Effect of sorption and desorption-resistance on biodegradation of chlorobenzene in two wetland soils

Bioavailability of chlorobenzenes (CBs) in soils to microbial populations has implications for remediation of waste sites with long histories of contamination. Bioavailability of CB was assessed using mineralization assays for two types of wetland soils with contrasting properties. The rate and extent of CB mineralization were greater than predicted by mathematical models which assume instantaneous desorption followed by biodegradation. The freshly added CB was degraded with initial mineralization rates (IMRs) of 0.14microgL(-1)h(-1) and 1.92microgL(-1)h(-1) for marsh soil and wetland soil respectively. These values indicate that CB-degrading bacteria had an access to the sorbed CB. Mineralization assays were also performed for wetland soils after the CB was aged for 1, 7 and 31 days. The results revealed that even a desorption-resistant part of the sorbed CB was degraded although the degradation occurred at lower rates and to a lesser extent.     

Low-temperature thermal desorption of diesel polluted soil: influence of temperature and soil texture on contaminant removal kinetics

Five soil size aggregate fractions, corresponding to coarse (500-840 μm), medium (200-350 μm), fine (75-200 μm) sand, silt (10-75 μm) and clay (<4 μm), were artificially contaminated with diesel, and thermally treated using a laboratory scale apparatus to investigate the effect of soil texture on contaminant adsorption and removal. Ex situ thermal process was simulated using helium as the carrier gas at a flow rate of 1.5 L min(-1), different temperatures (100-300 °C) and different treatment times (5-30 min). The amount of contaminant adsorbed on the soil and the residual amount after thermal treatment was determined by gas chromatography. Results showed that adsorption phenomena and desorption efficiency were affected by the soil texture and that temperature and time of treatment were key factors in remedial process. A temperature of 175 °C is sufficient to remedy diesel polluted sandy and silty soils, whereas a higher temperature (250 °C) is needed for clays. Thermal desorption of diesel polluted soil was shown to be governed by first-order kinetics. Results are of practical interest and may be used in scaling-up and designing desorption systems for preliminary cost and optimal condition assessment.     

Electrokinetic movement of hexachlorobenzene in clayed soils enhanced by Tween 80 and beta-cyclodextrin

This study describes the comparative behavior of hexachlorobenzene (HCB) contaminated clayed soils in an electrokinetic (EK) system enhanced by Tween 80 and beta-cyclodextrin (beta-CD). The pH of the soils was controlled by Na2CO3/NaHCO3 buffer. Negligible HCB movement was observed when NaOH or Na2CO3/NaHCO3 buffer was used as anodic flushing solution. While Tween 80 or beta-CD was introduced to Na2CO3/NaHCO3 buffer, obvious HCB movement was achieved. Although beta-CD led to a less desorption of HCB from kaolin than Tween 80, the removal of HCB with beta-CD was much higher than that with Tween 80 in the EK system. Tween 80 could be sorped by kaolin more than beta-CD, which was responsible for the result. The mechanism of the movement of HCB was proposed as the enhanced desorption of HCB from soil, the dissolving of HCB in the soil pore fluid and the movement of HCB with the electroosmotic flow. Obvious movement of HCB was also observed in the EK treatment of real HCB-contaminated clayed soil enhanced by beta-CD. It is an alternative approach to use facilitating agents such as beta-CD to enhance the EK movement of HCB in the contaminated clayed soils.     

Degradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils by Fenton's reagent: a multivariate evaluation of the importance of soil characteristics and PAH properties

In this study, we investigated how the chemical degradability of polycyclic aromatic hydrocarbons (PAHs) in aged soil samples from various contaminated sites is influenced by soil characteristics and by PAH physico-chemical properties. The results were evaluated using the multivariate statistical tool, partial least squares projections to latent structures (PLS). The PAH-contaminated soil samples were characterised (by pH, conductivity, organic matter content, oxide content, particle size, specific surface area, and the time elapsed since the contamination events, i.e. age), and subjected to relatively mild, slurry-phase Fenton's reaction conditions. In general, low molecular weight PAHs were degraded to a greater extent than large, highly hydrophobic variants. Anthracene, benzo(a)pyrene, and pyrene were more susceptible to degradation than other, structurally similar, PAHs; an effect attributed to the known susceptibility of these compounds to reactions with hydroxyl radicals. The presence of organic matter and the specific surface area of the soil were clearly negatively correlated with the degradation of bi- and tri-cyclic PAHs, whereas the amount of degraded organic matter correlated positively with the degradation of PAHs with five or six fused rings. This was explained by enhanced availability of the larger PAHs, which were released from the organic matter as it degraded. Our study shows that sorption of PAHs is influenced by a combination of soil characteristics and physico-chemical properties of individual PAHs. Multivariate statistical tools have great potential for assessing the relative importance of these parameters.     

Pilot study of temporal variations in lead bioaccessibility and chemical fractionation in some Chinese soils

The effect of ageing, following the addition of approximately 400mgkg(-1) lead (Pb) as Pb(NO(3))(2), on Pb bioaccessibility was examined in five typical Chinese soils using a physiologically based extraction test. Sequential extraction was employed to identify the source fraction(s) of bioaccessible Pb in the soils. Pb bioaccessibility decreased exponentially to nearly steady levels in mildly acidic or alkali (pH 6.09-7.43) soils, for both gastric (69.91-71.75%) and small intestinal (7.53-9.63%) phases within the first 2-4 weeks and 1-2 months of incubation, respectively; however, it took only 1-2 weeks for strongly acidic ( approximately pH 4.5) soils to reach nearly steady levels of Pb bioaccessibility (73.01-74.46% and 10.30-10.98% in the gastric and small intestinal phases, respectively). In addition to the water-soluble and exchangeable fractions, the carbonate fraction of mildly acidic or alkali soils appeared to be a third main source of bioaccessible Pb in the small intestinal phase; however, bioaccessible Pb was likely to derive principally from Pb in the water-soluble and exchangeable fractions of strongly acidic soils. Bioaccessible Pb in the gastric phase appeared to derive from all the fractions in all five studied soils, even the residual fraction.     

Mathematical model of the non-steady-state adsorption and biodegradation capacities of BAC filters

This research was focused on developing a non-steady-state numerical model to differentiate the adsorption and biodegradation quantities of a biological activated carbon (BAC) column. The mechanisms considered in this model included adsorption, biodegradation, convection and diffusion. Simulations were performed to evaluate the effects of some parameters such as specific biodegradation rates and diffusivities on adsorption and biodegradation performances for the removal of dissolved organic matter from water. The results show that the developed model can predict the experimental data well. The biofilm developed around the BAC granules can hinder the mass transfer of the substrate onto the GAC surface, and the adsorption process will be restricted by the biofilm thickness. Although increasing the specific biodegradation rate can increase the performance of biodegradation, the adsorption efficiency will be decreased by lowering the boundary concentration in the interface of GAC. On the contrary, increasing the diffusivity can increase both the adsorption and biodegradation efficiencies simultaneously; so that the overall removal efficiency can be promoted through the improvement of mass transfer.     

Soil washing for metal removal: a review of physical/chemical technologies and field applications

Soil washing is one of the few permanent treatment alternatives to remove metal contaminants from soils. This paper reviews the various technology types and pilot/full-scale field applications of soil washing applicable to soils highly contaminated with heavy metals. The physical separation technologies, the chemical extraction processes and the integrated processes that combine both physical and chemical methods are discussed separately. This paper reviews basic principles, applicability, advantages and limitations, methods of predicting and improving performance of each physical/chemical technology. The discussion is based on a review of 30 recent laboratory investigations and 37 field applications of soil washing systems which have been undertaken, mostly in the US, for the period 1990-2007. This paper also examines and compares the status of soil washing technology for remediation of soils contaminated with metals in the US, in Canada and in Europe.     

Effect of grain refinement and crystallographic texture produced by friction stir processing on the biodegradation behavior of a Mg-Nd-Zn alloy

The application of a single pass of friction stir processing(FSP) to Mg-Nd-Zn alloy resulted in grain refinement, texture evolution and redistribution of second phases, which improved corrosion resistance.In this work, an as-rolled Mg-Nd-Zn alloy was subjected to FSP. The microstructure in the processed zone of the FS-400 rpm alloy exhibited refined grains, a more homogenous grain size distribution, less second phases, and stronger basal plane texture. The corrosion behavior assessed using immersion tests and electrochemical tests in Hank's solution indicated that the FS-400 rpm alloy had a lower corrosion rate, which was attributed to the increase of basal plane intensity and grain refinement. The hardness was lowered slightly and the elongation was increased, which might be attributed to the redistribution of the crushed second phases.     

Investigation of the effective parameters in the growth of carbon nanotubes by thermal chemical vapour deposition method

Synthesis and growth of carbon nanotubes (CNTs) from C₂H₂ by thermal chemical vapour deposition (TCVD) using a mixture of different gases were investigated. A thin film of nickel was coated as catalyst on silicon substrates by ion beam sputtering technique. Various parameters such as thickness of oxide layer and time, as well as reduction temperature were investigated in view of obtaining the best conditions for CNTs growth. C₂H₂ was very effective as carbon feedstock and NH₃ pretreatments were crucial steps towards obtaining a high density of nucleation sites for CNTs growth by inhibiting amorphous carbon generation in the initial stage of the synthesis. The substrate oxide layer was analysed by secondary ion mass spectrometry. The prepared CNTs were confirmed by Raman spectroscopy and were further characterised using scanning electron microscopy and transmission electron microscopy.     

Pilot plant experiences using physical and biological treatment steps for the remediation of groundwater from a former MGP site

The production of manufactured gas at a site in Vienna, Austria led to the contamination of soil and groundwater with various pollutants including PAHs, hydrocarbons, phenols, BTEX, and cyanide. The site needs to be remediated to alleviate potential impacts to the environment. The chosen remediation concept includes the excavation of the core contaminated site and the setup of a hydraulic barrier to protect the surrounding aquifer. The extracted groundwater will be treated on-site. To design the foreseen pump-and-treat system, a pilot-scale plant was built and operated for 6 months. The scope of the present study was to test the effectiveness of different process steps, which included an aerated sedimentation basin, a submerged fixed film reactor (SFFR), a multi-media filter, and an activated carbon filter. The hydraulic retention time (HRT) was 7.0 h during normal flow conditions and 3.5h during high flow conditions. The treatment system was effective in reducing the various organic and inorganic pollutants in the pumped groundwater. However, it was also demonstrated that appropriate pre-treatment was essential to overcome problems with clogging due to precipitation of tar and sulfur compounds. The reduction of the typical contaminants, PAHs and BTEX, was more than 99.8%. All water quality parameters after treatment were below the Austrian legal requirements for discharge into public water bodies.     

Application of a titania thin film for the discrimination between diesel fuel and heating oil

The aim of the paper is to show that chemiresistors based on the TiO₂ thin film can be used for the discrimination between diesel fuel, heating oil and their blends if coupled with a suitable measuring procedure and pattern recognition technique. The titania layer was prepared with sol-gel technique. A film response of the TiO₂ layer was measured at the temperatures of 275, 360 and 440 °C. The response of chemiresistors to fuel vapours depended on temperature of the sensitive material. The most apparent differences between oils appeared at the temperature of 360 °C. Principal Component Analysis qualitatively indicated the possibility of discrimination between oils at the sensing layer temperature of 360 °C. The actual discrimination was obtained with Linear Discriminant Analysis. It used first two principal components extracted from the measurement data collected at 360 °C as input variables. Our results indicate the possibility to develop a method of discrimination between diesel fuel and heating oil, based on measurements of electrical signals generated by the film in the presence of detected vapours.     

微乳化乙醇柴油热物性计算与分析

车用清洁型微乳化油是内燃机的理想代用燃料之一．微乳化油热物性参数难以计算,从而影响在内燃机上对它的定量计算研究．以微乳化乙醇柴油为例,用经验公式计算其蒸发焓、生成焓、液体比热容、导热率和微乳化油蒸气的扩散系数,分析了温度和压力以及不同溶醇量对热物性参数的影响规律,为微乳化油热物性参数的计算提供一种工程方法．结果表明：随着温度的增加,微乳化乙醇柴油蒸发焓、导热率降低,定压比热容和微乳化油蒸气扩散系数增加;随着压力增加,微乳化油蒸气扩散系数降低;随着混合燃料中乙醇含量的增加,定压比热容和混合气扩散系数均增大,蒸发焓减小;乙醇含量对混合燃料导热率的影响与燃料温度有关,在一定温度下乙醇含量效应发生逆转;微乳化乙醇柴油中乙醇含量增加有利于燃料蒸发．     

Continuous high-shear granulation: Mechanistic understanding of the influence of process parameters on critical quality attributes via elucidating the internal physical and chemical microstructure

Over the past decade, continuous wet granulation has been emerging as a promising technology in drug product development. In this paper, the continuous high-shear mixer granulator, Lӧdige CoriMix® CM5, was investigated using a low-dose formulation with acetaminophen as the model drug. Design of experiments was deployed in conjunction with multivariate data analysis to explore the granulator design space and comprehensively understand the interrelation between process parameters and critical attributes of granules and tablets. Moreover, several complementary imaging techniques were implemented to unveil the underlying mechanisms of physical and chemical microstructure in affecting the tablet performance. The results indicated that L/S ratio and impeller speed outweighed materials feeding rate in modifying the granule and tablet properties. Increasing the degree of liquid saturation and mechanical shear input in the granulation system principally produced granules of larger size, smaller porosity, improved flowability and enhanced sphericity, which after compression generated tablets with slower disintegration process and drug release kinetics due to highly consolidated physical microstructure. Besides, in comparison to batch mixing, continuous mixing integrated with a conical mill enabled better powder de-agglomeration effect, thus accelerating the drug dissolution with increased surface area.     

Effect of soil organic matter (SOM) and soil texture on the fatality of indigenous microorganisms in intergrated ozonation and biodegradation

In situ ozonation has been proposed as a method to remediate soils contaminated with organic pollutants. Soil column experiments were performed on eight different soils in order to investigate the effects of soil properties, such as soil organic matter (SOM) and soil texture on the survival and regrowth of indigenous microorganisms after in situ ozonation. Indigenous microorganisms were found to be very sensitive to ozone in the soil column experiments. The microbial fatality revealed a linear relationship with the SOM content in the range of 1.72–2.42% of SOM content, whereas water content was poorly correlated. Four weeks of incubation of ozone-treated soil samples allowed for the regrowth of indigenous microorganisms with inverse relation to ozonation time. The regrowth was also significantly influenced by the SOM content in the same soil texture. Oxidation and removal rate of hexadecane was affected by particle size distribution. Especially, sand exhibited the highest oxidation rate of hexadecane, which resulted from having the lowest SOM content, water content, and surface area with respect to the other samples. The soil samples ozonated for 90–180 min were determined to exhibit the lowest concentration of hexadecane, with the exception of sand, after 4 weeks of incubation. This study provided insight into the influence of SOM and soil texture on indigenous microbial potential to degrade hexadecane in integrated ozonation and biodegradation.     

Correlation between the electro-optical Kerr effect and physical parameters of nematogens

The relationship between the Kerr effect in an isotropic phase in the vicinity of phase transition temperature (T_NI) from isotropic to nematic phase and material parameters of the nematogens has been investigated. We could conclude that a strong correlation was confirmed between the Kerr constant in the vicinity of T_NI and the material parameters; the larger Kerr effect was observed in the prepared nematogen that also had larger product value of Δn × Δε × K₃₃/K₁₁, which can be useful knowledge for designing novel nematogens with high Kerr constant.     

The effects of carbon sources and micronutrients in whey and fermented whey on the kinetics of phenanthrene biodegradation in diesel contaminated soil

This paper demonstrates significant effects on phenanthrene degradation in diesel contaminated soil by the addition of organic amendments such as whey and fermented whey. Both amount of amendment added and mode of administration was shown to be decisive. There was a strong positive effect on the ¹⁴C-mineralization of phenanthrene by multiple (bi-weekly) additions of fermented whey 210 mg dw kg⁻¹ soil dw (FW multi) and also by single dose addition of 2100 mg dw sweet whey kg⁻¹ soil dw (SW high). The most prominent effects on phenanthrene degradation kinetics were a five to fifteen fold increase in the linear growth term (k₂) and a 23-27% increase in bioavailability factor S₀ for SW high and FW multi respectively. Also, total mineralization at the end of the experiment increased from 46% in the control to 66 and 71% respectively and the lag time was reduced from 21 to 15 days by multiple addition of fermented whey. The most significant stimulating effects on phenanthrene degradation kinetics could be attributed to lactate and vitamins. This study demonstrates a more complex dependence of carbon sources and growth factors for an aromatic compound such as phenanthrene in comparison to hexadecane.     

Analysis and optimization of process parameters affecting classification performances indices of the turbo air classifier

Classification performance indices of a turbo air classifier mainly include cut size, classification precision, and Newton's classification efficiency, which would be effected by the process parameters including air inlet velocity, rotor cage's rotary speed and feeding speed. Orthogonal experiment method was used to analyze the influence of process parameters on the classification performance indices according to quartz sand powder classification experimental data as well as the calcium carbonate classification experimental data. Through range analysis of the orthogonal experiments for quartz sand and calcium carbonate, it is found that air inlet velocity and rotor cage's rotary speed play an important role on classification performance indices including classification accuracy, cut size and its corresponding Newton's classification efficiency. Feeding speed has slight impact on these performance indices. The best optimized combination of the process parameters for quartz sand was: when air inlet velocity was 20 m · s^–1, rotor cage rotary speed was 900 min^–1 and feeding speed was 56.69 kg · h^–1, the high Newton's classification efficiency and classification accuracy could be obtained and the corresponding values were 73% and 0.66. This best optimized combination was among the 9 group orthogonal experiments for quartz sand. The best optimized combination of the process parameters for calcium carbonate was: air inlet velocity was 14 m · s^–1, rotor cage rotary speed was 1200 min^–1 and feeding speed was 120 kg · h^–1. However this best optimized combination wasn't among the 9 group orthogonal experiments for calcium carbonate. The evaluated value of the Newton's classification efficiency of cut size can be obtained, which was 73%. In order to verify this evaluated value, the classification experiment for calcium carbonate with this best optimized combination of process parameters was carried out and experimental value of Newton's classification efficiency was 75%, which was close to the evaluated value. Through orthogonal experiment analysis, the influence law of process parameters on classification performances indices of the turbo air classifier can be acquired and the optimized combination of process parameters can be obtained. It paves the way of the development of the turbo air classifier.     

Accumulation of polycyclic aromatic hydrocarbons and heavy metals in lettuce grown in the soils contaminated with long-term wastewater irrigation

Accumulation of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) by crop plants from contaminated soils may pose health risks. A greenhouse pot experiment using lettuce (Lactuca satuva L.) as a representative vegetable was conducted to assess the concentrations of PAHs and HMs in vegetables grown in wastewater-contaminated soils. The concentrations of total PAHs were ranged from 1.5 to 3.4 mg kg(-1) in the contaminated soils, while 1.2 mg kg(-1) in the reference soil. Linear regression analyses showed that the relationships between soil and shoot PAH concentrations were stronger for LMW-PAHs (R(2) between 0.51 and 0.92) than for HMW-PAHs (R(2) 0.02 and 0.60), suggesting that translocation for LMW-PAHs is faster than HMW-PAHs. Furthermore, the data imply that root uptake was the main pathway for HMW-PAHs accumulation. The plant shoots were also highly contaminated with HMs, particularly Cd (0.4-0.9 mg kg(-1)), Cr (3.4-4.1 mg kg(-1)), Ni (11.7-15.1 mg kg(-1)) and Pb (2.3-5.3 mg kg(-1)), and exceed the guidance limits set by State Environmental Protection Administration (SEPA), China and the World Health Organization (WHO). This study highlights the potential health risks associated with cultivation and consumption of leafy vegetables on wastewater-contaminated soils.     

A comparative study of the mechanical strength of chemical vapor-deposited diamond and physical vapor-deposited hard coatings

Four mechanical parameters of physical vapor-deposited (PVD) hard coatings were obtained, which were the residual strain, Young's modulus, film toughness, and interface toughness, concerning titanium aluminum nitride (TiAlN) and titanium nitride (TiN) coatings deposited on WC-Co substrates. The results were quantitatively compared with the author's previous trials for the case of chemical vapor-deposited (CVD) diamond coatings. Due to the significant difference in the mechanical properties between PVD hard coatings and CVD diamond coatings, it was necessary to develop new experimental techniques, which could properly evaluate those parameters for the case of PVD hard coatings. As a conclusion, film toughness of PVD hard coatings was surprisingly brittle. It was an order of magnitude smaller than that of CVD diamond coatings. In contrast, no significant difference was found in interface toughness between these different kinds of coatings. Concerning the residual strain, TiN had far larger level than the other two. These differences in mechanical properties were further discussed in relation to the difference in their wear behavior.