Semi-volatile Fraction Research Articles

Attribution of aerosol particle number size distributions to main sources using an 11-year urban dataset

Abstract. Source apportionment was performed using size-segregated atmospheric particle number concentrations (PNCs) in 27 size channels over a diameter range of 6–1000 nm augmented by air pollutants with a time resolution of 1 h in Budapest for 11 full years. The input dataset was treated for the effect of the local meteorology using dispersion correction. Both the uncorrected dataset and corrected dataset were evaluated using positive matrix factorization for separate seasons. Six source types including nucleation, two road vehicle emission sources separated into a semi-volatile fraction and a solid-core fraction, a diffuse urban source, a secondary inorganic aerosol (SIA) source, and an ozone-associated secondary aerosol source were identified, characterized and quantified. The dispersion correction did not considerably change the profiles, diel variations or patterns of the sources, while it substantially modified the relative shares of the nucleation source in all seasons. The mean relative contributions of the traffic emissions (60 %) indicate that on-road motor vehicles were the leading source of particle numbers. The nucleation was responsible for 24 % of the PNC annually as a lower estimate. It exhibited a compound character consisting of photochemically induced nucleation and traffic-related nucleation. Its contributions were the highest in spring and the lowest in winter. The shares of the urban diffuse and SIA source types were the largest in autumn and winter and in spring and summer, respectively, but they were typically ⪅ 10 %. The O3-associated secondary aerosol made up the smallest (⪅ 3 %) contributions. The conditional bivariate probability function analysis showed considerable spatial variations in the source origin. The combination of the size-segregated particle number concentrations, wide overall range of the size channels, considerably long dataset, dispersion correction and modelling over separate seasons led jointly to a unique adaptation of the source apportionment and yielded novel and valuable insights into the urban aerosol sources and processes both for Budapest and in general.

Molecular Understanding of the Enhancement in Organic Aerosol Mass at High Relative Humidity.

The mechanistic pathway by which high relative humidity (RH) affects gas-particle partitioning remains poorly understood, although many studies report increased secondary organic aerosol (SOA) yields at high RH. Here, we use real-time, molecular measurements of both the gas and particle phase to provide a mechanistic understanding of the effect of RH on the partitioning of biogenic oxidized organic molecules (from α-pinene and isoprene) at low temperatures (243 and 263 K) at the CLOUD chamber at CERN. We observe increases in SOA mass of 45 and 85% with increasing RH from 10-20 to 60-80% at 243 and 263 K, respectively, and attribute it to the increased partitioning of semi-volatile compounds. At 263 K, we measure an increase of a factor 2-4 in the concentration of C10H16O2-3, while the particle-phase concentrations of low-volatility species, such as C10H16O6-8, remain almost constant. This results in a substantial shift in the chemical composition and volatility distribution toward less oxygenated and more volatile species at higher RH (e.g., at 263 K, O/C ratio = 0.55 and 0.40, at RH = 10 and 80%, respectively). By modeling particle growth using an aerosol growth model, which accounts for kinetic limitations, we can explain the enhancement in the semi-volatile fraction through the complementary effect of decreased compound activity and increased bulk-phase diffusivity. Our results highlight the importance of particle water content as a diluting agent and a plasticizer for organic aerosol growth.

Differentiating Semi-Volatile and Solid Particle Events Using Low-Cost Lung-Deposited Surface Area and Black Carbon Sensors

Low-cost particle sensors have proven useful in applications such as source apportionment, health, and reactivity studies. The benefits of these instruments increase when used in parallel, as exemplified with a 3-month long deployment in an urban background site. Using two lung-deposited surface area (LDSA) instruments, a low-cost method was developed to assess the solid component of an aerosol by applying a catalytic stripper to the inlet stream of one LDSA instrument, resulting in only the solid fraction of the sample being measured (LDSAc). To determine the semi-volatile fraction of the sample, the LDSAC was compared to the LDSA without a catalytic stripper, thus measuring all particles (LDSAN). The ratio of LDSA (LDSAC/LDSAN) was used to assess the fraction of solid and semi-volatile particles within a sample. Here, a low ratio represents a high fraction of semi-volatile particles, with a high ratio indicating a high fraction of solid particles. During the 3-month urban background study in Birmingham, UK, it is shown that the LDSA ratios ranged from 0.2–0.95 indicating a wide variation in sources and subsequent semi-volatile fraction of particles. A black carbon (BC) instrument was used to provide a low-cost measure of LDSA to BC ratio. Comparatively, the LDSA to BC ratios obtained using low-cost sensors showed similar results to high-cost analyses for urban environments. During a high LDSAC/LDSAN ratio sampling period, representing high solid particle concentrations, an LDSA to BC probability distribution was shown to be multimodal, reflecting urban LDSA to BC ratio distributions measured with laboratory-grade instrumentation. Here, a low-cost approach for data analyses presents insight on particle characteristics and insight into PM composition and size, useful in source apportionment, health, and atmospheric studies.

A sustainable approach for the reliable and simultaneous determination of terpenoids and cannabinoids in hemp inflorescences by vacuum assisted headspace solid-phase microextraction

• Headspace solid phase microextraction can be adopted for the recovery of terpenoids and cannabinoids from Cannabis sativa inflorescences. • Vacuum conditions in the Cannabis headspace ensure the recovery of cannabinoids with low sampling temperature and time. • The adoption of mild conditions allows to not discriminate volatile and semivolatile fractions. • The adoption of mild conditions decreases the formation of artefacts. • The separation of terpenoid and cannabinoids markers can be obtained in less than 30 min with short narrow bore columns. Cannabis sativa L. is an intriguing plant that has been exploited since ancient times for recreational, medical, textile and food purposes. The plant's most promising bioactive constituents discovered so far belong to the terpenoid and cannabinoid classes. These specialised metabolites are highly concentrated in the plant aerial parts and their chemical characterisation is crucial to guarantee the safe and efficient use of the plant material irrespective of which use it is. This study investigates for the first time the use of vacuum assisted HS-SPME as a sample preparation process in an analytical protocol based on HS-SPME combined to fast GC-MS analysis that aims at comprehensively characterising both the terpenoid and cannabinoid profiles of Cannabis inflorescences in a single step. The results proved that vacuum in the HS should be preferred over atmospheric pressure conditions as it ensures the fast recovery of cannabinoid markers at relatively lower sampling temperatures (i.e., 90°C) that do not discriminate the most volatile fraction nor cause the formation of artefacts when the sampling time is minimised.

TUBE Project: Transport-Derived Ultrafines and the Brain Effects.

The adverse effects of air pollutants on the respiratory and cardiovascular systems are unquestionable. However, in recent years, indications of effects beyond these organ systems have become more evident. Traffic-related air pollution has been linked with neurological diseases, exacerbated cognitive dysfunction, and Alzheimer’s disease. However, the exact air pollutant compositions and exposure scenarios leading to these adverse health effects are not known. Although several components of air pollution may be at play, recent experimental studies point to a key role of ultrafine particles (UFPs). While the importance of UFPs has been recognized, almost nothing is known about the smallest fraction of UFPs, and only >23 nm emissions are regulated in the EU. Moreover, the role of the semivolatile fraction of the emissions has been neglected. The Transport-Derived Ultrafines and the Brain Effects (TUBE) project will increase knowledge on harmful ultrafine air pollutants, as well as semivolatile compounds related to adverse health effects. By including all the major current combustion and emission control technologies, the TUBE project aims to provide new information on the adverse health effects of current traffic, as well as information for decision makers to develop more effective emission legislation. Most importantly, the TUBE project will include adverse health effects beyond the respiratory system; TUBE will assess how air pollution affects the brain and how air pollution particles might be removed from the brain. The purpose of this report is to describe the TUBE project, its background, and its goals.

Comprehensive characterization of mainstream marijuana and tobacco smoke

Recent increases in marijuana use and legalization without adequate knowledge of the risks necessitate the characterization of the billions of nanoparticles contained in each puff of smoke. Tobacco smoke offers a benchmark given that it has been extensively studied. Tobacco and marijuana smoke particles are quantitatively similar in volatility, shape, density and number concentration, albeit with differences in size, total mass and chemical composition. Particles from marijuana smoke are on average 29% larger in mobility diameter than particles from tobacco smoke and contain 3.4× more total mass. New measurements of semi-volatile fractions determine over 97% of the mass and volume of the particles from either smoke source are comprised of semi-volatile compounds. For tobacco and marijuana smoke, respectively, 4350 and 2575 different compounds are detected, of which, 670 and 536 (231 in common) are tentatively identified, and of these, 173 and 110 different compounds (69 in common) are known to cause negative health effects through carcinogenic, mutagenic, teratogenic, or other toxic mechanisms. This study demonstrates striking similarities between marijuana and tobacco smoke in terms of their physical and chemical properties.

Exploiting the versatility of vacuum-assisted headspace solid-phase microextraction in combination with the selectivity of ionic liquid-based GC stationary phases to discriminate Boswellia spp. resins through their volatile and semivolatile fractions.

The frankincense resins, secreted from Boswellia species, are an uncommon example of a natural raw material where every class of terpenoids is present in similar proportions. Diterpenoids (serratol, incensole, and incensole acetate) are used to discriminate samples from different species and origins. Headspace solid-phase microextraction has been used for frankincense analysis, although it requires long sampling time for medium- to low-volatility markers; headspace solid-phase microextraction under vacuum can overcome this limit. Gas chromatography is used for analysis but the separation of incensole and serratol needs polar stationary phases. In this study, we develop a method to discriminate frankincenses based on vacuum-assisted headspace solid-phase microextraction combined with fast gas chromatography-mass spectrometry with ionic liquid-based stationary phases. The optimized conditions for solid samples were: air evacuation below 0°C, 15min of incubation time, and 15min of extraction time. Losses of volatiles due to vial air-evacuation in the presence of the sample were minimized by sample amount above 100mg and low sample temperature. Fast gas chromatography provides the baseline separation of all markers in 20min. By applying vacuum sampling and fast gas chromatography, the total analysis was reduced to 50min compared to 120min (60min sampling plus 60min analysis) as previously reported. The method was successfully applied to commercial frankincense samples.

Study of Some Zanthoxylum Species by Chemical and DNA Analysis Approaches.

The authentication and traceability of spices is a major concern for industrials and consumers. We focused on species from Zanthoxylum genera which are used for many different applications by local populations and also for trading as spices (dried pericarps or whole fruits). In this case, literature gives contradictory data about botanical names, and commercial labelling is often confusing. We studied commercial fruits pericarps extracts obtained by supercritical CO2 and analyzed them by GC/MS. The very complex volatile and semi volatile fractions composition of each extract is described. The barcoding method including molecular biology and phylogenetic analyses was also developed in order to check the commercial botanical identification of the raw material. This is a robust method to identify species in berries samples. We used one genetic marker to identify two Rutaceae clusters, including several species of Zanthoxylum genus. These results indicate that Fagara and Zanthoxylum groups could be considered as two different genera. Combination of chemical analysis and DNA analysis provides an original approach to increase chemical and botanical Zanthoxylum genus knowledge.

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

Abstract. We present spatial measurements of particle volatility and mixing state at a site near a North Carolina interstate highway (I-40) applying several heating (thermodenuder; TD) experimental approaches. Measurements were conducted in summer 2015 and winter 2016 in a roadside trailer (10 m from road edge) and during downwind transects at different distances from the highway under favorable wind conditions using a mobile platform. Results show that the relative abundance of semi-volatile species (SVOCs) in ultrafine particles decreases with downwind distance, which is consistent with the dilution and mixing of traffic-sourced particles with background air and evaporation of semi-volatile species during downwind transport. An evaporation kinetics model was used to derive particle volatility distributions by fitting TD data. While the TD-derived distribution apportions about 20–30 % of particle mass as semi-volatile (SVOCs; effective saturation concentration, C∗ ≥ 1µm−3) at 10 m from the road edge, approximately 10 % of particle mass is attributed to SVOCs at 220 m, showing that the particle-phase semi-volatile fraction decreases with downwind distance. The relative abundance of semi-volatile material in the particle phase increased during winter. Downwind spatial gradients of the less volatile particle fraction (that remaining after heating at 180 °C) were strongly correlated with black carbon (BC). BC size distribution and mixing state measured using a single-particle soot photometer (SP2) at the roadside trailer showed that a large fraction (70–80 %) of BC particles were externally mixed. Heating experiments with a volatility tandem differential mobility analyzer (V-TDMA) also showed that the nonvolatile fraction in roadside aerosols is mostly externally mixed. V-TDMA measurements at different distances downwind from the highway indicate that the mixing state of roadside aerosols does not change significantly (e.g., BC mostly remains externally mixed) within a few hundred meters from the highway. Our analysis indicates that a superposition of volatility distributions measured in laboratory vehicle tests and of background aerosol can be used to represent the observed partitioning of near-road particles. The results from this study show that exposures and impacts of BC and semi-volatile organics-containing particles in a roadside microenvironment may differ across seasons and under changing ambient conditions.

Field Measurements for Quantifying Semi-Volatile Aerosol Influence on Physical and Optical Properties of Ambient Aerosols in the Kathmandu Valley, Nepal

ABSTRACT An intensive field campaign was conducted during the pre-monsoon season of 2015 in the urban atmosphere of the Kathmandu Valley to study the influence of the semi-volatile aerosol fraction on physical and optical properties of aerosols. Ambient air was siphoned through a specific ambient air inlet and then split into two parts. The first part connected directly with an ambient air sample while the second received the air sample through a thermodenuder (TDD). The aerosol properties, such as the aerosol number, size distribution, absorption, and scattering, were studied using Condensation Particle Counters (CPCs), Scanning Mobility Particle Sizers (SMPSs), Aethalometers (AE33) and Nephelometers, respectively. The differences in the properties of the aerosol fraction at room temperature and other TDD set temperatures (50°C, 100°C, 150°C, 200°C, 250°C, and 300°C) were calculated to study the influence of the semi-volatile aerosol fraction on ambient aerosols. The evaporated fraction of the semi-volatile aerosols increased with the TDD set temperature. The semi-volatile fraction of the aerosol number increased from 16% to 49% of ambient aerosol, while the peak mobility diameter of particles shifted from around 60 nm to 40 nm as the temperature increased from 50°C to 300°C. However, increasing the TDD set temperature had no influence on the effective diameter of the aerosol size distribution. Larger aerosol size bins of the SMPS experienced a significantly stronger influence (~70%) from temperature increments compared to smaller size bins (~20%). The semi-volatile aerosol fraction amplified BC absorption by up to 28%, while scattering by the semi-volatile aerosol fraction contributed up to 71% of the total.

Source and Biological Response of Biochar Organic Compounds Released into Water; Relationships with Bio-Oil Composition and Carbonization Degree.

Water-soluble organic compounds (WSOCs) were extracted from corn stalk biochar produced at increasing pyrolysis temperatures (350-650 °C) and from the corresponding vapors, collected as bio-oil. WSOCs were characterized by gas chromatography (semivolatile fraction), negative electron spray ionization high resolution mass spectrometry (hydrophilic fraction) and fluorescence spectroscopy. The pattern of semivolatile WSOCs in bio-oil was dominated by aromatic products from lignocellulose, while in biochar was featured by saturated carboxylic acids from hemi/cellulose and lipids with concentrations decreasing with decreasing H/C ratios. Hydrophilic species in poorly carbonized biochar resembled those in bio-oil, but the increasing charring intensity caused a marked reduction in the molecular complexity and degree of aromaticity. Differences in the fluorescence spectra were attributed to the predominance of fulvic acid-like structures in biochar and lignin-like moieties in bio-oil. The divergence between pyrolysis vapors and biochar in the distribution of WSOCs with increasing carbonization was explained by the hydrophobic carbonaceous matrix acting like a filter favoring the release into water of carboxylic and fulvic acid-like components. The formation of these structures was confirmed in biochar produced by pilot plant pyrolysis units. Biochar affected differently shoot and root length of cress seedlings in germination tests highlighting its complex role on plant growth.

Characterization of iodinated disinfection by-products in chlorinated and chloraminated waters using Orbitrap based gas chromatography-mass spectrometry.

Recent developments in gas chromatography (GC)-mass spectrometry (MS) have opened up the possibility to use the high resolution-accurate mass (HRAM) Orbitrap mass analyzer to further characterize the volatile and semivolatile fractions of environmental samples. This work describes the utilization of GC Orbitrap MS technology to characterize iodine-containing disinfection by-products (iodo-DBPs) in chlorinated and chloraminated DBP mixture concentrates. These DBP mixtures were generated in lab-scale disinfection reactions using Llobregat river water and solutions containing Nordic Lake natural organic matter (NOM). The DBPs generated were concentrated using XAD resins, and extracts obtained were analyzed in full scan mode with the GC Orbitrap MS. Integration of high resolution accurate mass information and fragment rationalization allowed the characterization of up to 11 different iodo-DBPs in the water extracts analyzed, including one new iodo-DBP reported for the first time. Overall, formation of iodo-DBPs was enhanced during chloramination reactions. As expected, NOM characteristics and iodide and bromide content of the tested waters affected the amount and type of iodo-DBPs generated.

Performance and gaseous and particle emissions from a liquefied petroleum gas (LPG) fumigated compression ignition engine

In this study, an LPG fumigation system was fitted to a Euro III compression ignition (CI) engine to explore its impact on performance, and gaseous and particulate emissions. LPG was introduced to the intake air stream (as a secondary fuel) by using a low pressure fuel injector situated upstream of the turbocharger. LPG substitutions were test mode dependent, but varied in the range of 14–29% by energy. The engine was tested over a 5 point test cycle using ultra low sulphur diesel (ULSD), and a low and high LPG substitution at each test mode. The results show that LPG fumigation coerces the combustion into pre-mixed mode, as increases in the peak combustion pressure (and the rate of pressure rise) were observed in most tests. The emissions results show decreases in nitric oxide (NO) and particulate matter (PM2.5) emissions; however, very significant increases in carbon monoxide (CO) and hydrocarbon (HC) emissions were observed. A more detailed investigation of the particulate emissions showed that the number of particles emitted was reduced with LPG fumigation at all test settings – apart from mode 6 of the ECE R49 test cycle. Furthermore, the particles emitted generally had a slightly larger median diameter with LPG fumigation, and had a smaller semi-volatile fraction relative to ULSD. Overall, the results show that with some modifications, LPG fumigation systems could be used to extend ULSD supplies without adversely impacting on engine performance and emissions.

Rapid organic aerosol formation downwind of a highway: Measured and model results from the FEVER study

AbstractThe Fast Evolution of Vehicle Emissions from Roadway (FEVER) study was undertaken to strategically measure pollutant gradients perpendicular to a major highway north of Toronto, Canada. A case study period was analyzed when there was an average perpendicular wind direction. Two independent, fast response measurements were used to infer rapid organic aerosol (OA) growth on a spatial scale from 34 m to 285 m at the same time as a decrease was observed in the mixing ratio of primary emitted species, such as CO2 and NOx. An integrated organic gas and particle sampler also showed that near the highway, the aerosol had a larger semivolatile fraction than lower volatile fraction, but over a relatively short distance downwind of the highway, the aerosol transformed to being more low volatile with the change being driven by both evaporation of semivolatile and production of lower volatile organic aerosol. A new 1‐D column Lagrangian atmospheric chemistry model was developed to help interpret the measured increase in the ∆OA/∆CO2 curve from 34 m to 285 m downwind of highway, where the ∆ refers to background‐corrected concentrations. The model was sensitive to the assumptions for semivolatile organic compounds (SVOCs). Different combinations of SVOC emissions and background mixing ratios were able to yield similar model curves and reproduce the observations. Future measurements of total gas‐phase SVOC in equilibrium with aerosol both upwind and downwind of the highway would be helpful to constrain the model.

Development of a parallel sampling and analysis method for the elucidation of gas/particle partitioning of oxygenated semi-volatile organics: a limonene ozonolysis study

Abstract. The gas/particle partitioning behaviour of the semi-volatile fraction of secondary organic matter and the associated multiphase chemistry are key features to accurately evaluate climate and health impacts of secondary organic aerosol (SOA). However, today, the partitioning of oxygenated secondary species is rarely assessed in experimental SOA studies and SOA modelling is still largely based on estimated partitioning data. This paper describes a new analytical approach, solvent-free and easy to use, to explore the chemical composition of the secondary organic matter at a molecular scale in both gas and particulate phases. The method is based on thermal desorption (TD) of gas and particulate samples, coupled with gas chromatography (GC) and mass spectrometry (MS), with derivatisation on sampling supports. Gaseous compounds were trapped on Tenax TA adsorbent tubes pre-coated with pentafluorobenzylhydroxylamine (PFBHA) or N-Methyl-N-(t-butyldimethylsilyl)trifluoroacetamide (MTBSTFA). Particulate samples were collected onto quartz or Teflon-quartz filters and subsequently subjected to derivatisation with PFBHA or MTBSTFA before TD-GC/MS analysis. Method development and validation are presented for an atmospherically relevant range of organic acids and carbonyl and hydroxyl compounds. Application of the method to a limonene ozonolysis experiment conducted in the EUPHORE simulation chamber under simulated atmospheric conditions of low concentrations of limonene precursor and relative humidity, provides an overview of the method capabilities. Twenty-five compounds were positively or tentatively identified, nine being in both gaseous and particulate phases; and twelve, among them tricarboxylic acids, hydroxyl dicarboxylic acids and oxodicarboxylic acids, being detected for the first time.

Prokaryotes in salt marsh sediments of Ria de Aveiro: Effects of halophyte vegetation on abundance and diversity

The aim of this study was to investigate the influence of monospecific colonization of sediment stands by Spartina maritima or Halimione portulacoides on benthic prokaryote assemblages in a salt marsh located in Ria de Aveiro (Portugal). The distribution of Bacteria, Archaea and sulfate-reducing bacteria (SRB) in sediments with monospecific plant stands and in unvegetated sediments was characterized by Fluorescence In Situ Hybridization (FISH). Total prokaryote abundance (0.4 × 109–1.7 × 109 cells gdw−1) was highest in sediments from the surface layer. The domain Bacteria comprised approximately 40% of total prokaryote communities with the highest percentages occurring in the surface layer. Archaeal cells corresponded to an average of 25% of total prokaryote population, with higher abundance in the vegetation banks, and displaying homogeneous vertical distribution. The relative abundance of SRB represented approximately 3% of total 4′, 6-diamidino-2-phenylindole dihydrochloride (DAPI) stained cells at unvegetated sediment and H. portulacoides stand and 7% at S. maritima stand. Headspace solid-phase microextraction (HS-SPME) combined with Comprehensive Two-Dimensional Gas Chromatography–Time-of-Flight Mass Spectrometry (GC × GC–ToFMS) was used to analyse the volatile and semi-volatile fraction of root exudates. A total of 171 compounds were identified and Principal Component Analysis showed a clear separation between the chemical composition (volatile and semi-volatile organic compounds) of the exudates of the two plants.The patterns of vertical distribution and differences in the proportion of SRB and Archaea in the prokaryote communities developing in sediments colonized by Spartina maritima or Halimione portulacoides suggest the existence of plant-specific interactions between halophyte vegetation and estuarine sediment bacteria in Ria de Aveiro salt marshes, exerted via sediment lithology and root-derived exudates.

Characterisation of lightly oxidised organic aerosol formed from the photochemical aging of diesel exhaust particles

Environmental contextThe effects of atmospheric fine particulate matter (aerosols) on climate and human health can be strongly influenced by the chemical transformations that the particles undergo in the atmosphere, but these ‘aging’ reactions are poorly understood. Here diesel exhaust particles are aged in the laboratory to better understand how they could evolve in the atmosphere, and subtle but unmistakable changes in their chemical composition are found. These results provide a more complete picture of the atmospheric evolution of aerosols for inclusion in atmospheric models. AbstractThe oxidative aging of the semivolatile fraction of diesel exhaust aerosol is studied in order to better understand the influence of oxidation reactions on particle chemical composition. Exhaust is sampled from an idling diesel truck, sent through a denuder to remove gas-phase species and oxidised by hydroxyl (OH•) radicals in a flow reactor. OH• concentrations are chosen to approximately match the OH• exposures a particle would experience over its atmospheric lifetime. Evolving particle composition is monitored using aerosol mass spectrometry in two different modes, electron impact ionisation (EI) for the measurement of elemental ratios and vacuum ultraviolet (VUV) photoionisation for the measurement of molecular components. Changes to mass spectra in both modes indicate major changes to particle composition over the range of OH• exposures studied. The product aerosol is only lightly oxidised (O/C < 0.3), suggesting an intermediate oxidation state between primary organics and the highly oxidised organic aerosol observed in the atmosphere. These lightly oxidised organics appear to be composed of secondary organic aerosol from semivolatile species, as well as from heterogeneously oxidised particle-phase organics. Key chemical characteristics (elemental ratios, oxidation kinetics and mass spectrometric features) of the reaction system are examined in detail. Similarities between this laboratory-generated aerosol and ‘hydrocarbon-like organic aerosol’ (HOA) reported in ambient studies suggest that HOA might not be entirely primary in origin, as is commonly assumed, but rather might include a significant secondary component.

Effectiveness of high-throughput miniaturized sorbent- and solid phase microextraction techniques combined with gas chromatography–mass spectrometry analysis for a rapid screening of volatile and semi-volatile composition of wines—A comparative study

In this study the feasibility of different extraction procedures was evaluated in order to test their potential for the extraction of the volatile (VOCs) and semi-volatile constituents (SVOCs) from wines. In this sense, and before they could be analysed by gas chromatography–quadrupole first stage masss spectrometry (GC–qMS), three different high-throughput miniaturized (ad)sorptive extraction techniques, based on solid phase extraction (SPE), microextraction by packed sorbents (MEPS) and solid phase microextraction (SPME), were studied for the first time together, for the extraction step. To achieve the most complete volatile and semi-volatile signature, distinct SPE (LiChrolut EN, Poropak Q, Styrene-Divinylbenzene and Amberlite XAD-2) and MEPS (C2, C8, C18, Silica and M1 (mixed C8-SCX)) sorbent materials, and different SPME fibre coatings (PA, PDMS, PEG, DVB/CAR/PDMS, PDMS/DVB, and CAR/PDMS), were tested and compared. All the extraction techniques were followed by GC–qMS analysis, which allowed the identification of up to 103 VOCs and SVOCs, distributed by distinct chemical families: higher alcohols, esters, fatty acids, carbonyl compounds and furan compounds. Mass spectra, standard compounds and retention index were used for identification purposes.SPE technique, using LiChrolut EN as sorbent (SPELiChrolut EN), was the most efficient method allowing for the identification of 78 VOCs and SVOCs, 63 and 19 more than MEPS and SPME techniques, respectively. In MEPS technique the best results in terms of number of extractable/identified compounds and total peak areas of volatile and semi-volatile fraction, were obtained by using C8 resin whereas DVB/CAR/PDMS was revealed the most efficient SPME coating to extract VOCs and SVOCs from Bual wine. Diethyl malate (18.8±3.2%) was the main component found in wine SPELiChrolut EN extracts followed by ethyl succinate (13.5±5.3%), 3-methyl-1-butanol (13.2±1.7%), and 2-phenylethanol (11.2±9.9%), while in SPMEDVB/CAR/PDMS technique 3-methyl-1-butanol (43.3±0.6%) followed by diethyl succinate (18.9±1.6%), and 2-furfural (10.4±0.4%), are the major compounds. The major VOCs and SVOCs isolated by MEPSC8 were 3-methyl-1-butanol (26.8±0.6%, from wine total volatile fraction), diethyl succinate (24.9±0.8%), and diethyl malate (16.3±0.9%). Regardless of the extraction technique, the highest extraction efficiency corresponds to esters and higher alcohols and the lowest to fatty acids.Despite some drawbacks associated with the SPE procedure such as the use of organic solvents, the time-consuming and tedious sampling procedure, it was observed that SPELiChrolut EN, revealed to be the most effective technique allowing the extraction of a higher number of compounds (78) rather than the other extraction techniques studied.

Chemical composition, antioxidant and antimicrobial activity of the extracts of the flowers of the Chinese plant Chimonanthus praecox

This study investigated the antimicrobial and antioxidant activity of the extracts of the flowers, essential oil (EO) and semi-volatile fractions (SVF) of Chimonanthus praecox. The chemical composition of the EO was analysed by gas chromatography-mass spectroscopy (GC–MS) which revealed that the EO contained elemene, muurolene, caryophyllene, cadinol and spathulenol. The effective antibacterial activity of the EO suggested that its different responses on the microorganisms studied depended on the synergistic effects of the compounds contained in the EO. The effective antioxidant activity of the EO showed that the EO had a more marked antioxidant effect on scavenging · and OH· than DPPH·, and SVF had a higher potential for scavenging DPPH· than the EO. Our data suggested that the flowers of Chimonanthus praecox had pharmaceutical benefits, and are also a potential source of natural antioxidants and biocides.

Characterization of aerosol chemical composition with aerosol mass spectrometry in Central Europe: an overview

Abstract. Real-time measurements of non-refractory submicron aerosols (NR-PM1) were conducted within the greater Alpine region (Switzerland, Germany, Austria, France and Liechtenstein) during several week-long field campaigns in 2002–2009. This region represents one of the most important economic and recreational spaces in Europe. A large variety of sites was covered including urban backgrounds, motorways, rural, remote, and high-alpine stations, and also mobile on-road measurements were performed. Inorganic and organic aerosol (OA) fractions were determined by means of aerosol mass spectrometry (AMS). The data originating from 13 different field campaigns and the combined data have been utilized for providing an improved temporal and spatial data coverage. The average mass concentration of NR-PM1 for the different campaigns typically ranged between 10 and 30 μg m−3. Overall, the organic portion was most abundant, ranging from 36% to 81% of NR-PM1. Other main constituents comprised ammonium (5–15%), nitrate (8–36%), sulfate (3–26%), and chloride (0–5%). These latter anions were, on average, fully neutralized by ammonium. As a major result, time of the year (winter vs. summer) and location of the site (Alpine valleys vs. Plateau) could largely explain the variability in aerosol chemical composition for the different campaigns and were found to be better descriptors for aerosol composition than the type of site (urban, rural etc.). Thus, a reassessment of classifications of measurements sites might be considered in the future, possibly also for other regions of the world. The OA data was further analyzed using positive matrix factorization (PMF) and the multi-linear engine ME (factor analysis) separating the total OA into its underlying components, such as oxygenated (mostly secondary) organic aerosol (OOA), hydrocarbon-like and freshly emitted organic aerosol (HOA), as well as OA from biomass burning (BBOA). OOA was ubiquitous, ranged between 36% and 94% of OA, and could be separated into a low-volatility and a semi-volatile fraction (LV-OOA and SV-OOA) for all summer campaigns at low altitude sites. Wood combustion (BBOA) accounted for a considerable fraction during wintertime (17–49% OA), particularly in narrow Alpine valleys BBOA was often the most abundant OA component. HOA/OA ratios were comparatively low for all campaigns (6–16%) with the exception of on-road, mobile measurements (23%) in the Rhine Valley. The abundance of the aerosol components and the retrievability of SV-OOA and LV-OOA are discussed in the light of atmospheric chemistry and physics.