Sources Of Carbonyl Compounds Research Articles

Summertime carbonyl compounds in an urban area in the North China Plain: Identification of sources, key precursors and their contribution to O3 formation

Carbonyl compounds are critical components of volatile organic compounds, which significantly participate in the photochemical formation of atmospheric ozone and thus threaten human health. Here we measured 15 C1–C8 carbonyl compounds at an urban site in Linyi, a typically industrialised city in the North China Plain (NCP). Formaldehyde (3.89 ppbv), acetaldehyde (1.66 ppbv) and acetone (2.03 ppbv) were found to be the top three carbonyl compounds, accounting for 76.11% of the total concentration of carbonyl compounds. Anthropogenic secondary formation was recognised as the main source of the top five carbonyl compounds, which included formaldehyde, acetaldehyde, acetone, butyraldehyde and benzaldehyde, and accounted for 46–54% of all sources. Alkenes were the most important precursors of formaldehyde and acetaldehyde, suggesting that reducing the emission of alkenes from anthropogenic sources is an effective way to control carbonyl compound pollution in Linyi. Furthermore, the photolysis of carbonyl compounds played a significant role (68–75%) as sources of HO2• and RO2• and thus made a significant contribution (14.6%) to the photochemical formation of O3. This study highlights the importance of anthropogenic secondary formation as a source of carbonyl compounds and provides a scientific basis for O3 pollution control in carbonyl compound-enriched cities in the NCP.

Pollution characteristics and sources of carbonyl compounds in a typical city of Fenwei Plain, Linfen, in summer

Field measurements of atmospheric carbonyl compounds (carbonyls) and essential precursors of O3 were carried out in the urban area of Linfen City (Linfen) where serious O3 pollution has occurred in recent years due to its unique terrain. Carbonyls were sampled using an automatic carbonyl sampler in August 2019 to determine their pollution characteristics and sources. An average concentration of ten carbonyls was 27 ± 5.7 μg m−3 detected using an HPLC-UV system. The concentrations of most detected carbonyls in August were significantly higher than those in the winter months in China. Acetone, formaldehyde and acetaldehyde were the most abundant species, accounting for 73% of all detected carbonyls. Formaldehyde, acetaldehyde, and methacrolein (MACR) were the most significant contributors to OH• reactivity and ozone generation, indicating that these three carbonyls were the key species influencing the production of O3. The concentrations of formaldehyde, acetaldehyde, and MACR showed similar diurnal variations on most days, with high values during the daytime reaching a peak at 10:00. However, the concentrations of the latter two species varied less than that of formaldehyde during the day. The acetone concentration generally increased continuously from morning to night, with the maximum value around 22:00. The C1/C2 ratio in summer was higher than that in winter. These results indicated that the carbonyls in Linfen were not only affected by anthropogenic sources such as vehicle exhaust but also by secondary photochemical production. The results of formaldehyde source apportionment showed that the contributions of background, primary, and secondary sources to the observed formaldehyde concentration were 27.6%, 36.6%, and 35.8%, respectively. Additionally, this study revealed for the first time that the vertical transport of air masses containing high concentrations of O3 and NO3 radicals above the boundary layer could increase the secondary generation of formaldehyde at night in summer.

Atmospheric Carbonyl Compounds in the Central Taklimakan Desert in Summertime: Ambient Levels, Composition and Sources

Although carbonyl compounds are a key species with atmospheric oxidation capacity, their concentrations and sources have not been sufficiently characterized in various atmospheres, especially in desert areas. In this study, atmospheric carbonyl compounds were measured from 16 May to 15 June 2018 in Tazhong in the central Taklimakan Desert, Xinjiang Uygur Autonomous Region, China. Concentrations, chemical compositions, and sources of carbonyl compounds were investigated and compared with those of different environments worldwide. The average concentration of total carbonyls during the sampling period was 11.79 ± 4.03 ppbv. Formaldehyde, acetaldehyde, and acetone were the most abundant carbonyls, with average concentrations of 6.08 ± 2.37, 1.68 ± 0.78, and 2.52 ± 0.68 ppbv, respectively. Strong correlations between formaldehyde and other carbonyls were found, indicating same or similar sources and sinks. A hybrid single-particle Lagrangian integrated trajectory was used to analyze 72 h back trajectories. The values of C1/C2 (formaldehyde to acetaldehyde, 3.22–4.59) and C2/C3 (acetaldehyde to propionaldehyde, 15.00–17.03) from different directions and distances of the trajectories were consistent with the characteristics of a remote area. Relative to various environments, the carbonyl concentration in the Tazhong desert site was lower than that in urban areas and higher than that in suburban and remote areas, implying contributions from local primary and secondary sources. The obtained data can be used to improve the source and sink estimation of carbonyls at the regional scale.

Exploratory analysis of the presence of 14 carbonyl compounds in bottled mineral water in polyethylene terephthalate (PET) containers

Carbonyl compounds (CCs) can migrate from bottles to mineral water because of plastic degradation. An exploratory analysis of the presence a significant number of CCs (14) in bottled mineral water with and without gas in polyethylene terephthalate (PET) containers was performed using ultra-fast liquid chromatography coupled to mass spectrometry (UFLC-MS). The data from the analysis was submitted to chemometric treatment (principal component analysis, PCA). Formaldehyde, acetaldehyde, and benzaldehyde were found in all samples (0.07–125 ng mL−1). Acrolein and acetone were present in 81% and 75% of the samples, respectively. The concentration of acrolein in carbonated water was up to 3.8 times greater than that measured in non-carbonated water (0.07–0.44 ± 0.01 ng mL−1). PCA analysis showed that gasification can influence the composition of CCs present in mineral water and that the plastic material of the bottles is a likely source of CCs. In addition, benzaldehyde levels may be associated with the use of recycled materials.

Unimolecular Dissociation of γ-Ketohydroperoxide via Direct Chemical Dynamics Simulations.

γ-Ketohydroperoxide [3-(hydroperoxy)propanal] is an important reagent in synthetic chemistry and, in particular, oxidation reactions. It is considered to be a precursor for secondary organic aerosol formation in the troposphere. Due to enhanced reactivity and limitations associated with analytical techniques, theoretical methods have been employed to study the unimolecular reactivity of hydroperoxides. A number of automated reaction discovery techniques have been used to study the reactivity of γ-ketohydroperoxide, and a large number of reactions have been reported in such studies. In the present work, we have investigated the unimolecular reaction dynamics of this molecule using electronic structure theory calculations and direct chemical dynamics simulations to assess the relevance of different reaction pathways. Classical trajectories were launched from the reactant well with fixed amounts of total energies and integrated on-the-fly using density functional B3LYP/6-31+G* model chemistry. Three dissociation channels among the previously reported reactions were identified as important. Korcek decomposition, which was proposed earlier as a source of carbonyl compounds from thermal decomposition of γ-ketohydroperoxide, was not observed in the present high-temperature simulations. However, trajectories showed the formation of carbonyl compounds such as aldehydes via other pathways. Results are compared with previous studies, and detailed atomic-level reaction mechanisms are presented.

AGE FEATURES OF THE EXCRETION OF CARBONILIC COMPOUNDS WITH URINE IN CHILDREN IN UNEXPOSED TERRITORY

Introduction. Carbonyl compounds (CC) are pollutants affecting the population and occupying an exceptional position in various fields of human activity. A significant source of CC is tobacco smoke. Material and methods. Urine samples of 278 children were analyzed by the method of gas chromatography. Additionally, there were studied dependencies of the content of the CC on the harmful chemical effects in living conditions: active and passive smoking. The assessment of the effect of smoking on formaldehyde emissions (FD) was carried out using the chi-square test for a 3x3 table. Results. The results obtained on the content of CC in the urine in several age groups. FD concentrations, in general, were shown to be in the range from 1.2 to 207.1 μg/dm3. The highest values were observed in the children’s population of the age group up to 7 years and in the group of 15-17 years. For representatives of the 1st (up to 7 years) and 3rd (15-17 years) age groups, the concentrations of acetaldehyde and acetone were in the range: for acetaldehyde - from 4.0 to 179.7 µg/dm3, acetone - from 0.35 to 11.95 µg/dm3. A statistically significant direct relationship was found between active smoking and FD content in urine (rsp = 0.24, p = 0.033); the reverse is with acetone content (rsp = 0.23, p = 0.042), and the inverse correlation between acetaldehyde content and passive smoking (rsp = 0.23, p = 0.038). Conclusion. The highest content of formaldehyde in the urine was found in groups “up to 7 years old” and “15-17 years old”. No age and gender differences in acetaldehyde and acetone concentrations were found.

Alkanes and aliphatic carbonyl compounds in wintertime PM2.5 in Beijing, China

Organic aerosol is one of the dominant components of PM2.5 in megacities. In order to understand the sources and formation processes of aliphatic carbonyl compounds, the concentrations of saturated and unsaturated aliphatic hydrocarbons and carbonyl compounds were determined in the PM2.5 from an urban area of Beijing sampled in November–December 2016 and analysed using two dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS). The data were separated into non-haze and haze days (PM2.5 ≥ 75 μg m−3). n-Alkanes (C10-C36) and n-alkenes (C12-C26) were abundant in the samples during the sampling campaign regardless of non-haze and haze conditions, and the middle chain length n–alkanes (C25–C34) were the most abundant. Aliphatic carbonyls, specifically n-alkanals (C8-C29), n-alkan-2-ones (C8-C31) and n-alkan-3-ones (C8-C30) were also detected in the PM2.5 at concentrations much lower than n-alkanes. The n-alkanals were the most abundant compounds amongst the aliphatic carbonyls, accounting for 65.4% on average of the total mass of aliphatic carbonyls. For the non-haze days, it seems likely that the OH oxidation of n-alkanes was a source of carbonyl compounds, whereas vehicle exhaust makes a significant contribution to the n-alkanes and n-alkanals, but makes a much smaller contribution to the n-alkan-2-ones and n-alkan-3-ones. It appears that primary sources are likely to be a major contributor to concentrations of the high molecular weight carbonyl compounds during the haze episodes, probably deriving from coal combustion. In addition, furanones (γ-lactones) and phytone (6, 10, 14-trimethylpentadecan-2-one) were also detected in our samples and are oxidation products of hydrocarbons and a marker of biogenic input, respectively. Cooking emissions also appear to be a likely contributor to the furanones. This study provides new information on the profiles of PM2.5-associated aliphatic hydrocarbons and carbonyl compounds, and gives insights into their sources. Differences in the concentrations and ratios of carbonyl compounds between Beijing and London are discussed.

Carbonyl compounds at Mount Tai in the North China Plain: Characteristics, sources, and effects on ozone formation

Carbonyl compounds, an important category of volatile organic compounds (VOCs), play important roles in ozone (O3) formation and atmospheric chemistry. To better understand the characteristics and sources of carbonyl compounds and their effects on O3 formation, C1-C8 carbonyls were measured at Mount Tai, the highest mountain in the North China Plain (NCP), in summer 2014. Acetone (3.57±0.55ppbv), formaldehyde (3.48±0.98ppbv) and acetaldehyde (1.27±0.78ppbv) are the three most abundant species, comprising as high as 90% of the total observed compounds. Isovaleraldehyde (0.37±0.17ppbv) presents another important carbonyl compound despite its high reactivity. Comparison with the observations available in China highlights the serious situation of carbonyls pollution in the NCP region. The sources of carbonyls are dominated by photo-oxidation of VOCs during the daytime and regional transport at night. Secondary sources from oxidation of hydrocarbons contribute on average 44% of formaldehyde, 31% of acetone, 85% of acetaldehyde, 78% of benzaldehyde, and 84% of isovaleraldehyde, demonstrating the dominant role of secondary formation in the ambient carbonyl levels. Formaldehyde, acetaldehyde and isovaleraldehyde are the most important contributors to the OH reactivity and O3 production among the measured carbonyls. This study shows that carbonyl compounds contribute significantly to the photochemical pollution in the NCP region and hence understanding their sources and characteristics is essential for developing the science-based O3 pollution control strategies.

Aldehydes and Ketones Formation: Copper-Catalyzed Aerobic Oxidative Decarboxylation of Phenylacetic Acids and α-Hydroxyphenylacetic Acids

Aromatic aldehydes or ketones from copper catalyzed aerobic oxidative decarboxylation of phenylacetic acids and α-hydroxyphenylacetic acids have been synthesized. This reaction combined decarboxylation, dioxygen activation, and C-H bond oxidation steps in a one-pot protocol with molecular oxygen as the sole terminal oxidant. This reaction represents a novel decarboxylation of an sp(3)-hybridized carbon and the use of a benzylic carboxylic acid as a source of carbonyl compounds.

Hierarchical cluster analysis of carbonyl compounds emission profiles from building and furniture materials

Emission profiles of carbonyl compounds from twenty-three indoor materials were assessed by chamber tests and compared by means of a hierarchical cluster analysis. This multivariate method provides a partition into six clusters of materials having statistically similar chemical profiles. Formaldehyde is the most dominant component of emissions mainly related to two types of wood composite products (chipboards and medium-density fibreboards (MDF)) and one finishing plaster. The analysis of clusters reveals that the emission profiles of materials belonging to a same category can have various degrees of variability. Some common pressed-wood products as chipboards and medium-density fibreboards have relatively uniform profiles characterized by its unique emission of formaldehyde. On the contrary, the profiles of Oriented Strand Boards (OSB) and finishing plasters appear very heterogeneous and unspecific in terms of relative dominance between different carbonyl compounds. The finishing plasters are identified as sources of carbonyl compounds (formaldehyde and acetaldehyde, especially). These finishing products have not yet been listed as potential formaldehyde and acetaldehyde emitters. According to these results, the wood composite products can also be ranked in the decreasing order of formaldehyde emission as follows: Chipboards > MDFs > Plywoods > OSBs. In light of these results, more systematic surveillance program on the emissions from materials should be set up by Public Health services to require or request product changes for building and furnishing applications.

Indoor and outdoor air carbonyl compounds correlation elucidated by principal component analysis

In this study indoor and outdoor air carbonyl compounds concentrations data are processed by means of principal component analysis (PCA). The analysis pointed to the carbonyl compounds sources as well as to their mutual interrelations. A global six sources (components) solution, accounting for the joint variability of the measured variables, was obtained. The existence of a linear function connecting outdoor and indoor components allowed for an exchange model between indoor and outdoor carbonyl compounds to be outlined. The different sources of carbonyl compounds were tentatively identified. Overall, this work demonstrates the presence of a delicate balance between indoor and outdoor carbonyl compounds contamination with the two compartments (indoor and outdoor) engaged in a close relationship.

Carbonyl compounds in boreal coniferous forest air in Hyytiälä, Southern Finland

Abstract. A variety of C1-C12 carbonyl compounds were measured in the air of a boreal coniferous forest located in Hyytiälä, Southern Finland. 24-hour samples were collected during March and April in 2003 using DNPH (2,4-dinitrophenyl hydrazine) coated C18-cartridges and analyzed by liquid chromatography-mass spectrometry (LC-MS). Altogether 22 carbonyl compounds were quantified. The most abundant carbonyls were acetone (24-hour average 1340ng/m3), formaldehyde (480ng/m3) and acetaldehyde (360ng/m3). Concentrations of monoterpene reaction products nopinone (9ng/m3) and limona ketone (5ng/m3) were low compared to the most abundant low molecular weight carbonyls. Trajectory analysis showed that highest concentrations of carbonyls were measured in the air masses coming from the East and the lowest in the air masses cycled long time over Scandinavia. The total concentration of carbonyl compounds in Hyytiälä in March/April 2003 was much higher than the concentration of aromatic hydrocarbons and monoterpenes in April 2002. Scaling the concentrations against reactivity with the OH-radical showed, that in spite of relatively low ambient concentrations higher molecular weight aldehydes contribute significantly to the total OH-reactive mass of carbonyls. The impact of carbonyl compounds on OH-radical chemistry is important. Contribution of carbonyls as an OH sink is comparable to that of NO2 and higher than monoterpenes and aromatic hydrocarbons. Lifetimes of the measured carbonyls with respect to reactions with OH radicals, ozone (O3), and nitrate (NO3) radicals as well as photolysis were estimated. The main sink reactions for most of the carbonyl compounds in Hyytiälä in springtime are expected to be reactions with the OH radical and photolysis. For 6-methyl-5-hepten-2-one and limona ketone also reactions with ozone are important. The sources of carbonyl compounds are presently highly uncertain. Based on the comparisons with urban concentrations the direct anthropogenic emissions are not as important as secondary biogenic and anthropogenic sources or primary biogenic sources in Hyytiälä.