₄ and N₂O. Nevertheless, more field measurements from newly converted orchard are highly needed to gain an insight into national and global accounting of CH₄ and N₂O emissions.     

Potassium-based sorbents from fly ash for high-temperature CO<Subscript>2</Subscript> capture

Potassium-fly ash (K-FA) sorbents were investigated for high-temperature CO₂ sorption. K-FAs were synthesised using coal fly ash as source of silica and aluminium. The synthesised materials were also mixed with Li₂CO₃ and Ca(OH)₂ to evaluate their effect on CO₂ capture. Temperature strongly affected the performance of the K-FA sorbents, resulting in a CO₂ uptake of 1.45 mmol CO₂/g sorbent for K-FA 1:1 at 700 °C. The CO₂ sorption was enhanced by the presence of Li₂CO₃ (10 wt%), with the K-FA 1:1 capturing 2.38 mmol CO₂/g sorbent at 700 °C in 5 min. This sorption was found to be similar to previously developed Li-Na-FA (2.54 mmol/g) and Li-FA (2.4 mmol/g) sorbents. The presence of 10 % Li₂CO₃ also accelerated sorption and desorption. The results suggest that the increased uptake of CO₂ and faster reaction rates in presence of K-FA can be ascribed to the formation of K-Li eutectic phase, which favours the diffusion of potassium and CO₂ in the material matrix. The cyclic experiments showed that the K-FA materials maintained stable CO₂ uptake and reaction rates over 10 cycles.     

Inactivation of <Emphasis Type="Italic">Escherichia coli</Emphasis> in fresh water with advanced oxidation processes based on the combination of O<Subscript>3</Subscript>, H<Subscript>2</Subscript>O<Subscript>2</Subscript>, and TiO<Subscript>2</Subscript>. Kinetic modeling

The purpose of this work was to study the efficiency of different treatments, based on the combination of O₃, H₂O₂, and TiO₂, on fresh surface water samples fortified with wild strains of Escherichia coli. Moreover, an exhaustive assessment of the influence of the different agents involved in the treatment has been carried out by kinetic modeling of E. coli inactivation results. The treatments studied were (i) ozonation (O₃), (ii) the peroxone system (O₃/0.04 mM H₂O₂), (iii) catalytic ozonation (O₃/1 g/L TiO₂), and (iv) a combined treatment of O₃/1 g/L TiO₂/0.04 mM H₂O₂. It was observed that the peroxone system achieved the highest levels of inactivation of E. coli, around 6.80 log after 10 min of contact time. Catalytic ozonation also obtained high levels of inactivation in a short period of time, reaching 6.22 log in 10 min. Both treatments, the peroxone system (O₃/H₂O₂) and catalytic ozonation (O₃/TiO₂), produced a higher inactivation rate of E. coli than ozonation (4.97 log after 10 min). While the combination of ozone with hydrogen peroxide or titanium dioxide thus produces an increase in the inactivation yield of E. coli regarding ozonation, the O₃/TiO₂/H₂O₂ combination did not enhance the inactivation results. The fitting of experimental values to the corresponding equations through non-linear regression techniques was carried out with Microsoft® Excel GInaFiT software. The inactivation results of E. coli did not respond to linear functions, and it was necessary to use mathematical models able to describe certain deviations in the bacterial inactivation processes. In this case, the inactivation results fit with mathematical models based on the hypothesis that the bacteria population is divided into two different subgroups with different degrees of resistance to treatments, for instance biphasic and biphasic with shoulder models.

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A system coupling hybrid biological method with UV/O<Subscript>3</Subscript> oxidation and membrane separation for treatment and reuse of industrial laundry wastewater

The possibilities of application of a three-step system combining hybrid biological treatment followed by advanced UV/O₃ oxidation with in situ generated O₃ and membrane separation (ultrafiltration (UF) and nanofiltration (NF)) to treat and reuse the wastewater from an industrial laundry are presented. By the application of a hybrid moving bed biofilm reactor (HMBBR), the total organic carbon concentration was reduced for about 90 %. However, since the HMBBR effluent still contained organic contaminants as well as high concentrations of inorganic ions and exhibited significant turbidity (8.2 NTU), its further treatment before a possible reuse in the laundry was necessary. The UV/O₃ pretreatment prior to UF was found to be an efficient method of the membrane fouling alleviation. During UF, the turbidity of wastewater was reduced below 0.3 NTU. To remove the inorganic salts, the UF permeate was further treated during NF. The NF permeate exhibited very low conductivity (27–75 μS/cm) and contained only small amounts of Ca²⁺ and Mg²⁺; thus ,it could be reused at any stage of the laundry process.     

Chemical characteristics and source apportionment of PM<Subscript>2.5</Subscript> using PCA/APCS,UNMIX, and PMF at an urban site of Delhi,India

The present study investigated the comprehensive chemical composition [organic carbon (OC), elemental carbon (EC), water-soluble inorganic ionic components (WSICs), and major & trace elements] of particulate matter (PM_2.5) and scrutinized their emission sources for urban region of Delhi. The 135 PM_2.5 samples were collected from January 2013 to December 2014 and analyzed for chemical constituents for source apportionment study. The average concentration of PM_2.5 was recorded as 121.9 ± 93.2 μg m^?3 (range 25.1–429.8 μg m^?3), whereas the total concentration of trace elements (Na, Ca, Mg, Al, S, Cl, K, Cr, Si, Ti, As, Br, Pb, Fe, Zn, and Mn) was accounted for ～17% of PM_2.5. Strong seasonal variation was observed in PM_2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon seasons. The chemical composition of the PM_2.5 was reconstructed using IMPROVE equation, which was observed to be in good agreement with the gravimetric mass. Source apportionment of PM_2.5 was carried out using the following three different receptor models: principal component analysis with absolute principal component scores (PCA/APCS), which identified five major sources; UNMIX which identified four major sources; and positive matrix factorization (PMF), which explored seven major sources. The applied models were able to identify the major sources contributing to the PM_2.5 and re-confirmed that secondary aerosols (SAs), soil/road dust (SD), vehicular emissions (VEs), biomass burning (BB), fossil fuel combustion (FFC), and industrial emission (IE) were dominant contributors to PM_2.5 in Delhi. The influences of local and regional sources were also explored using 5-day backward air mass trajectory analysis, cluster analysis, and potential source contribution function (PSCF). Cluster and PSCF results indicated that local as well as long-transported PM_2.5 from the north-west India and Pakistan were mostly pertinent.     

Nano-MnO<Subscript>2</Subscript>-mediated transformation of triclosan with humic molecules present: kinetics,products, and pathways

It has been shown that manganese dioxide (MnO₂) can mediate transformation of phenolic contaminants to form phenoxyl radical intermediates, and subsequently, these intermediates intercouple to form oligomers via covalent binding. However, the reaction kinetics and transformation mechanisms of phenolic contaminants with humic molecules present in nano-MnO₂-mediated systems were still unclear. In this study, it was proven that nano-MnO₂ were effective in transforming triclosan under acidic conditions (pH 3.5–5.0) during manganese reduction, and the apparent pseudo first-order kinetics rate constants (k?=?0.0599–1.5314 h^?1) increased as the pH decreased. In particular, the transformation of triclosan by nano-MnO₂ was enhanced in the presence of low-concentration humic acid (1–10 mg L^?1). The variation in the absorption of humic molecules at 275 nm supported possible covalent binding between humic molecules and triclosan in the nano-MnO₂-mediated systems. A total of four main intermediate products were identified by high-resolution mass spectrometry (HRMS), regardless of humic molecules present in the systems or not. These products correspond to a suite of radical intercoupling reactions (dimers and trimers), ether cleavage (2,4-dichlorophenol), and oxidation to quinone-like products, triggered by electron transfer from triclosan molecules to nano-MnO₂. A possible reaction pathway in humic acid solutions, including homo-coupling, decomposition, oxidation, and cross-coupling, was proposed. Our findings provide valuable information regarding the environmental fate and transformation mechanism of triclosan by nano-MnO₂ in complex water matrices.     

Synthesis of Fe-doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocatalyst and its sonophotocatalytic activity on synthetic dye and real textile wastewater

The catalysts such as Fe, Bi₂O₃, and Fe-doped Bi₂O₃ were synthesized for the sonophotocatalytic treatment of synthetic dye and real textile wastewater. The resultant catalysts were characterized for its size and uniform shape using x-ray diffractogram (XRD) and scanning electron microscopy (SEM) which signified the nanorod shape formed Bi₂O₃. The higher ultraviolet light absorbance capacity of the catalysts was also evident using diffuse reflectance spectroscopy (DRS). Initially, the effect of conventional parameters such as initial pH, gas bubbling (argon, oxygen, air and nitrogen) and oxidant addition (H₂O₂ and peroxymonosulfate) in the presence of sonolysis (22 and 37 kHz frequency) and photolysis (UV-C light) on 10 ppm Basic Brown 1 dye was studied. The results showed that highest decolorization of 62 % was attained for 3 g/L peroxymonosulfate under 37 kHz frequency sonolysis treatment. Secondly, with the catalyst study, highest of 46 % dye color removal was obtained with 4 g/L Fe under 37 kHz frequency sonolysis treatment. The sonophotocatalytic treatment of dye with Fe-doped Bi₂O₃ catalyst in combination with peroxymonosulfate showed highest color removal of 99 %. Finally, the sonophotocatalytic treatment of real textile wastewater in the presence of 3 g/L Fe-doped Bi₂O₃ and 6 g/L peroxymonosulfate reduced the total organic carbon (TOC) and chemical oxygen demand (COD) level to 77 and 91 %, respectively, in 180 min. The reported treatment process was found to treat the synthetic dye and real textile wastewater effectively.     

Biosorption and degradation of decabromodiphenyl ether by <Emphasis Type="Italic">Brevibacillus brevis</Emphasis> and the influence of decabromodiphenyl ether on cellular metabolic responses

There is global concern about the effects of decabromodiphenyl ether (BDE209) on environmental and public health. The molecular properties, biosorption, degradation, accumulation, and cellular metabolic effects of BDE209 were investigated in this study to identify the mechanisms involved in the aerobic biodegradation of BDE209. BDE209 is initially absorbed by wall teichoic acid and N-acetylglucosamine side chains in peptidoglycan, and then, BDE209 is transported and debrominated through three pathways, giving tri-, hepta-, octa-, and nona-bromodiphenyl ethers. The C–C bond energies decrease as the number of bromine atoms on the diphenyl decreases. Polybrominated diphenyl ethers (PBDEs) inhibit protein expression or accelerate protein degradation and increase membrane permeability and the release of Cl^?, Na⁺, NH₄ ⁺, arabinose, proteins, acetic acid, and oxalic acid. However, PBDEs increase the amounts of K⁺, Mg²⁺, PO₄ ^3?, SO₄ ^2?, and NO₃ ^? assimilated. The biosorption, degradation, accumulation, and removal efficiencies when Brevibacillus brevis (1 g L^?1) was exposed to BDE209 (0.5 mg L^?1) for 7 days were 7.4, 69.5, 16.3, and 94.6 %, respectively.     

Physiological and biochemical responses of <Emphasis Type="Italic">Machilus ichangensis</Emphasis> Rehd. et Wils and <Emphasis Type="Italic">Taxus chinensis</Emphasis> (Pilger) Rehd. to elevated O<Subscript>3</Subscript> in subtropical China

Considerable researches have documented the negative effects of ozone on woody species in North America and Europe; however, little is known about how woody tree species respond to elevated O₃ in subtropical China, and most of the previous studies were conducted using pot experiment. In the present study, Machilus ichangensis Rehd. et Wils (M. ichangensis) and Taxus chinensis (Pilger) Rehd. (T. chinensis), evergreen tree species in subtropical China, were exposed to non-filtered air (NF), 100 nmol mol^?1 O₃ (E1) and 150 nmol mol^?1 O₃ (E2), in open-top chambers under field conditions from 21st March to 2nd November 2015. In this study, O₃ fumigation significantly reduced net photosynthesis rate (Pn) in M. ichangensis in the three measurements and in T. chinensis in the last measurement. Also, non-stomatal factors should be primarily responsible for the decreased Pn. O₃ fumigation-induced increase in malondialdehyde, superoxide dismutase, and reduced ascorbic acid levels indicated that antioxidant defense mechanism had been stimulated to prevent O₃ stress and repair the oxidative damage. Yet, the increase of antioxidant ability was not enough to counteract the harm of O₃ fumigation. Because of the decrease in CO₂ assimilation, the growth of the two tree species was restrained ultimately. The sensitivity of the two tree species to O₃ can be determined: M. ichangensis > T. chinensis. It suggests a close link between the rising O₃ concentrations and the health risk of some tree species in subtropics in the near future.     

Antioxidant response of soybean seedlings to joint stress of lanthanum and acid rain

Excess of rare earth elements in soil can be a serious environmental stress on plants, in particular when acid rain coexists. To understand how such a stress affects plants, we studied antioxidant response of soybean leaves and roots exposed to lanthanum (0.06, 0.18, and 0.85 mmol L^?1) under acid rain conditions (pH 4.5 and 3.0). We found that low concentration of La³⁺ (0.06 mmol L^?1) did not affect the activity of antioxidant enzymes (catalase and peroxidase) whereas high concentration of La³⁺ (≥0.18 mmol L^?1) did. Compared to treatment with acid rain (pH 4.5 and pH 3.0) or La³⁺ alone, joint stress of La³⁺ and acid rain affected more severely the activity of catalase and peroxidase, and induced more H₂O₂ accumulation and lipid peroxidation. When treated with high level of La³⁺ (0.85 mmol L^?1) alone or with acid rain (pH 4.5 and 3.0), roots were more affected than leaves regarding the inhibition of antioxidant enzymes, physiological function, and growth. The severity of oxidative damage and inhibition of growth caused by the joint stress associated positively with La³⁺ concentration and soil acidity. These results will help us understand plant response to joint stress, recognize the adverse environmental impact of rare earth elements in acidic soil, and develop measures to eliminate damage caused by such joint stress.     

The styrene purification performance of biotrickling filter with toluene-styrene acclimatization under acidic conditions

The obvious disadvantages of biotrickling filters (BTFs) are the long start-up time and low removal efficiency (RE) when treating refractory hydrophobic volatile organic compounds (VOCs), which limits its industrial application. It is worthwhile to investigate how to reduce the start-up period of the BTF for treating hydrophobic VOCs. Here, we present the first study to evaluate the strategy of toluene induction combined with toluene-styrene synchronous acclimatization during start-up in a laboratory-scale BTF inoculated with activated sludge for styrene removal, as well as the effects of styrene inlet concentration (0.279 to 2.659 g·m^?3), empty bed residence time (EBRT) (i.e., 136, 90, 68, 45, 34 sec), humidity (7.7% to 88.9%), and pH (i.e., 4, 3, 2.5, 2) on the performance of the BTF system. The experiments were carried out under acidic conditions (pH 4.5) to make fungi dominant in the BTF. The start-up period for styrene in the BTF was shortened to about 28 days. A maximum elimination capacity (EC_max) of 126 g·m^?3·hr^?1 with an RE of 80% was attained when styrene inlet loading rate (ILR) was below 180 g·m^?3·hr^?1. The highest styrene RE(s) [of BTF] that could be achieved were 95% and 93.4%, respectively, for humidity of 7.7% and at pH 2. A single dominant fungal strain was isolated and identified as Candida palmioleophila strain MA-M11 based on the 26S ribosomal RNA gene. Overall, the styrene induction with the toluene-styrene synchronous acclimatization could markedly reduce the start-up period and enhance the RE of styrene. The BTF dominated by fungi exhibited good performance under low pH and humidity and great potential in treating styrene with higher inlet concentrations.

Implications: The application of the toluene induction combined with toluene-styrene synchronous acclimatization demonstrated to be a promising approach for the highly efficient removal of styrene. The toluene induction can accelerate biofilm formation, and the adaptability of microorganisms to styrene can be improved rapidly by the toluene-styrene synchronous acclimatization. The integrated application of two technologies can shorten the start-up period of biotrickling filters markedly and promote its industrial application.     

Hydrogen production using thermocatalytic decomposition of methane on Ni<Subscript>30</Subscript>/activated carbon and Ni<Subscript>30</Subscript>/carbon black

Hydrogen is an energy carrier of the future need. It could be produced from different sources and used for power generation or as a transport fuel which mainly in association with fuel cells. The primary challenge for hydrogen production is reducing the cost of production technologies to make the resulting hydrogen cost competitive with conventional fuels. Thermocatalytic decomposition (TCD) of methane is one of the most advantageous processes, which will meet the future demand, hence an attractive route for CO_x free environment. The present study deals with the production of hydrogen with 30 wt% of Ni impregnated in commercially available activated carbon and carbon black catalysts (samples coded as Ni₃₀/AC and Ni₃₀/CB, respectively). These combined catalysts were not attempted by previous studies. Pure form of hydrogen is produced at 850 °C and volume hourly space velocity (VHSV) of 1.62 L/h g on the activity of both the catalysts. The analysis (X-ray diffraction (XRD)) of the catalysts reveals moderately crystalline peaks of Ni, which might be responsible for the increase in catalytic life along with formation of carbon fibers. The activity of carbon black is sustainable for a longer time compared to that of activated carbon which has been confirmed by life time studies (850 °C and 54 sccm of methane).     

Short chain nitrocompounds as a treatment of layer hen manure and litter; effects on in vitro survivability of Salmonella,generic E. coli and nitrogen metabolism

The current study was conducted to assess the bactericidal effectiveness of several nitrocompounds against pathogens in layer hen manure and litter. Evidence from an initial study indicated that treatment of layer hen manure with 12 mM nitroethane decreased populations of generic E. coli and total coliforms by 0.7 and 2.2 log₁₀ colony forming units (CFU) g^?1, respectively, after 24 h aerobic incubation at ambient temperature when compared to untreated populations. Salmonella concentrations were unaffected by nitroethane in this study. In a follow-up experiment, treatment of 6-month-old layer hen litter (mixed with 0.4 mL water g^?1) with 44 mM 2-nitroethanol, 2-nitropropanol or ethyl nitroacetate decreased an inoculated Salmonella typhimurium strain from its initial concentration (3 log₁₀ CFU g^?1) by 0.7 to 1.7 log₁₀ CFU g^?1 after 6 h incubation at 37°C in covered containers. After 24 h incubation, populations of the inoculated S. Typhmiurium in litter treated with 44 mM 2-nitroethanol, 2-nitropropanol, ethyl nitroacetate or nitroethane were decreased more than 3.2 log₁₀ CFU g^?1 compared to populations in untreated control litter. Treatment of litter with 44 mM 2-nitroethanol, 2-nitropropanol, ethyl nitroacetate decreased rates of ammonia accumulation more than 70% compared to untreated controls (0.167 µmol mL^?1 h^?1) and loses of uric acid (< 1 µmol mL^?1) were observed only in litter treated with 44 mM 2-nitropropanol, indicating that some of these nitrocompounds may help prevent loss of nitrogen in treated litter. Results warrant further research to determine if these nitrocompounds can be developed into an environmentally sustainable and safe strategy to eliminate pathogens from poultry litter, while preserving its nitrogen content as a nutritionally valuable crude protein source for ruminants.