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• Key volatile pollutants in the gaseous emissions of MSW were assessed. • Ethanol, methyl mercaptan and H 2 S were key pollutants during airtight storage stage. • DMDS, 1,2-dichloroethane and trichloroethylene were key pollutants during ventilation. Gaseous emissions from municipal solid waste (MSW) have raised many concerns and complaints. Identifying the key volatile pollutants in the complex gaseous emissions from MSW is significant for the efficient mitigation of their odor nuisances and health risks. For this purpose, we present an integrated investigation of the key volatile pollutants in the gaseous emissions of MSW from the perspectives of emission patterns, odor concentrations and health risks. Air samples were collected during four different emission stages of the waste matrix for both chemical and olfactometric analyses. The total chemical concentrations of the volatile compounds in the air samples were in the range of 21.49 mg m−3 to 295.61 mg m−3, and the odor concentrations varied from 1122 ou E m−3 to 17,782 ou E m−3. The odor concentrations in the air samples were well correlated with the odor activity values (OAV s) of sulfur compounds, oxygenated compounds and ammonia (r = 0.922, 0.879 and 0.780, respectively, for n = 17 and p < 0.01). Moreover, from an integrated perspective involving chemical emissions, the proportions of odor concentrations and health risks, ethanol, methyl mercaptan and hydrogen sulfide were identified as the key volatile pollutants in the gaseous emissions from the waste matrix during the airtight storage stage, and dimethyl disulfide, 1,2-dichloroethane and trichloroethylene were the key volatile pollutants during the ventilation stage. [ABSTRACT FROM AUTHOR]

Abstract The three-layered structured AA7075-B 4 C systems functionally graded materials (FGMs) were successfully synthesized via plasma activated sintering (PAS). In the current study, the results indicated that the multi-level gradient structures, including the reinforcements, dislocations and precipitates, could be observed based on the microstructural characterization. This type of FGMs exhibited a significantly high bending strength of ~1291 MPa with AA7075 being loaded in tensile, which could be ascribed to the excellent bonding between different layers as well as the multi-level gradient structures. [ABSTRACT FROM AUTHOR]

Abstract Dry building material is a complex porous medium with a fractal structure. A developed fractional mass transfer model can accurately simulate anomalous diffusion in complex media, such as dry building material. In this work, a new time and space fractional diffusion model is first established to study the transport and emission behaviors of volatile organic compounds (VOCs) in a dry building material in an environmental chamber. In this model, the space fractional derivative is expressed by the weight coefficients of the upward and downward transfer probabilities, and the time fractional derivative and areal porosity of the material are introduced to describe anomalous diffusion. With the newly developed finite difference and parameter estimation methods, the present model can describe the early breakthrough and heavy-tailed phenomena well. Furthermore, the results of the present model show good agreement with the experimental data, as the error value (67.44 μg/m3) is much less than that of Deng and Kim's model (190 μg/m3). The advantages of long-term prediction are shown. Moreover, the effects of key parameters on VOC transport are revealed. Highlights • A mass transfer model is built with time and space fractional derivatives. • A modified fractional Fick's law is developed for VOC emissions. • Space fractional derivatives are expressed by different weight coefficients. • The boundary condition of convective mass transfer related porosity is developed. • A parameter estimation method is utilized to optimize the relevant parameters. [ABSTRACT FROM AUTHOR]

Abstract We reported an investigation of the influence of length scale on stabilization of boron carbide (B 4 C) during plasma activated sintering. In the current work, AA7075/B 4 C powders containing two types of B 4 C particles (Micro-B 4 C and Nano-B 4 C) were cryomilled for 8 h in liquid nitrogen, respectively. The characterization of as-cryomilled powders indicated that both Micro-B 4 C particles and Nano-B 4 C particles could distribute homogeneously in the matrix. AA7075/Nano-B 4 C powder have a finer particle size and grain size relative to that of the AA7075/Micro-B 4 C powder. The influence of length scale on stabilization of B 4 C particles during plasma activated sintering was investigated in details. The statistical grain diameter analysis from transmission electron microscopy observation revealed that the grain size of AA7075/Nano-B 4 C bulk (~77.4 nm) is finer relative to those of the AA7075 bulk (~193.5 nm) and AA7075/Micro-B 4 C bulk (~184.7 nm). The coupling effect of ex-situ Nano-B 4 C particles and in-situ dispersion particles contribute to the enhancement of the stabilization of the AA7075/Nano-B 4 C bulk. Graphical abstract Unlabelled Image Highlights • The grain refinement of the AA7075/B 4 C powders was conducted via cryomilling • Length scale on stabilization of B 4 C particles was investigated • The enhanced stabilization of AA7075/Nano-B 4 C was obtained [ABSTRACT FROM AUTHOR]

As a major group of plasticizers and flame-retardants, organophosphate esters (OPEs) have attracted particular attention due to their wide occurrence and potential impacts on human health and ecosystems. In the present study, the occurrence and distribution of 14 OPEs, including seven Alkyl-OPEs, three Cl-OPEs, and four Aryl-OPEs, were investigated in 65 road dust samples collected from November to December 2014 in Beijing, China. Cl-OPEs were the predominant compounds in the road dust samples, with the median concentration of 646 μg/kg, followed by the Alkyl-OPEs (median 135 μg/kg) and Aryl-OPEs (median 129 μg/kg). Tris(2-chloro-1-methylethyl) phosphate (TCPP) was the most abundant OPE with the median concentration of 384 μg/kg. In addition, OPEs levels showed significant difference (p < 0.05) in the spatial distribution. Markedly higher levels of OPEs were observed in 2nd and 3rd ring road with heavy traffic and high population density, indicating that the traffic and population were important factors for this distribution pattern. It was further supported by the analysis of OPEs in roadside soil and indoor dust in the vicinity of road dust sample sites. Finally, the average daily dose (ADD) for OPEs via inhalation, dermal absorption, and ingestion was calculated to evaluate the carcinogenic and non-carcinogenic risks to residents exposed to OPEs in the road dust. Risk assessment revealed that the risk originating from exposure to OPEs of road dust is currently low in Beijing, China. [ABSTRACT FROM AUTHOR]

Municipal solid waste (MSW) landfills are a source of odorous and toxic compounds. In this work, we present an integrated assessment of the odor concentration and human health risks of volatile compounds to evaluate the environmental quality at a MSW landfill. Air samples were collected seasonally from six areas of the landfill with different functions. The total concentrations of the compounds ranged from 204.0 to 7426.7 μg m −3 , and the concentrations in temporarily and permanently capped areas were 50.3 and 83.4% lower than those in the tipping area, respectively. The odor concentration was greatest at the leachate collection tank (1732–6254 ou E m −3 ) and tipping area (1573–4113 ou E m −3 ) and was mainly caused by hydrogen sulfide (57.9 and 49.1%, respectively). Moreover, the odor concentration was positively correlated with the temperature ( r  = 0.500, p  < 0.05, n  = 24). Although the non-carcinogenic (HI) and carcinogenic (R) risks of most compounds were largely below the acceptable levels (HI = 1, R = 1.0E-6), HI values of hydrogen sulfide (2.3), trichloropropane (2.0), and naphthalene (1.2) as well as R values of naphthalene (1.3E-4) and trimethylbenzene (1.2E-4) in the waste areas exceeded acceptable levels. Moreover, the cumulative HI (2.5–5.7) and R (1.0E-04 to 3.4E-04) in the waste areas should receive special attention since they were above acceptable levels during all of the seasons. Aromatic and halogenated compounds dominated the cumulative R, accounting for 79 and 21% of the total, on average, while for the cumulative HI, sulfur compounds contributed the most (67%). [ABSTRACT FROM AUTHOR]

In this study, the impacts of sucrose addition and the application of beet pulp as carbon source on nitrogen loss during sewage sludge composting were evaluated in a lab-scale reactor. Response surface methodology (RSM) was used to optimize the method of sucrose addition. The relationship between biodegradability (5 day biochemical oxygen demand (BOD 5 ) content) of sludge extraction solution and ammonia emission was investigated. With the nitrogen loss ratio as a dependent variable, the conditions (adding ratio of 0.02 (w (sucrose):w (sewage sludge)), adding time of 59.3 h and adding solid sucrose (without water) were chosen. The developed model was verified to have a high degree of accuracy. The BOD 5 content of sludge extraction was obviously increased to 62.3 mg/g volatile solid (VS) and 213.9 mg/gVS by adding sucrose and beet pulp. Ammonia emission could be further reduced by 56.7% through adding beet pulp. The results suggested that the high biodegradability of carbon source might be the main reason that beet pulp could efficiently reduce the nitrogen loss during composting. [ABSTRACT FROM AUTHOR]

Odorous gases emitted from landfills have always been a public concern, but studies evaluating the odour contribution and the correlation between the odour concentrations are limited. The objectives of this study were to assess the odour contribution and to correlate the measured odour concentration C OD with the calculated odour concentration SOAV , which was calculated as sum of individual odour activity value ( OAV ). Odorous air samples from a landfill in Beijing were collected seasonally and measured by both gas chromatography and an olfactometer. Different from previous studies, we measured the odour threshold of 51 detected compounds using a uniform methodology to minimize the imprecision of citing odour threshold from disparate literature. The odour threshold is used to convert the individual chemical concentration into the OAV , which is used as a surrogate of the odour concentration. Evaluation of the OAV revealed that hydrogen sulfide (65.9%), dimethyl sulfide (14.4%) and trimethylamine (8.6%) contributed the most to the odour at the landfill. Moreover, the correlation between the calculated odour concentration SOAV and the measured odour concentration C OD resulted in a linear regression equation of C OD = 6.28 SOAV ( r = 0.914, n = 24, p < 0.01). Based on the scaling factor K = 6.28, the average ratio of calculated odour concentration to measured odour concentration could be improved from less than 0.2 to 1.1. By the calibration of the calculated odour concentration SOAV , it is possible to use continuous measurements of chemical concentrations to derive odour concentration for this site for monitoring purposes. [ABSTRACT FROM AUTHOR]

In the present study a novel bilayer composite consisting of a tough layer (AA7075) and hard layer (AA7075/B 4 C composite), was successfully synthesized using plasma activated sintering. No obvious defects such as porosity, cracks, or delamination were observed in the as-processed bilayer composite. Transmission electron microscopy results suggest that dislocation density in the vicinity of B 4 C particles is higher relative to that of the unreinforced layer, as imaged with the [011] zone axis. The precipitation behavior is significantly different in the two layers, despite identical process conditions. Moreover, no obvious precipitates free zones were observed in the interfacial region between the two layers. To provide insight into the mechanical behavior of the bilayer composites, we measured the bending strength on two different load-bearing surfaces. Our results indicate that when the AA7075/B 4 C layer was loaded under tensile conditions, the AA7075/B 4 C composite was prone to crack formation and catastrophic failure. In contrast, when the AA7075 layer was loaded in tensile, the bilayer composite achieved a notable bending strength value of 1234 ± 72 MPa, which is higher relative to that of aforementioned case (938 ± 85 MPa). Interestingly, no interfacial cracks or delamination were observed under these testing conditions. In addition, the fracture mechanisms that are active in the bilayer composites for the load bearing conditions studied were discussed in detail. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) emitted from indoor building materials may cause indoor air pollution and adverse health effects to residents. However, limited information is available on the odor and health risks of VOCs and SVOCs emissions from polyvinyl chloride (PVC) materials, which are widely used for interior decoration. In this study, the concentration of VOCs and SVOCs emitted from PVC wallpaper and flooring were tested by the emission chamber method and micro-chamber method. Hazards of PVC building materials to people in terms of odor contribution and inhalation health risks were then illustrated. Results showed that 14 VOCs (including four alkanes, one aromatic, and nine oxygenated compounds) and 4 SVOCs (including methyl hexadecanoate, di(2-ethylhexyl) phthalate (DEHP), bis(2-ethylhexyl) adipate (DOA), and di-2-ethylhexyl terephthalate (DOTP)) were detected in the PVC wallpaper and flooring sample emissions. Triethyl phosphate (55.3%) was the main VOC emitted from PVC wallpaper materials, while cyclohexanone (22.4%), n-butyl acetate (21.6%), and 4-methyl-2-pentanone (12.7%) were major VOCs emitted from PVC flooring materials. DOA (1.76 mg/m3) and methyl hexadecanoate (13.0 mg/m3) were the SVOCs with the highest emission concentrations in PVC flooring and wallpaper, respectively. The dominant substances causing odor pollution from PVC wallpaper and flooring were methyl hexadecanoate and cyclohexanone, and cyclohexanone and n-butyl acetate, respectively. The health risk results indicated that the carcinogenic risks (R) of DEHP were below the acceptable level, and the non-carcinogenic effects (HQ) of 2-ethyl-1-hexanol and cyclohexanone were much greater than the acceptable level (HQ = 1) and should be given special attention. • VOCs and SVOCs emitted from commonly used PVC building materials were analyzed. • Concentrations were measured by emission chamber method and micro-chamber method. • Hazards in terms of odor pollution and inhalation health risk were illustrated. [ABSTRACT FROM AUTHOR]

Volatile pollutants emitted from building materials are an important source of indoor air pollution. The development of rapid determination methods for the chemical concentration and odor concentration of these volatile pollutants is of great importance. The present work investigated the difference in the concentration of pollutants emitted by various paint samples, from which key pollutants (methyl isobutyl ketone, ethylbenzene, and xylene) were screened based on their concentration and odor contribution. Then, an electronic nose (E-nose) device was developed to determine the chemical concentrations of key pollutants and the odor concentration of gas emitted by paint samples. A total of 135 gas samples emitted by the selected paint were measured by the developed E-nose, by gas chromatography–mass spectrometry and by olfactory testing. The obtained sensor response values and chemical and odor concentrations were divided randomly and used for training and testing of the E-nose pattern recognition algorithm. The trained pattern recognition algorithm was able to accurately output the target values, with average relative errors of 10.0%, 10.4%, 7.6%, and 10.0% (test set, n = 13) for the methyl isobutyl ketone, ethylbenzene, and xylene chemical concentrations and the odor concentration, respectively. In addition, the cross-sensitive nature of the E-nose showed a unique advantage in determining odor concentration compared to the odor conversion model. The excellent performance of the developed E-nose demonstrates that this work provides a practical solution for the rapid determination of the chemical concentration and odor concentration of pollutants emitted by building materials. [Display omitted] • Pollutants emitted by various paint samples were identified and quantified. • An electronic nose was developed and used for odor concentration determination. • The average relative error of E-nose determined odor concentration is about 10%. [ABSTRACT FROM AUTHOR]

We report on an investigation of the influence of reinforcement particle size on the microstructure and mechanical behavior of Al metal matrix composites. In our work, Al 7075/B 4 C composites containing three types of B 4 C particle sizes (56.9 µm, 4.2 µm and 2.0 µm) were synthesized and studied. For a constant value of volume fraction of B 4 C, the composite with coarse reinforcement particles exhibited a relatively homogeneous and discrete distribution of the B 4 C particles while the composites with fine reinforcement exhibited agglomeration of the B 4 C particles. The composite with the smallest B 4 C particles possessed the highest yield strength and fracture strength. Quantitative analysis of the strengthening mechanisms revealed that smaller B 4 C particles lead to larger values in strain gradient strengthening as well as CTE mismatch strengthening, which are significantly correlated to the geometrically necessary dislocations caused by the presence of B 4 C. In addition, the different spatial distributions of the B 4 C particles contributed to different fracture mechanisms in the composites. [ABSTRACT FROM AUTHOR]

Continuous odour measurements both of emissions as well as ambient concentrations are seldom realised, mainly because of their high costs. They are therefore often substituted by concentration measurements of odorous substances. Then a conversion of the chemical concentrations C (mg m −3 ) into odour concentrations C OD (ou E m −3 ) and odour intensities OI is necessary. Four methods to convert the concentrations of single substances to the odour concentrations and odour intensities of an odorous mixture are investigated: (1) direct use of measured concentrations, (2) the sum of the odour activity value SOAV , (3) the sum of the odour intensities SOI , and (4) the equivalent odour concentration EOC , as a new method. The methods are evaluated with olfactometric measurements of seven substances as well as their mixtures. The results indicate that the SOI and EOC conversion methods deliver reliable values. These methods use not only the odour threshold concentration but also the slope of the Weber–Fechner law to include the sensitivity of the odour perception of the individual substances. They fulfil the criteria of an objective conversion without the need of a further calibration by additional olfactometric measurements. [ABSTRACT FROM AUTHOR]

In this study, the impacts of reused and sucrose-decorated pumice as bulking agents on the composting of sewage sludge were evaluated in the lab-scale reactor. The variations of temperature, pH, NH 3 and CO 2 emission rate, moisture content (MC), volatile solid, dissolved organic carbon, C/N and the water absorption characteristics of pumice were detected during the 25 days composting. The MC of pumice achieved 65.23% of the 24 h water absorptivity within the first 2 h at the mass ratio of 0.6:1 (pumice:sewage sludge). Reused pumice increased 23.68% of CO 2 production and reduced 21.25% of NH 3 emission. The sucrose-decorated pumice reduced 43.37% of nitrogen loss. These results suggested that adding pumice and sucrose-decorated pumice in sludge composting matrix could not only adjust the MC of materials, but also improve the degradation of organic matters and reduce nitrogen loss. [ABSTRACT FROM AUTHOR]

Odor activity value (OAV) has been widely used for the assessment of odor pollution from various sources. However, little attention has been paid to the extreme OAV variation and potential inaccuracies of odor contribution assessment caused by odor interaction effects. The objective of this study is to assess the odor interaction effect for precise assessment of odor contribution. In this paper, samples were collected from a food waste disposal plant, and analyzed by instrumental and olfactory method to conclude odorants' occurrence and OAV. Then odor activity value coefficient (γ) was first proposed to evaluate the type and the level of binary interaction effects based on determination of OAV variation. By multiplying OAV and γ, odor activity factor (OAF) was used to reflect the real OAV. Correlation between the sum of OAF and odor concentration reached 80.0 ± 5.7%, which was 10 times higher than the sum of OAV used before. Results showed that hydrogen sulfide contributed most (annual average 66.4 ± 15.8%) to odor pollution in the waste disposal plant. However, as odor intensity of samples in summer rising, odor contribution of trimethylamine increased to 48.3 ± 3.7% by the strong synergistic interaction effect, while odor contribution of phenol decreased to 0.1 ± 0.02% for the increasing antagonistic interaction effect. [ABSTRACT FROM AUTHOR]

Highlights: [•] Al-7075/B4C composites were fabricated by plasma activated sintering. [•] The high mechanical properties of Al-7075/B4C composites were measured. [•] A strong interfacial bonding of Al-7075/B4C composites was investigated. [ABSTRACT FROM AUTHOR]