Behavior Of Volatile Organic Compounds Research Articles

Interaction of composite fume suppression and odor elimination agents with crumb rubber modified asphalt: Inhibition behavior of volatile organic compounds (VOCs) and inorganic fume

The production and construction of crumb rubber modified asphalt (RMA) at high temperatures can produce a large amount of toxic fume, which is detrimental to human health and environment. In this study, a series of composite fume suppression and odor elimination agents (CSEAs) with both physical adsorption and chemical capture functions were adopted to reduce the emissions of volatile organic compounds (VOCs) and hydrogen sulfide (H2S). The material composition, microstructure, and specific surface area of CSEA were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and N2 adsorption-desorption isotherm (BET). The inhibitory effects of adding CSEA on toxic fume emissions from RMA at high temperatures were investigated through a combination of fume emission tests, H2S gas detection, gel permeation chromatography (GPC), and gas chromatography–mass spectrometry technology (GC–MS). The adsorption behavior of CSEA on H2S was analyzed through adsorption dynamics. Results showed that the physical and chemical properties of CSEA are stable while chemical adsorption dominates the CSEA's effect on H2S. ZnO and Ca(OH)2 exhibit good crystallization effects on the surface of the carrier by forming mesoporous structures mostly above 3.4 nm in size. The incorporation of CSEA significantly reduced the total emissions of RMA fume and the main components of VOCs in which the average inhibition rate of H2S can reach 44 % at an initial 30 mins.

Insights into the role of VOCs properties on thermal desorption behaviors of two porous polymeric resins

Desorption is a critical process in the recovery or post-treatment of adsorbents saturated with volatile organic compounds (VOCs). In this study, the thermal desorption behaviors for eight VOCs on hypercrosslinked polymeric resin (HPR) and macroporous polymeric resin (MPR) were investigated through isothermal desorption and temperature programmed desorption (TPD). Compared with MPR, HPR with more micropores exhibited a lower desorption rate constant, lower desorption efficiency and higher desorption activation energy due to the strong binding energy generated between VOCs molecules and narrow micropores. As the polarizability of VOCs increased, the desorption rate constants on two porous polymeric resins decreased, while the desorption activation energy showed an incremental trend. Excellent linear correlations were observed between VOC polarizability and desorption rate constants (R2 = 0.957 for HPR and R2 = 0.940 for MPR) as well as between VOC polarizability and desorption activation energy (R2 = 0.981 for HPR and R2 = 0.969 for MPR). Furthermore, a polyparameter linear free energy relationship (PP-LFER) was developed to explore the influences of intermolecular interactions on desorption behaviors of VOCs on porous polymeric resins. The results indicated that the dispersive interaction, which is directly related to polarizability of VOCs, was the primary factor influencing the desorption activation energy of VOCs on porous polymeric resins. The find from this study helps evaluate fleetly and availably the desorption properties of VOCs based on their polarizability.

Volatile Compound Markers in Beef Irradiated with Accelerated Electrons.

This study focuses on the behavior of volatile organic compounds in beef after irradiation with 1 MeV accelerated electrons with doses ranging from 0.25 kGy to 5 kGy to find reliable dose-dependent markers that could be used for establishing an effective dose range for beef irradiation. GC/MS analysis revealed that immediately after irradiation, the chemical yield and accumulation rate of lipid oxidation-derived aldehydes was higher than that of protein oxidation-derived aldehydes. The nonlinear dose-dependent relationship of the concentration of volatile organic compounds was explained using a mathematical model based on the simultaneous occurrence of two competing processes: decomposition of volatile compounds due to direct and indirect action of accelerated electrons, and accumulation of volatile compounds due to decomposition of other compounds and biomacromolecules. A four-day monitoring of the beef samples stored at 4 °C showed that lipid oxidation-derived aldehydes, protein oxidation-derived aldehydes and alkanes as well as alcohol ethanol as an indicator of bacterial activity were dose-dependent markers of biochemical processes occurring in the irradiated beef samples during storage: oxidative processes during direct and indirect action of irradiation, oxidation due to the action of reactive oxygen species, which are always present in the product during storage, and microbial-enzymatic processes. According to the mathematical model of the change in the concentrations of lipid oxidation-derived aldehydes over time in the beef samples irradiated with different doses, it was found that doses ranging from 0.25 kGy to 1 kGy proved to be most effective for beef irradiation with accelerated electrons, since this dose range decreases the bacterial content without considerable irreversible changes in chemical composition of chilled beef during storage.

Distance-Based Analysis of Early Fire Indicators on a New Indoor Laboratory Dataset with Distributed Multi-Sensor Nodes

This work analyzes a new indoor laboratory dataset looking at early fire indicators in controlled and realistic experiments representing different incipient fire scenarios. The experiments were performed within the constraints of an indoor laboratory setting using multiple distributed sensor nodes in different room positions. Each sensor node collected data of particulate matter (PM), volatile organic compounds (VOCs), carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), ultraviolet radiation (UV), air temperature, and humidity in terms of a multivariate time series. These data hold immense value for researchers within the machine learning and data science communities who are keen to explore innovative and advanced statistical and machine learning techniques. They serve as a valuable resource for the development of early fire detection systems. The analysis of the collected data was carried out depending on the Manhattan distance between the fire source and the sensor node. We found that especially larger particles (>0.5 μm) and VOCs show a significant dependency with respect to the intensity as a function of the Manhattan distance to the source. Moreover, we observed differences in the propagation behavior of VOCs, PM, and CO, which are particularly relevant in incipient fire scenarios due to the presence of strand propagation effects.

Enrichment cultivation of VOC-degrading bacteria using diffusion bioreactor and development of bacterial-immobilized biochar for VOC bioremediation

Volatile organic compounds (VOCs) have been globally reported at various sites. Currently, limited literature is available on VOC bioremediation using bacterial-immobilized biochar (BC–B). In this study, multiple VOC-degrading bacteria were enriched and isolated using a newly designed diffusion bioreactor. The most effective VOC-degrading bacteria were then immobilized on rice husk-derived pristine biochar (BC) to develop BC-B. Finally, the performances of BC and BC-B for VOCs (benzene, toluene, xylene, and trichloroethane) bioremediation were evaluated by establishing batch microcosm experiments (Control, C; bioconsortium, BS; pristine biochar, BC; and bacterial-immobilized biochar, BC-B). The results revealed that the newly designed diffusion bioreactor effectively simulated native VOC-contaminated conditions, easing the isolation of 38 diverse ranges of VOC-degrading bacterial strains. Members of the genus Pseudomonas were isolated in the highest (26.33%). The most effective bacterial strain was Pseudomonas sp. DKR-23, followed by Rhodococcus sp. Korf-18, which degraded multiple VOCs in the range of 52–75%. The batch microcosm experiment data showed that BC-B remediated the highest >90% of various VOCs, which was comparatively higher than that of BC, BS, and C. In addition, compared with C, the BS, BC, and BC-B microcosms abundantly reduced the half-life of various VOCs, implying a beneficial impact on the degradation behavior of VOCs. Altogether, this study suggests that a diffusion bioreactor system can be used as a cultivation device for the isolation of a wide range of VOC-degrading bacterial strains, and a compatible combination of biochar and bacteria may be an attractive and promising approach for the sustainable bioremediation of multiple VOCs.

Emission characteristics of volatile organic compounds from regenerated PET fibers based on the headspace gas chromatograph

AbstractThe emission behaviors of volatile organic compounds (VOCs) can be characterized by the key parameters: the initial concentration (m0), partition coefficient (K) and the diffusion coefficient (D). The MHE‐GC method was validated to determine the emission characteristics of VOCs (Benzene, Toluene, Ethylbenzene, P‐xylene, M‐xylene, Styrene, and O‐xylene) in regenerated PET fibers. This work has studied the effects of fiber size, sample weight incubation time and incubation temperature on the detection of these VOCs. It showed finer fiber sample with less sample facilitated the emission of VOCs in fibers above detectable limit. The optimized headspace incubation time, fiber sample weight, and headspace incubation temperature were selected as 60 min, about 0.8 g and 110 °C, respectively. In addition, incubation temperature has a negative effect on the gas/fiber partition coefficient. The fibers with greater fineness showed higher activation energy, which revealed a positive release of VOCs from fibers. The relative standard deviation (RSD/%) of detection was 3%–10%. The present method is reliable and suitable for use in testing of the VOCs content in fiber‐related materials.

Analytical solution of coupled heat-moisture-VOCs transfer process in liquid desiccant dehumidifier for indoor VOCs removal

Indoor volatile organic compounds (VOCs) have a serious impact on human health. Liquid dehumidification shows a potential to remove VOCs during dehumidification process. To improve its VOCs removal performance, it's important to analyze mass transfer behaviors of VOCs at design stage. However, previous research methods mainly focused on experimental or numerical simulation, by neglecting the analytical solution. In fact, the analytical solution shows many advantages in terms of time, cost, and intuition etc. Therefore, in this study, an analytical solution is proposed to characterize heat-moisture-VOCs transfer performance in liquid dehumidifier. The proposed analytical solution is derived based on the existing theoretical model. Moreover, a piecewise function method is proposed to address the nonlinear and complex relationship between Henry's law constant and temperature in the VOCs transfer model. Thus, the analytical solution is set as a piecewise function considering both accuracy and gas-liquid flow rate ratio. Using the proposed analytical solution, the influences of some key operating parameters on VOCs removal performances are demonstrated. The results indicate that the analytical solutions are basically consistent with the numerical solutions and it can effectively predict the trend of VOCs removal performance with key parameters change. Comprehensive analysis of the mass transfer behavior of VOCs in liquid dehumidifier is effective with the analytical solution. This work provides a theoretical support for indoor VOCs removal with liquid dehumidifier.

Dynamic adsorption behavior of benzene, toluene, and xylene VOCs in single- and multi-component systems by activated carbon derived from defatted black cumin (Nigella sativa L.) biowaste

In the current study, activated carbon (AC) was produced from defatted black cumin (Nigella sativa L.) biowaste (DBCB) with ZnCl2 activation by means of the response surface methodology. The optimum process conditions for the production of DBCB-AC with a high iodine number of 1055.02 mg/g were predicted as an activation time of 57 min, activation temperature of 550 °C, and impregnation ratio of 105%. The surface and textural properties of the optimal DBCB-AC were characterized by SEM, FTIR, and BET analysis techniques. The DBCB-AC exhibited a highly porous structure with a specific surface area of 1213.32 m2/g, total pore volume of 0.89 cm3/g, and micropore surface area of 787.65 m2/g. Exploring the comparative and competitive adsorption behavior of volatile organic compounds (VOCs) is of both practical and scientific interest. Therefore, the competitive adsorption of multi-component benzene, toluene, and xylene (BTX) vapors by the DBCB-AC was elucidated. In the single-component system, the adsorption capacities of the BTX vapors at inlet concentrations of 20 mg/L were determined as 495, 580, and 674 mg/g, respectively. In contrast, in the binary-component system, the adsorption capacity of the B-vapor at 20 mg/L B + 10 mg/L T and 20 mg/L B + 10 mg/L X decreased by approximately 42% and 56%, respectively. Similarly, the adsorption capacity of the T-vapor at 20 mg/L T + 10 mg/L X decreased by approximately 47%. In the ternary-component system, the adsorption capacity of the X-vapor remained consistent. The adsorption mechanism of the BTX was explained by adsorption kinetic and isotherm models. The reuse efficiency of the DBCB-AC for the BTX was assessed through five cycles of adsorption-desorption tests and was found to be 89.45%, 88.02%, and 87.25%, respectively. The DBCB-AC, which had high-performance in terms of both reuse efficiency and adsorption capacity, can be recommended as a promising adsorbent for removal of VOC pollutants.

Role of water in unexpectedly large changes in emission flux of volatile organic compounds in soils under dynamic temperature conditions

Understanding the diffusive transport behavior of volatile organic compounds (VOCs) in near-surface soils is important because soil VOC emissions affect atmospheric conditions and climate. Previous studies have suggested that temperature changes affect the transport behavior; however, the effect of these changes are poorly understood. Indeed, under dynamic temperature conditions, the change in VOC flux is much larger than that expected from the temperature dependency of the diffusion coefficient of VOCs in air. However, the mechanism is not well understood, although water in soil has been considered to play an important role. Here, we present the results of experiments for the upward vertical vapor-phase diffusive transport of two VOCs (benzene and tetrachloroethylene) in sandy soil under sinusoidal temperature variations of 20–30 °C, as well as its numerical representation. The results clarify that the unexpectedly large changes in emission flux can occur as a result of changes in the VOC concentration gradient due to VOC release (volatilization) from/trapping (dissolution) into water, and that such flux changes may occur in various environments. This study suggests the importance of a global evaluation of soil VOC emissions by continuous measurements in various soil environments and/or predictions through numerical simulations with thorough consideration of the role of water in dynamic soil environments.

New insights into the photo-degraded polystyrene microplastic: Effect on the release of volatile organic compounds

Excessive use of plastics leads to the ubiquity of plastic waste in the environment. Weathering can cause changes in the properties of plastics and lead to the release of various chemicals especially the volatile organic compounds (VOCs). Possible photodegradation pathway of polystyrene (PS) microplastics (MPs) was proposed and verified by the detection of VOCs. Headspace solid phase microextraction (HS-SPME) was employed to investigate the release behavior of VOCs from PS MPs exposed to simulated ultraviolet (UV). Results indicated that although the physicochemical properties of the PS MPs showed no significantly change after UV-irradiation, a variety of toxic VOCs, such as benzene, toluene, and phenol were detected from the irradiated MPs. UV irradiation progressively enhanced the release amount of VOCs with total concentration up to 66 μg g-1 after 30 d of exposure, about 2.4 times higher than that stored in the darkness (27 μg g-1). Some compounds (e.g., benzene and toluene) showed an upward trend over irradiation time, while others (e.g., styrene and 2-propenylbenzene) reduced over time. Results also found that the size of MPs could affect the release amounts but without consistent pattern for different VOCs detected in the headspace of the vial. In general, current study provided a new insight on the photo-aging process of MPs.

Research on Behavior of Volatile Organic Compounds from Clothes Washed with Fabric Softener and Fragrance Reagent

Research on Behavior of Volatile Organic Compounds from Clothes Washed with Fabric Softener and Fragrance Reagent

AVALIAÇÃO DE COMPOSTOS ORGÂNICOS VOLÁTEIS AROMÁTICOS NA ATMOSFERA EM CAMPOS DOS GOYTACAZES E ITAPERUNA APLICANDO A ANÁLISE MULTIVARIADA DE DADOS

EVALUATION OF AROMATIC VOLATILE ORGANIC COMPOUNDS IN THE ATMOSPHERE IN CAMPOS DOS GOYTACAZES AND ITAPERUNA APPLYING MULTIVARIATE DATA ANALYSIS. Volatile Organic Compounds (VOCs) are air pollutants emitted from different sources, mainly by industries and motor vehicles. The evaluation of the emission of these compounds into the atmosphere should be done systematically and with a varied class of compounds. The large number of data generated during the monitoring of these VOCs requires the use of multivariate data tools to interpret the results. In this sense, this work aimed to monitor 10 aromatic VOCs present in the atmosphere of the largest cities in the Norte Fluminense (Campos dos Goytacazes) and Noroeste Fluminense (Itaperuna) regions. The VOCs were actively sampled and analyzed by gas chromatography with mass spectrometry detection after thermal desorption. After treatment of analytical results, it was observed that in both cities there is influence of vehicular emissions. In the city of Itaperuna, due to the relief and lower dispersion of contaminants, there is a higher occurrence of photochemical reactions. The exploratory analysis of the data allowed identifying the variables that were more significant and correlating these variables with the main sources of emission of the compounds. This is the first study of VOCs evaluation in Campos dos Goytacazes and Itaperuna, demonstrating the relevance of this research for understanding the behavior of VOCs in these cities, which have different reliefs and high traffic of cars and trucks in the studied sites.

Adsorption of Gas-Phase Cyclohexanone on Atmospheric Water Films

The fate of atmospheric volatile organic compounds (VOCs) strongly depends on the partitioning processes on the surface of aerosols, which are coated with a thin water film. However, the behavior of VOCs in the aqueous film of aerosols is difficult to measure. In this work, the interfacial partition constant of cyclohexanone was determined using a novel flow-tube reactor. A thin, aqueous film placed in the reactor was exposed to cyclohexanone gas. The subsequent partitioning was measured using chromatography techniques. The quality control tests were first conducted to ensure the accuracy of the adsorption experiments. The cyclohexanone concentration was then plotted as a function of film thickness to obtain the partitioning constants. As the thickness of the water film decreased, the aqueous concentration of cyclohexanone increased, indicating that surface adsorption played a dominant role in the uptake of cyclohexanone. According to the temperature dependence of the interfacial partition constant, the solvation enthalpy and entropy of cyclohexanone were obtained. The results of this study would help to elucidate the effect of atmospheric water film on the gas–aerosol partitioning of VOCs, and thus can help to better understand the fate of VOCs in the atmosphere.

Influence of physical structures and chemical modification on VOCs adsorption characteristics of molecular sieves

The adsorption method using molecular sieves as adsorbent is one of the effective ways to control the emission of volatile organic compounds (VOCs), while the unclear adsorption mechanism between different molecular sieves and VOCs blocks its industrial application. The effects of physical structure and chemical modification of molecular sieves on the adsorption of VOCs were studied by computer simulation and adsorption experiment. Grand Classical Monte Carlo (GCMC) simulation was employed to investigate the adsorption behaviors of VOCs in a variety of pure silica molecular sieves with different physical structures, including aldehydes, ketones and benzenes. Further, combined with density functional theory (DFT) calculations, the influences of chemical modification on the adsorption of VOCs were investigated. Finally, the theoretical results were verified through adsorption experiments. The results revealed that the molecular sieve topology, the pore diameter of the molecular sieve, and the molecular kinetic diameters of VOCs all markedly influenced the adsorption of VOCs. Pure silica molecular sieves exhibited considerable adsorption ability for polar adsorbates. For nonpolar adsorbates, the adsorption ability decreased as the molecular volume increased. The DFT results indicated that the adsorption of VOCs is stronger at Cu2+ site than [Cu-OH]+ site in modified MFI. The experimental results of toluene adsorption for MFI, BEA, and Y-type zeolites strongly supported the theoretical results.

Adsorption behaviors of VOCs under coal-combustion flue gas environment using activated carbon injection coupled with bag filtering system

Adsorbent injection is a simple and efficient technique for flue gas purification. Performances of volatile organic compounds (VOCs) removal in coal-combustion flue gas environment were investigated by activated carbon (AC) injection coupled with bag filtering (ACI + BF). Results showed that the removal efficiency of toluene and p-xylene was not only related to the micropore volume of AC but also to the pore size distribution and mesopore volume. Waste AC could be reused without desorption, the removal efficiency of mixed ACs was close to the fresh AC when the proportion of waste AC was 25%. Under complex coal-combustion flue gas environment, the adsorption efficiency of p-xylene was decreased by 19.0%. The fly ash in flowing state had less influence on the adsorption of VOCs on AC. On the adsorption layer of filter bag, fly ash decreased the AC concentration and blocked some important mass transfer channels of VOCs, restricting the diffusion of VOCs to the AC outer surface and decreasing utilization efficiency of adsorption sites. Although the concentration of SO2 was high, the inhibitory effect on VOCs adsorption was not significant. As the water vapor and SO2 coexisted, the H2SO4 was formed and blocked some micropores. Then the VOCs diffusion in the AC inner pores was influenced and some micropores could not adsorb VOCs. The removal of VOCs in both pipeline and adsorption layer was influenced by SO2 and water vapor.

Transient migration behavior of VOC vapor in layered unsaturated soils subjected to multiple time-dependent point pollution sources: Analytical study

Predicting the migration behavior of volatile organic compounds (VOCs) vapor is essential for the remediation of subsurface contamination such as soil vapor extraction. Previous analytical prediction models of VOCs migration are mostly limited to constant-concentration nonpoint sources in homogeneous soil. Thus, this study presents a novel analytical model for two-dimensional transport of VOCs vapor subjected to multiple time-dependent point sources involving transient diffusion, sorption and degradation in layered unsaturated soils. Two representative time-dependent sources, i.e., an instantaneous source and a finite pulse source, are used to describe the short-term and long-term leakage. Results reveal that soil heterogeneity can cause pollution accumulation, especially in low-diffusivity capillary fringe. The assumption of an equivalent plane source from multiple point sources would significantly overestimate the vapor concentration and the contaminated range. The previous single point source model is no longer inapplicable when the relative distance and/or the release interval between sources is small, giving a strong interaction between multiple sources. Moreover, a faster vapor degradation rate or a higher groundwater level will reduce the area of vapor plume linearly. Hence, close attention should be paid to the time-variation characteristics of multiple sources, the vapor degradation and the groundwater level fluctuation in practice to facilitate soil remediation. The proposed model is a promising tool for addressing the above issue.

Study on Air Pollution Behavior of VOCs with Photochemical Monitoring Stations Using EGARCH Model in Southern Taiwan

This study adopted the exponential generalized autoregressive conditional heteroscedasticity (EGARCH) model to examine the 10 ozone precursors of the highest concentrations among the 54 that were assessed over a number of years at the four photochemical assessment monitoring stations (PAMSs) in the Kaohsiung–Pingtung Area in Taiwan. First, the 10 ozone precursors, which were all volatile organic compounds (VOCs), were analyzed using the factor analyses in multiple statistical analyses that had the most significant impact on the area’s ozone formation: mobile pollution factor, which included 1,2,4-Trimethylbenzene (C9H12), toluene (C7H8), and Isopropyl benzene (C9H12). Then, taking into consideration that the number sequences might be affected by standardized residuals, this study applied the vector autoregressive moving average-EGARCH (VARMA-EGARCH) model to analyze the correlation between the three VOCs under different polluting activities. The VARMA-EGARCH model in this research included dummy variables representing changing points of variance structures in the variance formula to predict the conditional variance. This process proved able to effectively estimate the relevant coefficients of the three VOCs’ dynamic conditions that changed with time. The model also helped to prevent errors from occurring when estimating the conditional variance. Based on the testing results, this study determined the VARMA(2,1)-EGARCH(1,0) as the most suitable model for exploring the correlation between the three VOCs and meteorological phenomena, as well as the interplay between them in regard to interaction and formation. With the most representative of the three, toluene (TU), as the dependent variable and 1,2,4-Trimethylbenzene (TB) and Isopropyl benzene (IB) as the independent variables, this study found it impossible to calculate the TU concentration with TB and IB concentrations in the same period; estimations of TB and IB concentrations with a period of lag time were required because TU was mainly contributed by automobiles and motorcycles in Kaohsiung. TB and IB resulted from other stationary pollution sources in the region besides cars and motorbikes. When TU was evenly distributed and stayed longer in the atmosphere, the TB and IB concentrations were lower, so distribution conditions and concentrations could not be used to effectively estimate the concentration of toluene. This study had to wait until the next period, or when stationary pollution sources started producing TB and IB of higher concentrations during the daytime, in order to estimate the TU concentrations in a better photochemical situation.

Water-Enhanced Flux Changes under Dynamic Temperatures in the Vertical Vapor-Phase Diffusive Transport of Volatile Organic Compounds in Near-Surface Soil Environments

The quantitative understanding of the transport behavior of volatile organic compounds (VOCs) in near-surface soils is highly important in light of the potential impacts of soil VOC emissions on the air quality and climate. Previous studies have suggested that temperature changes affect the transport behavior; however, the effects are not well understood. Indeed, much larger changes in the VOC flux under in situ dynamic temperatures than those expected from the temperature dependence of the diffusion coefficients of VOCs in the air have been suggested but rarely investigated experimentally. Here, we present the results of a set of experiments on the upward vertical vapor-phase diffusive transport of benzene and trichloroethylene (TCE) in sandy soils with water contents ranging from an air-dried value to 10 wt% during sinusoidal temperature variation between 20 and 30 °C. In all experiments, the flux from the soil surface was correlated with the temperature, as expected. However, the changes in flux under wet conditions were unexpectedly large and increased with increasing water content; they were also larger for TCE, the volatility of which depended more strongly on the temperature. Additionally, the larger flux changes were accompanied by a recently discovered water-induced inverse correlation between temperature and flux into the overlying soil. These results demonstrated that the flux changes of VOCs under dynamic temperatures could be increased by volatilization-dissolution interactions of VOCs with water. Future extensive studies on this newly discovered phenomenon would contribute to a better understanding of the impacts of soil VOC emissions on the air quality and climate.

Measurement of the key parameters of VOC emissions from wooden furniture, and the impact of temperature

Volatile organic compounds (VOCs) emitted from furniture severely influence indoor air quality. Prior studies have mainly focused on the emissions from building materials and vehicle cabin materials, but rarely refer to indoor furniture. Considering the complex internal structure of furniture, this study presents a two-layer numerical model to describe the emission behaviors of VOCs from wooden furniture. A multi-parameter regression method was then proposed to determine the key parameters in the furniture, i.e., the initial emittable concentration, the diffusion coefficient and the partition coefficient. Experiments were conducted in a 1 m3 environmental chamber for VOC emissions from two kinds of wooden furniture (panel furniture and solid wood furniture). The agreement between model predictions and test data (R2 = 0.97–0.99) demonstrated the effectiveness of the model and measured key parameters. Compared with the traditional single-layer model, the two-layer numerical model can characterize the whole emission process from furniture better. In addition, the impact of temperature on the key parameters for furniture emissions was explored. With an increase in temperature from 23 °C to 35 °C, the diffusion coefficients for different VOCs from different wooden furniture, increase by 200%–2993%, while partition coefficients decrease by 41%–94%. This pattern conforms with that of VOC emissions from building materials. The present study should be helpful for source characterization of furniture and the associated exposure assessment.

Heating events drive the seasonal patterns of volatile organic compounds in a typical semi-arid city

The emission characteristics, source apportionment and chemical behavior of volatile organic compounds (VOCs) are important for strategy-making on ozone (O3) and fine particulate matter (PM2.5) control. Based on the continuous observation during four seasons, the seasonal characteristics, chemical reactivity and source apportionment of 116 VOCs species were studied in a typical semi-arid city with no relevant research. The results showed that the annual average concentrations of total volatile organic compounds (TVOCs) in Hohhot was 44.67 ± 46.59 ppbv with the predominant of alkanes and oxygenated volatile organic compounds (OVOCs). The sharp increment of TVOCs were explained by the elevating OVOCs and alkanes in autumn, while alkanes and alkenes in winter. The levels of alkenes presented negative and positive correlations with solar radiation and PM10, respectively. The mixing ratios accounted for 30% (alkanes) and 23% (alkenes and aromatics) of the TVOCs, respectively; while their ozone formation potential (OFP) ~15% and nearly 50% (even 75% in winter), respectively, indicating that the OFP of different VOCs species depends not only on their concentrations but more importantly on their chemical activity in atmosphere. According to the seasonal source apportionment, both the high levels of short-chain alkanes, alkenes and aromatics and the increasing coal sales volume suggested that the combustion sources were the predominant in heating seasons, while solvent uses was extracted as the most predominant during non-heating seasons. In non-heating seasons, the biogenic emission sources, ranking as the second contributor, were significantly higher than heating seasons. Isoprene was the most active biogenic VOCs species, bagging test results showed that deciduous trees were the predominant contributors for isoprene (~99%), while coniferous trees and shrub for monoterpenes (>95%). It will be helpful for understanding the characteristics of VOCs in Chinese national key development areas and informing policy to control semi-arid regional VOCs air pollution.