Search Results (23)

With the rapid development of urbanization, municipal waste incineration (MWI) has become the primary method of waste disposal in urban areas, leading to growing concerns about volatile organic compounds (VOC) emissions. This study conducted full-process VOC field sampling at a representative MWI plant in China to investigate the emission characteristics and removal efficiencies of air pollution control devices (APCDs). A total of 59 VOC species were identified in the flue gas, including 5 alkanes/alkenes, 14 aromatics, 8 oxygenated-VOCs, and 32 halogenated hydrocarbons. The activated carbon injection combined with fabric filters and wet desulfurization tower demonstrated varying removal efficiencies across VOC groups, with synergistic removal efficiencies being ranked as follows: alkanes/alkenes (90.9%) > aromatics (87.0%) > halogenated hydrocarbons (61.3%) > O-VOCs (42.2%). The total VOC removal efficiency reached 77.5%. The VOCs emission factor of the MWI plant was calculated as (1.9 ± 0.6) × 10³ ng/g-waste, which would rise to (8.4 ± 2.1) × 10³ ng/g-waste in the absence of APCDs. This indicates that the current APCD system reduces VOC emissions by approximately 6.52 × 10⁴ g annually from this MWI plant, highlighting the crucial role of multistage APCDs in mitigating VOC pollution. Full article

Polyvinyl chloride (PVC), owing to its excellent electrical properties and low cost, is widely applied in the inner insulation and outer sheath of cables. To achieve early fault warning based on characteristic gases, this study integrates experimental testing with molecular simulations to systematically reveal the decomposition and gas generation characteristics of different PVC layers under electrical and thermal stresses. The results indicate that inner-layer PVC under electrical stress predominantly generates small-molecule olefins and halogenated hydrocarbons, while outer-layer PVC during thermal decomposition mainly produces hydrogen chloride, alkanes, and fragments of plasticizers. The surrounding atmosphere significantly regulates the gas generation pathways: air promotes the formation of CO₂ and H₂O, whereas electrical discharges accelerate the release of unsaturated hydrocarbons such as acetylene. By employing TG-FTIR, ReaxFF molecular dynamics, and DFT spectral calculations, a normalized infrared spectral library covering typical products was established and combined with the non-negative least squares method to realize quantitative deconvolution of mixed gases. Ultimately, a diagnostic system was constructed based on the concentration ratios of characteristic gases, which can effectively distinguish the failure modes of inner and outer PVC layers as well as different stress types. This provides a feasible approach for early detection of cable faults and supports intelligent maintenance strategies. Full article

To characterize the temporal variation in and source contribution of volatile organic compounds (VOCs) in a polymer industrial park, a two-year offline monitoring campaign (2018–2019) at Shangyu Industrial Park in the Yangtze River Delta was conducted. The study quantified the VOCs composition, seasonal variation, and ozone formation potential (OFP), with source apportionment performed using the Positive Matrix Factorization (PMF) model. During the observation period, the average concentration of total VOCs in 2019 was 286.1 ppb, showing a 22.6% reduction compared to that in 2018. Seasonal analysis revealed decreases in the total VOCs concentration by 41.8%, 38.4%, and 6.1% during spring, summer and winter, respectively, while an increase of 13.8% was observed in autumn, primarily attributed to industrial restructuring in the second half of 2019. Notable reductions were observed in specific VOCs components: oxygen-containing volatile organic compounds (OVOCs), alkane, halogenated hydrocarbon, alkene, and alkyne decreased by 34.5%, 27.9%, 26.3%, 24.6%, and 20.4%, respectively. The average OFP in 2019 was 2402.0 μg/m³, representing a 1.8% reduction from 2018. Contributions to total OFP from alkane, OVOCs, alkyne, and alkene decreased by 32.9%, 26.0%, 20.7%, and 15.0%, respectively, while halogenated hydrocarbons and aromatic hydrocarbons increased by 50.1% and 7.0%. PMF analysis identified four major VOCs sources: industrial production (44.9%), biomass combustion (17.8%), vehicle exhaust (11.0%), and solvent usage (26.3%). From 2018 to 2019, contributions from vehicle exhaust and solvent usage increased by 4.8% and 5.9%, respectively, while industrial production and biomass combustion decreased by 10.5% and 0.3%. Full article

The intriguing characteristics of nanoparticles have fueled recent advancement in the field of nanotechnology. In the current study, a microbial-based bioflocculant made from the SCOBY of Kombucha tea broth was purified, profiled, and utilized to biosynthesize iron nanoparticles as a capping and reducing agent. UV–visible absorption spectroscopy, transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and TGA were used to characterize the Fe nanoparticles. The FT-IR spectra showed functional groups such as hydroxyl, a halogen (C-Br), and carbonyl, and the alkane (C-H) functional groups were present in both samples (bioflocculant and FeNPs) with the exception of the Fe-O bond, which represented the successful biosynthesis of FeNPs. The TEM investigation revealed that the sizes of the produced iron nanoparticles were between 2.6 and 6.2 nm. The UV-vis spectra revealed peaks at 230 nm for the bioflocculant and for the as-fabricated FeNPs, peaks were around 210, 265, and 330 nm, which confirms the formation of FeNPs. X-ray diffraction presented planes (012), (104), (110), (113), (024), (116), and (533) and these planes correspond to 17.17, 32.58, 33.75, 38.18, 45.31, 57.40, and 72.4° at 2Ө. The presence of Fe nanoparticles presented with 0.82 wt% from the EDX spectrum of the biosynthesized FeNPs. However, Fe content was not present from the bioflocculant. SEM images reported cumulus-like particles of the bioflocculant, while that of FeNPs were agglomerated and hexagonal with sizes between 18 and 50 nm. The TGA of FeNPs showed thermal stability by retaining above 60% of its weight at high temperatures. It can therefore be deduced that the purified bioflocculant produced by a yeast Pichia kudraivzevii can be utilized to synthesize FeNPs with the current simple and effective method. Full article

It is well established that the reaction cycles involving some halogenated alkanes (so-called ozone-depleting substances—ODSs) contribute to the depletion of ozone in the stratosphere, prompting the Montreal Protocol (initially signed in 1987), and later amendments. The Protocol called for the scheduled phase-out of ODSs, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride (CCl₄), halon, methyl chloroform (CH₃CCl₃), methyl chloride (CH₃Cl), and even hydrofluorocarbons (HFCs). In view of the urgent importance of ozone layer protection to the global ecological environment, the Taiwanese government has taken regulatory actions to reduce ODS consumption since 1993, through the joint venture of the central competent authorities. Under the government’s regulatory requirements, and the industry’s efforts to adopt both alternatives to ODSs and abatement technologies, the phase-out of some ODSs (i.e., CFCs, CCl₄, halon, and CH₃CCl₃) was achieved prior to 2010. The consumption of HCFCs and methyl chloride has significantly declined over the past three decades (1993–2022). However, HFC emissions indicated a V-type variation during this period. Due to local production and extensive use of HFCs in Taiwan, the country’s emissions increased from 663 kilotons of carbon dioxide equivalents (CO_2eq) in 1993 to 2330 kilotons of CO_2eq in 2001, and then decreased to 373 kilotons of CO_2eq in 2011. Since then, the emissions of HFCs largely used as the alternatives to ODSs showed an upward trend, increasing to 1555 kilotons of CO_2eq in 2022. To be in compliance with the Kigali Amendment (KA-2015) to the Montreal Protocol for mitigating global warming, the Taiwanese government has taken regulatory actions to reduce the consumption of some HFC substances with high global warming potential (GWP) under the authorization of the Climate Change Response Act in 2023, aiming at an 80% reduction by 2045 of the baseline consumption in 2024. Full article

In recent years, commercial air transport has increased considerably. However, the compositions and source profiles of volatile organic compounds (VOCs) emitted from aircraft are still not clear. In this study, the characteristics of VOCs (including oxygenated VOCs (OVOCs)) emitted from airport sources were measured at Shenzhen Bao’an International Airport. The results showed that the compositions and proportions of VOC species showed significant differences as the aircraft operating state changed. OVOCs were the dominant species and accounted for 63.17%, 58.44%, and 51.60% of the total VOC mass concentration during the taxiing, approach, and take-off stages. Propionaldehyde and acetone were the main OVOCs, and dichloromethane and 1,2-dichloroethane were the main halohydrocarbons. Propane had the highest proportion among all alkanes, while toluene and benzene were the predominant aromatic hydrocarbons. Compared with the source profiles of VOCs from construction machinery, the proportions of halogenated hydrocarbons and alkanes emitted from aircraft were significantly higher, as were those of propionaldehyde and acetone. OVOCs were still the dominant VOC species in aircraft emissions, and their calculated ozone formation potential (OFP) was much higher than that of other VOC species at all stages of aircraft operations. Acetone, propionaldehyde, formaldehyde, acetaldehyde, and ethylene were the greatest contributors to ozone production. This study comprehensively measured the distribution characteristics of VOCs, and its results will aid in the construction of a source profile inventory of VOCs emitted from aircraft sources in real atmospheric environments. Full article

As “fuel” for atmospheric photochemical reactions, volatile organic compounds (VOCs) play a key role in the secondary generation of ozone (O₃) and fine particulate matter (PM_2.5, an aerodynamic diameter ≤ 2.5 μm). To determine the characteristics of VOCs in a high-level ozone period, comprehensive monitoring of O₃ and its precursors (VOCs and NOx) was continuously conducted in an industrial area in Shanghai from 18 August to 30 September 2021. During the observation period, the average concentration of VOCs was 47.33 ppb, and alkanes (19.64 ppb) accounted for the highest proportion of TVOCs, followed by oxygenated volatile organic compounds (OVOCs) (13.61 ppb), alkenes (6.92 ppb), aromatics (4.65 ppb), halogenated hydrocarbons (1.60 ppb), and alkynes (0.91 ppb). Alkenes were the predominant components that contributed to the ozone formation potential (OFP), while aromatics such as xylene, toluene, and ethylbenzene contributed the most to the secondary organic aerosol production potential (SOAFP). During the study period, O₃, NOx, and VOCs showed significant diurnal variations. Industrial processes were the main source of VOCs, and the second largest source of VOCs was vehicle exhaust. While the largest contribution to OFP was from vehicle exhaust, the second largest contribution was from liquid petroleum gas (LPG). High potential source contribution function (PSCF) values were observed in western and southeastern areas near the sampling sites. The results of a health risk evaluation showed that the Hazard Index was less than 1 and there was no non-carcinogenic risk, but 1,3-butadiene, benzene, chloroform, 1,2-dibromoethane, and carbon tetrachloride pose a potential carcinogenic risk to the population. Full article

The chemical complexity and toxicity of volatile organic compounds (VOCs) are primarily encountered through intensive anthropogenic emissions in suburban areas. Here, pollution characteristics, impacts on secondary pollution formation, and health risks were investigated through continuous in-field measurements from 1–30 June 2020 in suburban Nanjing, adjacent to national petrochemical industrial parks in China. On average, the total VOCs concentration was 34.47 ± 16.08 ppb, which was comprised mostly by alkanes (41.8%) and halogenated hydrocarbons (29.4%). In contrast, aromatics (17.4%) dominated the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) with 59.6% and 58.3%, respectively. Approximately 63.5% of VOCs were emitted from the petrochemical industry and from solvent usage based on source apportionment results, followed by biogenic emissions of 22.3% and vehicle emissions of 14.2%. Of the observed 46 VOC species, hexachlorobutadiene, dibromoethane, butadiene, tetrachloroethane, and vinyl chloride contributed as high as 98.8% of total carcinogenic risk, a large fraction of which was ascribed to the high-level emissions during ozone pollution episodes and nighttime. Therefore, the mitigation of VOC emissions from petrochemical industries would be an effective way to reduce secondary pollution and potential health risks in conurbation areas. Full article

Traditional butyl rubber halogenation technology involves the halogenation of IIR using molecular chlorine or bromine in a solution. However, this method is technologically complex. This study investigated a novel method for the halogenation of butyl rubber to enhance its stability and resistance to thermal oxidation and aggressive media. The butyl rubber was modified through mechanochemical modification, induced by solvent swelling in a polychlorinated n-alkane solution. During the modification, samples were obtained with chlorine content ranging from 3 to 15%. After extraction, the halogen content was quantitatively determined with the oxygen flask combustion method and X-ray photoelectron spectroscopy. It was shown that for samples with total chlorine content of up to 6%, there was almost no leaching of chlorine from the samples. The chemical structure of the extracted rubbers was ascertained using FT-IR and ¹H NMR spectroscopy, and it was demonstrated that all samples showed absorption peaks and signals typical for chlorobutyl rubbers. It was observed that modification with polychlorinated n-alkanes improved the thermal and oxidative stability (the oxygen absorption rate decreased by 40%) and chemical resistance, estimated by the degree of swelling, which decreased with the increase in the chlorine content. This technology allows the production of a chlorinated rubber solution that can be directly used by rubber goods manufacturers and suppliers. Full article

Alkane functionalization using safe and low-energy processes is of great interest to industry and academia. Aiming to contribute to the process of saturated hydrocarbon functionalization, we have studied a set of three manganese(III) complexes as catalysts for promoting the oxidation of saturated hydrocarbons (cyclohexane and methylcyclohexane) in the presence of hydrogen peroxide or trichloroisocyanuric acid (TCCA). The mononuclear manganese(III) compounds were prepared using the ligands H₂L^Met4 (6,6’-((1,4-diazepane-1,4-diyl)bis(methylene))bis(2,4-dimethylphenol), H₂salen (2,2’-((1E,1’E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))diphenol) and H₂salan (2,2’-((ethane-1,2-diylbis(azanediyl))bis(methylene))diphenol). The catalytic processes were carried out in acetonitrile at 25 and 50 °C for 24 h. The increase in the temperature was important to get a better conversion. The compounds did not promote cyclohexane oxidation in the presence of H₂O₂. However, they were active in the presence of TCCA, employing a ratio of 1000:333:1 equivalents of the substrate:TCCA:catalyst. The best catalytic activity was shown by the compound [Mn(salen)Cl], reaching conversions of 14.5 ± 0.3% (25 °C) and 26.3 ± 1.1% (50 °C) (yield for chlorocyclohexane) and up to 12.1 ± 0.5% (25 °C) and 29.8 ± 2.2% (50 °C) (total yield for the mixture of the products 1-chloro-4-methylcyclohexane, 3-methylcyclohexene and 1-methylcyclohexene). The interaction of the catalysts with TCCA was studied using electron paramagnetic resonance (EPR), suggesting that the catalysts [Mn(L^Met4)Cl] and [Mn(salan)Cl] act via a different mechanism from that observed for [Mn(salen)Cl]. Full article

According to online monitoring data on atmospheric ozone and the pollution characteristics of its precursors obtained in Jinan in June 2021, we analyzed different sites: urban sites (city monitoring station, Quancheng Square), an industrial park site (oil refinery), and a suburban site (Paomaling). The relative incremental reactivity of different precursors was calculated using a photochemical observation-based model to explore the sensitivity of O₃ generation at each site and to draw a curve using the empirical kinetics modeling approach. The PMF model was used to analyze the origin of volatile organic compounds (VOCs) pollution in Jinan. The results showed that the concentration of O₃ at the industrial park was higher than that in the urban area in Jinan, which may be related to the fact that ozone precursor concentrations in the industrial park were significantly higher than those in the urban area (the AVOCs concentration at the industrial park site was 56.9 ppbv, approximately twice that of the urban site), and there are emission peaks at night; alkanes, oxygenated compounds, and halogenated hydrocarbons were the main components of the AVOCs, and olefins, alkanes, and aromatic hydrocarbons were the main active components in Jinan. The O₃ generation in urban areas generally occurred in the VOCs-sensitive zones, while the O₃ generation in the other areas occurred in the VOCs-NO_x transition zone; there was a clear diurnal variation in the sensitivity of the industrial park, with the site being in the obvious VOCs-sensitive zone from nighttime to morning hours and shifting to the VOCs-NO_x transition zone in the afternoon hours; the relative incremental reactivity (RIR) value of AVOCs for O₃ generation in Jinan was the largest, and olefins were the most sensitive component of O₃. The AVOCs in Jinan mainly originated from motor vehicle exhaust, oil and gas volatilization, industrial emissions, and solvent use, and ozone prevention and control in summer should strengthen the control of these sources. Full article

This work comprehensively investigated the constituents, sources, and associated health risks of ambient volatile organic compounds (VOCs) sampled during the autumn of 2020 in urban Nanjing, a megacity in the densely populated Yangtze River Delta region in China. The total VOC (TVOC, sum of 108 species) concentration was determined to be 29.04 ± 14.89 ppb, and it was consisted of alkanes (36.9%), oxygenated VOCs (19.9%), halogens (19.1%), aromatics (9.9%), alkenes (8.9%), alkynes (4.9%), and others (0.4%). The mean TVOC/NO_x (ppbC/ppbv) ratio was only 3.32, indicating the ozone control is overall VOC-limited. In terms of the ozone formation potential (OFP), however, the largest contributor became aromatics (41.9%), followed by alkenes (27.6%), and alkanes (16.9%); aromatics were also the dominant species in secondary organic aerosol (SOA) formation, indicative of the critical importance of aromatics reduction to the coordinated control of ozone and fine particulate matter (PM_2.5). Mass ratios of ethylbenzene/xylene (E/X), isopentane/n-−pentane (I/N), and toluene/benzene (T/B) ratios all pointed to the significant influence of traffic on VOCs. Positive matrix factorization (PMF) revealed five sources showing that traffic was the largest contributor (29.2%), particularly in the morning. A biogenic source, however, became the most important source in the afternoon (31.3%). The calculated noncarcinogenic risk (NCR) and lifetime carcinogenic risk (LCR) of the VOCs were low, but four species, acrolein, benzene, 1,2-dichloroethane, and 1,2-dibromoethane, were found to possess risks exceeding the thresholds. Furthermore, we conducted a multilinear regression to apportion the health risks to the PMF-resolved sources. Results show that the biogenic source instead of traffic became the most prominent contributor to the TVOC NCR and its contribution in the afternoon even outpaced the sum of all other sources. In summary, our analysis reveals the priority of controls of aromatics and traffic/industrial emissions to the efficient coreduction of O₃ and PM_2.5; our analysis also underscores that biogenic emissions should be paid special attention if considering the direct health risks of VOCs. Full article

Midu pork roll (MPR), produced in Midu County, Dali Bai Autonomous Prefecture, Yunnan, China, is a traditional fermented meat product with a long history. This study aims to enhance the physical and flavor profile of MPR by improving its process, fermentation conditions and formulations. There were three different formulations, including traditional craft (control group: C), optimization process of Sichuan spicy flavor formula (Test group 1: T1) and optimization process of halogen flavor formula (Test group 2: T2). Higher moisture content, L*, a* and b* values and lower hardness, chewiness and shear force were observed in T1 and T2 compared to C (p < 0.05). A total of 15 free amino acids were detected throughout the fermentation process, during which the content of umami amino acids, sweet amino acids and bitter amino acids underwent significant changes. A total of 88, 85 and 75 volatile compounds were detected in C, T1 and T2, respectively, in which the relative content of alkanes and ketones in T1 and T2 were higher than those in C (p < 0.05). The process and formulas have improved the color, texture characteristics and tenderness of MPR to a certain extent, meanwhile, they have enhanced the flavor of MPR. Full article

The reactions of CuX₂ (X = Cl, Br) with dipinodiazafluorenes yielded four new complexes [CuX₂L₁]₂ (X = Cl (1), Br (2), L₁ = (1R,3R,8R,10R)-2,2,9,9-Tetramethyl-3,4,7,8,9,10-hexahydro-1H-1,3:8,10-dimethanocyclopenta [1,2-b:5,4-b’]diquinolin-12(2H)-one) and [(CuX₂)₂L₂]n (X = Cl (3), Br (4), L₂ = (1R,3R,8R,10R,1’R,3’R,8’R,10’R)-2,2,2’,2’,9,9,9’,9’-Octamethyl-1,1’,2,2’,3,3’,4,4’,7,7’,8,8’,9,9’,10,10’-hexadecahydro-1,3:1’,3’:8,10:8’,10’-tetramethano-12,12’-bi(cyclopenta [1,2-b:5,4-b’]diquinolinylidene). The complexes were characterized by IR and EPR spectroscopy, HR-ESI-MS and elemental analysis. The crystal structures of compounds 1, 2 and 4 were determined by X-ray diffraction (XRD) analysis. Complexes 1–2 have a monomeric structure, while complex 4 has a polymeric structure due to additional coordinating N,N sites in L₂. All complexes contain a binuclear fragment {Cu₂(μ-X)_2×2} (X = Cl, Br) in their structures. Each copper atom has a distorted square-pyramidal coordination environment formed by two nitrogen atoms and three halogen atoms. The Cu-N_ax distance is elongated compared to Cu-N_eq. The EPR spectra of compounds 1–4 in CH₃CN confirm their paramagnetic nature due to the d⁹ electronic configuration of the copper(II) ion. The magnetic properties of all compounds were studied by the method of static magnetic susceptibility. For complexes 1 and 2, the effective magnetic moments are µ_eff ≈ 1.87 and 1.83 µ_B (per each Cu²⁺ ion), respectively, in the temperature range 50–300 K, which are close to the theoretical spin value (1.73 µ_B). Ferromagnetic exchange interactions between Cu(II) ions inside {Cu₂(μ-X)₂X₂} (X = Cl, Br) dimers (J/k_B ≈ 25 and 31 K for 1 and 2, respectively) or between dimers (θ′ ≈ 0.30 and 0.47 K for 1 and 2, respectively) were found at low temperatures. For compounds 3 and 4, the magnetic susceptibility is well described by the Curie–Weiss law in the temperature range 1.77–300 K with µ_eff ≈ 1.72 and 1.70 µ_B for 3 and 4, respectively, and weak antiferromagnetic interactions (θ ≈ −0.4 K for 3 and −0.65 K for 4). Complexes 1–4 exhibit high catalytic activity in the oxidation of alkanes and alcohols with peroxides. The maximum yield of cyclohexane oxidation products reached 50% (complex 3). Based on the data on the study of regio- and bond-selectivity, it was concluded that hydroxyl radicals play a decisive role in the oxidation reaction. The initial products in reactions with alkanes are alkyl hydroperoxides. Full article

Polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, are potential health risks due to their carcinogenic and mutagenic effects. Bacteria from the genus Rhodococcus are able to metabolise a wide variety of pollutants such as alkanes, aromatic compounds and halogenated hydrocarbons. A naphthalene dioxygenase from Rhodococcus sp. strain NCIMB12038 has been characterised for the first time, using electron paramagnetic resonance (EPR) spectroscopy and UV-Vis spectrophotometry. In the native state, the EPR spectrum of naphthalene 1,2-dioxygenase (NDO) is formed of the mononuclear high spin Fe(III) state contribution and the oxidised Rieske cluster is not visible as EPR-silent. In the presence of the reducing agent dithionite a signal derived from the reduction of the [2Fe-2S] unit is visible. The oxidation of the reduced NDO in the presence of O₂-saturated naphthalene increased the intensity of the mononuclear contribution. A study of the “peroxide shunt”, an alternative mechanism for the oxidation of substrate in the presence of H₂O₂, showed catalysis via the oxidation of mononuclear centre while the Rieske-type cluster is not involved in the process. Therefore, the ability of these enzymes to degrade recalcitrant aromatic compounds makes them suitable for bioremediative applications and synthetic purposes. Full article