Investigation of formaldehyde and other carbonyls in a small urban atmosphere using passive samplers. A comprehensive data analysis

Comprehensive observations of carbonyls of Mt. Hua in Central China: Vertical distribution and effects on ozone formation

Oxygenated volatile organic compounds (OVOCs) play important roles in tropospheric chemistry, regulating the oxidation capacity and ozone (O3) formation potential of the atmosphere. However, the evolution of OVOCs composition during vertical transport from the near surface to the upper atmosphere layer and the roles of OVOCs in the alpine atmospheric O3 formation are still poorly understood. In this study, we investigated the carbonyl compounds, the most important chemical group of OVOCs, and other gaseous pollutants simultaneously collected at the top (2060 m a.s.l, Top) and the foot (402 m a.s.l, Foot) of Mt. Hua in August 2020. The average concentrations of the total quantified carbonyl compounds (∑carbonyls) at the Top and Foot were 16.05 ± 3.69 and 15.32 ± 5.63 ppbv, respectively. Acetone was the most abundant carbonyl (4.19 ± 1.01 ppbv) at the Top, followed by formaldehyde and n-Nonanal, accounting for ∼58.8 % of ∑carbonyls, while formaldehyde (5.40 ± 2.26 ppbv), acetone, and acetaldehyde were the three most abundant species at the Foot, accounting for 64.7 % of ∑carbonyls. The n-Nonanal, acetone and acetaldehyde showed positive correlations between the Top and Foot during daytime, confirming the vertical transport of carbonyls from the foot to the top of Mt. Hua under the influence of valley winds. The direct emissions from vegetation, transport processes of anthropogenic emissions and photochemical oxidation contributed significantly to the measured carbonyls at the Top, especially for acetone. Formaldehyde, acetaldehyde, glyoxal, and methylglyoxal were the most important contributors to the O3 generation in Mt. Hua. This study could advance our understanding of the vertical distribution of the carbonyls and the effects on O3 formation in the alpine region of China.

Sources of atmospheric oxygenated volatile organic compounds in different air masses in Shenzhen, China

As precursors of photochemical secondary pollutants, oxygenated volatile organic compounds (OVOCs) play an important role in atmospheric photochemistry. In this study, 23 OVOCs were monitored using a commercial proton transfer reaction time-of-flight mass spectrometer at an urban site in Shenzhen, China. During the campaign, the mean total concentration of OVOCs was 23.3 ± 15.5 ppb (mean ± standard deviation), with a total ozone formation potential (TOFP) of 87.3 ± 58.7 ppb. Aldehydes contributed the most to the concentration and TOFP of OVOCs, followed by ketones, alcohols, and carboxylic acids. Formaldehyde, acetone, and acetaldehyde were the three most abundant atmospheric carbonyls. An optimized photochemical age-based parameterization method was locally applied for the source apportionment of OVOCs. OVOCs in Shenzhen primarily originated from biogenic sources during the summer. Secondary anthropogenic sources were also important contributors of most carbonyl compounds. The campaign was divided into four periods. Two periods were dominated by the east wind from the relatively clean coastal areas, with the mean concentration of anthropogenic OVOCs largely decreasing during the Chinese National Day holidays. The other two periods were dominated by northwest wind and northeast wind, respectively, with larger OVOC contributions from anthropogenic sources, suggesting that pollution transport from the inland was a main contributor to OVOCs. This study highlights the important contributions of both local and regional OVOC sources in urban atmospheres.

Assessment of atmospheric levels of carbonyls in an urban environment of Argentina

It is well-documented that carbonyl compounds have adverse effects on human health. On the other hand, these oxygenated volatile organic compounds (OVOCs) are precursors of secondary pollutants such as tropospheric ozone or peroxy acetyl nitrate (PAN). In particular, formaldehyde, the simplest carbonyl, is the most abundant carbonyl in the air generated from the degradation of most volatile organic compounds (VOCs). This work presents for the first time the characterization and determination of levels of carbonyl compounds by passive monitoring performed from April-December 2021 in the city of Córdoba, Argentina, the second most populated Mediterranean city located in the center of the country. Annual concentrations, considering the 11 carbonyls measured, were in the range of 0.13-8.75 μgm-3. Formaldehyde and acetaldehyde were the carbonyls detected in the highest annual average concentrations of 4.44 ± 1.75 μgm-3 and 3.85 ± 1.44 μgm-3, respectively. These carbonyls represent a contribution of around 40-57% on total carbonyls measured. Statistical analysis to determine significant differences and Pearson correlations with the meteorological parameters were performed. Spring and summer were found to be the seasons with the highest carbonyl concentration linked to forest fire episodes, especially in springtime. The values for the C1/C2 and C2/C3 ratios showed that sources of carbonyl formation are anthropogenic. In addition, the prop-Equiv concentration was determined, where formaldehyde and acetaldehyde were the main producers of tropospheric ozone. The ozone formation potential (OFP) showed that spring and summer are the seasons where carbonyls contribute to the formation of tropospheric ozone.This study represents a first approach of the carbonyl concentration in the city and of the influence of meteorological parameters on the behavior of carbonyls.

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. They significantly participate in the photochemical formation of atmospheric ozone and thus threaten human health. This study 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.

Characteristics, sources and health risk assessment of atmospheric carbonyls during multiple ozone pollution episodes in urban Beijing: Insights into control strategies

Carbonyls have attracted continuous attention due to their critical roles in atmospheric chemistry and their potential hazards to the ecological environment and human health. In this study, atmospheric carbonyls were measured during several ground-level-ozone (O₃) pollution episodes at three urban sites (CRAES, IEP and BJUT) in Beijing in 2019 and 2020. Comparative analysis revealed that the carbonyl concentrations were 20.25 ± 6.91 ppb and 13.43 ± 5.13 ppb in 2019 and 2020 in Beijing, respectively, with a significant spatial trend from north to south, and carbonyl levels in urban Beijing were in an upper-intermediate range in China, and higher than those in other countries reported in the literature. A particularly noteworthy phenomenon is the consistency of carbonyl concentrations with variations in O₃ concentrations. On O₃ polluted days, the carbonyl concentrations were 1.3-1.5 times higher than those on non-O₃ polluted days. Secondary formation contributed more to formaldehyde (FA) and acetaldehyde (AA) on O₃ polluted days, while the anthropogenic emissions were more significant for acetone (AC) on non-O₃ polluted days. Vehicle exhaust and solvent utilization were the main primary contributors to carbonyls. Due to reduced anthropogenic emissions caused by the COVID-19 lockdown and the "Program for Controlling Volatile Organic Compounds in 2020" in China, the contributions of primary emissions to carbonyls decreased in 2020 in Beijing. Human cancer risks to exposed populations from FA and AA increased with elevated O₃ levels, and the risks still remained on non-O₃ polluted days. The residents around the BJUT site might experience relatively higher human cancer risks than those around the other two sites. The findings in this study confirmed that atmospheric carbonyl pollution and its potential human health hazards cannot be ignored in urban Beijing; therefore, more strict control strategies for atmospheric carbonyls are urgently needed to better protect human health in Beijing in the future.

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.

Pollution mechanisms and photochemical effects of atmospheric HCHO in a coastal city of southeast China

Formaldehyde (HCHO) is a vital reactive carbonyl compound, which plays an important role in the photochemical process and atmospheric oxidation capacity. However, the current studies on the quantification of HCHO impacts on atmospheric photochemistry in southeast coastal areas of China with an obvious upward trend of ozone remain scarce and unclear, thus limiting the full understanding of formation mechanism and control strategy of photochemical pollution. Here, systematic field campaigns were conducted at a typical coastal urban site with good air quality to reveal HCHO mechanism and effects on O₃ pollution mechanism during spring and autumn, when photochemical pollution events still frequently appeared. Positive Matrix Factorization model results showed that secondary photochemical formation made the largest contributions to HCHO (69 %) in this study. Based on the photochemical model, the HCHO loss rates in autumn were significantly higher than those in spring (P < 0.05), indicating that strong photochemical conditions constrain high HCHO levels in certain situations. HCHO mechanism increased the ROx concentrations by 36 %, and increased net O₃ production rates by 31 %, manifesting that the reduction of HCHO and its precursors' emissions would effectively mitigate O₃ pollution. Therefore, the pollution characteristics and photochemical effects of HCHO provided significant guidance for future photochemical pollution control in relatively clean areas.

Good and bad get together: Inactivation of SARS-CoV-2 in particulate matter pollution from different fuels

Air pollution and associated particulate matter (PM) affect environmental and human health worldwide. The intense vehicle usage and the high population density in urban areas are the main causes of this public health impact. Epidemiological studies have provided evidence on the effect of air pollution on airborne SARS-CoV-2 transmission and COVID-19 disease prevalence and symptomatology. However, the causal relationship between air pollution and COVID-19 is still under investigation. Based on these results, the question addressed in this study was how long SARS-CoV-2 survives on the surface of PM from different origin to evaluate the relationship between fuel and atmospheric pollution and virus transmission risk. The persistence and viability of SARS-CoV-2 virus was characterized in 5 engine exhaust PM and 4 samples of atmospheric PM₁₀. The results showed that SARS-CoV-2 remains on the surface of PM₁₀ from air pollutants but interaction with engine exhaust PM inactivates the virus. Consequently, atmospheric PM₁₀ levels may increase SARS-CoV-2 transmission risk thus supporting a causal relationship between these factors. Furthermore, the relationship of pollution PM and particularly engine exhaust PM with virus transmission risk and COVID-19 is also affected by the impact of these pollutants on host oxidative stress and immunity. Therefore, although fuel PM inactivates SARS-CoV-2, the conclusion of the study is that both atmospheric and engine exhaust PM negatively impact human health with implications for COVID-19 and other diseases.

Investigation of PAHs, nitrated PAHs and oxygenated PAHs in PM10 urban aerosols. A comprehensive data analysis

Polycyclic aromatic compounds (PACs) in particulate matter contribute considerably to the health risk of air pollution. As such, we have optimized a method to determine the levels of polycyclic aromatic hydrocarbons, especially nitrated and oxygenated polycyclic aromatic hydrocarbons, in samples of PM₁₀ particulate matter using microwave-assisted extraction (MAE) and gas chromatography coupled to a triple quadrupole mass spectrometer (GC-MS/MS). The proposed method was applied to the analysis of real samples collected in the urban area of Ciudad Real (Spain) during one year. The median total concentrations of eighteen PAHs (∑PAHs) and seven OPAHs (∑OPAHs) were 0.54 and 0.23 ng m^-3, respectively, with the corresponding value for NPAH (∑NPAHs) being 0.03 ng m^-3 (only detected in 40% of samples). A clear seasonal trend was observed, with higher levels in the cold season and lower in the warm season for ∑PAHs. The same effect was observed for ∑OPAHs, which exhibited a median concentration of 0.72 ng m^-3 in the cold season and 0.10 ng m^-3 in the warm season, and for ∑NPAH, which exhibited a median of 0.04 ng m^-3 in the cold season but were not detected in the warm season. Molecular diagnostic ratios and PCA (principal component analysis) showed a predominantly traffic origin for PACs. The sources of PAHs also depend on meteorological conditions and/or atmospheric reactions, as confirmed by means of statistical analysis. The ∑OPAH/∑PAH and ∑NPAH/∑PAH ratios were higher in the cold season than the warm season, thus suggesting that PAH derivatives originated from primary combustion emission sources together with their parent PAHs. The concentration range found for benzo(a)pyrene was 0.006-0.542 ng m^-3, which is below the threshold value of 1 ng m^-3 established in European legislation as the annual average value. The lifetime lung risk from inhalation of PM₁₀-bound PACs was estimated to be six cancer cases per million people using the World Health Organization method.

Formaldehyde, acrolein and other carbonyls in dwellings of university students. Levels and source characterization

Fifteen carbonyl compounds were investigated in the living rooms and bedrooms of 25 university student flats in the urban area of Ciudad Real (Central Southern Spain) in wintertime. Carbonyls were sampled using Radiello ® passive samplers refilled in the laboratory according to the method described in ISO 16000-3 Standard. The most abundant carbonyls in the living rooms and bedrooms were formaldehyde, acetone, acetaldehyde, hexaldehyde and butyraldehyde. The median concentration levels in the living rooms and bedrooms were: 28.6 and 34.2 μg m^-3 for formaldehyde, 18.3 and 23.1 μg m^-3 for acetone, 14.3 and 15.8 μg m^-3 for acetaldehyde, 11.4 and 14.1 μg m^-3 for hexaldehyde and 10.8 and 12.4 μg m^-3 for butyraldehyde. The median concentration of formaldehyde, benzaldehyde, valeraldehyde and hexaldehyde was significantly higher in the bedrooms than in the living rooms. Indoor concentrations were significantly higher than outdoor concentrations for all carbonyl measured, indicating that sources in the indoor environment are prevailing in all flats. Principal component analysis, multiple linear regressions and Spearman correlation coefficients were used to investigate the origin, the indoor pollutants determinants and to establish common sources between carbonyls. Eight components were extracted from the application of PCA to the indoor and outdoor measurements accounting for 97.7% of the total variance. Formaldehyde, acetone, acetaldehyde and acrolein presented different indoor sources. In the multiple linear regression analysis, higher formaldehyde concentrations were found in those living rooms with wood floor and smoking was positively associated to acetone, propionaldehyde, benzaldehyde and isovaleraldehyde. Formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde and benzaldehyde concentrations were compared with relevant international guidelines, being their concentrations below recommended values except acrolein, where all measured flats exceeded the reference levels; it would be important to focus on the characterization of emission sources of acrolein in indoor air in order to minimise the exposure and health risk.