<p>An intercomparison of different aerosol chemical characterization techniques has been performed as part of a chamber study of biogenic secondary organic aerosol (BSOA) formation and aging at the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber). Three different aerosol sampling techniques &ndash; the aerosol collection module (ACM), the chemical analysis of aerosol online (CHARON) and the collection thermal-desorption unit (TD) were connected to proton transfer reaction time-of-flight mass spectrometers (PTR-ToF-MSs) to provide chemical characterization of the SOA. The techniques were compared among each other and to results from an aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS). The experiments investigated SOA formation from the ozonolysis of β-pinene, limonene, a β-pinene&ndash;limonene mix and real plant emissions from Pinus sylvestris L. (Scots pine). The SOA was subsequently aged by photo-oxidation, except for limonene SOA, which was aged by NO3 oxidation. Despite significant differences in the aerosol collection and desorption methods of the PTR-based techniques, the determined chemical composition, i.e. the same major contributing signals, was found by all instruments for the different chemical systems studied. These signals could be attributed to known products expected from the oxidation of the examined monoterpenes. The sampling and desorption method of ACM and TD provided additional information on the volatility of individual compounds and showed relatively good agreement. Averaged over all experiments, the total aerosol mass recovery compared to an SMPS varied within 80 &plusmn; 10, 51 &plusmn; 5 and 27 &plusmn; 3 % for CHARON, ACM and TD, respectively. Comparison to the oxygen-to-carbon ratios (O : C) obtained by AMS showed that all PTR-based techniques observed lower O : C ratios, indicating a loss of molecular oxygen either during aerosol sampling or detection. The differences in total mass recovery and O : C between the three instruments resulted predominantly from differences in the field strength (E∕N) in the drift tube reaction ionization chambers of the PTR-ToF-MS instruments and from dissimilarities in the collection/desorption of aerosols. Laboratory case studies showed that PTR-ToF-MS E∕N conditions influenced fragmentation which resulted in water and further neutral fragment losses of the detected molecules. Since ACM and TD were operated in higher E∕N than CHARON, this resulted in higher fragmentation, thus affecting primarily the detected oxygen and carbon content and therefore also the mass recovery. Overall, these techniques have been shown to provide valuable insight on the chemical characteristics of BSOA and can address unknown thermodynamic properties such as partitioning coefficient values and volatility patterns down to a compound-specific level.</p>

<p>Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR-ToF-MS) is a direct injection MS technique, allowing for the sensitive and real-time detection, identification and quantification of volatile organic compounds (VOCs). When aiming to employ PTR-ToF-MS for targeted VOC analysis some methodological questions must be addressed, such as the need to correctly identify product ions, or evaluating the quantitation accuracy. This work proposes a workflow for PTR-ToF-MS method development, addressing the main issues affecting the reliable identification and quantification of target compounds. We determined the fragmentation patterns of 13 selected compounds (aldehydes, fatty acids, phenols). Experiments were conducted under breath-relevant conditions (100% humid air), and within an extended range of reduced electric field values (E/N = 48-144 Td), obtained by changing drift tube voltage. Reactivity was inspected using H3O+, NO+ and O2+ as primary ions. The results show that a relatively low (&lt; 90 Td) E/N often permits to reduce fragmentation enhancing sensitivity and identification capabilities, particularly in the case of aldehydes using NO+, where a 4-fold increase in sensitivity is obtained by means of drift voltage reduction. We developed a novel calibration methodology, relying on diffusion tubes used as gravimetric standards. For each of the tested compounds, it was possible to define suitable conditions whereby experimental error, defined as difference between gravimetric measurements and calculated concentrations, was 8% or lower.</p>

<p>The use of proton transfer reaction mass spectrometry (PTR-MS) for freshness classification of chicken and turkey meat samples was investigated. A number of volatile organic compounds (VOCs) were selected based on the correlation (&gt; 95%) of their concentration during storage at 4 &deg;C over a period of 5 days with the results of the microbial analysis. In order to verify if the selected compounds are not sample-specific, a number of samples sourced from various retailers were classified using the concentration of these compounds in the samples&rsquo; volatile fraction as input variables. The classification was performed using the support vector machines (SVM) supervised pattern recognition algorithm. It was concluded that it is possible to evaluate the shelf life of meat samples obtained from the same source based on the results of a prior analysis. The PTR-MS fingerprint approach might supplement the currently used methods of shelf life evaluation of poultry due to the short time and nondestructive nature of measurement and ease of quantitative analysis.</p>

<p>Biogenic sources contribute to cloud condensation nuclei (CCN) in the clean marine atmosphere, but few measurements exist to constrain climate model simulations of their importance. The chemical composition of individual atmospheric aerosol particles showed two types of sulfate-containing particles in clean marine air masses in addition to mass-based Estimated Salt particles. Both types of sulfate particles lack combustion tracers and correlate, for some conditions, to atmospheric or seawater dimethyl sulfide (DMS) concentrations, which means their source was largely biogenic. The first type is identified as New Sulfate because their large sulfate mass fraction (63% sulfate) and association with entrainment conditions means they could have formed by nucleation in the free troposphere. The second type is Added Sulfate particles (38% sulfate), because they are preexisting particles onto which additional sulfate condensed. New Sulfate particles accounted for 31% (7 cm&minus;3) and 33% (36 cm&minus;3) CCN at 0.1% supersaturation in late-autumn and late-spring, respectively, whereas sea spray provided 55% (13 cm&minus;3) in late-autumn but only 4% (4 cm&minus;3) in late-spring. Our results show a clear seasonal difference in the marine CCN budget, which illustrates how important phytoplankton-produced DMS emissions are for CCN in the North Atlantic.</p>

<p>The OH-initiated atmospheric degradation of tert-butylamine (tBA), (CH3)3CNH2, was investigated in a detailed quantum chemistry study and in laboratory experiments at the European Photoreactor (EUPHORE) in Spain. The reaction was found to mainly proceed via hydrogen abstraction from the amino group, which in the presence of nitrogen oxides (NOx), generates tert-butylnitramine, (CH3)3CNHNO2, and acetone as the main reaction products. Acetone is formed via the reaction of tert-butylnitrosamine, (CH3)3CNHNO, and/or its isomer tert-butylhydroxydiazene, (CH3)3CN═NOH, with OH radicals, which yield nitrous oxide (N2O) and the (CH3)3Ċ radical. The latter is converted to acetone and formaldehyde. Minor predicted and observed reaction products include formaldehyde, 2-methylpropene, acetamide and propan-2-imine. The reaction in the EUPHORE chamber was accompanied by strong particle formation which was induced by an acid&ndash;base reaction between photochemically formed nitric acid and the reagent amine. The tert-butylaminium nitrate salt was found to be of low volatility, with a vapor pressure of 5.1 &times; 10&ndash;6 Pa at 298 K. The rate of reaction between tert-butylamine and OH radicals was measured to be 8.4 (&plusmn;1.7) &times; 10&ndash;12 cm3 molecule&ndash;1 s&ndash;1 at 305 &plusmn; 2 K and 1015 &plusmn; 1 hPa.</p>

<p>The exchange of nonmethane volatile organic compounds (NMVOC) at the surface&ndash;atmosphere interface is a fundamental constraint and important boundary condition for atmospheric chemistry and its effects on climate. Anthropogenic emissions are thought to account for about half of the NMVOC flux into the atmosphere of the Northern Hemisphere, yet their budget is considerably uncertain due to the scarcity of appropriate top-down constraints. Here we present direct flux measurements of NMVOCs based on the eddy covariance technique, showing that the contribution of typical urban emission sources is comprised of a surprisingly large portion of oxygenated NMVOC. These results suggest that typical urban NMVOC emission sources could be significantly higher than currently projected in air chemistry and climate models.</p>

<p>Wildfires emit significant amounts of pollutants that degrade air quality. Plumes from three wildfires in the western U.S. were measured from aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) and the Biomass Burning Observation Project (BBOP), both in summer 2013. This study reports an extensive set of emission factors (EFs) for over 80 gases and 5 components of submicron particulate matter (PM1) from these temperate wildfires. These include rarely, or never before, measured oxygenated volatile organic compounds and multifunctional organic nitrates. The observed EFs are compared with previous measurements of temperate wildfires, boreal forest fires, and temperate prescribed fires. The wildfires emitted high amounts of PM1 (with organic aerosol (OA) dominating the mass) with an average EF that is more than 2 times the EFs for prescribed fires. The measured EFs were used to estimate the annual wildfire emissions of carbon monoxide, nitrogen oxides, total nonmethane organic compounds, and PM1 from 11 western U.S. states. The estimated gas emissions are generally comparable with the 2011 National Emissions Inventory (NEI). However, our PM1 emission estimate (1530 &plusmn; 570 Gg yr&minus;1) is over 3 times that of the NEI PM2.5 estimate and is also higher than the PM2.5 emitted from all other sources in these states in the NEI. This study indicates that the source of OA from biomass burning in the western states is significantly underestimated. In addition, our results indicate that prescribed burning may be an effective method to reduce fine particle emissions.</p>

<p>In the coming decades, as we experience global population growth and global aging issues, there will be corresponding concerns about the quality of the air we experience inside and outside buildings. Because we can anticipate that there will be behavioral changes that accompany population growth and aging, we examine the relationship between home occupant behavior and indoor air quality. To do this, we collect both sensor-based behavior data and chemical indoor air quality measurements in smart home environments. We introduce a novel machine learning-based approach to quantify the correlation between smart home features and chemical measurements of air quality, and evaluate the approach using two smart homes. The findings may help us understand the types of behavior that measurably impact indoor air quality. This information could help us plan for the future by developing an automated building system that would be used as part of a smart city.</p>

<p>We report on a new method for analyzing atmospheric submicrometer particulate organic matter which combines direct particle sampling and volatilization with online chemical ionization mass spectrometric analysis. Technically, the method relies on the combined use of a CHARON (&ldquo;Chemical Analysis of Aerosol Online&rdquo;) particle inlet and a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS). Laboratory studies on target analytes showed that the ionization conditions in the PTR-ToF-MS lead to extensive fragmentation of levoglucosan and cis-pinonic acid, while protonated oleic acid and 5α-cholestane molecules remain intact. Potential problems and biases in quantitative and qualitative analyses are discussed. Side-by-side atmospheric comparison measurements of total particulate organic mass and levoglucosan with an aerosol mass spectrometer (AMS) were in good agreement. Complex and clearly distinct organic mass spectra were obtained from atmospheric measurements in three European cities (Lyon, Valencia, Innsbruck). Data visualization in reduced-parameter frameworks (e.g., oxidation state of carbon vs carbon number) revealed that the CHARON-PTR-ToF-MS technique adds significant analytical capabilities for characterizing particulate organic carbon in the Earth&rsquo;s atmosphere. Positive matrix factorization (PMF) was used for apportioning sources of atmospheric particles in late fall in Innsbruck. The m/z signatures of known source marker compounds (levoglucosan and resin acids, polycyclic aromatic hydrocarbons, nicotine) in the mass spectra were used to assign PMF factors to biomass burning, traffic, and smoking emission sources.</p>

<p>A proton-transfer-reaction time-of-flight mass spectrometer combined with the novel CHARON (&ldquo;chemical analysis of aerosol online&rdquo;) aerosol inlet was used for characterization of submicrometer particulate organic matter in ship engine exhaust. Particles were sampled from diluted and cooled exhaust of a marine test bench engine that was operated on residual heavy fuel oil (HFO) and low-sulfur distillate marine gas oil (MGO), respectively. In both fuel operation modes, exhaust particle mass spectra were dominated by polycycloalkanes in the C20-to-C39 range, which are typical main constituents of lubricating oils. Exhaust particle mass spectra were closely reproduced when the engine&rsquo;s lubricant oil was directly measured in aerosolized form. We report emission profiles of lubricant oil hydrocarbons as a function of their volatility and as a function of their carbon atom number. Total emissions of lubricant oil amounted to 183 and 74 mg kW&ndash;1 h&ndash;1 for HFO and MGO combustion, respectively. These values resemble typical oil loss rates of marine four-stroke trunk piston engines in which most of the lubricant is known to be lost through the combustion chamber and the tailpipe. We conclude that marine trunk piston engines are generally prone to high emissions of particles mainly composed of unburned lubricating oil.</p>

<p>Multiple trace-gas instruments were deployed during the fourth Fire Lab at Missoula Experiment (FLAME-4), including the first application of proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOFMS) and comprehensive two-dimensional gas chromatography&ndash;time-of-flight mass spectrometry (GC&thinsp;&times;&thinsp;GC-TOFMS) for laboratory biomass burning (BB) measurements. Open-path Fourier transform infrared spectroscopy (OP-FTIR) was also deployed, as well as whole-air sampling (WAS) with one-dimensional gas chromatography&ndash;mass spectrometry (GC-MS) analysis. This combination of instruments provided an unprecedented level of detection and chemical speciation. The chemical composition and emission factors (EFs) determined by these four analytical techniques were compared for four representative fuels. The results demonstrate that the instruments are highly complementary, with each covering some unique and important ranges of compositional space, thus demonstrating the need for multi-instrument approaches to adequately characterize BB smoke emissions. Emission factors for overlapping compounds generally compared within experimental uncertainty, despite some outliers, including monoterpenes. Data from all measurements were synthesized into a single EF database that includes over 500 non-methane organic gases (NMOGs) to provide a comprehensive picture of speciated, gaseous BB emissions. The identified compounds were assessed as a function of volatility; 6&ndash;11 % of the total NMOG EF was associated with intermediate-volatility organic compounds (IVOCs). These atmospherically relevant compounds historically have been unresolved in BB smoke measurements and thus are largely missing from emission inventories. Additionally, the identified compounds were screened for published secondary organic aerosol (SOA) yields. Of the total reactive carbon (defined as EF scaled by the OH rate constant and carbon number of each compound) in the BB emissions, 55&ndash;77 % was associated with compounds for which SOA yields are unknown or understudied. The best candidates for future smog chamber experiments were identified based on the relative abundance and ubiquity of the understudied compounds, and they included furfural, 2-methyl furan, 2-furan methanol, and 1,3-cyclopentadiene. Laboratory study of these compounds will facilitate future modeling efforts.</p>

<p>Obesity is a global health threat on the rise, and its prevalence continues to grow. Yet suitable biomedical sensors to monitor body fat burn rates in situ, to guide physical activity or dietary interventions toward efficient weight loss, are missing. Here, we introduce a compact and inexpensive breath acetone sensor based on Si-doped WO3 nanoparticles that can accurately follow body fat burn rates in real time. We tested this sensor on 20 volunteers during exercise and rest and measured their individual breath acetone concentrations in good agreement with benchtop proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS). During exercise, this sensor reveals clearly the onset and progression of increasing breath acetone levels that indicate intensified body fat metabolism, as validated by parallel venous blood β-hydroxybutyrate (BOHB) measurements. Most importantly, we found that the body fat metabolism was especially pronounced for most volunteers during fasting for 3 h after exercise, with strong variation between subjects, and this was displayed correctly by the sensor in real-time. As a result, this simple breath acetone sensor enables easily applicable and hand-held body fat burn monitoring for personalized and immediate feedback on workout effectiveness that can guide dieting as well.</p>

The lack of standardization of breath sampling is a major contributing factor to the poor repeatability of results and hence represents a barrier to the adoption of breath tests in clinical practice. On-line and bag breath sampling have advantages but do not suit multicentre clinical studies whereas storage and robust transport are essential for the conduct of wide-scale studies. Several devices have been developed to control sampling parameters and to concentrate volatile organic compounds (VOCs) onto thermal desorption (TD) tubes and subsequently transport those tubes for laboratory analysis. &#13; We conducted three experiments to investigate (i) the fraction of breath sampled (whole vs. lower expiratory exhaled breath); (ii) breath sample volume (125, 250, 500 and 1000ml) and (iii) breath sample flow rate (400, 200, 100 and 50 ml/min). The target VOCs were acetone and potential volatile biomarkers for oesophago-gastric cancer belonging to the aldehyde, fatty acids and phenol chemical classes. We also examined the collection execution time and the impact of environmental contamination.&#13; The experiments showed that the use of exhaled breath-sampling devices requires the selection of optimum sampling parameters. The increase in sample volume has improved the levels of VOCs detected. However, the influence of the fraction of exhaled breath and the flow rate depends on the target VOCs measured. The concentration of potential volatile biomarkers for oesophago-gastric cancer was not significantly different between the whole and lower airway exhaled breath. While the recovery of phenols and acetone from TD tubes was lower when breath sampling was performed at a higher flow rate, other VOCs were not affected. A dedicated 'clean air supply' overcomes the contamination from ambient air, but the breath collection device itself can be a source of contaminants. In clinical studies using VOCs to diagnose gastro-oesophageal cancer, the optimum parameters are 500mls sample volume of whole breath with a flow rate of 200ml/min. &#13;

<p>Proton-transfer-reaction mass spectrometry (PTR-MS) has been widely used to study the emissions, distributions, and chemical evolution of volatile organic compounds (VOCs) in the atmosphere. The applications of PTR-MS have greatly promoted understanding of VOC sources and their roles in air-quality issues. In the past two decades, many new mass spectrometric techniques have been applied in PTR-MS instruments, and the performance of PTR-MS has improved significantly. This Review summarizes these developments and recent applications of PTR-MS in the atmospheric sciences. We discuss the latest instrument development and characterization work on PTR-MS instruments, including the use of time-of-flight mass analyzers and new types of ion guiding interfaces. Here we review what has been learned about the specificity of different product ion signals for important atmospheric VOCs. We present some of the recent highlights of VOC research using PTR-MS including new observations in urban air, biomass-burning plumes, forested regions, oil and natural gas production regions, agricultural facilities, the marine environment, laboratory studies, and indoor air. Finally, we will summarize some further instrument developments that are aimed at improving the sensitivity and specificity of PTR-MS and extending its use to other applications in atmospheric sciences, e.g., aerosol measurements and OH reactivity measurements.</p>

<p>One of the most common volatile organic compounds (VOCs) group is monoterpenes. Monoterpenes share the molecular formula C10H16, they are usually cyclic and have a pleasant smell. The most common monoterpenes are limonene (present in citrus fruits) and α-pinene (present in conifers&rsquo; resin). Different monoterpenes have different chemical, biological and ecological properties thus it is experimentally very important to be able to differentiate between them in real time. Real time instruments such as Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS), offer a real time solution for monoterpene measurement but at the cost of selectivity resulting in all monoterpenes being seen at the same m/z. In this work we used Selective Reagent Ion-Time of Flight-Mass Spectrometry (SRI/PTR-ToF-MS) in order to explore the differences in ion branching when different ionizations (H3O+, NO+ and O2+) and different drift tube reduced field energies (E/N) were used. We report a comprehensive ion library with many unique features, characteristic for individual monoterpenes.</p>

<p>Ambient volatile organic compounds play a key role in atmospheric chemistry and air pollution studies due to their chemical reactivity and in several instances high toxicity. Quantification of ambient whole air samples which contain reactive and short-lived VOCs such as acetaldehyde, isoprene, dimethylsulphide and trimethylbenzenes at ppt-ppb concentrations is analytically challenging and generally accomplished using online proton transfer reaction mass spectrometry. Deployment of online instrumentation is still not feasible in several regions of the world due to practical constraints (power, safety issues). Consequently there is paucity of VOC data in vast regions of the world. We present here, the validation and application of a novel method for ambient VOC speciation and emission factor studies using low cost (&lt;100 USD) whole air glass flask samplers and offline proton transfer reaction mass spectrometry that can help reduce the paucity of VOC datasets. Experiments to assess the stability during storage of thirteen VOCs, many of which are very reactive, showed that acetaldehyde, acetonitrile, acetone, dimethylsulphide, methyl vinyl and methyl ethyl ketones, benzene, xylenes, trimethylbenzenes and monoterpenes can be quantified reproducibly within the respective precision error (e.g. 40% at 100ppt α-pinene and 3% at 13 ppb acetaldehyde) between collection and storage (at &gt;95% confidence), for samples analyzed within 10 days of collection. For toluene and isoprene, similar results were obtained until day 9 and 1, respectively and at confidence &gt;70%, over the 10 day period. A storage artefact was observed for methanol resulting in higher analytical uncertainty of upto 40%. We applied the method for measuring toluene/benzene emission ratios and aromatic VOCs in traffic plumes, and determining VOC emission factors (gVOC/kg fuel) from an agricultural wheat straw fire in India. The results of this study demonstrate that use of the low cost glass flask samplers described herein can significantly improve acquisition of spatially and temporally resolved datasets for atmospheric chemistry and air quality studies at sites where online deployment of instruments remains unfeasible.</p>

<p>Between April and June 2013 fluxes of volatile organic compounds (VOCs) were measured in a Scots pine and Norway spruce forest using the eddy covariance (EC) method with a proton transfer reaction time of flight (PTR-TOF) mass spectrometer. The observations were performed above a boreal forest at the SMEAR II site in Southern Finland. We found a total of 25 different compounds with exchange and investigated their seasonal variations from spring to summer. The majority of the net VOC flux was comprised of methanol, monoterpenes, acetone and butene. The VOC emissions followed a seasonal trend, the released amount increased from spring to summer. Only a three compounds were emitted in April while in June emissions of some 19 VOCs were observed. During the measurements in April, the emissions were dominated by butene, while in May and June methanol was the most emitted compound. The main source of methanol is likely the growth of new biomass. During a 21-day period in June, the net VOC flux was 2.3&thinsp;nmol&thinsp;m&minus;2&thinsp;s&minus;1. This is on the lower end of PTR-TOF flux measurements from other ecosystems, which range from 2 to 10&thinsp;nmol&thinsp;m&minus;2&thinsp;s&minus;1. The EC flux results were compared with surface layer profile measurements, an indirect method using a proton transfer reaction quadrupole mass spectrometer, which is permanently installed at the SMEAR II site was used. For most of the compounds the fluxes, measured with the two different methods, agreed well.</p>

<p>The objectives of the Winter Fog Experiment (WIFEX) over the Indo-Gangetic Plains of India are to develop better now-casting and forecasting of winter fog on various time- and spatial scales. Maximum fog occurrence over northwest India is about 48 days (visibility &lt; 1000 m) per year, and it occurs mostly during the December-February time-period. The physical and chemical characteristics of fog, meteorological factors responsible for its genesis, sustenance, intensity and dissipation are poorly understood. Improved understanding on the above aspects is required to develop reliable forecasting models and observational techniques for accurate prediction of the fog events. Extensive sets of comprehensive groundbased instrumentation were deployed at the Indira Gandhi International Airport, New Delhi. Major in situ sensors were deployed to measure surface micrometeorological conditions, radiation balance, turbulence, thermodynamical structure of the surface layer, fog droplet and aerosol microphysics, aerosol optical properties, and aerosol and fog water chemistry to describe the complete environmental conditions under which fog develops. In addition, Weather Forecasting Model coupled with chemistry is planned for fog prediction at a spatial resolution of 2 km. The present study provides an introductory overview of the winter fog field campaign with its unique instrumentation. Winter Fog Experiment Over the Indo-Gangetic Plains of India (PDF Download Available). Available from: https://www.researchgate.net/publication/314118438_Winter_Fog_Experiment_Over_the_Indo-Gangetic_Plains_of_India [accessed Aug 9, 2017].</p>

<p>{The applicability of the emerging non-destructive technique, proton transfer reaction mass spectrometry (PTR-MS), was explored for the first time in the quality control of saffron. Monitoring of volatile organic compounds (VOCs) was achieved using a minute sample (35 mg). Fresh saffron was stored under selected conditions (25 and 40 &deg;C</p>

<p>High time resolution measurements of volatile organic compounds (VOCs) were collected using a proton-transfer-reaction quadrupole mass spectrometry (PTR-QMS) instrument at the Platteville Atmospheric Observatory (PAO) in Colorado to investigate how oil and natural gas (O&amp;NG) development impacts air quality within the Wattenburg Gas Field (WGF) in the Denver-Julesburg Basin. The measurements were carried out in July and August 2014 as part of NASA&#39;s &ldquo;Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality&rdquo; (DISCOVER-AQ) field campaign. The PTR-QMS data were supported by pressurized whole air canister samples and airborne vertical and horizontal surveys of VOCs. Unexpectedly high benzene mixing ratios were observed at PAO at ground level (mean benzene&thinsp;=&thinsp;0.53 ppbv, maximum benzene&thinsp;=&thinsp;29.3 ppbv), primarily at night (mean nighttime benzene&thinsp;=&thinsp;0.73 ppbv). These high benzene levels were associated with southwesterly winds. The airborne measurements indicate that benzene originated from within the WGF, and typical source signatures detected in the canister samples implicate emissions from O&amp;NG activities rather than urban vehicular emissions as primary benzene source. This conclusion is backed by a regional toluene-to-benzene ratio analysis which associated southerly flow with vehicular emissions from the Denver area. Weak benzene-to-CO correlations confirmed that traffic emissions were not responsible for the observed high benzene levels. Previous measurements at the Boulder Atmospheric Observatory (BAO) and our data obtained at PAO allow us to locate the source of benzene enhancements between the two atmospheric observatories. Fugitive emissions of benzene from O&amp;NG operations in the Platteville area are discussed as the most likely causes of enhanced benzene levels at PAO.</p>

<p>Cooking processes produce gaseous and particle emissions that are potentially deleterious to human health. Using a highly controlled experimental setup involving a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), we investigate the emission factors and the detailed chemical composition of gas phase emissions from a broad variety of cooking styles and techniques. A total of 95 experiments were conducted to characterize nonmethane organic gas (NMOG) emissions from boiling, charbroiling, shallow frying, and deep frying of various vegetables and meats, as well as emissions from vegetable oils heated to different temperatures. Emissions from boiling vegetables are dominated by methanol. Significant amounts of dimethyl sulfide are emitted from cruciferous vegetables. Emissions from shallow frying, deep frying and charbroiling are dominated by aldehydes of differing relative composition depending on the oil used. We show that the emission factors of some aldehydes are particularly large which may result in considerable negative impacts on human health in indoor environments. The suitability of some of the aldehydes as tracers for the identification of cooking emissions in ambient air is discussed.</p>

<p>Honey, in particular monofloral varieties, is a valuable commodity. Here, we present proton transfer reaction-time of flight-mass spectrometry, PTR-ToF-MS, coupled to chemometrics as a successful tool in the classification of monofloral honeys, which should serve in fraud protection against mispresentation of the floral origin of honey. We analyzed 7 different honey varieties from citrus, chestnut, sunflower, honeydew, robinia, rhododendron and linden tree, in total 70 different honey samples and a total of 206 measurements. Only subtle differences in the profiles of the volatile organic compounds (VOCs) in the headspace of the different honeys could be found. Nevertheless, it was possible to successfully apply 6 different classification methods with a total correct assignment of 81-99% in the internal validation sets. The most successful methods were stepwise linear discriminant analysis (LDA) and probabilistic neural network (PNN), giving total correct assignments in the external validation sets of 100 and 90%, respectively. Clearly, PTR-ToF-MS/chemometrics is a powerful tool in honey classification.</p>

<p>In the north west Indo-Gangetic Plain (N.W.IGP), large scale post-harvest paddy residue fires occur every year during the months of October&ndash;November. This anthropogenic perturbation causes contamination of the atmospheric environment with adverse impacts on regional air quality posing health risks for the population exposed to high concentrations of carcinogens such as benzene and toxic VOCs such as isocyanic acid. These gases and carbon monoxide are known to be emitted from biomass fires along with acetonitrile. Yet no long-term in-situ measurements quantifying the impact of this activity have been carried out in the N.W. IGP. Using high quality continuous online in-situ measurements of these gases at a strategic downwind site over a three year period from 2012 to 2014, we demonstrate the strong impact of this anthropogenic emission activity on ambient concentrations of these gases. In contrast to the pre-paddy harvest period, excellent correlation of benzenoids, isocyanic acid and CO with acetonitrile (a biomass burning chemical tracer); (r &ge; 0.82) and distinct VOC/acetonitrile emission ratios were observed for the post-paddy harvest period which was also characterized by high ambient concentrations of these species. The average concentrations of acetonitrile (1.62 &plusmn; 0.18 ppb), benzene (2.51 &plusmn; 0.28 ppb), toluene (3.72 &plusmn; 0.41 ppb), C8-aromatics (2.88 &plusmn; 0.30 ppb), C9-aromatics (1.55 &plusmn; 0.19 ppb) and CO (552 &plusmn; 113 ppb) in the post-paddy harvest periods were about 1.5 times higher than the annual average concentrations. For isocyanic acid, a compound with both primary and secondary sources, the concentration in the post-paddy harvest period was 0.97 &plusmn; 0.17 ppb. The annual average concentrations of benzene, a class A carcinogen, exceeded the annual exposure limit of 1.6 ppb at NTP mandated by the National Ambient Air Quality Standard of India (NAAQS). We show that mitigating the post-harvest paddy residue fires can lower the annual average concentration of benzene and ensure compliance with the NAAQS. Calculations of excessive lifetime cancer risk due to benzene amount to 25 and 10 per million inhabitants for children and adults, respectively, exceeding the USEPA threshold of 1 per million inhabitants. Annual exposure to isocyanic acid was close to 1 ppb, the concentration considered to be sufficient to enhance risks for cardiovascular diseases and cataracts. This study makes a case for urgent mitigation of post-harvest paddy residue fires as the unknown synergistic effect of multi-pollutant exposure due to emissions from this anthropogenic source may be posing grave health risks to the population of the N.W. IGP.</p>

<p>Most plants produce and emit a wide blend of biogenic volatile organic compounds (BVOCs). Among them, many isoprenoids exhibit a high atmospheric reactivity toward OH radicals and ozone. In the last few years, Proton Transfer Reaction&ndash;Mass Spectrometry (PTR&ndash;MS) has been widely used in both field and laboratory determination of BVOCs, complementing the traditional methods using gas chromatography&ndash;mass spectrometry (GC&ndash;MS) for their identification in air and emission sources. This technical note reports a number of experiments carried out with a PTR- (Time-of-Flight) TOF-MS equipped with a prototype fast-GC system, allowing a fast separation of those isobaric isoprenoid compounds that cannot be identified by a direct PTR-TOF-MS analysis. The potential of this fast-GC system to adequately complement the information provided by PTR-TOF-MS was investigated by using the BVOC emissions of Quercus ilex and Eucalyptus camaldulensis as reliable testing systems, due to the different blend of isoprenoid compounds emitted and the different dependence of their emission from environmental parameters. While the oak species is a strong monoterpene emitter, the eucalyptus used is one of the few plant species emitting both isoprene and monoterpenes. The performances provided by the type of fast-GC used in the new PTR-TOF-MS instrument were also compared with those afforded by conventional GC&ndash;MS methods. The results obtained in this investigation showed that this new instrument is indeed a quick and handy tool to determine the contribution of isoprene and eucalyptol to m/z 69.070 and monoterpenes and (Z)-3-hexenal to m/z 81.070, integrating well the on-line information provided by PTR-TOF-MS. However, some limitations emerged in the instrument as compared to traditional GC&ndash;MS, which can only be solved by implementing the injection and separation processes.</p>