Special Issue "Atmospheric Volatile Organic Compounds (VOCs)"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Quality".

Deadline for manuscript submissions: closed (31 March 2020).

Special Issue Editor

Dr. Barkley C. Sive
E-Mail Website
Guest Editor
US National Park Service, Air Resources Division, Lakewood, CO, USA
Interests: analytical techniques for atmospheric VOC measurements; oil and natural gas production emissions; local and regional air quality; climate change; biogenic emissions; nonmethane hydrocarbons (NMHCs); oxygenated VOCs (OVOCs); organic nitrates; halocarbons; sulfur compounds; gas chromatography; mass spectrometry

Special Issue Information

Dear Colleagues,

Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and play an important role in determining the composition and chemistry on varying spatial scales. VOCs can have a significant impact on local and regional air quality as their oxidation in the presence of nitrogen oxides leads to tropospheric ozone formation. VOCs also directly and indirectly affect the oxidative capacity of the atmosphere because they can directly influence hydroxyl radical concentrations, thereby influencing the lifetimes of other atmospheric constituents. Oxidation processes affect the distribution and trends of a large variety of trace gases emitted from natural and anthropogenic sources, and VOC oxidation products can partition into the particle phase, becoming a significant component of fine aerosol mass. The impact of oxidation on radiatively important trace gases and particulate formation are also important for radiative forcing and climate. For these reasons, it is critical to understand the individual sources and sinks in the atmosphere that can influence the chemistry and regional distribution of these trace gases.

Scientific findings from the last decade have demonstrated the need for a more comprehensive approach to, and understanding of, both anthropogenic and natural VOC perturbations to the atmosphere, their influence on tropospheric ozone and other photochemical oxidants, and the ultimate effects on human health and ecosystem welfare. Advances in technology and analytical measurement techniques over the past decades have improved our ability to better characterize and accurately quantify atmospheric VOCs at mole fractions of 10-12 or less, and at high temporal resolutions such that instrumentation can be deployed on a wide range of mobile platforms. Biosphere–atmosphere chemical interactions, impacts of oil and natural gas production operations, and wildfire emissions are topics of timely interest concerning atmospheric VOCs. Furthermore, atmospheric variability coupled with the complexity of the chemical cycling for VOCs has facilitated the development of highly sophisticated models to interpret observations, especially for short-lived VOCs, and to evaluate our theoretical understanding of the photochemistry and dynamics of VOC oxidation, and ultimately to predict how future atmospheric composition will change. 

As the nature of atmospheric VOCs is highly complex and covers a wide range of disciplines, manuscripts on all aspects of atmospheric VOCs are welcome for this Special Issue.

Dr. Barkley C. Sive
Guest Editor

Manuscript Submission Information

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Keywords

  • volatile organic compounds (VOCs)
  • sources, sinks, and atmospheric lifetimes
  • secondary organic aerosol formation
  • kinetics and photochemistry
  • budgets and emission inventories
  • oil and natural gas production
  • urban and regional pollution
  • wildfires, prescribed burns and smoke
  • agricultural emissions
  • isotope ratios
  • biosphere/atmosphere interactions (e.g., fluxes, deposition, impacts, etc.)
  • air/sea fluxes
  • climate change

Published Papers (12 papers)

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Research

Open AccessArticle
Modeling Functional Organic Chemistry in Arctic Rivers: An Idealized Siberian System
Atmosphere 2020, 11(10), 1090; https://doi.org/10.3390/atmos11101090 - 13 Oct 2020
Viewed by 556
Abstract
Rivers of the Arctic will become ever more important for the global climate, since they carry a majority of continental dissolved organic carbon flux into the rapidly changing polar ocean. Aqueous organics comprise a wide array of functional groups, several of which are [...] Read more.
Rivers of the Arctic will become ever more important for the global climate, since they carry a majority of continental dissolved organic carbon flux into the rapidly changing polar ocean. Aqueous organics comprise a wide array of functional groups, several of which are likely to impact coastal and open water biophysical properties. Light attenuation, interfacial films, aerosol formation, gas release and momentum exchange can all be cited. We performed Lagrangian kinetic modeling for the evolution of riverine organic chemistry as the molecules in question make their way from the highlands to Arctic outlets. Classes as diverse as the proteins, sugars, lipids, re-condensates, humics, bio-tracers and small volatiles are all included. Our reduced framework constitutes an idealized northward flow driving a major hydrological discharge rate and primarily representing the Russian Lena. Mountainous, high solute and tundra sources are all simulated, and they meet up at several points between soil and delta process reactors. Turnover rates are parameterized beginning with extrapolated coastal values imposed along a limited tributary network, with connections between different terrestrial sub-ecologies. Temporal variation of our total dissolved matter most closely resembles the observations when we focus on the restricted removal and low initial carbon loads, suggesting relatively slow transformation along the water course. Thus, channel combinations and mixing must play a dominant role. Nevertheless, microbial and photochemical losses help determine the final concentrations for most species. Chemical evolution is distinct for the various functionalities, with special contributions from pre- and post-reactivity in soil and delta waters. Several functions are combined linearly to represent the collective chromophoric dissolved matter, characterized here by its absorption. Tributaries carry the signature of lignin phenols to segregate tundra versus taiga sources, and special attention is paid to the early then marine behaviors of low molecular weight volatiles. Heteropolycondensates comprise the largest percentage of reactive carbon in our simulations due to recombination/accumulation, and they tend to be preeminent at the mouth. Outlet concentrations of individual structures such as amino acids and absorbers lie above threshold values for biophysical influence, on the monolayer and light attenuation. The extent of coastal spreading is examined through targeted regional box modeling, relying on salinity and color for calibration. In some cases, plumes reach the scale of peripheral arctic seas, and amplification is expected during upcoming decades. Conclusions are mapped from the Lena to other boreal discharges, and future research questions are outlined regarding the bonding type versus mass release as permafrost degrades. Dynamic aqueous organic coupling is recommended for polar system models, from headwaters to coastal diluent. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Natural Seepage of Methane and Light Alkanes at Three Locations in Southern California
Atmosphere 2020, 11(9), 979; https://doi.org/10.3390/atmos11090979 - 12 Sep 2020
Viewed by 700
Abstract
Methane and light (C2–C5) alkane fluxes were measured from three geologic seepage sites in Southern California during May and June of 2019. Samples were collected from visible macroseeps in Carpinteria, McKittrick, and Ojai using an aluminum flux chamber with [...] Read more.
Methane and light (C2–C5) alkane fluxes were measured from three geologic seepage sites in Southern California during May and June of 2019. Samples were collected from visible macroseeps in Carpinteria, McKittrick, and Ojai using an aluminum flux chamber with attached stainless-steel canisters and were analyzed for C1 to C5 alkanes via gas chromatography. Carpinteria fluxes were characterized by a lower percentage of volatile organic compounds relative to methane but greatly enhanced (~20:1) ratios of i-butane to n-butane. McKittrick and Ojai exhibited less methane-rich emissions and i-butane to n-butane ratios of less than 2:1. The differences between gas ratios observed at the surface and those previously reported from underground gas deposits at Ojai suggest that gases undergo alterations to their molecular composition between deposit and surface. The ratios of emitted gases in this study show that not only does geologic seepage have a much different volatile organic compound profile than oil and natural gas extraction and pipeline natural gas, but also that individual geologic seepage locations exhibit large variability. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Monoterpene Chemical Speciation with High Time Resolution Using a FastGC/PTR-MS: Results from the COV3ER Experiment on Quercus ilex
Atmosphere 2020, 11(7), 690; https://doi.org/10.3390/atmos11070690 - 30 Jun 2020
Cited by 2 | Viewed by 662
Abstract
Monoterpenes (MTs) represent an important family of biogenic volatile organic compounds (BVOCs) in terms of amount and chemical diversity. This family has been extensively studied using gas chromatography (GC) and proton transfer reaction-mass spectrometry (PTR-MS). Upon recent advances with Fast Gas Chromatography (FastGC), [...] Read more.
Monoterpenes (MTs) represent an important family of biogenic volatile organic compounds (BVOCs) in terms of amount and chemical diversity. This family has been extensively studied using gas chromatography (GC) and proton transfer reaction-mass spectrometry (PTR-MS). Upon recent advances with Fast Gas Chromatography (FastGC), it was also commercialized with proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) instruments. The combination of both techniques showed promising results in the near real-time separation of isomers, with the need of further improvements. In this study, a FastGC prototype was coupled to a conventional PTR-MS (PTR-QuadMS). Extensive laboratory experiments were performed, in order to test the system’s performance and to optimize its operational parameters for MT separation. The detection limit was determined to be around 0.8–1.7 ppbv, depending on the MT. The system was afterwards deployed during a three-week field campaign in a mixed holm oak (Quercus ilex) forest known for its important MT emissions. MTs were measured in the incoming and the outgoing air of dynamic enclosures installed on the branches of four different trees. Three chemotypes of holm oak trees could be distinguished showing consistently different proportions of the emitted MTs throughout the measurement campaign: pinene-type, myrcene-type and limonene-type. Measurements showed a systematic diel variation in emissions typical of light and temperature-dependent, de novo-synthesized VOCs. The results demonstrated the feasibility of the FastGC/PTR-MS system for continuous measurements from dynamic chambers in the field, whereas further improvements would be necessary to lower the detection limit for ambient air measurements. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Exploring Effective Chemical Indicators for Petrochemical Emissions with Network Measurements Coupled with Model Simulations
Atmosphere 2020, 11(5), 439; https://doi.org/10.3390/atmos11050439 - 27 Apr 2020
Viewed by 858
Abstract
A large petrochemical complex, dubbed Petro–complex, situated in a rather rural region of Taiwan, was used as a test bed to detect emissions from the Petro–complex to its surroundings. Hourly observations of speciated non–methane hydrocarbons (NMHCs) by the photochemical assessment monitoring stations (PAMSs), [...] Read more.
A large petrochemical complex, dubbed Petro–complex, situated in a rather rural region of Taiwan, was used as a test bed to detect emissions from the Petro–complex to its surroundings. Hourly observations of speciated non–methane hydrocarbons (NMHCs) by the photochemical assessment monitoring stations (PAMSs), as well as the total amounts of NMHCs, SO2, and NOx provided by the air quality stations (AQSs), were utilized to find useful petro–emission indication methods. The analytical aspect of NMHCs either as a speciated form or as total amounts was demonstrated through field comparison to illustrate data quality. Using ethyne to offset traffic influence, the ratios of ethene to ethyne (acetylene) (E/A) and propene to ethyne (P/A) were proven to be effective indicators of petro–emissions owing to pronounced emissions of ethene and propene, revealed as tall spikes in PAMS measurements. SO2 and NOx were also explored as petro–emission indicators mainly for stack sources. By coordinating with three–dimensional modeling, SO2 from petro–emissions could be distinguished from other prominent sources, such as coal–fired power plants. An attempt was also made to use SO2 and NOx as indicators of broader petro–emissions with stringent criteria to minimize traffic interference and increase specificity. Similar findings were observed with the three indicators, that is, volatile organic compounds (VOCs) ratios, SO2 and NOx, to identify the southwest area of the Petro–region as the most affected area, as represented by Taisi station (F2). The percent affected time of a year at F2 was 10%–14%, owing to the dominant wind field of northeast monsoonal (NEM) in the region, as compared with other sites in the east and north of 1–5%. Using VOC ratios as petro–emission indicators is more effective than using other gases, owing to the compositional advantage to minimize traffic interference. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Variability of BVOC Emissions from Commercially Used Willow (Salix spp.) Varieties
Atmosphere 2020, 11(4), 356; https://doi.org/10.3390/atmos11040356 - 07 Apr 2020
Viewed by 970
Abstract
Willow (Salix spp.) trees are commonly used in short rotation coppices (SRC) to produce renewable energy. However, these plants are also known to emit high concentrations of biogenic volatile organic compounds (BVOCs), which have a large influence on air quality. Many different [...] Read more.
Willow (Salix spp.) trees are commonly used in short rotation coppices (SRC) to produce renewable energy. However, these plants are also known to emit high concentrations of biogenic volatile organic compounds (BVOCs), which have a large influence on air quality. Many different clones of commercially used Salix varieties exist today, but only a few studies have focused on BVOC emissions from these newer varieties. In this study, four varieties commercially propagated for biofuel production have been studied on a leaf-scale in the southern part of Sweden. The trees had either their first or second growing season, and measurements on BVOC emissions were done during the growing season in 2017 from the end of May to the beginning of September. Isoprene was the dominant emitted compound for all varieties but the average emission amongst varieties varied from 4.00 to 12.66 µg gdw−1 h−1. Average monoterpene (MT) (0.78–1.87 µg gdw−1 h−1) and sesquiterpene (SQT) emission rates (0.22–0.57 µg gdw−1 h−1) differed as well among the varieties. Besides isoprene, other compounds like ocimene, linalool and caryophyllene also showed a response to light but not for all varieties. Younger plants had several times higher emissions of non-isoprenoids (other VOCs) than the corresponding 1-year-old trees. The conclusions from this study show that the choice of variety can have a large impact on the regional BVOC emission budget. Genetics, together with stand age, should be taken into account when modelling BVOC emissions on a regional scale, for example, for air quality assessments. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Consumption of Hydrocarbons and Its Relationship with Ozone Formation in Two Chinese Megacities
Atmosphere 2020, 11(4), 326; https://doi.org/10.3390/atmos11040326 - 27 Mar 2020
Viewed by 608
Abstract
Continuous measurements of ozone and its precursors were performed at sites in two Chinese megacities, i.e., an urban site in Beijing and a suburban site in the Pearl River Delta (PRD). At both sites, the total oxidants (O3 + NO2) [...] Read more.
Continuous measurements of ozone and its precursors were performed at sites in two Chinese megacities, i.e., an urban site in Beijing and a suburban site in the Pearl River Delta (PRD). At both sites, the total oxidants (O3 + NO2) varied with the ratio of ethylbenzene to m,p-xylenes, which serves as an indicator of photochemical aging. An observation-based method (OBM) was derived for calculating the photochemical consumption of individual non-methane hydrocarbons (NMHCs) based on the observed NMHC concentrations and the ratio of ethylbenzene to m,p-xylenes. The results show a strong correlation between the oxidant level and the derived consumption of precursors at the two sites (R2 = 0.81 for the PRD site and R2 = 0.83 for the Beijing site), demonstrating a strong cause–effect relationship. The relative “consumption efficiency” among NMHCs was calculated based on the integrated amount of hydroxyl radicals derived from the ratio of ethylbenzene to xylenes. Thus, the percent contributions to ozone formation from each individual NMHC can be calculated. This concept of consumption is purely observation-based and provides an easy way to bypass complicated modeling and the necessity of knowing instantaneous concentrations of hydroxyl radicals, which are highly illusive in nature. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Optimization of a Method for the Detection of Biomass-Burning Relevant VOCs in Urban Areas Using Thermal Desorption Gas Chromatography Mass Spectrometry
Atmosphere 2020, 11(3), 276; https://doi.org/10.3390/atmos11030276 - 11 Mar 2020
Cited by 1 | Viewed by 1096
Abstract
Forest fire smoke influence in urban areas is relatively easy to detect at high concentrations but more challenging to detect at low concentrations. In this study, we present a simplified method that can reliably quantify smoke tracers in an urban environment at relatively [...] Read more.
Forest fire smoke influence in urban areas is relatively easy to detect at high concentrations but more challenging to detect at low concentrations. In this study, we present a simplified method that can reliably quantify smoke tracers in an urban environment at relatively low cost and complexity. For this purpose, we used dual-bed thermal desorption tubes with an auto-sampler to collect continuous samples of volatile organic compounds (VOCs). We present the validation and evaluation of this approach using thermal desorption gas chromatography mass spectrometry (TD-GC-MS) to detect VOCs at ppt to ppb concentrations. To evaluate the method, we tested stability during storage, interferences (e.g., water and O3), and reproducibility for reactive and short-lived VOCs such as acetonitrile (a specific chemical tracer for biomass burning), acetone, n-pentane, isopentane, benzene, toluene, furan, acrolein, 2-butanone, 2,3-butanedione, methacrolein, 2,5- dimethylfuran, and furfural. The results demonstrate that these VOCs can be quantified reproducibly with a total uncertainty of ≤30% between the collection and analysis, and with storage times of up to 15 days. Calibration experiments performed over a dynamic range of 10–150 ng loaded on to each thermal desorption tube at different relative humidity showed excellent linearity (r2 ≥ 0.90). We utilized this method during the summer 2019 National Oceanic and Atmospheric Administration (NOAA) Fire Influence on Regional to Global Environments Experiment–Air Quality (FIREX-AQ) intensive experiment at the Boise ground site. The results of this field study demonstrate the method’s applicability for ambient VOC speciation to identify forest fire smoke in urban areas. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Characterization of Total OH Reactivity in a Rapeseed Field: Results from the COV3ER Experiment in April 2017
Atmosphere 2020, 11(3), 261; https://doi.org/10.3390/atmos11030261 - 05 Mar 2020
Viewed by 792
Abstract
Croplands remain poorly studied ecosystems in terms of total hydroxyl radical (OH) reactivity, especially when compared to forests. As part of the COV3ER project, total OH reactivity (ROH), defined as the total loss rate of OH due to its reaction with [...] Read more.
Croplands remain poorly studied ecosystems in terms of total hydroxyl radical (OH) reactivity, especially when compared to forests. As part of the COV3ER project, total OH reactivity (ROH), defined as the total loss rate of OH due to its reaction with reactive species in the atmosphere, was characterized in a rapeseed field (Grignon, France) during the blooming season in April 2017. Measurements were performed in a dynamic chamber as well as in ambient air using the Comparative Reactivity Method (CRM). Complementary measurements of organic (including a proton transfer reaction quadrupole ion–time of flight mass spectrometry, PTRQi-ToFMS) and inorganic compounds were also performed in order to calculate the expected OH reactivity and evaluate the missing fraction. Measured ROH varied diurnally in the dynamic chamber (mROHchamber) with maxima around 20 to 30 s−1 at midday and minima during dark hours, following the variability of the enclosed branch VOCsrapeseed, which is light- and temperature-dependent. Oxygenated VOCs were the major compounds emitted by the rapeseed crop. However, in terms of contribution to OH reactivity, isoprene accounted for 40% during the daytime, followed by acetaldehyde (21%) and monoterpenes (18%). The comparison between mROHchamber and calculated ROH (cROHchamber) exhibited little or no difference during dark hours, whereas a maximum difference appeared around midday, highlighting a significant missing fraction (46% on average during daytime) mainly related to biogenic temperature- and/or light-dependent emissions. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Passively Sampled Ambient Hydrocarbon Abundances in a Texas Oil Patch
Atmosphere 2020, 11(3), 241; https://doi.org/10.3390/atmos11030241 - 29 Feb 2020
Viewed by 942
Abstract
The United States has experienced exceptional growth in oil production via unconventional extraction for over a decade. This boom has led to an increase in hydrocarbon emissions to the atmosphere. With Texas as the leading contributor to growing oil production, it is important [...] Read more.
The United States has experienced exceptional growth in oil production via unconventional extraction for over a decade. This boom has led to an increase in hydrocarbon emissions to the atmosphere. With Texas as the leading contributor to growing oil production, it is important to assess the effects the boom has had on the environment and communities at local and regional levels. We conducted a pilot study to investigate the use of passive samplers for evaluating potential off-site risk from hydrocarbon emissions in a relatively low production activity area of the Texas Eagle Ford shale. Emissions from production sites include benzene, a hazardous air pollutant and known carcinogen. Passive hydrocarbon sampling devices (Radiello samplers) were used to monitor hydrocarbon levels on a rural property near a production site with an occasional flare for one year. Selected hydrocarbons were analyzed using thermal desorption and gas chromatography with flame ionization detection. Benzene concentrations were found to be correlated with changes in season, with higher abundance in the winter months. Benzene levels at this site were similar or higher than those observed in urban areas, away from shale oil and gas production. Increased benzene concentrations were distinguished when winds advected hydrocarbons from the production site, suggesting that oil and gas site emissions have a greater impact on the local community when winds advect them towards those living downwind; however, hydrocarbon levels in this low production area never exceeded state air monitoring comparison standards. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Analysis of Volatile Organic Compounds during the OCTAVE Campaign: Sources and Distributions of Formaldehyde on Reunion Island
Atmosphere 2020, 11(2), 140; https://doi.org/10.3390/atmos11020140 - 27 Jan 2020
Cited by 2 | Viewed by 993
Abstract
The Oxygenated Compounds in the Tropical Atmosphere: Variability and Exchanges (OCTAVE) campaign aimed to improve the assessment of the budget and role of oxygenated volatile organic compounds (OVOCs) in tropical regions, and especially over oceans, relying on an integrated approach combining in situ [...] Read more.
The Oxygenated Compounds in the Tropical Atmosphere: Variability and Exchanges (OCTAVE) campaign aimed to improve the assessment of the budget and role of oxygenated volatile organic compounds (OVOCs) in tropical regions, and especially over oceans, relying on an integrated approach combining in situ measurements, satellite retrievals, and modeling. As part of OCTAVE, volatile organic compounds (VOCs) were measured using a comprehensive suite of instruments on Reunion Island (21.07° S, 55.38° E) from 7 March to 2 May 2018. VOCs were measured at a receptor site at the Maïdo observatory during the entire campaign and at two source sites: Le Port from 19 to 24 April 2018 (source of anthropogenic emissions) and Bélouve from 25 April to 2 May 2018 (source of biogenic emissions) within a mobile lab. The Maïdo observatory is a remote background site located at an altitude of 2200 m, whereas Bélouve is located in a tropical forest to the east of Maïdo and Le Port is an urban area located northwest of Maïdo. The major objective of this study was to understand the sources and distributions of atmospheric formaldehyde (HCHO) in the Maïdo observatory on Reunion Island. To address this objective, two different approaches were used to quantify and determine the main drivers of HCHO at Maïdo. First, a chemical-kinetics-based (CKB) calculation method was used to determine the sources and sinks (biogenic, anthropogenic/primary, or secondary) of HCHO at the Maïdo site. The CKB method shows that 9% of the formaldehyde formed from biogenic emissions and 89% of HCHO had an unknown source; that is, the sources cannot be explicitly described by this method. Next, a positive matrix factorization (PMF) model was applied to characterize the VOC source contributions at Maïdo. The PMF analysis including VOCs measured at the Maïdo observatory shows that the most robust solution was obtained with five factors: secondary biogenic accounting for 17%, primary anthropogenic/solvents (24%), primary biogenic (14%), primary anthropogenic/combustion (22%), and background (23%). The main contributions to formaldehyde sources as described by the PMF model are secondary biogenic (oxidation of biogenic VOCs with 37%) and background (32%). Some assumptions were necessary concerning the high percentage of unknown HCHO sources of the CKB calculation method such as the biogenic emission factor resulting in large discrepancies between the two methods. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Natural Formation of Chloro- and Bromoacetone in Salt Lakes of Western Australia
Atmosphere 2019, 10(11), 663; https://doi.org/10.3390/atmos10110663 - 30 Oct 2019
Viewed by 1363
Abstract
Western Australia is a semi-/arid region known for saline lakes with a wide range of geochemical parameters (pH 2.5–7.1, Cl 10–200 g L−1). This study reports on the haloacetones chloro- and bromoacetone in air over 6 salt lake shorelines. Significant [...] Read more.
Western Australia is a semi-/arid region known for saline lakes with a wide range of geochemical parameters (pH 2.5–7.1, Cl 10–200 g L−1). This study reports on the haloacetones chloro- and bromoacetone in air over 6 salt lake shorelines. Significant emissions of chloroacetone (up to 0.2 µmol m−2 h−1) and bromoacetone (up to 1. 5 µmol m−2 h−1) were detected, and a photochemical box model was employed to evaluate the contribution of their atmospheric formation from the olefinic hydrocarbons propene and methacrolein in the gas phase. The measured concentrations could not explain the photochemical halogenation reaction, indicating a strong hitherto unknown source of haloacetones. Aqueous-phase reactions of haloacetones, investigated in the laboratory using humic acid in concentrated salt solutions, were identified as alternative formation pathway by liquid-phase reactions, acid catalyzed enolization of ketones, and subsequent halogenation. In order to verify this mechanism, we made measurements of the Henry’s law constants, rate constants for hydrolysis and nucleophilic exchange with chloride, UV-spectra and quantum yields for the photolysis of bromoacetone and 1,1-dibromoacetone in the aqueous phase. We suggest that heterogeneous processes induced by humic substances in the quasi-liquid layer of the salt crust, particle surfaces and the lake water are the predominating pathways for the formation of the observed haloacetones. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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Open AccessArticle
Aromatic Hydrocarbons in Urban and Suburban Atmospheres in Central China: Spatiotemporal Patterns, Source Implications, and Health Risk Assessment
Atmosphere 2019, 10(10), 565; https://doi.org/10.3390/atmos10100565 - 20 Sep 2019
Cited by 4 | Viewed by 975
Abstract
Ambient aromatic hydrocarbons (AHs) are hazardous air pollutants and the main precursors of ozone (O3). In this study, the characteristics of ambient AHs were investigated at an urban site (Ziyang, ZY) and a suburban site (Jiangxia, JX) in Wuhan, Central China, [...] Read more.
Ambient aromatic hydrocarbons (AHs) are hazardous air pollutants and the main precursors of ozone (O3). In this study, the characteristics of ambient AHs were investigated at an urban site (Ziyang, ZY) and a suburban site (Jiangxia, JX) in Wuhan, Central China, in 2017. The positive matrix factorization (PMF) model was used to investigate the sources of AHs, and a health risk assessment was applied to estimate the effects of AHs on human health. The concentrations of total AHs at ZY (2048 ± 1364 pptv) were comparable (p > 0.05) to that (2023 ± 1015 pptv) at JX. Source apportionment results revealed that vehicle exhaust was the dominant source of both, total AHs, and toluene, contributing 51.9 ± 13.1% and 49.3 ± 9.5% at ZY, and 44.7 ± 12.6% and 43.2 ± 10.2% at JX, respectively. Benzene was mainly emitted from vehicle exhaust at ZY (50.2 ± 15.5%), while it was mainly released from biomass and coal burning sources at JX (50.6 ± 16.7%). The health risk assessment results indicated that AHs did not have a significant non-carcinogenic risk, while the carcinogenic risks of benzene exceeded the regulatory limits set by the USEPA for adults (1 × 10−6) at both sites. Hence, controlling the emissions of vehicular and biomass/coal burning sources will be an effective way to reduce ambient AHs and the health risk of benzene exposure in this region. These findings will enhance our knowledge of ambient AHs in Central China and be helpful for local governments to formulate air pollution control strategies. Full article
(This article belongs to the Special Issue Atmospheric Volatile Organic Compounds (VOCs))
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