Composition analysis and health risk assessment of the hazardous compounds in cooking fumes emitted from heated soybean oils with different refining levels.

The cooking fumes generated from thermal cooking oils contains various of hazardous components and shows deleterious health effects. The edible oil refining is designed to improve the oil quality and safety. While, there remains unknown about the connections between the characteristics and health risks of the cooking fumes and oils with different refining levels. In this study, the hazardous compounds, including aldehydes, ketones, polycyclic aromatic hydrocarbons (PAHs), and particulate matter (PM) in the fumes emitted from heated soybean oils with different refining levels were characterized, and their health risks were assessed. Results demonstrated that the concentration range of aldehydes and ketones (from 328.06 ± 24.64 to 796.52 ± 29.67 µg/m3), PAHs (from 4.39 ± 0.19 to 7.86 ± 0.51 µg/m3), and PM (from 0.36 ± 0.14 to 5.08 ± 0.15 mg/m3) varied among soybean oil with different refining levels, respectively. The neutralized oil showed the highest concentration of aldehydes and ketones, whereas the refined oil showed the lowest. The highest concentration levels of PAHs and PM were observed in fumes emitted from crude oil. A highly significant (p < 0.001) positive correlation between the acid value of cooking oil and the concentrations of PM was found, suggesting that removing free fatty acids is critical for mitigating PM concentration in cooking fumes. Additionally, the incremental lifetime cancer risk (ILCR) values of PAHs and aldehydes were 5.60 × 10-4 to 8.66 × 10-5 and 5.60 × 10-4 to 8.66 × 10-5, respectively, which were substantially higher than the acceptable levels (1.0 × 10-6) established by US EPA. The present study quantifies the impact of edible oil refining on hazardous compound emissions and provides a theoretical basis for controlling the health risks of cooking fumes via precise edible oil processing.

Biological effects of inhaled crude oil vapor. III. Pulmonary inflammation, cytotoxicity, and gene expression profile.

OBJECTIVE: Workers may be exposed to vapors emitted from crude oil in upstream operations in the oil and gas industry. Although the toxicity of crude oil constituents has been studied, there are very few in vivo investigations designed to mimic crude oil vapor (COV) exposures that occur in these operations. The goal of the current investigation was to examine lung injury, inflammation, oxidant generation, and effects on the lung global gene expression profile following a whole-body acute or sub-chronic inhalation exposure to COV. MATERIALS AND METHODS: To conduct this investigation, rats were subjected to either a whole-body acute (6 hr) or a sub-chronic (28 d) inhalation exposure (6 hr/d × 4 d/wk × 4 wk) to COV (300 ppm; Macondo well surrogate oil). Control rats were exposed to filtered air. One and 28 d after acute exposure, and 1, 28, and 90 d following sub-chronic exposure, bronchoalveolar lavage was performed on the left lung to collect cells and fluid for analyses, the apical right lobe was preserved for histopathology, and the right cardiac and diaphragmatic lobes were processed for gene expression analyses. RESULTS: No exposure-related changes were identified in histopathology, cytotoxicity, or lavage cell profiles. Changes in lavage fluid cytokines indicative of inflammation, immune function, and endothelial function after sub-chronic exposure were limited and varied over time. Minimal gene expression changes were detected only at the 28 d post-exposure time interval in both the exposure groups. CONCLUSION: Taken together, the results from this exposure paradigm, including concentration, duration, and exposure chamber parameters, did not indicate significant and toxicologically relevant changes in markers of injury, oxidant generation, inflammation, and gene expression profile in the lung.

Safety assessment of charcoal usage and effects of common charcoal ignition aiders on combustion indices.

Charcoal is a popular form of biofuel embraced for domestic and industrial purposes. However, the use of Charcoal has some associated challenges, such as the required charcoal pot and setting it into the fire at first by using Charcoal-Ignition-Aiders (CIA) (e.g. discarded paper, nylon, rubber, plastics, petrol, the residue of processed palm oil, maise cob, wood, and kerosene). Coupled with the chemical properties of Charcoal, the resulting gases from CIA are capable of polluting the environment with perceived Adverse-Health-Implications (AHI) on the ecosystem. Therefore, this study conducted a safety assessment of charcoal biofuel usage and the effects of common CIA on combustion indices. This study followed standard methods and the use of peculiar equipment. This study established that Charcoal is commonly used in the studied area because it is cheap, readily available and requires less technical know-how. Considering the combustion indices, using paper as a CIA generated the lowest carbon monoxide (CO) value, 28.1 ppm, with 3,434.54 ppm volatile organic compound, VOC. Compared with the ACGIH standard permissible exposure level of ≤ 30 ppm, the paper gave a lesser CO value of 28.10 ppm among all the CIA. At the same time, all the CIA recorded higher VOC compared with EPA standard permissible exposure level of ≤ 15 ppm. ANOVA analysis conducted on the socio-demographic profile of the respondents, cooking attributes of the respondents, and use of charcoal pot types by the respondents in Zone 1, Zone 2, and Zone 3 gave p-values of 0.032, 0.028, and 0.039, respectively. These imply significant differences within the zones in each of the indices. The average energy content reported for charcoals sourced from oak trees, afara, obeche, mahogany, and iroko woods is 3,2149 kJ/kg compared to the lower ones. Therefore, this study recommended using these charcoals alongside discarded paper as CIA because they are a better combination to reduce AHI.

Insights to the 3D internal morphology and metal oxidation states of single atmospheric aerosol particles by synchrotron-based methodology.

The morphology and metal oxidation states of atmospheric aerosols are pertinent to their formation processes and ensuing interactions with surrounding gases, vapors and other environments upon deposition, such as human respiratory tract, soil and water. Although much progress has been made in recent years through single-particle techniques, considerably less is known with respect to the three-dimensional (3D) internal morphology of single atmospheric aerosol particles due to the limited penetration depth of electron microscopy. In this study, for the first time, a novel synchrotron-based transmission X-ray microscopy (TXM) methodology has been developed to visualize the 3D internal chemical mixing state and structure of single particles. The results show that the TXM is more applicable to the imaging of solid particles containing high-density elements, e.g., iron (Fe), aluminum (Al), silicone (Si), carbon (C) and sulfur (S), and/or solid particles of sizes larger than about 100 nm. In addition, the TXM is capable to reveal the fine 3D topographic features of single particles. The derived 3D internal and external information would be difficult to discern in the 2D images from electron microscopy. The TXM 3D images illustrate that aerosol particles exhibit complex internal mixing state and structure, e.g., homogeneously-, heterogeneously-mixed, multiple inclusions, fibrous, porous, and core-shell configuration. When coupled with the synchrotron-based X-ray fluorescence spectrometry (XRF) and absorption near-edge spectroscopy (XANES) of an X-ray nanoprobe in the energy range of 4-15 keV, the 3D morphology of single particles is further supplemented with the spatial distribution and oxidation sates of selected elements, including Fe, vanadium (V), manganese (Mn), chromium (Cr) and arsenic (As). The presented cross-platform, synchrotron-based methodology shows promise in complementing existing single-particle techniques and providing new insights to the heterogeneity of single-particle micro-physicochemical states relevant to the aerosol chemistry, optical properties, and their environmental and health impacts.

PM2.5 in Carlsbad Caverns National Park: Composition, sources, and visibility impacts.

Carlsbad Caverns National Park in southeastern New Mexico is adjacent to the Permian Basin, one of the most productive oil and gas regions in the country. The 2019 Carlsbad Caverns Air Quality Study (CarCavAQS) was designed to examine the influence of regional sources, including urban emissions, oil and gas development, wildfires, and soil dust on air quality in the park. Field measurements of aerosols, trace gases, and deposition were conducted from 25 July through 5 September 2019. Here, we focus on observations of fine particles and key trace gas precursors to understand the important contributing species and their sources and associated impacts on haze. Key gases measured included aerosol precursors, nitric acid and ammonia, and oil and gas tracer, methane. High-time resolution (6-min) PM2.5 mass ranged up to 31.8 µg m-3, with an average of 7.67 µg m-3. The main inorganic ion contributors were sulfate (avg 1.3 µg m-3), ammonium (0.30 µg m-3), calcium (Ca2+) (0.22 µg m-3), nitrate (0.16 µg m-3), and sodium (0.057 µg m-3). The WSOC concentration averaged 1.2 µg C m-3. Sharp spikes were observed in Ca2+, consistent with local dust generation and transport. Ion balance analysis and abundant nitric acid suggest PM2.5 nitrate often reflected reaction between nitric acid and sea salt, forming sodium nitrate, and between nitric acid and soil dust containing calcium carbonate, forming calcium nitrate. Sulfate and soil dust are the major contributors to modeled light extinction in the 24-hr average daily IMPROVE observations. Higher time resolution data revealed a maximum 1-hr extinction value of 90 Mm-1 (excluding coarse aerosol) and included periods of significant light extinction from BC as well as sulfate and soil dust. Residence time analysis indicated enrichment of sulfate, BC, and methane during periods of transport from the southeast, the direction of greatest abundance of oil and gas development.Implications: Rapid development of U.S. oil and gas resources raises concerns about potential impacts on air quality in National Parks. Measurements in Carlsbad Caverns National Park provide new insight into impacts of unconventional oil and gas development and other sources on visual air quality in the park. Major contributors to visibility impairment include sulfate, soil dust (often reacted with nitric acid), and black carbon. The worst periods of visibility and highest concentrations of many aerosol components were observed during transport from the southeast, a region of dense Permian Basin oil and gas development.

Systematic study on dynamic pyrolysis behaviors, products, and mechanisms of weathered petroleum-contaminated soil with Fe2O3.

Weathered petroleum-contaminated soil (WPCS) with a high proportion of heavy hydrocarbons is difficult to remediate. Our previous research demonstrated that Fe2O3-assisted pyrolysis was a cost-effective technology for the remediation of WPCS. However, the pyrolysis behaviors, products, and mechanisms of the WPCS with Fe2O3 are still unclear. In this study, a combination of Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) techniques were used to explore these pyrolysis characteristics. The thermal desorption/degradation of light and heavy hydrocarbons in the WPCS mainly occurred at 200-400 °C and 400-550 °C, respectively. The activation energy of thermal reaction of heavy hydrocarbons was decreased in the presence of Fe2O3 during the WPCS pyrolysis processes. In the process, the released inorganic gaseous products were mainly H2O and CO2, while the released organic gaseous compounds were primarily cycloalkanes, alkanes, acids/esters, alcohols, and aldehydes. Compared with the WPCS pyrolysis without Fe2O3, the yields of gaseous products released during the WPCS pyrolysis with Fe2O3 were reduced significantly, and some gaseous products were even not detected. This phenomenon was contributed by the following two reasons: 1) heavy hydrocarbons in the WPCS were more easily transformed into coke in the presence of Fe2O3 during pyrolysis; 2) some released gaseous products were reacted with Fe2O3 and fixed on the soil particles. Therefore, the WPCS pyrolysis with Fe2O3 can effectively reduce the burden of tail gas treatment. Criado method analysis results suggested that the reaction mechanism of heavy hydrocarbons during the WPCS pyrolysis with Fe2O3 was rendered as the synergic effects of diffusion, order-based, and random nucleation and growth reactions.

Preservation of vapor samples on adsorbent alumina capillaries and implications for field sampling.

Dynamic vapor microextraction (DVME) is a vapor preconcentration method that employs a capillary trap coated with an adsorbent, followed by solvent elution to recover the sample. DVME has been developed for applications in the laboratory, including highly precise vapor pressure measurements, and in the field. When vapor collection is conducted outside the laboratory, samples must almost always undergo some interval of storage representing the time between collection and analysis. This interval may be hours, days, or longer, depending on the situation. Regardless, in all situations there must be confidence that the integrity of the samples is maintained until processing and analysis. In this paper, we present results of two studies that tested the stability of a 50% weathered gasoline headspace sample on alumina PLOT (porous layer open tubular) capillaries stored at room temperature for periods from 24 h up to 20 wk. We used principal component analysis (PCA) to reduce the dimensionality of the chromatographic and mass spectral data and elucidate trends in stability with respect to the complex sample's range of hydrocarbon classes and molecular weights. Both analyses identified changes over storage periods of six weeks or more. The hydrocarbon class analysis, which used selected ion monitoring (SIM) data as input, proved more sensitive to changes over shorter storage periods. Sample integrity was preserved for at least 24 h, but losses, especially of high-volatility compounds, occurred by 168 h (7 d). Near total loss of sample occurred by 20 wk. These findings, which are specific to the sample, adsorbent, and storage conditions, will guide choices in experimental and instrumental design to ensure that data from future field studies is reliable.

Highly efficient electrochemical gas reduction on a three-dimensional foam electrode: mechanism and application for the determination of hazardous mercury in complex matrix.

For the first time a nickel foam electrode (NFE) is applied in the field of electrochemical vapor generation (EVG) to carry out the electrochemical vapor phase conversion of mercury. Systematical electrochemical and morphological research has demonstrated that the specific surface area of the NFE was several times larger than that of the metal/non-metal electrode with the same geometric size. At the same time, the 3D porous channel composed of multi-layer nickel wire ensures the full contact between reactant and interface. The evident enhancement of spectral signals on a Ni electrode (283%), compared with Pt (27%) and graphite (109%), confirmed that the NFE effectively enhances the yield of mercury reduction. The NFE exhibits low limit of detection (0.017 µg L-1) and a wide linear range (0.2-20 µg L-1) with recoveries of actual samples in the range 87.8-117% towards Hg2+. Although the NFE has no advantage in electronic transmission and catalytic performance, its excellent stability, especially anti-interference and other characteristics, is sufficient for the analysis of hazardous mercury in complex matrix including certified reference materials and real samples.

Gas ebullition from petroleum hydrocarbons in aquatic sediments: A review.

Gas ebullition in sediment results from biogenic gas production by mixtures of bacteria and archaea. It often occurs in organic-rich sediments that have been impacted by petroleum hydrocarbon (PHC) and other anthropogenic pollution. Ebullition occurs under a relatively narrow set of biological, chemical, and sediment geomechanical conditions. This process occurs in three phases: I) biogenic production of primarily methane and dissolved phase transport of the gases in the pore water to a bubble nucleation site, II) bubble growth and sediment fracture, and III) bubble rise to the surface. The rate of biogenic gas production in phase I and the resistance of the sediment to gas fracture in phase II play the most significant roles in ebullition kinetics. What is less understood is the role that substrate structure plays in the rate of methanogenesis that drives gas ebullition. It is well established that methanogens have a very restricted set of compounds that can serve as substrates, so any complex organic molecule must first be broken down to fermentable compounds. Given that most ebullition-active sediments are completely anaerobic, the well-known difficulty in degrading PHCs under anaerobic conditions suggests potential limitations on PHC-derived gas ebullition. To date, there are no studies that conclusively demonstrate that weathered PHCs can alone drive gas ebullition. This review consists of an overview of the factors affecting gas ebullition and the biochemistry of anaerobic PHC biodegradation and methanogenesis in sediment systems. We next compile results from the scholarly literature on PHCs serving as a source of methanogenesis. We combine these results to assess the potential for PHC-driven gas ebullition using energetics, kinetics, and sediment geomechanics analyses. The results suggest that short chain 

Inhibition of polychlorinated dibenzo-p-dioxins and dibenzofurans by phosphorus-containing compounds in model fly ash.

Waste incineration is a preferred method in China to dispose the municipal solid waste, but controlling the production of highly toxic polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans effectively during incineration is both challenging and imperative. In this study, the suppression of PCDD/Fs by various phosphorus-containing compounds was explored, and the mechanisms responsible for the inhibition were studied in detail. The experiments took place in a lab-scale vertical tubular reactor at 350 °C under a simulated flue gas (12 vol% O2 in N2 flow), and both the off-gases and residues were collected for PCDD/Fs analysis. The scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize the reaction residues. The experimental results revealed that NH4H2PO4 and (NH4)2·HPO4 showed the highest inhibitory effect (57.2% and 57.3%, respectively) on the PCDD/Fs formation, followed by CaHPO4 with inhibition efficiency of 39.1%. In contrast, KH2PO4 and K2HPO4 barely inhibited the generation of the PCDD/Fs. The inhibitory effect of NH4H2PO4 and (NH4)2·HPO4 was similar to that of nitrogen-based inhibitors. At the same time, it was proven that the inhibitory activity of CaHPO4 might be due to the reaction of it with Cu2+ forming stable compounds.

A lab-developed interface for liquid-gas chromatography coupling based on the use of a modified programmed-temperature-vaporizing injector.

The main focus of the present research was the on-line coupling of two separation techniques, namely liquid chromatography (LC) and gas chromatography (GC). For such an analytical combination, a dedicated interface is required to remove solvent from the sample, leaving the latter in a sharp band at the head of the GC column. Considering such an objective, a lab-developed LC-GC interface is herein presented, based on the use of a six-port two-position valve and a programmed-temperature-vaporizing (PTV) injector. The PTV injector was derived from a commercial split/splitless injector body, heated using a resistance heating wire, and enabled a satisfactory recovery of low boiling compounds (≤ C13), working in the normal-phase mode. The lab-developed PTV injector allowed the use of a larger-volume liner (compared to the commercial one initially used), it being characterized by dimensions 95 mm length × 5.0 mm O.D. × 3.4 mm I.D. and a volume of 862 µL, thus facilitating the transfer of larger LC fractions. The developed system is fully automatized and controlled without the use of additional software. The interface was evaluated and used for the analysis of mineral oil saturated hydrocarbons in vegetable oils. Detection was carried out by using a flame ionization detector (FID), with quantification performed through external calibration, across the 5-1000 mg kg-1 range. The LC-GC-FID method linearity, limits of detection and quantification, accuracy and precision were measured. The resulting limits of detection and quantification values were 0.4 and 1.3 mg kg-1, respectively. The average accuracy at the 100 mg kg-1 level was 95.5% (ranging between 93.3 and 99.7%). Intra-day repeatability at levels of 5 and 100 mg kg-1 were 2.4% and 3.5%, respectively.

Shift of microbial diversity and function in high-efficiency performance biotrickling filter for gaseous xylene treatment.

Xylene is the main component of many volatile industrial pollution sources, and the use of biotechnology to remove volatile organic compounds (VOCs) has become a growing trend. In this study, a biotrickling filter for gaseous xylene treatment was developed using activated sludge as raw material to study the biodegradation process of xylene. Reaction conditions were optimized, and long-term operation was performed. The optimal pH was 7.0, gas-liquid ratio was 15:1 (v/v), and temperature was 25 °C. High-throughput sequencing technique was carried out to analyze microbial communities in the top, middle, and bottom layers of the reactor. Characteristics of microbial diversity were elucidated, and microbial functions were predicted. The result showed that the removal efficiency (RE) was stable at 86%-91%, the maximum elimination capacity (EC) was 303.61 g·m-3·hr-1, residence time was 33.75 sec, and the initial inlet xylene concentration was 3000 mg·m-3, which was the highest known degradation concentration reported. Kinetic analysis of the xylene degradation indicated that it was a very high-efficiency-activity bioprocess. The rmax was 1059.8 g·m-3·hr-1, and Ks value was 4.78 g·m-3 in stationary phase. In addition, microbial community structures in the bottom and top layers were significantly different: Pseudomonas was the dominant genus in the bottom layer, whereas Sphingobium was dominant in the top layer. The results showed that intermediate metabolites of xylene could affect the distribution of community structure. Pseudomonas sp. can adapt to high concentration xylene-contaminated environments. Implications: We combined domesticated active sludge and reinforced microbial agent on biotrickling filter. This system performed continuously under a reduced residence time at 33.75 sec and high elimination capacity at 303.61 g·m-3·hr-1 in the biotrickling reactor for about 260 days. In this case, predomestication combined with reinforcing of microorganisms was very important to obtaining high-efficiency results. Analysis of microbial diversity and functional prediction indicated a gradient distribution along with the concentration of xylene. This implied a rational design of microbial reagent and optimizing the inoculation of different sites of reactor could reduce the preparation period of the technology.

Inclusion of fish waste silage in broiler diets affects gut microflora, cecal short-chain fatty acids, digestive enzyme activity, nutrient digestibility, and excreta gas emission.

A study was conducted to determine the impacts of dietary inclusion of fish waste silage (FWS) substituting soybean meal (SBM) on the performance, gut microflora, cecal short-chain fatty acid, apparent ileal digestibility (AID), digestive enzyme activity, and excreta noxious gas emission in broiler chickens. A total of 720-day-old male broilers (Cobb 500) were randomly allocated to 3 dietary treatments with 12 replicates each accommodating 20 birds for 42 d. Birds received diets as follows: a corn-SBM-based diet (CON) and 2 diets that replaced SBM with FWS at 60 g/kg (FWS60) and 120 g/kg (FWS120). During the entire period, replacing SBM with FWS60 and FWS120 increased body weight gain and decreased feed conversion ratio (P < 0.05). The lowest pH values in the crop, proventriculus, duodenum, ileum, and ceca were observed in birds fed diets containing FWS60 and FWS120 (P < 0.05). Likewise, birds fed FWS60 and FWS120 had lower numbers of coliform and E. coli and higher Bifidobacterium and Lactobacillus count in the ceca than those fed CON (P < 0.05). Feeding FWS60 and FWS120 diets increased cecal butyrate and lactic acid contents (P < 0.05). Birds fed FWS120 diets had greater intestinal amylase and protease activity than birds fed CON (P < 0.05); however, no significant differences were recorded between the treatment groups for digestive enzymes activity in the pancreas. The use of both levels of FWS in broiler diet increased AID of crude protein and ether extract (P < 0.05). The lowest excreta ammonia concentration was recorded in birds fed FWS120 diet (P < 0.05). In conclusion, the inclusion of FWS in broiler diets could improve the performance by enhancing gut function, derived from the improved digestive enzyme activity and nutrient digestibility, as well as by elevating the population of beneficial bacteria and short-chain fatty acid contents. Therefore, the biological silage can be considered as a promising option for recycling and recovery of fish wastes and effectively be used in broiler diets.

Effects of multi-enzyme on production performance, egg quality, nutrient digestibility, and excreta noxious gas emission of early phase Hy-line brown hens.

The purpose of this study was to investigate the effects of dietary supplementation of non-starch polysaccharide multi-enzyme (NME) in early laying phase of hens on production performance, egg quality, nutrient digestibility, and excreta noxious gas emission. In total, 432 Hy-line brown laying hens at 18 wk of age were used in a 10-wk feeding trail. Hens were randomly assigned to 1 of 3 treatments with 24 replication and 6 hens per replication (1 hen per cage). Dietary treatments were corn-soybean meal-DDGS-based diets supplemented with 0 (based diet, CON), 0.05% (NME1), and 0.1% (NME2) of NME. No significant (P > 0.05) response to increasing NME supplementation was observed for damaged egg rate shown throughout the experiment. Significant (P < 0.05) linear increase was observed for egg production at week 4, 6, and 8; moreover, egg production at week 8 also showed quadratic (P = 0.0344) increase. No significant effects were found on yolk color, eggshell strength, and eggshell thickness during the experiment (P > 0.05) with the increase in NME supplemental levels. Albumin height, haugh unit, and egg color values were linearly (P < 0.05) increased at week 2 and 6 following the increasing NME supplementation, respectively. Additionally, quadratic (P = 0.0013) effect was observed on egg weight at week 6 with the increasing level of NME. Moreover, apparent total tract digestibility of nitrogen and excreta ammonia emission was linearly (P < 0.05) affected increasing NME supplementation. In summary, inclusion of NME containing xylanase, ß-glucanase, galactosidase, and galactomannanase activities in corn-soybean meal-DDGS-based diets increased nitrogen digestibility, decreased excreta ammonia emission, and had no negative effects on production performance and egg quality parameters.

Characteristics and mechanism of toluene removal from gas by novelty array double dielectric barrier discharge combined with TiO2/Al2O3 catalyst.

A new reactor of array double dielectric barrier discharge (DDBD) combined with catalysis was prepared, and the effect of different factors on removal efficiency of toluene at pilot scale were investigated. The possible degradation mechanism was explored. The results indicate that the removal efficiency of toluene in the exhaust gas decreases with the increasing of the toluene initial concentration and the gas flow rate, but increases with the increasing of the specific energy density. When the air relative humidity is 55%, the removal efficiency of toluene is higher than that of the relative humidity by 85%. The results of XPS, FT-IR and GC-MS analysis show that the main intermediate products of removing toluene by DDBD combined with TiO2/Al2O3 catalyst are phenol, benzaldehyde, benzyl alcohol, benzoic acid, N-benzyl formamide, dimethyl terephthalate, dimethyl isophthalate and other substances. There are five possible pathways to degrade toluene by DDBD combined with TiO2/Al2O3.

Long-term effects of grass roots on gas permeability in unsaturated simulated landfill covers.

Landfill cover is a barrier that can reduce landfill gas emission. Vegetation could affect soil hydraulic properties of landfill cover, while its effects on gas permeability is not well understood. This paper investigated the effects of plant roots on the evolution of gas permeability (kg) in unsaturated landfill cover over a two-year period. One grass species (Cynodon dactylon) was selected for testing in the laboratory and there were six replications. Bare soil was used as a reference. kg was determined after 6, 15 and 24 months of grass growth. The test results show that with the increase of suction, kg increased linearly in log scale for both bare and grass-covered soils. kg of grass-covered can be lower or higher than that of bare soil, depending on the plant age. After 6 months, kg of grass-covered soil was smaller than that of bare soil by 85%, due to the root occupancy of soil pore space. However, after 15 and 24 months, kg of grass-covered soil increased by 2-3 orders of magnitude within the root zone over the suction range considered (2-86 kPa). After 2 years, kg of grass-covered soil was up to one order of magnitude higher than that in bare soil. It implies that mature vegetation is not beneficial for reducing gas emission in final landfill covers.

Investigation of a rapid infrared heating assisted mineralization of soybean matrices for trace element analysis.

A fast sample preparation procedure based on use of infrared (IR) assisted heating for mineralization of soybean derived samples has been developed for their subsequent multielement analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) and flame atomic absorption spectrometry (FAAS). A cold finger was examined for refluxing of acid vapors to determine its impact on efficiency and economy of digestion. The optimized procedure, based on 1 g subsamples, 8 mL of HNO3 (65% w/w) and exposure of the mixture to a 500 W IR source for 5 min without refluxing, permitted accurate determination of all analytes in NIST SRM 1568b (rice flour). Detection limits using ICP-OES were (µg/kg) 97, 1.0, 39, 185, 0.47 and 1200 for Ca, Cu, Fe, K, Mn and P, respectively, and 18 for Zn by FAAS. The IR-assisted digestion approach provided a low cost, easy to use system having great potential for implementation in routine analysis of trace elements in soybean and similar matrices.

A slow release brown coal-urea fertiliser reduced gaseous N loss from soil and increased silver beet yield and N uptake.

Increasing crop yield and fertiliser nitrogen (N)-use efficiency is important for productive agricultural systems with a reduced environmental footprint. The aim of this study was to assess the effect of slow release brown coal-urea (BCU) fertiliser on the gaseous N losses, biomass yield and N uptake by silver beet (Beta vulgaris L.) compared to commercial urea. Two soils were amended with urea, BCU 1 (22% N) or BCU 2 (17% N) as N-fertiliser at the rate of 50 or 100 kg N ha-1. Five gas sampling periods were undertaken to measure the loss of N as N2O and NH3. After 10 weeks, biomass, N concentration, and N uptake of silver beet, and mineral and mineralisable N of post-harvest soil were measured. BCU substantially increased fertiliser N availability and uptake by silver beet, reduced N2O emission by 29% and NH3 emission by 36% compared to urea alone, irrespective of soil type. Compared to urea, BCU blends increased biomass yield by 27% and 23% in a Tenosol and Dermosol soil, respectively. In addition, application of BCU fertiliser substantially enhanced the potentially mineralisable N and organic carbon content of soil. These results provide evidence that granulation of urea with brown coal (BC) can increase silver beet N-use efficiency and yield in different soil types, and more work is now required to validate this technology for other crops.

Red Phosphorus: An Elementary Semiconductor for Room-Temperature NO2 Gas Sensing.

Black and blue phosphorus (both allotropes of elementary phosphorus) have recently been widely explored as an active material for electronic devices, and their potential in gas sensing applications has been demonstrated. On the other hand, amorphous red phosphorus (a-RP), a much cheaper and readily available phosphorus allotrope, has seldom been investigated as an electronic material, and its gas sensing properties have never been studied. In this work we have investigated these properties of a-RP by combining experimental characterizations with theoretical calculations. We found that a-RP exhibited an amphoteric character for detecting both commonly regarded reducing and oxidizing gas molecules, featuring a negative correlation between the electrical resistance of a-RP and the gas concentration. Interestingly, the a-RP based sensors appear to be particularly suitable for room-temperature NO2 detection, exhibiting excellent sensitivity and selectivity, as well as fast temporal response and recovery. A unique sensing feature of a-RP toward NO2 was identified, which is associated with the expansion of P-P bonds upon NO2 chemisorption. Based on density functional theory calculations we proposed a physiochemical model to elaborate the synergistic effects of the P-P bond expansion and Langmuir isotherm adsorption on the electronic properties and gas sensing processes of a-RP.

Thermoelectric Array Sensors with Selective Combustion Catalysts for Breath Gas Monitoring.

Inflammable breath gases such as H2 and CH4 are used as bio markers for monitoring the condition of the colon. However, their typical concentrations of below 100 ppm pose sensitivity and selectivity challenges to current gas sensing systems without the use of chromatography. We fabricated a compact, gas-selective thermoelectric array sensor (TAS) that uses micro-machined sensor devices with three different combustion catalysts to detect gases such as H2, CO, and CH4 in breath. Using Pt/Pt-W thin-film micro-heater meanders, Pd/Al2O3, Pt,Pd,Au/Co3O4, and Pt/Al2O3 catalysts were heated to 320, 200, and 125 °C, respectively, and the gas sensing performances of the TAS for each gas and for a model breath gas mixture of 100 ppm H2, 25 ppm CO, 50 ppm CH4, and 199 ppm CO2 in air were investigated. Owing to its high catalyst temperature, the Pd/Al2O3 catalyst burned all three gases, while the Pt,Pd,Au/Co3O4 burned CO and H2 and the Pt/Al2O3 burned H2 selectively. To calibrate the gas concentration of the mixture gas without the use of a gas separation tool, linear discriminant analysis was applied to measure the sensing performance of TAS. To enhance the gas selectivity against H2, a double catalyst structure was integrated into the TAS sensor.