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Surface acoustic wave (SAW) gas sensors are simulated and discussed for the detection of the Dichloromethane (DCM) volatile organic gases (VOC) gas. The simulation was performed using Comsol Multip...

Environmental chamber studies are widely employed to investigate atmospheric chemistry and aerosol formation. However, the large surface area-to-volume ratio of a chamber leads to effects that need...

Atmospheric water-soluble organic gases such as pyruvic acid are produced in large quantities by photochemical oxidation of biogenic and anthropogenic emissions and undergo water-mediated reactions in aerosols and hydrometeors. These reactions can contribute to aerosol mass by forming less-volatile compounds. Although progress is being made in understanding the relevant aqueous chemistry, little is known about the chemistry that takes place during droplet evaporation. Here, we examine the evaporation of aqueous pyruvic acid droplets using both the vibrating orifice aerosol generator (VOAG) and an electrodynamic balance (EDB). In some cases, pyruvic acid was first oxidized by OH radicals. The evaporation behavior of oxidized mixtures was consistent with expectations based on known volatilities of reaction products. However, independent VOAG and EDB evaporation experiments conducted without oxidation also resulted in stable residual particles; the estimated volume yield was 10–30% of the initial pyruvic acid. Yields varied with temperature and pyruvic acid concentration across cloud-, fog-, and aerosol-relevant concentrations. The formation of low-volatility products, likely cyclic dimers, suggests that pyruvic acid accretion reactions occurring during droplet evaporation could contribute to the gas-to-particle conversion of carbonyls in the atmosphere.

Recently, nanoparticle-based immobilization of biocatalytic systems is getting interested in bioremediation efficiency. Therefore, hollow nanosphere particles of TiO2 - Cu (

Pathologic halitosis has been classified into 5 types: oral, airway, gastroesophageal, blood-borne and subjective, respectively. Type 1 (oral) halitosis mostly takes origin from anaerobic bacterial activities on oral surfaces. The role of anaerobic bacterial activities is clearly demonstrated, but despite the large number of anectodal claims, the role of Candida in patients with halitosis has not been adequately investigated. The aim of this study was to confirm the relationship between Candida and halitosis. A total of 136 subjects were enrolled and divided into two groups. The study group comprised of 69 patients with halitosis who had over 0.7 ppm H2S concentration in their oral cavity and the control group comprised of 67 healthly subjects. Self assesment scores for halitosis, Candida colony counts in saliva samples, oral NH3, SO2, H2S, H2 and volatile organic gas concentrations were recorded. H2S producing capacity of subjects was quantified by applying cysteine challenge test. Candida samples were taken from the mouths of the patients with and without halitosis, and Candida albicans isolates were inoculated into broth medium. After 3 days of incubation at 37oC, gas concentrations of the headspace of the flasks were read by a portable multigas detector. The rate of Candida positivity was 44.9% in the study group while it was 46.3% in the control group. There was no statistical significant difference between the groups according to the Candida growth (p= 0.561). The oral gas concentrations were comparable in both groups (p< 0.05). Oral H2S concentration increased 9.65 fold with 20 mM cysteine rinse in patients with halitosis while it was increased 5.8 fold in controls. Self assesment for halitosis were well correlated with clinical signs (p= 0.001, r= 0.8). Concentrations of hidrogen and organic gases were found to be increased in all Candida culture media. In this study, no relationship between the presence of Candida and oral halitosis was detected. As a result, there is no need for diets similar to Candida diet in the treatment of halitosis. On the other hand, cysteine challenge can be a useful diagnostic tool. In addition, portable gas detectors can be used as a convenient and practical halitometer to quantify halitosis.

We describe simulations using an updated version of the Community Multiscale Air Quality model version 5.3 (CMAQ v5.3) to investigate the contribution of intermediate-volatility organic compounds (IVOCs) to secondary organic aerosol (SOA) formation in southern California during the CalNex study. We first derive a model-ready parameterization for SOA formation from IVOC emissions from mobile sources. To account for SOA formation from both diesel and gasoline sources, the parameterization has six lumped precursor species that resolve both volatility and molecular structure (aromatic versus aliphatic). We also implement new mobile-source emission profiles that quantify all IVOCs based on direct measurements. The profiles have been released in SPECIATE 5.0. By incorporating both comprehensive mobile-source emission profiles for semivolatile organic compounds (SVOCs) and IVOCs and experimentally constrained SOA yields, this CMAQ configuration best represents the contribution of mobile sources to urban and regional ambient organic aerosol (OA). In the Los Angeles region, gasoline sources emit 4 times more non-methane organic gases (NMOGs) than diesel sources, but diesel emits roughly 3 times more IVOCs on an absolute basis. The revised model predicts all mobile sources (including on- and off-road gasoline, aircraft, and on- and off-road diesel) contribute ∼1 µg m−3 to the daily peak SOA concentration in Pasadena. This represents a ∼70 % increase in predicted daily peak SOA formation compared to the base version of CMAQ. Therefore, IVOCs in mobile-source emissions contribute almost as much SOA as traditional precursors such as single-ring aromatics. However, accounting for these emissions in CMAQ does not reproduce measurements of either ambient SOA or IVOCs. To investigate the potential contribution of other IVOC sources, we performed two exploratory simulations with varying amounts of IVOC emissions from nonmobile sources. To close the mass balance of primary hydrocarbon IVOCs, IVOCs would need to account for 12 % of NMOG emissions from nonmobile sources (or equivalently 30.7 t d−1 in the Los Angeles–Pasadena region), a value that is well within the reported range of IVOC content from volatile chemical products. To close the SOA mass balance and also explain the mildly oxygenated IVOCs in Pasadena, an additional 14.8 % of nonmobile-source NMOG emissions would need to be IVOCs (assuming SOA yields from the mobile IVOCs apply to nonmobile IVOCs). However, an IVOC-to-NMOG ratio of 26.8 % (or equivalently 68.5 t d−1 in the Los Angeles–Pasadena region) for nonmobile sources is likely unrealistically high. Our results highlight the important contribution of IVOCs to SOA production in the Los Angeles region but underscore that other uncertainties must be addressed (multigenerational aging, aqueous chemistry and vapor wall losses) to close the SOA mass balance. This research also highlights the effectiveness of regulations to reduce mobile-source emissions, which have in turn increased the relative importance of other sources, such as volatile chemical products.

The three-dimensional (3D) finite element (FE) simulation and analysis of Love wave sensors based on polyisobutylene (PIB) layers/SiO2/ST-90°X quartz structure are presented in this paper, as well as the investigation of coupled resonance effect on the acoustic properties of the devices. The mass sensitivity of the basic Love wave device with SiO2 guiding layers is solved analytically. And the highest mass sensitivity of 128 m2/kg is obtained as h s/λ = 0.175. The sensitivity of the Love wave sensors for sensing volatile organic compounds (VOCs) is greatly improved due to the presence of coupled resonance induced by the PIB nanorods on the device surface. The frequency shifts of the sensor corresponding to CH2Cl2, CHCl3, CCl4, C2Cl4, CH3Cl and C2HCl3 with the concentration of 100 ppm are 1.431 kHz, 5.507 kHz, 13.437 kHz, 85.948 kHz, 0.127 kHz and 17.879 kHz, respectively. The viscoelasticity influence of the sensitive material on the characteristics of SAW sensors is also studied. By taking account of the viscoelasticity of the PIB layers, the sensitivities of the SAW sensors with the PIB film and PIB nanorods decay in different degree. The gas sensing property of the Love wave sensor with PIB nanorods is superior to that of the PIB films. Meanwhile, the Love wave sensors with PIB sensitive layers show good selectivity to C2Cl4, making it an ideal selection for gas sensing applications.

Mist chambers (MC) have been used for decades to sample water-soluble gases in atmospheric studies. Herein, we characterize the use of a mist chamber for the collection of oxygenated organic gases, with a focus on intermediate solubility compounds to better constrain the transition from low-to-high collection efficiency. The investigated compounds span a range in Henry's law constants (KH, 2.5 × 101 M atm−1 to 4.1 × 105 M atm−1) and include moieties abundant in tropospheric gases (carboxylic acids, alcohols, and carbonyls). Under the configuration used here, the MC achieved greater than 90% collection efficiency for compounds with KH > 4.9 × 102 M atm−1. This represents an improvement over prior MC characterizations, likely due to the increased number of intermediate solubility compounds investigated. We apply the MC collection efficiency to simulations of VOC photooxidation. The results indicate that the MC is likely to collect the majority of gas-phase oxidation products for ten different VOCs, with the highest collection efficiency (94%) predicted for the oxidation products of α-pinene under low-NOx conditions.

The most significant negative environmental impacts of urban trucking result largely from travel in congested traffic. To illustrate the potential of innovative solutions to this problem, this paper presents new research on the emission reductions associated with off-hour freight deliveries (OHD). The paper uses fine-level GPS data of delivery operations during regular-hours (6 AM to 7 PM), and off-hours (7 PM to 6 AM), to quantify emissions in three major cities in the Americas. Using second-by-second emissions modeling, the paper compares emissions under both delivery schedules for: reactive organic gases, total organic gases, carbon monoxide, carbon dioxide, oxides of nitrogen, and particulate matter. The results show that the magnitude of the emission reductions depends on the extent of the change of delivery time. In the case of the “Full” OHD programs of New York City and Sao Paulo—where the deliveries were made during the late night and early morning periods (7 PM to 6 AM)—the emission reductions are in the range of 45–67%. In the case of the “Partial” OHD used in Bogota (where OHD took place between 6 PM and 10 PM), the reductions were about 13%. The emission reductions per kilometer are used to estimate the total reductions for the cities studied, and for all metropolitan areas in the world with more than two million residents. The results indicate the considerable potential of OHD as an effective—business friendly—sustainability tool to improve the environmental performance of urban deliveries. The chief implication is that public policy should foster off-hour deliveries, and all forms of Freight Demand Management, where practicable.

Antoine is mainly known for the equation usually used for predicting vapor pressure of pure compounds that bears his name. In this article we show a little known equation of state (EoS), as well as its functionality to predict current PvT properties of more than forty compounds including industrial, noble, and organic gases. The Antoine EoS has been parameterized in three regions: P r 1.2 , 1.2 ⩽ P r ⩽ 10 and P r > 10 in order to improve its performance in the widest possible area. The proposed sets of optimized parameters were fitted by minimizing deviations after comparing predicted values with available experimental data in open literature. The volumes predicted with the optimized Antoine EoS have been compared with those calculated with the widely-known Soave-Redlich-Kwong (SRK), Peng-Robinson-Stryjek-Vera (PRSV2) and Valderrama-Patel-Teja (VPT) equations of state. Results obtained by using the optimized Antoine EoS show better accuracy in the zone of high reduced pressures for all compounds and, in a more general way, for most of the compounds in the remaining zones than the other equations of state. The extension to noble gases and other compounds originally not taken into account by Antoine have been successfully achieved.

Purpose of Review: Climate factors may considerably impact on natural aerosol emissions and atmospheric distributions. The interdependencies of processes within the aerosol-climate system may thus cause climate feedbacks that need to be understood. Recent findings on various major climate impacts on aerosol distributions are summarized in this review. Recent Findings: While generally atmospheric aerosol distributions are influenced by changes in precipitation, atmospheric mixing, and ventilation due to circulation changes, emissions from natural aerosol sources strongly depend on climate factors like wind speed, temperature, and vegetation. Aerosol sources affected by climate are desert sources of mineral dust, marine aerosol sources, and vegetation sources of biomass burning aerosol and biogenic volatile organic gases that are precursors for secondary aerosol formation. Different climate impacts on aerosol distributions may offset each other. Summary: In regions where anthropogenic aerosol loads decrease, the impacts of climate on natural aerosol variabilities will increase. Detailed knowledge of processes controlling aerosol concentrations is required for credible future projections of aerosol distributions.

Due to the continuous increase in industrial pollution and modern lifestyle, several types of air contaminants and their concentrations are emerging in the atmosphere. Besides, photocatalysis has gained much attention in the elimination of air pollution. Several ultraviolet and visible light active photocatalysts were tested in air pollutant treatment and thereby, the number of reports was increased in the past few years. In this context, this review describes the photocatalytic treatment of gaseous inorganic contaminants like NOx, H2S, and organic pollutants like formaldehyde, acetaldehyde, and benzene derivatives. Different photocatalysts with their air pollutant removal efficiency were explained. Improving strategies such as metal/non-metal doping, composite formation for photocatalyst activities have been studied. Moreover, an analysis is presented from each of the existing photocatalytic immobilization approaches. Also, factors responsible for effective photocatalysis were explained. Overall, the photocatalytic abatement technique is an auspicious way to eliminate different air contaminants. Besides, existing drawbacks and future challenges are also discussed.

Cooking emissions have been identified as a major source of primary organic aerosol (POA) in urban environments. Cooking may also be a potential source of secondary organic aerosol (SOA) because of the abundant emissions of non-methane organic gases. We studied SOA formation from the photooxidation of emissions from seven vegetable oils heated at 200 °C under high-NOx conditions in a smog chamber. After the samples had been aged under an OH exposure of 1.0 × 1010 molecules cm–3 s, the SOA formation rate was generally 1 order of magnitude higher than the POA emission rate. We determined that alkenals, which are not traditional SOA precursors in chemical transport models, accounted for 5–34% of the observed SOA. The unexplained SOA may be attributed to the oxidation of primary semivolatile and intermediate-volatility organic compounds (SVOCs and IVOCs, respectively), which were estimated to contribute an additional 9–106% of the observed SOA assuming the volatility distribution of heated cooking oils is the...

New treatments for organic aerosol (OA) formation have been added to a modified version of the CESM/CAM5 model (CESM‐NCSU). These treatments include a volatility basis set treatment for the simulation of primary and secondary organic aerosols (SOAs), a simplified treatment for organic aerosol (OA) formation from glyoxal, and a parameterization representing the impact of new particle formation (NPF) of organic gases and sulfuric acid. With the inclusion of these new treatments, the concentration of oxygenated organic aerosol increases by 0.33 µg m−3 and that of primary organic aerosol (POA) decreases by 0.22 µg m−3 on global average. The decrease in POA leads to a reduction in the OA direct effect, while the increased OOA increases the OA indirect effects. Simulations with the new OA treatments show considerable improvement in simulated SOA, oxygenated organic aerosol (OOA), organic carbon (OC), total carbon (TC), and total organic aerosol (TOA), but degradation in the performance of HOA. In simulations of the current climate period, despite some deviations from observations, CESM‐NCSU with the new OA treatments significantly improves the magnitude, spatial pattern, seasonal pattern of OC and TC, as well as, the speciation of TOA between POA and OOA. Sensitivity analysis reveals that the inclusion of the organic NPF treatment impacts the OA indirect effects by enhancing cloud properties. The simulated OA level and its impact on the climate system are most sensitive to choices in the enthalpy of vaporization and wet deposition of SVOCs, indicating that accurate representations of these parameters are critical for accurate OA‐climate simulations., Key Points VBS and other OA updates significantly improve OA model performanceOA‐climate interactions are the most sensitive to enthalpy of vaporization and semivolatile organic compounds wet depositionThe updated CESM‐NCSU OA treatments reasonably simulate OA in the current climate

Purpose This paper aims to show how a range of new and emerging applications are driving technological innovations in gas sensing. Design/methodology/approach Following a short introduction, this paper first considers developments relating to the needs of the military and security sectors. Wearable gas sensors, energy harvesting and self-powered gas sensors are then discussed. The role of gas sensors in mobile phones is then considered, together with details of new developments in sensors for carbon-dioxide, particulates and formaldehyde. Finally, brief conclusions are drawn. Findings This paper shows that a technologically diverse range of gas sensors is being investigated and developed in response to a number of new and emerging requirements and applications. The gas sensors respond to numerous inorganic and organic gases and vapours over a wide range of application-specific concentrations and are based on a multitude of often innovative sensing techniques, technologies and materials. Originality/value This paper provides technical details of a selection of gas sensor research activities and product developments that reflect the needs of a range of new and emerging applications.

Volatile organic compound (VOCs) emissions from sources often need to be compressed or “lumped” into species classes for use in emissions inventories intended for air quality modeling. This needs to be done to ensure computational efficiency. The lumped profiles are usually reported for one value of ambient temperature. However, temperature-specific detailed profiles have been constructed in the recent past - the current study investigates how the lumping of species from those profiles into different atmospheric chemistry mechanisms is affected by temperature, considering three temperatures (−18 °C, −7 °C and 24 °C). The mechanisms considered differed on the assumptions used for lumping: CB05 (carbon bond type), SAPRC (ozone formation potential) and RACM2 (molecular surrogate and reactivity weighting). In this space, four sub-mechanisms for SAPRC were considered. Scaling factors were developed for each lumped model species and mechanism in terms of moles of lumped species per unit mass. Species which showed a direct one-to-one mapping (SAPRC/RACM2) reported scaling factors that were unchanged across mechanisms. However, CB05 showed different trends since one compound often is mapped onto multiple model species, out of which the paraffinic double bond (PAR) is predominant. Temperature-dependent parameterizations for emission factors pertaining to each lumped species class and mechanism were developed as part of the study. Here, the same kind of model species showed varying lumping parameters across the different mechanisms. These differences could be attributed to differing approaches in lumping. The scaling factors and temperature-dependent parameterizations could be used to update emissions inventories such as MOVES or SMOKE for use in chemical transport modeling.

The determination of non-methane organic gases (NMOG) emissions according to United States Environmental Protection Agency (EPA) regulations is currently a multi-step process requiring separate measurement of various emissions components by a number of independent on-line and off-line techniques. The Fourier transform infrared spectroscopy (FTIR) method described in this paper records all required components using a single instrument. It gives data consistent with the regulatory method, greatly simplifies the process, and provides second by second time resolution. Non-methane hydrocarbons (NMHCs) are measured by identifying a group of hydrocarbons, including oxygenated species, that serve as a surrogate for this class, the members of which are dynamically included if they are present in the exhaust above predetermined threshold levels. This yields an FTIR equivalent measure of NMHC that correlates within 5% to the regulatory flame ionization detection (FID) method. NMOG is then determined per regulatory calculation solely from FTIR recorded emissions of NMHC, ethanol, acetaldehyde, and formaldehyde, yielding emission rates that also correlate within 5% with the reference method. Examples are presented to show how the resulting time resolved data benefit aftertreatment development for light duty vehicles.

Secondary organic aerosols (SOA) are products of the reaction of reactive organic gases (ROGs) and ozone. Most SOA are in the nanometer or submicron range, and thus SOA may be harmful to human health. Concentrations of ROGs may be high in newly decorated rooms, which may result in high SOA concentrations, especially during seasons with high ozone concentration. The objective of this study was to investigate the concentrations of SOA and the extent to which SOA contribute to indoor PM2.5 concentrations in newly decorated residential buildings. We measured concentrations of ROGs in 24 rooms of eight newly decorated (within the preceding three months) residential buildings in Beijing, China. Using previously measured indoor ozone decay rates, air change rates, and corresponding monitored ozone concentrations, we estimated the indoor ozone concentrations for the newly decorated rooms. Subsequently SOA concentrations were calculated using an aerosol mass fraction (AMF) model. We further estimated the fractions of SOA concentrations in indoor PM2.5. The SOA concentrations in 18 of the rooms ranged from 0.88 to 18.18 μg/m3, contributing to between 3.77% and 78.57% of indoor PM2.5 concentrations. The other six rooms had much lower SOA concentrations, less than 0.1 μg/m3, contributing to less than 0.39% of indoor PM2.5 concentrations. The results indicate that the concentrations and contribution of SOA in most newly decorated residential rooms are much higher than those in rooms with long-term occupancy, while some newly decorated rooms can still have low SOA concentrations.

Soils both emit and take up different biogenic volatile organic compounds, altering the chemical composition of the atmosphere and influencing local, regional, and global climate.

To study the fate of cyclic volatile methyl siloxanes (cVMS) undergoing photooxidation in the environment and to assess the acute toxicity of inhaled secondary aerosols from cVMS, we used an oxidative flow reactor (OFR) to produce aerosols from oxidation of decamethylcyclopentasiloxane (D5). The aerosols produced from this process were characterized for size, shape, and chemical composition. We found that the OFR produced aerosols composed of silicon and oxygen, arranged in chain agglomerates, with primary particles of approximately 31 nm in diameter. Lung cells were exposed to the secondary organosilicon aerosols at estimated doses of 54–116 ng/cm2 using a Vitrocell air-liquid interface system, and organic gases and ozone exposure was minimized through a series of denuders. Siloxane aerosols were not found to be highly toxic.

Room Temperature Ionic Liquids (RTILs) are innovative materials that have the potential to be used as gas sensing films without special operating conditions. We measured the frequency shift and also the resistance change with Vector Network Analyzers in order to observe the behavior of RTILs during the adsorption. Both the frequency and the resistance of QCM coated with RTIL selectively responded to sample gases. Consequently, the experimental result shows the possibility of the utilization of RTILs for sensing films.

Marine photosynthetic organisms emit organic gases, including the polyolefins isoprene (C_5H_8) and monoterpenes (MTPs, C_(10)H_(16)), into the boundary layer. Their atmospheric processing produces particles that influence cloud formation and growth and, as a result, the Earth’s radiation balance. Here, we report that the heterogeneous ozonolysis of dissolved α-pinene by O_3(g) on aqueous surfaces is dramatically accelerated by I–, an anion enriched in the ocean upper microlayer and sea spray aerosols (SSAs). In our experiments, liquid microjets of α-pinene solutions, with and without added I–, are dosed with O_3(g) for τ < 10 μs and analyzed online by pneumatic ionization mass spectrometry. In the absence of I–, α-pinene does not detectably react with O_3(g) under present conditions. In the presence of ≥ 0.01 mM I–, in contrast, new signals appear at m/z = 169 (C_9H_(13)O_3–), m/z = 183 (C_(10)H_(15)O_3–), m/z = 199 (C_(10)H_(15)O_4–), m/z = 311 (C_(10)H_(16)IO_3–), and m/z = 461 (C_(20)H_(30)IO_4–), plus m/z = 175 (IO_3–), and m/z = 381 (I_3–). Collisional fragmentation splits CO_2 from C_9H_(13)O_3–, C_(10)H_(15)O_3– and C_(10)H_(15)O_4–, and I– plus IO– from C_(10)H_(16)IO_3– as expected from a trioxide IOOO•C_(10)H_(16)– structure. We infer that the oxidative processing of α-pinene on aqueous surfaces is significantly accelerated by I– via the formation of IOOO– intermediates that are more reactive than O_3. A mechanism in which IOOO– reacts with α-pinene (and likely with other unsaturated species) in competition with its isomerization to IO_3–accounts for present results and the fact that soluble iodine in SSA is mostly present as iodine-containing organic species rather than the thermodynamically more stable iodate. By this process, a significant fraction of biogenic MTPs and other unsaturated gases may be converted to water-soluble species rather than emitted to the atmosphere.

Water-soluble organic gas (WSOG) concentrations are elevated in homes. However, WSOG sources, sinks, and concentration dynamics are poorly understood. We observed substantial variations in 23 residential indoor WSOG concentrations measured in real time in a North Carolina, U.S. home over several days with a high-resolution time-of-flight chemical ionization mass spectrometer equipped with iodide reagent ion chemistry (I-HR-ToF-CIMS). Concentrations of acetic, formic, and lactic acids ranged from 30 – 130, 15 – 53, and 2.5 – 360 μg m(−3), respectively. Concentrations of several WSOGs, including acetic and formic acids, decreased considerably (~ 30-50%) when the air conditioner (AC) cycled on, suggesting that the AC system is an important sink for indoor WSOGs. In contrast to non-polar organic gases, indoor WSOG loss rate coefficients were substantial for compounds with high O:C ratios (e.g., 1.6 – 2.2 h(−1) for compounds with O:C > 0.75 when the AC system was off). Loss rate coefficients in the AC system were more uncertain, but were estimated to be 1.5 hr(−1). Elevated concentrations of lactic acid coincided with increased human occupancy and cooking. We report several WSOGs emitted from cooking and cleaning as well as transported in from outdoors. In addition to indoor air chemistry, these results have implications to exposure and human health.

WO 3 nanorod bundles were prepared via a facile hydrothermal method with Na 2 SO 4 as structure directing agent. Field-emission scanning electron microscopy (FESEM) and transmission electronic microscopy (TEM) images indicate that the WO 3 nanorod bundles consist of hierarchically nanostructured bundles assembled with smaller nanorod subunits. Furthermore, the gas-sensing properties of the as-prepared WO 3 were tested to a series of organic gases. The WO 3 nanorod bundles display a significantly better sensing performance (100 ppm formic acid, R a / R g = 51.3) than commercial WO 3 (100 ppm formic acid, R a / R g = 1.8) for the detection of formic acid. The results demonstrated that the WO 3 nanorod bundles have a potential application in formic acid sensors.

Organic gases undergoing conversion to form secondary organic aerosol (SOA) during atmospheric aging are largely unidentified, particularly in regions influenced by anthropogenic emissions. SOA dominates the atmospheric organic aerosol burden and this knowledge gap contributes to uncertainties in aerosol effects on climate and human health. Here we characterize primary and aged emissions from residential wood combustion using high resolution mass spectrometry to identify SOA precursors. We determine that SOA precursors traditionally included in models account for only ~3–27% of the observed SOA, whereas for the first time we explain ~84–116% of the SOA by inclusion of non-traditional precursors. Although hundreds of organic gases are emitted during wood combustion, SOA is dominated by the aging products of only 22 compounds. In some cases, oxidation products of phenol, naphthalene and benzene alone comprise up to ~80% of the observed SOA. Identifying the main precursors responsible for SOA formation enables improved model parameterizations and SOA mitigation strategies in regions impacted by residential wood combustion, more productive targets for ambient monitoring programs and future laboratories studies, and links between direct emissions and SOA impacts on climate and health in these regions.

Gas-to-particle partitioning of organic aerosols (OA) is represented in most models by Raoult's law, and depends on the existing mass of particles into which organic gases can dissolve. This raises the possibility of non-linear response of particle-phase OA mass to the emissions of precursor volatile organic compounds (VOCs) that contribute to this partitioning mass. Implications for air quality management are evident: a strong non-linear dependence would suggest that reductions in VOC emission would have a more-than-proportionate benefit in lowering ambient OA concentrations. Chamber measurements on simple VOC mixtures generally confirm the non-linear scaling between OA and VOCs, usually stated as a mass-dependence of the measured OA yields. However, for realistic ambient conditions including urban settings, no single component dominates the composition of the organic particles, and deviations from linearity are presumed to be small. Here we re-examine the linearity question using volatility spectra from several sources: (1) chamber studies of selected aerosols, (2) volatility inferred for aerosols sampled in two megacities, Mexico City and Paris, and (3) an explicit chemistry model (GECKO-A). These few available volatility distributions suggest that urban OA may be only slightly super-linear, with most values of the normalized sensitivity exponent in the range 1.1–1.3, also substantially lower than seen in chambers for some specific aerosols. The rather low exponents suggest that OA concentrations in megacities are not an inevitable convergence of non-linear effects, but can be addressed (much like in smaller urban areas) by proportionate reductions in emissions.

Gas sensors are critical components when adhering to health safety and environmental policies in various manufacturing industries, such as the petroleum and oil industry, scent and makeup production, food and beverage manufacturing, chemical engineering, pollution monitoring. In recent times, gas sensors have been introduced to medical diagnostics, bioprocesses, and plant disease diagnosis processes. There could be an adverse impact on human health due to the mixture of various gases (e.g., acetone (A), ethanol (E), propane (P)) that vent out from industrial areas. Therefore, it is important to accurately detect and differentiate such gases. Towards this goal, this paper presents a novel electronic nose (e-nose) detection method to classify various explosive gases. To detect explosive gases, metal oxide semiconductor (MOS) sensors are used as reliable tools to detect such volatile gases. The data received from MOS sensors are processed through a multivariate analysis technique to classify different categories of gases. Multivariate analysis was done using three variants&mdash, differential, relative, and fractional analyses&mdash, in principal components analysis (PCA). The MOS sensors also have three different designs: loading design, notch design, and Bi design. The proposed MOS sensor-based e-nose accurately detects and classifies three different gases, which indicates the reliability and practicality of the developed system. The developed system enables discrimination of these gases from the mixture. Based on the results from the proposed system, authorities can take preventive measures to deal with these gases to avoid their potential adverse impacts on employee health.

Herein, the effect of material structure on photocatalytic activity in the decomposition of nocuous organic gases (1,3,5-trimethylbenzene (TMB) and o-xylene (XYL)) was investigated by synthesizing tricomposite photocatalysts of N-doped carbon quantum dots, ZnFe2O4, and BiOBr (NCQDs/ZFO/BOB) with different junctions. The NCQDs/ZFO/BOB material (NCQDs/ZFO/BOB1) synthesized using a one-pot method revealed the highest photocatalytic efficiency. The NCQDs in NCQDs/ZFO/BOB1 exhibited photoluminescence property that expanded the photo-absorption nature and acted as a mediator to enhance the Z-scheme charge transfer between ZFO and BOB. The photocatalytic activity exhibited by NCQDs/ZFO/BOB1 was higher than that exhibited by the selected reference materials (CQDs/ZFO/BOB, NCQDs/BOB, ZFO/BOB, BOB, NCQDs/ZFO, and ZFO). Results showed that the decomposition efficiencies of TMB and XYL in the presence of NCQDs/ZFO/BOB1 under specified operational conditions were 94.5% and 72.5%, respectively. Moreover, the synthesized NCQDs/ZFO/BOB photocatalysts displayed excellent stability. Herein, the conversion ratios of TMB and XYL into CO2 with NCQDs/ZFO/BOB1 and the intermediates formed during photocatalysis were assessed. Furthermore, a potential mechanism for the NCQDs/ZFO/BOB1-catalyzed organic gas decomposition was proposed. The hybridization access introduced herein thus provides a method for the intelligent synthesis of a new type of multicomponent nanocomposites for environmental remediation.

Indoor particles represent a combination of outdoor-originating particles, indoor-emitted particles and indoor secondary organic aerosol (SOA). It is important to distinguish the contributions of different particle sources to indoor PM2.5 (particulate matter with an aerodynamic diameter of 2.5 μm or less) because of the differences in concentration, composition, toxicity and management approaches among these sources. The objective of this study is to estimate the extent to which outdoor-originating particles, indoor-emitted particles and SOA contribute to the residential indoor PM2.5 concentration in Beijing, China. Based on measurements of reactive organic gases (ROGs), their concentrations in 90 residential rooms and an experimental verification of the O 3 surface removal rate, a mass-balance model was employed to estimate the different sources' contributions to the indoor PM2.5 concentration. The results show that SOA contribute little (less than 3%) to the indoor PM2.5 concentration. Outdoor-originating particles contribute the most to indoor PM2.5 concentration, with a contribution of 54%–63% when windows are closed and over 92% when windows are open. The indoor-emitted particles contribution varies over a wide range, from approximately 4% when windows are open to 37%–46% when windows are closed. The outdoor PM2.5 concentration and PM2.5 deposition rate are the most important two factors affecting indoor PM2.5 concentration. Air exchange rate, cooking and smoking emission strength can clearly also change the indoor PM2.5 concentration. The effect of the PM2.5 penetration factor is very small.

As a typical n-type semiconductor, WO3 is considered to be the promising material to fabricate the gas sensor, which has a widespread utilization in the environment detecting and the safety monitoring. This review details the different structures of WO3 synthesized in recent studies, classifying them into five sections according to their dimensionality, then elucidates the research progress of the gas sensitivity towards H2, CO, H2S, NH3, NOx, O3 as well as some organic gases, based on which two models are proposed to explain the corresponding gas sensing mechanisms. Besides these, some unsolved problems and possible future directions are also discussed.

Dampness affects a substantial percentage of homes and is associated with increased risk of respiratory ailments; yet the effects of dampness on indoor chemistry are largely unknown. We hypothesize that the presence of water-soluble gases and their aqueous processing alters the chemical composition of indoor air and thereby affects inhalation and dermal exposures in damp homes. Herein, we use the existing literature and new measurements to examine the plausibility of this hypothesis, summarize existing evidence, and identify key knowledge gaps. While measurements of indoor volatile organic compounds (VOCs) are abundant, measurements of water-soluble organic gases (WSOGs) are not. We found that concentrations of total WSOGs were, on average, 15 times higher inside homes than immediately outside (N=13). We provide insights into WSOG compounds likely to be present indoors using peer-reviewed literature and insights from atmospheric chemistry. Finally, we discuss types of aqueous chemistry that may occur on indoor surfaces and speculate how this chemistry could affect indoor exposures. Liquid water quantities, identities of water-soluble compounds, the dominant chemistry, and fate of aqueous products are poorly understood. These limitations hamper our ability to determine the effects of aqueous indoor chemistry on dermal and inhalation exposures in damp homes. This article is protected by copyright. All rights reserved.

On-road gasoline vehicles are a major source of secondary organic aerosol (SOA) in urban areas. We investigated SOA formation by oxidizing dilute, ambient-level exhaust concentrations from a fleet of on-road gasoline vehicles in a smog chamber. We measured less SOA formation from newer vehicles meeting more stringent emissions standards. This suggests that the natural replacement of older vehicles with newer ones that meet more stringent emissions standards should reduce SOA levels in urban environments. However, SOA production depends on both precursor concentrations (emissions) and atmospheric chemistry (SOA yields). We found a strongly nonlinear relationship between SOA formation and the ratio of nonmethane organic gas to oxides of nitrogen (NOx) (NMOG:NOx), which affects the fate of peroxy radicals. For example, changing the NMOG:NOx from 4 to 10 ppbC/ppbNOx increased the SOA yield from dilute gasoline vehicle exhaust by a factor of 8. We investigated the implications of this relationship for the Los Angeles area. Although organic gas emissions from gasoline vehicles in Los Angeles are expected to fall by almost 80% over the next two decades, we predict no reduction in SOA production from these emissions due to the effects of rising NMOG:NOx on SOA yields. This highlights the importance of integrated emission control policies for NOx and organic gases.

In this paper, we have designed a SAW gas sensor based on MEMS technology to detect volatile organic gases. Finite element analysis of the device had been carried out to observe the changes in the sensor behaviour with the applied gases. Also, the designed SAW Gas Sensor is analysed with different piezoelectric substrate. Lithium Tantalate is found to be best suited for the design which defines the resonant frequency of the device to be approximately 1.184 GHz. The device is further simulated with different volatile organic gases which give corresponding shift in frequency.

Introducción. El Laboratorio de Anatomía Humana dispone de cadáveres que han sido sometidos al proceso de fijación y conservación de tejidos mediante la aplicación de formaldehído (al 10%), sustancia tóxica y cancerígena para el ser humano, según lo estipulado por la International Agency for Research on Cancer (iarc), a la que están expuestos estudiantes, profesores y técnicos. La presente investigación tuvo como propósito medir las concentraciones de formaldehído en el ambiente dentro de las instalaciones de un laboratorio de Anatomía Humana y compararlas con estándares laborales internacionales. Metodología. El diseño del estudio fue transversal con enfoque descriptivo. La muestra del estudio fue de 640 mediciones realizadas con el aparato digital hal-hfx105 HalTech y aplicando la norma técnica de prevención ntp 587, validada para la determinación de gases y vapores orgánicos en el aire dentro del laboratorio. Resultado. La concentración de formaldehído promedio estimada en general dentro de las instalaciones del Laboratorio de Anatomía fue de 0.24 ppm. ConclusIón. El promedio de concentración de formaldehído encontrado en el presente estudio es inferior al límite de exposición profesional estimado por la American Conference of Industrial Hygienists (acgih), cuyo valor tlv-twa (Threshold Limit Value-Time Weighted Average) para un día laboral de 8 horas y una semana de 40 horas, y como límite máximo a las concentraciones que cualquier trabajador puede ser expuesto día tras día sin efectos adversos, es de 0.3 ppm.CREA CIENCIA Vol. 11 No 1-2 ISSN 1818-202X enero-diciembre 2017, p. 7-13

Measurements of the water-soluble organic nitrogen (WSON) in the aerosols were conducted over three years at two sites; an urban site in Kofu and a forested site in Fujiyoshida, Japan. Our preliminary experiment demonstrated that the adsorption of organic gases on the filter had little effect on the measurement of the WSON. The mean concentration of the WSON in the aerosols at the urban site was 0.221 μg m−3, which was higher than that of 0.101 μg m−3 at the forested site. Large portions of the WSON were found in the fine-mode range; 90.3% at the urban site and 86.4% at the forested site. The WSON constituted a significant fraction of the water-soluble total nitrogen (WSTN) in the aerosols; 11.1% and 16.2% of the WSTN in the coarse and fine particles, respectively, at the urban site, and 11.5% and 13.1% in the coarse and fine particles, respectively, at the forested site. The fine-mode WSON would be derived from the reaction of its basic precursor gases with particulate or gaseous acidic species. Photochemical reactions and combustion emissions could also be important sources of the fine-mode WSON. In the coarse-mode range, on the other hand, vegetation sources could be an important source of the WSON. The mean concentration of urea in the aerosols at the urban site was 1.7 ngN m−3. A large portion (87.2%) of the urea was partitioned into the fine-mode range. Urea is a minor compound in the particulate WSON in this region with contributions to about 1% of the WSON. Approximately 26% of the dry deposition of the WSTN was attributed to the WSON in the cold season. The significant part (96.5%) of the WSON was deposited by coarse aerosols. Coarse-mode WSON is important for discussing the dry deposition fluxes of the WSON and fixed nitrogen.

Carbon fiber reinforced plastics (CFRP) show high potential for use in lightweight applications not only in aircraft design, but also in the automotive or wind energy industry. However, processing of CFRP is complex and expensive due to their outstanding mechanical properties. One possibility to manufacture CFRP structures flexibly at acceptable process speeds is high-power laser cutting. Though showing various advantages such as contactless energy transfer, this process is connected to potentially hazardous emission of respirable dust and organic gases. Moreover, the emitted particles may be fibrous, thus requiring particular attention. Here, a systematic analysis of the hazardous substances emitted during laser cutting of CFRP with thermoplastic and thermosetting matrix is presented. The objective is to evaluate emission rates for the total particulate and gaseous fractions as well as for different organic key components. Furthermore, the influence of the laser process conditions shall be assessed, and first proposals to handle the emissions adequately are made.

A Z-scheme g-C3N4/V2O5 heterostructure was freshly applied to the removal of indoor noxious gases. In addition, to continuously remove noxious organic gases with minimal photocatalyst loss in a steady-flow chamber, the Z-scheme g-C3N4/V2O5 photocatalytic system having a three-dimensional monolithic structure was realized by immobilizing the photocatalytic nanocomposite powder into a melamine sponge. The g-C3N4/V2O5 monolith (CN/VOM) exhibited the best photocatalytic capability, followed in order by the g-C3N4 and V2O5 ones; specifically, the nonanaldehyde removal efficiency over the CN/VOM photocatalyst was as high as 97% under certain experimental conditions. The removal efficiency patterns of these three photocatalytic systems were consistent with their photoelectrochemical properties. In addition, a reusability test revealed prominent photocatalytic stability of the CN/VOM system, which was supported by X-ray diffraction analysis of used and unused samples. The good capability and stability of the CN/VOM were ascribable to its elevated charge-separation ability given by the Z-scheme charge transmission process at the interfaces between g-C3N4 and V2O5. The effects of the V2O5 content and the pollutant feed concentration on the CN/VOM photocatalytic performance were also investigated; a Z-scheme process was defined in the removal of gas pollutants over these CN/VOM systems. This study demonstrates that improved photocatalytic performance of designed materials in the removal of model pollutants can expedite the development of upcoming photocatalytic systems for the continuous removal of noxious organic gas gases without significant photocatalyst losses.

Gas-phase water-soluble organic matter (WSOMg) is ubiquitous in the troposphere. In the summertime, the potential for these gases to partition to particle-phase liquid water (H2Optcl) where they can form secondary organic aerosol (SOAAQ) is high in the Eastern US and low elsewhere, with the exception of an area near Los Angeles, CA. This spatial pattern is driven by mass concentrations of H2Optcl, not WSOMg. H2Optcl mass concentrations are predicted to be high in the Eastern US, largely due to sulfate. The ability of sulfate to increase H2Optcl is well established and routinely included in atmospheric models; however WSOMg partitioning to this water and subsequent SOA formation is not. The high mass concentrations of H2Optcl in the southeast (SE) US but not the Amazon may help explain why biogenic SOA mass concentrations are high in the SE US but low in the Amazon. Furthermore, during the summertime in the Eastern US, the potential for organic gases to partition into liquid water is greater than their potential to partition into organic matter (OM) because concentrations of WSOMg and H2Optcl are higher than semi-volatile gases and OM. Thus, unless condensed phase yields are substantially different (> ~ order of magnitude), we expect that SOA formed through aqueous-phase pathways (SOAAQ) will dominate in the Eastern US. These findings also suggest that H2Optcl is largely anthropogenic and provide a previously unrecognized mechanism by which anthropogenic pollutants impact the amount of SOA mass formed from biogenic organic emissions. The previously reported estimate of the controllable fraction of biogenic SOA in the Eastern US (50%) is likely too low.

The authors propose a new “three-layer” conceptual model for the air-sea exchange of organic gases, which includes a dynamic surface microlayer with photochemical and biological processes. A parame...

To investigate the influence of the activated carbon pore structure on the adsorption of volatile organic compounds (VOCs), three commercial activated carbon samples were chosen. The fixed-bed thermostatic adsorption experiments were conducted under certain conditions, where toluene, acetone, and 1, 2-dichloroethane acted as adsorbents. Then, the incidence relation between the experimental results and the activated carbon pore structure was analyzed. After that, the results of the correlation analysis were verified in accordance with fractal theory and adsorption characteristic curve analysis. The results show that the pore diameter gradient is helpful for strengthening the internal diffusion. Under the same condition, the adsorption of organic gases tends to be selective, and the positions of toluene, acetone and 1, 2-dichloroethane adsorbed on the activated carbon are mainly in the ranges of 1.27–1.49 nm, 0.67–0.84 nm and 1.39–1.75 nm, respectively. The relationship between adsorption capacity and activated carbon pore volume can accurately explain the spreading process of the adsorbents in the activated carbon.

The relative importance of NO3-initiated source and heterogeneous sink of organic aerosol in the western United States is investigated using the WRF/Chem regional weather and chemistry model. The model is run for the four individual months, representing the four seasons, of January, May, August, and October, to produce hourly spatial maps of surface concentrations of NO3, organic aerosol (OA), and reactive organic gases (ROG, a sum of alkene species tracked in the lumped chemical mechanism employed). These "baseline" simulations are used in conjunction with literature data on secondary organic aerosol (SOA) mass yields, average organic aerosol composition, and reactive uptake coefficients for NO3 on organic surfaces to predict SOA source and OA heterogeneous loss rates due to reactions initiated by NO3. We find both source and sink rates maximized downwind of urban centers, therefore with a varying location that depends on wind direction. Both source and sink terms are maximum in summer, and SOA source dominates over OA loss by approximately three orders of magnitude, with large day-to-day variability. The NO3 source of SOA (peak production rates of 0.4–3.0 μg kg−1 h−1) is found to be significantly larger than the heterogeneous sink of OA via NO3 surface reactions (peak loss rates of 0.5–8 × 10−4 μg kg−1 h−1).

Different organic compounds exhibit different propensities for ozone formation. Two approaches were used to study the ozone formation potentials or source reactivities of different anthropogenic organic compounds emission categories in California's South Coast Air Basin (SoCAB). The first approach was based on the combination of total organic gases (TOG) emission speciation profiles and the maximum incremental reactivity (MIR) scale of organic species. The second approach quantified ozone impacts from different emission sources by performing 3-dimensional air quality model sensitivity analysis involving increased TOG emissions from particular sources. The source reactivities derived from these two approaches agree reasonably well for 58 anthropogenic organic compounds emission categories in the SoCAB. Both approaches identify TOG emissions from mobile sources as having the highest reactivity. Source reactivities from both approaches were also combined with TOG emissions from each source category to produce a 2005 reactivity-based anthropogenic TOG emission inventory for the SoCAB. The top five reactivity-based anthropogenic TOG emission sources in the SoCAB during 2005 were: light-duty passenger cars, off-road equipment, consumer products, light-duty trucks category 2 (i.e., 3751–5750 lb), and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that livestock waste and composting emission categories were two of the five largest mass-based anthropogenic TOG emission sources. The reactivity-based TOG emission inventory is an important addition to the mass-based TOG emission inventory because it represents the ozone formation potentials from emission sources and can be used to assist in determining targeted sources for developing organic compounds reduction policies.

A simple gas chromatographic method has been developed for the simultaneous and sensitive analysis of inorganic (H2, CO, and CO2) and organic gaseous compounds (CH4, C2H4, C2H6, C3H6, C3H8, iso-C4H10, and n-C4H10). The analysis of these gases generally requires multi-columns and/or multi-detectors, whereas the proposed method uses a single micropacked column and a single pulsed discharge helium ionization detector (PDHID). All of the investigated peaks (except for the N2 and O2 peaks, which are the major components of air) show good separation when using an oven temperature program from 40°C to 300°C. This gas chromatography‐PDHID system yielded good linearity and a relative standard deviation of less than 5%. This sensitive and convenient method shows great potential in analyses of various types of gaseous compounds.

Rapid identification of different compounds has been proven to be one of the most dynamic fields in analytical chemistry. Herein, a very simple cataluminescence-sensor-based (CTL-based) method suitable for rapid identification of compounds is reported. The oxidation of analytes was catalyzed in a closed reaction cell (CRC) containing enough air to facilitate complete luminescent response profiles with several peaks. The multipeaked response profiles are characteristic of analytes and can be used for identifying compounds. In existing CTL-based sensors, CTL reactions take place in an airstream flow reaction cell (AFRC) in which a continuous airstream carries the analytes flow across the catalyst's surface. The luminescent response profiles obtained are transitory and lack characteristic features, so they cannot be used to identify different compounds. To illustrate the new method, 12 medicines and 4 organic gases were examined in CRC sensors. Results showed that these compounds could be successfully identified through their unique luminescent response profiles. The response was rapid and the system was inexpensive and easy to handle. We believe that it has great potential for real-world use.