Removal of organic content from diesel exhaust particles alters cellular responses of primary human bronchial epithelial cells cultured at an air-liquid interface

Background Exposure to air pollutants, including diesel particulate matter, has been linked to adverse respiratory health effects. Inhaled diesel particulate matter contains adsorbed organic compounds. It is not clear whether the adsorbed organics or the residual components are more deleterious to airway cells. Using a physiologically relevant model, we investigated the role of diesel organic content on mediating cellular responses of primary human bronchial epithelial cells (HBECs) cultured at an air-liquid interface (ALI). Methods Primary HBECs were cultured and differentiated at ALI for at least 28 days. To determine which component is most harmful, we compared primary HBEC responses elicited by residual (with organics removed) diesel emissions (DE) to those elicited by neat (unmodified) DE for 30 and 60 minutes at ALI, with cigarette smoke condensate (CSC) as the positive control, and filtered air as negative control. Cell viability (WST-1 cell proliferation assay), inflammation (TNF-α, IL-6 and IL-8 ELISA) and changes in gene expression (qRT-PCR for HO-1, CYP1A1, TNF-α and IL-8 mRNA) were measured. Results Immunofluorescence and cytological staining confirmed the mucociliary phenotype of primary HBECs differentiated at ALI. Neat DE caused a comparable reduction in cell viability at 30 or 60 min exposures, whereas residual DE caused a greater reduction at 60 min. When corrected for cell viability, cytokine protein secretion for TNF-α, IL-6 and IL-8 were maximal with residual DE at 60 min. mRNA expression for HO-1, CYP1A1, TNF-α and IL-8 was not significantly different between exposures. Conclusion This study provides new insights into epithelial cell responses to diesel emissions using a physiologically relevant aerosol exposure model. Both the organic content and residual components of diesel emissions play an important role in determining bronchial epithelial cell response in vitro. Future studies should be directed at testing potentially useful interventions against the adverse health effects of air pollution exposure.

An extravariation model for improving confidence intervals of population size estimates from removal data

We propose a new model for estimating the size of a population from successive catches taken during a removal experiment. The data from these experiments often have excessive variation, known as overdispersion, as compared with that predicted by the multinomial model. The new model allows catchability to vary randomly among samplings, which accounts for overdispersion. When the catchability is assumed to have a beta distribution, the likelihood function, which is refered to as beta-multinomial, is derived, and hence the maximum likelihood estimates can be evaluated. Simulations show that in the presence of extravariation in the data, the confidence intervals have been substantially underestimated in previous models (Leslie-DeLury, Moran) and that the new model provides more reliable confidence intervals. The performance of these methods was also demonstrated using two real data sets: one with overdispersion, from smallmouth bass (Micropterus dolomieu), and the other without overdispersion, from rat (Rattus rattus).

Estimating equations for removal data analysis

We consider the problem of estimating a population size from successive catches taken during a removal experiment and propose two estimating functions approaches, the traditional quasi-likelihood (TQL) approach for dependent observations and the conditional quasi-likelihood (CQL) approach using the conditional mean and conditional variance of the catch given previous catches. Asymptotic covariance of the estimates and the relationship between the two methods are derived. Simulation results and application to the catch data from smallmouth bass show that the proposed estimating functions perform better than other existing methods, especially in the presence of overdispersion.

Estimating the efficiency of a small beam trawl for sampling tiger prawns Penaeus esculentus and P. semisulcatus in seagrass by removal experiments

The efficiency with which a small beam trawl (1 x 0.5 m mouth) sampled postlarvae and juveniles of tiger prawns Penaeus esculentus and P, semisulcatus at night was estimated in 3 tropical seagrass communities (dominated by Thalassia hemprichii, Syringodium isoetifolium and Enhalus acoroides, respectively) in the shallow waters of the Gulf of Carpentaria in northern Australia. An area of seagrass (40 x 3 m) was enclosed by a net and the beam trawl was repeatedly hand-hauled over the substrate. Net efficiency (q) was calculated using 4 methods: the unweighted Leslie, weighted Leslie, DeLury and Maximum-likelihood (ML) methods. The Maximum-likelihood is the preferred method for estimating efficiency because it makes the fewest assumptions and is not affected by zero catches. The major difference in net efficiencies was between postlarvae (mean ML q +/- 95% confidence limits = 0.66 +/- 0.16) and juveniles of both species (mean q for juveniles in water less than or equal to 1.0 m deep = 0.47 +/- 0.05), i.e. the beam trawl was more efficient at capturing postlarvae than juveniles. There was little difference in net efficiency for P, esculentus between seagrass types (T, hemprichii versus S. isoetifolium), even though the biomass and morphologies of seagrass in these communities differed greatly (biomasses were 54 and 204 g m(-2), respectively). The efficiency of the net appeared to be the same for juveniles of the 2 species in shallow water, but was lower for juvenile P, semisulcatus at high tide when the water was deeper (1.6 to 1.9 m) (0.35 +/- 0.08). The lower efficiency near the time of high tide is possibly because the prawns are more active at high than low tide, and can also escape above the net. Factors affecting net efficiency and alternative methods of estimating net efficiency are discussed.

Evaluation of residence time on nitrogen oxides removal in non-thermal plasma reactor

Non-thermal plasma (NTP) has been introduced over the last few years as a promising after- treatment system for nitrogen oxides and particulate matter removal from diesel exhaust. NTP technology has not been commercialised as yet, due to its high rate of energy consumption. Therefore, it is important to seek out new methods to improve NTP performance. Residence time is a crucial parameter in engine exhaust emissions treatment. In this paper, different electrode shapes are analysed and the corresponding residence time and NOx removal efficiency are studied. An axisymmetric laminar model is used for obtaining residence time distribution numerically using FLUENT software. If the mean residence time in a NTP plasma reactor increases, there will be a corresponding increase in the reaction time and consequently the pollutant removal efficiency increases. Three different screw thread electrodes and a rod electrode are examined. The results show the advantage of screw thread electrodes in comparison with the rod electrode. Furthermore, between the screw thread electrodes, the electrode with the thread width of 1 mm has the highest NOx removal due to higher residence time and a greater number of micro-discharges. The results show that the residence time of the screw thread electrode with a thread width of 1 mm is 21% more than for the rod electrode.

From spent Mg/Al layered double hydroxide to porous carbon materials

Adsorption has been considered as an efficient method for the treatment of dye effluents, but properdisposal of the spent adsorbents is still a challenge. This work attempts to provide a facile methodto reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II(OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washedwith acid to obtain porous carbon materials. Thermogravimetric analysis results suggested that thecarbonization could be well achieved above 600◦C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000 ◦C, respectively. Scanning electron microscope showed that the obtained carbon materials possessed a crooked flaky morphology. Nitrogen adsorption–desorption results showed that the carbon materials had large BET surface area and pore volume, e.g., 1426 m2/g and 1.67 cm3/g for the sample carbonized at 800 ◦C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon materials had high efficiency in toluene removal. This work provided a facile approach for synthesizing porous carbon materials using spent Mg/Al-LDH.

Dynamics of nitrate-nitrogen removal in experimental stormwater biofilters under intermittent wetting and drying

High concentrations of nitrate-nitrogen degrade the quality of aquatic environments. The primary mechanism by which nitrate-nitrogen is removed (denitrification) requires anoxic conditions and electron donors. While removal of total and ammonium-nitrogen is often high in stormwater biofilters, poor removal or even the release of nitrate-nitrogen in the outflow has often been observed. Five Perspex biofilter columns (94 mm internal diameter) were fabricated with a filter layer that contained 8% organic material. Columns were operated at 875  mm/h 875  mm/h and fed with simulated stormwater with different antecedent dry days (ADDs) and concentrations of nitrate-nitrogen. Samples were collected from the outflow at different time intervals between 2 and 150 min and were tested for nitrate-nitrogen. The removal of nitrate-nitrogen varied during an event from a high removal percentage (60–90%) in the initial outflow that gradually decreased in the first 30 min and settled at 0–15% removal thereafter. This remained consistent during all simulated events independent of the number of ADDs or inflow concentrations. ADDs and previous event feed concentrations affected the outflow nitrate-nitrogen concentration in the first 30 min of the current event. Therefore, from this study it is concluded that denitrification within stormwater biofilters occurs mainly during drying periods rather than wetting periods.

Environmental applications of inorganic-organic clays for recalcitrant organic pollutants removal: Bisphenol A

Bisphenol-A (BPA) adsorption onto inorganic-organic clays (IOCs) was investigated. For this purpose, IOCs synthesised using octadecyltrimethylammonium bromide (ODTMA, organic modifier) and hydroxy aluminium (Al13, inorganic modifier) were used. Three intercalation methods were employed with varying ODTMA concentration in the synthesis of IOCs. Molecular interactions of clay surfaces with ODTMA and Al13 and their arrangements within the interlayers were determined using Fourier transform infrared spectroscopy (FTIR). Surface area and porous structure of IOCs were determined by applying Brunauer, Emmett, and Teller (BET) method to N2 adsorption-desorption isotherms. Surface area decreased upon ODTMA intercalation while it increased with Al13 pillaring. As a result, BET specific surface area of IOCs was considerably higher than those of organoclays. Initial concentration of BPA, contact time and adsorbent dose significantly affected BPA adsorption into IOCs. Pseudo-second order kinetics model is the best fit for BPA adsorption into IOCs. Both Langmuir and Freundlich adsorption isotherms were applicable for BPA adsorption (R2 > 0.91) for IOCs. Langmuir maximum adsorption capacity for IOCs was as high as 109.89 mg g‒1 and it was closely related to the loaded ODTMA amount into the clay. Hydrophobic interactions between long alkyl chains of ODTMA and BPA are responsible for BPA adsorption into IOCs.

A dye-sensitized visible light photocatalyst-Bi24 O31 Cl10

The p-block semiconductors are regarded as a new family of visible-light photocatalysts because of their dispersive and anisotropic band structures as well as high chemical stability. The bismuth oxide halides belong to this family and have band structures and dispersion relations that can be engineered by modulating the stoichiometry of the halogen elements. Herein, we have developed a new visible-light photocatalyst Bi 24 O 31 Cl 10 by band engineering, which shows high dye-sensitized photocatalytic activity. Density functional theory calculations reveal that the p-block elements determine the nature of the dispersive electronic structures and narrow band gap in Bi 24 O 31 Cl 10. Bi 24 O 31 Cl 10 exhibits excellent visible-light photocatalytic activity towards the degradation of Rhodamine B, which is promoted by dye sensitization due to compatible energy levels and high electronic mobility. In addition, Bi 24 O 31 Cl 10 is also a suitable photoanode material for dye-sensitized solar cells and shows power conversion efficiency of 1.5%.

3D hierarchical rutile TiO2 and metal-free organic sensitizer producing dye-sensitized solar cells 8.6% conversion efficiency

Three-dimensional (3D) hierarchical nanoscale architectures comprised of building blocks, with specifically engineered morphologies, are expected to play important roles in the fabrication of 'next generation' microelectronic and optoelectronic devices due to their high surface-to-volume ratio as well as opto-electronic properties. Herein, a series of well-defined 3D hierarchical rutile TiO2 architectures (HRT) were successfully prepared using a facile hydrothermal method without any surfactant or template, simply by changing the concentration of hydrochloric acid used in the synthesis. The production of these materials provides, to the best of our knowledge, the first identified example of a ledgewise growth mechanism in a rutile TiO2 structure. Also for the first time, a Dye-sensitized Solar Cell (DSC) combining a HRT is reported in conjunction with a high-extinction-coefficient metal-free organic sensitizer (D149), achieving a conversion efficiency of 5.5%, which is superior to ones employing P25 (4.5%), comparable to state-of-the-art commercial transparent titania anatase paste (5.8%). Further to this, an overall conversion efficiency 8.6% was achieved when HRT was used as the light scattering layer, a considerable improvement over the commercial transparent/reflector titania anatase paste (7.6%), a significantly smaller gap in performance than has been seen previously.

Morphology-controllable 1D–3D nanostructured TiO2 bilayer photoanodes for dye-sensitized solar cells

Morphology-controlled bilayer TiO2 nanostructures consisting of one-dimensional (1D) nanowire bottom arrays and a three-dimensional (3D) dendritic microsphere top layer were synthesized via a one-step hydrothermal method. These novel 1D-3D bilayer photoanodes demonstrated the highest energy conversion efficiency of 7.2% for rutile TiO2 dye-sensitized solar cells to date, with TiCl4 post-treatment.

Structurally stabilized mesoporous TiO2 nanofibres for efficient dye-sensitized solar cells

One-dimensional (1D) TiO2 nanostructures are very desirable for providing fascinating properties and features, such as high electron mobility, quantum confinement effects, and high specific surface area. Herein, 1D mesoporous TiO2 nanofibres were prepared using the electrospinning method to verify their potential for use as the photoelectrode of dye-sensitized solar cells (DSSCs). The 1D mesoporous nanofibres, 300 nm in diameter and 10-20 μm in length, were aggregated from anatase nanoparticles 20-30 nm in size. The employment of these novel 1D mesoporous nanofibres significantly improved dye loading and light scattering of the DSSC photoanode, and resulted in conversion cell efficiency of 8.14%, corresponding to an ∼35% enhancement over the Degussa P25 reference photoanode.

Improved photovoltaic performance of dye-sensitized solar cells with modified self-assembling highly ordered mesoporous TiO 2 photoanodes

Strategies for improving the photovoltaic performance of dye-sensitized solar cells (DSSCs) are proposed by modifying highly transparent and highly ordered multilayer mesoporous TiO 2 photoanodes through nitrogen-doping and top-coating with a light-scattering layer. The mesoporous TiO 2 photoanodes were fabricated by an evaporation-induced self-assembly method. In regard to the modification methods, the light-scattering layer as a top-coating was proved to be superior to nitrogen-doping in enhancing not only the power conversion efficiency but also the fill factor of DSSCs. The optimized bifunctional photoanode consisted of a 30-layer mesoporous TiO 2 thin film (4.15 μm) and a Degussa P25 light-scattering top-layer (4 μm), which gives rise to a ∼200% higher cell efficiency than for unmodified cells and a fill factor of 0.72. These advantages are attributed to its higher dye adsorption, better light scattering, and faster photon-electron transport. Such a photoanode configuration provides an efficient way to enhance the energy conversion efficiency of DSSCs.

Continually adjustable oriented 1D TiO2 nanostructure arrays with controlled growth of morphology and their application in dye-sensitized solar cells

Oriented, single-crystalline, one-dimensional (1D) TiO2 nanostructures would be most desirable for providing fascinating properties and features, such as high electron mobility or quantum confinement effects, high specific surface area, and even high mechanical strength, but achieving these structures has been limited by the availability of synthetic techniques. In this study, a concept for precisely controlling the morphology of 1D TiO2 nanostructures by tuning the hydrolysis rate of titanium precursors is proposed. Based on this innovation, oriented 1D rutile TiO2 nanostructure arrays with continually adjustable morphologies, from nanorods (NRODs) to nanoribbons (NRIBs), and then nanowires (NWs), as well as the transient state morphologies, were successfully synthesized. The proposed method is a significant finding in terms of controlling the morphology of the 1D TiO2 nano-architectures, which leads to significant changes in their band structures. It is worth noting that the synthesized rutile NRIBs and NWs have a comparable bandgap and conduction band edge height to those of the anatase phase, which in turn enhances their photochemical activity. In photovoltaic performance tests, the photoanode constructed from the oriented NRIB arrays possesses not only a high surface area for sufficient dye loading and better light scattering in the visible light range than for the other morphologies, but also a wider bandgap and higher conduction band edge, with more than 200% improvement in power conversion efficiency in dye-sensitized solar cells (DSCs) compared with NROD morphology.