Ratios Of Volatile Organic Compounds Research Articles

Quantification of cancer biomarkers in urine using volatilomic approach

Urine analysis is an attractive approach for non-invasive cancer diagnostics. In this study, a procedure for the determination of volatile organic compounds (VOCs) in human urine (acetone, acetonitrile, dimethylsulfide, dimethyl disulfide, dimethyl trisulfide, hexane, benzene, toluene, 2-butanone, 2-pentanone, pentanal) has been described including sample preparation using preconcentration of analytes in sorbent tubes followed by gas chromatography with mass spectrometry (GC-MS). Fractional factorial design and constrained surfaces design were used to optimize preconcentration of VOCs in sorbent tubes. The procedure was validated by analysis of synthetic urine containing VOC standards in the concentration range of 1–5000 ng/mL. Optimized procedure was applied to analyze urine samples of 89 healthy volunteers and 85 patients with cancer of various localizations: 42 patients with lung cancer, 25 – colon, 3 – stomach, 2 – prostate, 2 – esophageal, 2 – pancreas, 2 – kidney, 1 – ovarian, 1 – cervical, 1 – skin, 1 – liver. Concentrations of 2-butanone, 2-pentanone, acetonitrile, and benzene were found different in urine of patients with cancer and healthy individuals. Influence of cancer localization and tumor, nodule, metastasis stage on urine VOC profile was considered. The approach of using ratios of VOCs to the main ones instead of concentrations was considered. A diagnostic model based on significantly different VOC ratios was created to classify healthy individuals and patients with cancer using artificial neural network (ANN). The model was validated during construction by means of 3-fold cross-validation. Average area under receiver operating characteristic (ROC) curve on test dataset was 0.886. Average sensitivity and specificity of the created model were 91 % and 82 %.

Characterization and Sources of VOCs during PM2.5 Pollution Periods in a Typical City of the Yangtze River Delta

To investigate the characteristics and sources of volatile organic compounds (VOCs) as well as their impacts on secondary organic aerosols (SOAs) formation during high-incidence periods of PM2.5 pollution, a field measurement was conducted in December 2019 in Hefei, a typical city of the Yangtze River Delta (YRD). During the whole process, the mixing ratios of VOCs were averaged as 21.1 ± 15.9 ppb, with alkanes, alkenes, alkyne, and aromatics accounting for 59.9%, 15.3%, 15.0%, and 9.8% of the total VOCs, respectively. It is worth noting that the contributions of alkenes and alkyne increased significantly during PM2.5 pollution periods. Based on source apportionment via the positive matrix factorization (PMF) model, vehicle emissions, liquefied petroleum gas/natural gas (LPG/NG), and biomass/coal burning were the main sources of VOCs during the research in Hefei. During pollution periods, however, the contribution of biomass/coal burning to VOCs increased significantly, reaching as much as 47.6%. The calculated SOA formation potential (SOAFP) of VOCs was 0.38 ± 1.04 µg m−3 (range: 0.04–7.30 µg m−3), and aromatics were the dominant contributors, with a percentage of 96.8%. The source contributions showed that industrial emissions (49.1%) and vehicle emissions (28.3%) contributed the most to SOAFP during non-pollution periods, whereas the contribution of biomass/coal burning to SOA formation increased significantly (32.8%) during PM2.5 pollution periods. These findings suggest that reducing VOCs emissions from biomass/coal burning, vehicle, and industrial sources is a crucial approach for the effective control of SOA formation in Hefei, which provides a scientific basis for controlling PM2.5 pollution and improving air quality in the YRD region.

Ambient volatile organic compounds in a typical industrial city in southern China: Impacts of aromatic hydrocarbons from new industry

New industrial parks, including fine chemical, medical manufacturers, etc., are emerging in modern cities in China, whereas their emissions and impacts have not been fully illuminated. In this study, ambient volatile organic compounds (VOCs) in Huizhou were measured in three functional zones, namely new industrial, roadside, and residential zones. The average mixing ratios of total VOCs were as follow: industrial (56.22 ± 15.06 ppbv) > roadside (39.30 ± 12.96 ppbv) > residential (26.03 ± 7.31 ppbv). The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP) of VOCs in the industrial zone were 1.5–2.3 and 1.7–3.1 times those in the other zones, respectively. Aromatics contributed the most to OFP (39.8 % - 44.8 %) and SOAP (78.9 % - 91.0 %), with much less contributions to VOCs mixing ratios (18.3 % - 21.2 %). Naphthalene was the most abundant aromatic species across the three zones and ranked among the top contributors to OFP and SOAP among all VOCs species. Source apportionment identified that new industrial emissions and solvent use was the largest VOCs contributor in the industrial zone (53.9 %), traffic-related emissions dominated in the roadside zone (40.7 %), while new industrial and traffic-related emissions contributed similar in the residential zone (32.9 % and 34.7 %, respectively). The carcinogenic and non-carcinogenic risks of hazardous VOCs were above the acceptable threshold, primarily due to new industrial and traffic-related emissions. Our results suggested to strengthen the control of new industrial emissions and aromatics sources in Huizhou city to improve air quality and protect human health.

Ozone response to precursors changes in the Chengdu-Chongqing economic circle, China, from satellite and ground-based observations

Ozone (O3) pollution has become a noticeable problem in the Chengdu-Chongqing Economic Circle in China. The April–September MDA8 O3 level increases significantly by 2.26 μg m−3 year−1 from 2015 to 2023, with meteorological factors occupying merely 18 % in line with multivariate linear regression. To reveal the impact of anthropogenic emissions on O3 increase, O3 production sensitivity is accurately diagnosed by deriving localized thresholds for satellite formaldehyde (HCHO) to NO2 ratio and validated by in-situ measurements and observation-based model. Tracking volatile organic compounds (VOCs) and NOx through satellite HCHO and NO2, the O3 responses to precursor changes are assessed for long-term and special cases, and appropriate precursor reduction ratios are inferred. The results present that the transition range of satellite HCHO/NO2 from VOC-limited to NOx-limited in the region ranges from 2.7 to 4.3. The VOC-limited regime is concentrated in the urban areas of Chongqing and Chengdu as well as the central of the neighboring cities such as Deyang, Mianyang, and Meishan. The relative incremental reactivity from in-situ observations and box model at three sites in August 2019 demonstrates that O3 is most sensitive to anthropogenic VOC at urban and suburban sites, consistent with satellite results. Satellite and surface NO2 decrease at an annual rate of −2.1 % and − 2.9 % between 2015 and 2023, with larger decreases in Chengdu and Chongqing. In contrast, the trend of satellite HCHO is insignificant, indicating effective reduction in NOx but no significant reduction in VOC. This inappropriate reduction results in an increase in urban O3. The three short-term cases further validate the need for synergistic NOx and VOC reductions. Based on the relationship between O3 and satellite NO2 and HCHO, the minimum and optimal reduction ratios of VOC to NOx are 0.4:1 and 2.4:1 for the entire region, with higher ratios in Chengdu and Chongqing.

Sensitivity Analysis of Atmospheric Ozone and Source Apportionment of Volatile Organic Compounds in Yinchuan City

Based on the observation data of O3 concentration in Yinchuan in 2022, the monthly variation characteristics of O3 concentrations were analyzed. Further, based on the observation data of meteorological elements, conventional pollutants, and volatile organic compounds （VOCs） concentrations at an urban site in Yinchuan from May to July, the difference in meteorological elements and precursor concentrations between the polluted days and the non-polluted days were compared. Then, the O3 sensitivity and the VOCs sources were discussed using the Framework for 0-D Atmospheric Modeling （F0AM） and positive matrix factorization （PMF） model, respectively. The results showed that： ① The O3 pollution occurred from May to July in 2022, and the concentrations of O3-8h-90per were 156 μg·m-3, 170 μg·m-3, and 174 μg·m-3, respectively, with exceeding standard rates of 9.7%, 26.7%, and 29.0%, respectively. ② Compared with those on the non-polluted days, the hourly mean values of temperature, total solar radiation, and concentrations of various precursors on the O3-polluted days increased, including the volume concentrations of propane, isobutane, ethane, n-butane, and dichloromethane, which increased significantly by 33.1%, 29.1%, 25.0%, 22.7%, and 21.3%, respectively. The results showed that the combined increase in pollutant emissions and adverse meteorological conditions contributed to the formation of O3. ③ From May to July 2022, the top five VOCs species in terms of ozone formation potential （OFP） value on whole, non-polluted, and polluted days were the same. They were acetaldehyde, m/p-xylene, ethylene, isoprene, and toluene, mainly from solvent use sources, natural sources, and chemical industry emissions. ④ The local O3 production was mostly controlled by VOCs, and the relative incremental reactivity （RIR） results revealed that O3 production showed strong positive sensitivity to alkene and aromatic hydrocarbon but showed negative sensitivity to NOx on both polluted and non-polluted days. The relative contributions of active species such as acetone, ethylene, and isobutane to O3 production were high, and the implementation of an emission reduction scheme with the ratio of VOCs to NOx emission reduction much greater than 1 could effectively reduce the local O3 concentration. ⑤ The main sources of atmospheric VOCs in Yinchuan were motor vehicle emission sources （32.3%）, process sources （20.7%）, combustion sources （19.2%）, solvent use sources （12.7%）, gasoline volatile sources （9.1%）, and natural sources （6%）, and the contribution rate of motor vehicle emission sources on polluted days increased by 4.6% compared with that on non-polluted days, indicating that the motor vehicle emission source was an important object of summer VOCs control in Yinchuan.

Evaluation of modelled versus observed non-methane volatile organic compounds at European Monitoring and Evaluation Programme sites in Europe

Abstract. Atmospheric volatile organic compounds (VOCs) constitute a wide range of species, acting as precursors to ozone and aerosol formation. Atmospheric chemistry and transport models (CTMs) are crucial to understanding the emissions, distribution, and impacts of VOCs. Given the uncertainties in VOC emissions, lack of evaluation studies, and recent changes in emissions, this work adapts the European Monitoring and Evaluation Programme Meteorological Synthesizing Centre – West (EMEP MSC-W) CTM to evaluate emission inventories in Europe. Here we undertake the first intensive model–measurement comparison of VOCs in 2 decades. The modelled surface concentrations are evaluated both spatially and temporally, using measurements from the regular EMEP monitoring network in 2018 and 2019, as well as a 2022 campaign. To achieve this, we utilised the UK National Atmospheric Emissions Inventory to derive explicit emission profiles for individual species and employed a tracer method to produce pure concentrations that are directly comparable to observations. The degree to which the modelled and measured VOCs agree varies depending on the specific species. The model successfully captures the overall spatial and temporal variations of major alkanes (e.g. ethane, n-butane) and unsaturated species (e.g. ethene, benzene) but less so for propane, i-butane, and ethyne. This discrepancy underscores potential issues in the boundary conditions for the latter species and in their primary emissions from, in particular, the solvent and road transport sectors. Specifically, potential missing propane emissions and issues with its boundary conditions are highlighted by large model underestimations and smaller propane-to-ethane ratios compared to the measurement. Meanwhile, both the model and measurements show strong linear correlations among butane isomers and among pentane isomers, indicating common sources for these pairs of isomers. However, modelled ratios of i-butane to n-butane and i-pentane to n-pentane are approximately one-third of the measured ratios, which is largely driven by significant emissions of n-butane and n-pentane from the solvent sector. This suggests issues with the speciation profile of the solvent sector, underrepresented contributions from transport and fuel evaporation sectors in current inventories, or both. Furthermore, the modelled ethene-to-ethyne and benzene-to-ethyne ratios differ significantly from measured ratios. The different model performance strongly points to shortcomings in the spatial and temporal patterns and magnitudes of ethyne emissions, especially during winter. For OVOCs, the modelled and measured concentrations of methanal and methylglyoxal show a good agreement, despite a moderate underestimation by the model in summer. This discrepancy could be attributed to an underestimation of contributions from biogenic sources or possibly a model overestimation of their photolytic loss in summer. However, the insufficiency of suitable measurements limits the evaluation of other OVOCs. Finally, model simulations employing the CAMS inventory show slightly better agreements with measurements than those using the Centre on Emission Inventories and Projections (CEIP) inventory. This enhancement is likely due to the CAMS inventory's detailed segmentation of the road transport sector, including its associated sub-sector-specific emission profiles. Given this improvement, alongside the previously mentioned concerns about the model's biased estimations of various VOC ratios, future efforts should focus on a more detailed breakdown of dominant emission sectors (e.g. solvents) and the refinement of their speciation profiles to improve model accuracy.

Analysis of Ozone and VOCs Pollution Characteristics, Sources, and Abatement Control Strategies in Hebi

In order to control the increasing ozone （O3） pollution in Hebi, Henan Province, clarifying the pollution characteristics of ozone and its precursors is vital. Therefore, we conducted a comprehensive analysis of O3 pollution utilizing the OFP-PMF-EKMA method combined with online hourly resolution monitoring data of conventional pollutants and volatile organic compounds （VOCs） in the summer of 2022 （June-September）. Ozone formation potential （OFP） was used to identify the key VOCs species, and the PMF model was used to identify the VOCs emission sources, whereas EKMA curves and scenario analysis were used to identify the main ozone control area in Hebi and to determine the reduction ratio of VOCs and NOx in a scientifically refined way. In 2022, Hebi had persistent O3 pollution, with the highest concentration in June. Conditions of high temperature, low humidity, and low atmospheric pressure contributed to the O3 accumulation. Aromatic and oxygenated volatile organic compounds （OVOCs） contributed significantly to the OFP and VOCs fraction, which were the dominant active substance and concentration dominant species. The results of the VOCs source analysis indicated that vehicle exhaust sources （25.3%） were the main source of atmospheric VOCs, followed by process sources （17.7%） and biomass combustion sources （17.6%）. Thus, emission sources associated with the combustion of fossil fuels and industrial production emissions were the most urgent sources of atmospheric VOCs to be controlled in Hebi. The O3 generation in Hebi occurred in the VOCs-sensitive zones, and the emission reduction results showed that a synergistic emission reduction of VOCs and nitrogen oxide （NOx） could effectively control O3 pollution with a 75% reduction in VOCs and a 10% reduction in NOx.

Vertical Features of Volatile Organic Compounds and Their Potential Photochemical Reactivities in Boundary Layer Revealed by In-Situ Observations and Satellite Retrieval

Based on in-situ vertical observations of volatile organic compounds (VOCs) in the lower troposphere (0–1.0 km) in Nanjing, China, during the summer and autumn, we analyzed the VOCs vertical profiles, diurnal variation, and their impact factors in meteorology and photochemistry. The results showed that almost all the concentrations of VOC species decreased with height, similar to the profiles of primary air pollutants, as expected. However, we found the ratios of inactive species (e.g., acetylene) and secondary VOCs (e.g., ketones and aldehydes) in total VOCs (TVOCs) increased with height. Combined with satellite-retrieved data, we found the average HCHO tropospheric column concentrations were 2.0 times higher in the summer than in the autumn. While the average of tropospheric NO2 column concentrations was 3.0 times lower in the summer than in the autumn, the seasonal differences in the ratio of oxygenated VOCs (OVOCs) to NO2 (e.g., HCHO/NO2) shown in TROPOMI satellite-retrieved data were consistent with in-situ observations (e.g., acetone/NO2). On average, during autumn daytime, the mixing layer (ML), stable boundary layer (SBL), and residual layer (RL) had OH loss rates (LOH) of 6.9, 6.3, and 5.5 s−1, respectively. The LOH of alkenes was the largest in the ML, while the LOH of aromatics was the largest in the SBL and RL. At autumn night, the NO3 loss rates (LNO3) in the SBL and RL were 2.0 × 10−2 and 1.6 × 10−2 s−1, respectively, and the LNO3 of aromatics was the largest in the SBL and RL. In the daytime of summer, the LOH of VOCs was ~40% lower than that in autumn in all layers, while there was no significant difference in LNO3 at night between the two seasons. This study provides data support and a theoretical basis for VOC composite pollution control in the Nanjing region.

Roles of photochemical consumption of VOCs on regional background O3 concentration and atmospheric reactivity over the pearl river estuary, Southern China

Understanding of the photochemical ozone (O3) pollution over the Pearl River Estuary (PRE) of southern China remains limited. We performed an in-depth analysis of volatile organic compounds (VOCs) data collected on an island (i.e., the Da Wan Shan Island, DWS) located at the downwind of Pearl River Delta (PRD) from 26 November to 15 December 2021. Abundances of O3 and its precursors were measured when the air masses originated from the inland PRD. We observed that the VOCs levels at the DWS site were lower, while the mixing ratio of O3 was higher, compared to those reported at inland PRD, indicating the occurrence of photochemical consumption of VOCs during the air masses transport, which was further confirmed by the composition and diurnal variations of VOCs, as well as ratios of specific VOCs. The simulation results from a photochemical box model showed that the O3 level in the outflow air masses of inland PRD (O3(out-flow)) was the dominant factor leading to the intensification of O3 pollution and the enhancement of atmospheric radical concentrations (ARC) over PRE, which was mainly contributed by the O3 production via photochemical consumption of VOCs during air masses transport. Overall, our findings provided direct quantitative evidence for the roles of outflow O3 and its precursors from inland PRD on O3 abundance and ARC over the PRE area, highlighting that alleviation of O3 pollution over PRE should focus on the impact of photochemical loss of VOCs in the outflow air masses from inland PRD.

Characteristics of Volatile Organic Compounds Distribution in Downtown Ansan Near Industrial Complexes

There are four industrial complexes located around Ansan City, which is one of the areas with the highest VOCs emissions in Gyeonggi region based on the emissions provided by the clean policy support system (CAPSS), Korea. In this study, proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) was used to determine the distribution of volatile organic compounds (VOCs) in urban areas near industrial complexes in Ansan City in 2023 (May to June). The PTR-TOF-MS was operated over the mass range of 10-400amu at a drift tube pressure of 2.3mbar and temperature 80<sup>o</sup>C (E/N ~ 130Td) that enabled the collection of VOC data at 0.1Hz resolution. The mixing ratio calculations for methanol, acetaldehyde, acetonitrile, acetone, acetic acid, dimethyl sulfide, isoprene, methyl vinyl ketone (MVK), methyl ethyl ketone (MEK), benzene, toluene, styrene, xylene, trimethylbenzene and pinene reported in this study were done using the sensitivity factors obtained from the PTR-TOF-MS calibrations. As a result of the intensive measurement in springtime, among the substances constituting VOCs, methanol was the most abundant with 16.27±7.13 ppb, followed by acetone, acetaldehyde, acetic acid, methyl ethyl ketone (MEK), toluene, and xylene. VOCs compositions were dominated by oxidized VOCs, with CxHyO1 at 74%, CxHyO2 at 11%, aromatic CxHy at 10.5%, and CxHyN at 3.1%, respectively. As a result of the diurnal variations and conditional probability function (CPF) analysis, it was found that toluene and MEK were locally greatly influenced by industrial complexes distributed around Ansan City. Related with the ozone creating contribution, the ratio of VOCs to nitrogen oxide (NOx) was 6.5 (1.4 to 18.2), which appeared in the NOx-limited (4:1) and the VOCs-limited (15:1). Therefore it is suggested that the management of emission source NOx and VOCs are very important for the reduction of ozone in Ansan.

VOC source apportionment, reactivity, secondary transformations, and their prioritization using fuzzy-AHP method in a coal-mining city in India.

This study assessed the air quality status in different functional zones of Dhanbad-a coal-mining and industrial hub, based on the measurement of aromatic and halogenated volatile organic compounds (VOCs) using gas chromatography. The study encompasses source apportionment of VOCs and their chemical reactivity in terms of OH radical loss rate (LOH), ozone-forming potential (OFP), and their secondary organic aerosol forming potential (SOAp). Furthermore, prioritization of VOCs based on a fuzzy-analytical hierarchical process (F-AHP) has also been done. The results found xylene species to have the highest concentration in all three seasons across traffic-intersection and industrial zones and toluene at the institutional zone. The study identified four sources using positive matrix factorization (PMF) model, viz., mixed traffic exhaust (35%), coal combustion sources (30%), industrial (26%), and solvent usage (9%). LOH and SOAp were ~ 16 times more at the industrial and traffic-intersection zone than the institutional zone. The aromatic species contributed 97% to the OFP, and many species exhibited less contribution to the mixing ratio of VOCs but displayed a high contribution to LOH, OFP, and SOAp, suggesting the need to prefer reactivity-based strategies in addition to concentration-based strategies in the future for their regulation. The F-AHP-based priority component analysis identified 16 species out of 29 in the priority watch list (nine in tier-1, four in tier-2, and three in tier-3). The paucity of data and lack of ambient air quality standards on VOCs (except benzene) make it difficult to determine which aspect should be dealt with first and which species require more attention. Therefore, the F-AHP method used in this study could help identify the influencing parameters to be considered while devising efficient VOC management policies.

Current status of model predictions of volatile organic compounds and impacts on surface ozone predictions during summer in China

Abstract. Volatile organic compounds (VOCs) play a crucial role in the formation of tropospheric ozone (O3) and secondary organic aerosols. VOC emissions are generally considered to have larger uncertainties compared to other pollutants, such as sulfur dioxide and fine particulate matter (PM2.5). Although predictions of O3 and PM2.5 have been extensively evaluated in air quality modeling studies, there has been limited reporting on the evaluation of VOCs, mainly due to a lack of routine VOC measurements at multiple sites. In this study, we utilized VOC measurements from the “Towards an Air Toxic Management System in China” (ATMSYC) project at 28 sites across China and assessed the predicted VOC concentrations using the Community Multiscale Air Quality (CMAQ) model with the widely used Multi-resolution Emission Inventory for China (MEIC). The ratio of predicted to observed total VOCs was found to be 0.74 ± 0.40, with underpredictions ranging from 2.05 to 50.61 ppbv (5.77 % to 85.40 %) at 24 sites. A greater bias in VOC predictions was observed in industrial cities in the north and southwest, such as Jinan, Shijiazhuang, Lanzhou, Chengdu, and Guiyang. In terms of different VOC components, alkanes, alkenes, non-naphthalene aromatics (ARO2MN), alkynes, and formaldehyde (HCHO) had prediction-to-observation ratios of 0.53 ± 0.38, 0.51 ± 0.48, 0.31 ± 0.38, 0.41 ± 0.47, and 1.21 ± 1.61, respectively. Sensitivity experiments were conducted to assess the impact of the VOC prediction bias on O3 predictions. While emission adjustments improved the model performance for VOCs, resulting in a change in the ratio of total VOCs to 0.86 ± 0.47, they also exacerbated O3 overprediction relative to the base case by 0.62 % to 6.27 % across the sites. This study demonstrates that current modeling setups and emission inventories are likely to underpredict VOC concentrations, and this underprediction of VOCs contributes to lower O3 predictions in China.

Analysis of Influencing Factors of Ozone Pollution Difference Between Chengdu and Chongqing in August 2022

In August 2022, Chengdu and Chongqing showed significant differences in ozone (O3) pollution. Chengdu had O3 pollution days for 20 days, whereas Chongqing had no O3 pollution days. In this study, we analyzed the influencing factors of this difference from the emission level of precursors and meteorological conditions. The results showed that:① the total mixing ratio of 52 VOCs (volatile organic compounds) (including 26 alkanes, 16 aromatics, and 10 alkenes) in Chengdu (18.8×10-9) was 2.8 times that of Chongqing (6.6×10-9), and the total O3 formation potential (OFP) (51.2×10-9) was 2.0 times that of Chongqing (25.0×10-9). The·OH radical loss rate (L·OH) (3.9 s-1) was 1.7 times that of Chongqing (2.3 s-1). The top three OFP in Chengdu were ethylene, m/p-xylene, and isoprene, and those in Chongqing were isoprene, ethylene, and propylene. The contribution rate of alkenes to O3 in Chongqing was 60.7%, whereas the OFP of alkenes and aromatics in Chengdu were 1.6 times and 2.9 times that in Chongqing. In conclusion, the total mixing ratio of VOCs, atmospheric photochemical activity, and O3 formation potential of Chengdu were higher than those of Chongqing. ② Isoprene was ranked first place in L·OH in both Chengdu and Chongqing, indicating that the contribution of biogenic sources to O3 pollution in August was significant. However, the biogenic source emission activity was in response to temperature. From August 14 to 24, the high temperature in Chongqing (38.3℃) decreased biogenic source emission activity, whereas the temperature in Chengdu (34.9℃) increased the biogenic sources emission activity. ③ The horizontal and vertical atmospheric diffusion conditions of Chongqing were better than those of Chengdu, and Chengdu was affected by regional pollution transmission.

Ozone Sensitivity Analysis and Ozone Formation Regimes Division in the Beijing–Tianjin–Hebei Region Based on Satellite Remote Sensing Data

In recent years, the concentration of surface ozone (O3) has increased in China. The formation regime of ozone is closely related to the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NOx). To explain this increase in ozone, we determined the sensitivity of ozone generation by determining the regional threshold of the ratio of formaldehyde to nitrogen dioxide (HCHO/NO2) in the satellite troposphere. The different FNR(HCHO/NO2) ratio ranges indicate three formation regimes: VOC limited, transitional, and NOx limited. Polynomial fitting models were used to determine the threshold range for the transitional regime in the BTH region (2.0, 3.1). The ozone formation regime in the BTH (Beijing–Tianjin–Hebei) region mainly exhibited a transitional and NOx-limited regime. VOC-limited regimes are mainly distributed in urban agglomeration areas, transitional regimes are mainly concentrated in urban expansion areas, and non-urban areas are mainly controlled by NOx. The concentrations of HCHO and NO2 in the BTH region showed a trend of urban agglomeration areas > urban expansion areas > non-urban areas in different land types from 2019 to 2022, whereas the FNR showed an opposite trend.

Observations of ozone, acyl peroxy nitrates, and their precursors during summer 2019 at Carlsbad Caverns National Park, New Mexico

ABSTRACT Carlsbad Caverns National Park (CAVE) is located in southeastern New Mexico and is adjacent to the Permian Basin, one of the most productive oil and natural gas (O&G) production regions in the United States. Since 2018, ozone (O3) at CAVE has frequently exceeded the 70 ppbv 8-hour National Ambient Air Quality Standard. We examine the influence of regional emissions on O3 formation using observations of O3, nitrogen oxides (NOx = NO + NO2), a suite of volatile organic compounds (VOCs), peroxyacetyl nitrate (PAN), and peroxypropionyl nitrate (PPN). Elevated O3 and its precursors are observed when the wind is from the southeast, the direction of the Permian Basin. We identify 13 days during the July 25 to September 5, 2019 study period when the maximum daily 8-hour average (MDA8) O3 exceeded 65 ppbv; MDA8 O3 exceeded 70 ppbv on 5 of these days. The results of a positive matrix factorization (PMF) analysis are used to identify and attribute source contributions of VOCs and NOx. On days when the winds are from the southeast, there are larger contributions from factors associated with primary O&G emissions; and, on high O3 days, there is more contribution from factors associated with secondary photochemical processing of O&G emissions. The observed ratio of VOCs to NOx is consistently high throughout the study period, consistent with NOx-limited O3 production. Finally, all high O3 days coincide with elevated acyl peroxy nitrate abundances with PPN to PAN ratios > 0.15 ppbv ppbv−1 indicating that anthropogenic VOC precursors, and often alkanes specifically, dominate the photochemistry. Implications: The results above strongly indicate NOx-sensitive photochemistry at Carlsbad Caverns National Park indicating that reductions in NOx emissions should drive reductions in O3. However, the NOx-sensitivity is largely driven by emissions of NOx into a VOC-rich environment, and a high PPN:PAN ratio and its relationship to O3 indicate substantial influence from alkanes in the regional photochemistry. Thus, simultaneous reductions in emissions of NOx and non-methane VOCs from the oil and gas sector should be considered for reducing O3 at Carlsbad Caverns National Park. Reductions in non-methane VOCs will have the added benefit of reducing formation of other secondary pollutants and air toxics.

Characteristics and Health Risk Assessment of Volatile Organic Compounds in Different Functional Zones in Baoji in Summer

The situation of air pollution in Guanzhong Plain has been increasing in recent years; hence, it is very important to study the characteristics of volatile organic compounds (VOCs) and their health risks in urban functional zones. We analyzed 115 VOCs using gas chromatography-mass spectrometry/hydrogen ion flame detector (GC-MS/FID) and high performance liquid chromatography (HPLC) at four sampling sites in the traffic, comprehensive, industrial, and scenic zones of Baoji. We analyzed the main components and key species in the different functional zones. Ozone formation potential (OFP),·OH consumption rate (L·OH), and secondary organic aerosol formation potential (SOAFP) were used to evaluate the environmental impact, and the hazard index (HI) and lifetime cancer risk (LCR) methods were employed. The results revealed that the mean values of φ(TVOCs) in the traffic, comprehensive, industrial, and scenic zones were (59.63±23.85)×10-9, (42.92±11.88)×10-9, (60.27±24.09)×10-9, and (55.54±7.44)×10-9, respectively. The dominant contributors at the traffic zone were alkanes, and those at the other functional zones were OVOCs. Acetaldehyde, acetone, n-butane, and isopentane were abundant at different functional zones. According to the characteristic ratios of VOCs, the average ratio of toluene to benzene (T/B) at the traffic, comprehensive, industrial, and scenic zones were 1.84, 2.39, 1.28, and 1.64, respectively, and the ratio of iso-pentane to n-pentane (i/n) was mainly between 1 and 4. The results indicated that VOCs in Baoji were significantly affected by vehicle emissions and gasoline evaporation, biomass and coal combustion, and industrial coatings and foundry. The ratio of m/p-xylene to ethylbenzene (X/E) was lower than 2 at the four functional zones, and the minimum was 1.79 at the scenic zones; the results revealed that X/E was small, and the aging degree of air masses was high, indicating the influence of regional transport. According to the ratio of formaldehyde to acetaldehyde (C1/C2) and the ratio of acetaldehyde to propanal (C2/C3), it was suggested that there may have been evident anthropogenic emission sources, and the photochemical reaction had an important effect on aldehydes and ketones. Environmental impact assessment results revealed that OVOCs and alkenes contributed significantly to OFP and OFP from large to small was as follows:industrial zone>scenic zone>traffic zone>comprehensive zone. The range of L·OH in each functional zone was 8.77-15.82 s-1, with isoprene contributing the most in the industrial zone and acetaldehyde contributing the most at other functional zones. The SOAFP of each functional zone was as follows:scenic zone>comprehensive zone>traffic zone>industrial zone. Toluene, m/p-xylene, and isoprene were the notable species. According to the health risk assessment of EPA, the HI of toxic VOCs in all functional zones was lower than 1, which was at an acceptable level. However, the number of days with HI>1 in industrial zones accounted for 42.86% of the total sampling days, indicating a high risk. The lifetime carcinogenic risk (LCR) of the traffic, comprehensive, industrial, and scenic zones were 1.83×10-5, 1.21×10-5, 1.85×10-5, and 1.63×10-5, respectively, which were all in grade Ⅲ of the rating system, indicating a high probability of cancer risk. Species with LCR greater than 10-6 were formaldehyde; acetaldehyde; 1,2-dibromoethane; 1,2-dichloroethane; 1,2-dichloropropane; and chloroform.

Impact of spatial scales of control measures on the effectiveness of ozone pollution mitigation in eastern China

Ozone (O3) pollution is becoming the primary air pollution issue with the large decrease in fine particulate concentrations in eastern China. The development of widely recognized policies for controlling O3 pollution episodes is urgent. This study aims to provide actionable and comprehensive suggestions for O3 control policy development, with an emphasis on the precursor emission reductions.Here, we compared the impacts of different spatial scale reductions on a widespread O3 pollution episode in eastern China by a state-of-the-art regional air quality model. We find that region-scale joint control (in >30 cities) is much more effective than city-scale sporadic reduction in reducing O3 concentration. Sporadic controls only reduce the maximum daily 8-h average (MDA8) O3 by ∼1 μg/m3 in the controlled city, whereas regional controls lead to a MDA8 O3 decrease of ∼8 μg/m3 in the controlled region. In addition, the emission reduction effectiveness increased by 2.6 times from <5 cities to >30 cities. Continuous reductions have a cumulative effect on the decrease of MDA8 O3, showing the strongest effects within 24 h and diminishing after 48 h, which underscores the importance of reducing emissions 24 h prior to an episode. Moreover, the effect of control measures on MDA8 O3 varies spatially depending on the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NOx) (VOCs/NOx). Both the reductions of VOC and NOx emissions have a positive effect on the decrease of MDA8 O3 in summer, but the effects of VOC reductions are 1.2 to 1.7 times higher than those of NOx reductions. The residential sector, due to its high VOCs/NOx emission ratio, exhibits the highest efficiency in the reduction of O3 concentrations. Our results highlight the importance of regional joint control and synergistic reduction of VOCs and NOx in eastern China.

Volatile organic compounds in school environments of Hawassa city, Ethiopia and assessment of possible human health risks

Volatile organic compounds (VOCs) have become a major human wellbeing and environmental concern worldwide. However, evidence on VOC concentrations in primary school environments in Africa, including Ethiopia, is scarce. The goal of this research was to examine VOCs in primary schools in Hawassa, Ethiopia, and to evaluate possible health threats. Concentrations of 76 VOCs were investigated in air samples from classrooms and playgrounds of eight primary schools in Hawassa, Ethiopia. Air samples were taken via passive sampling method using Tenax TA as a sorbent and analyzed by using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Highest total VOCs (TVOCs) concentration (83 μg/m3) was observed in the classroom of School 2 followed by the classroom of School 1 (76 μg/m3), while the smallest TVOC concentration, 37 μg/m3 in the playground of School 8. Among the BTEX, toluene was the most dominant in all samples, ranging from 33% in School 4–38% in School 1 of ∑BTEX. I/O ratios of individual VOC in the schools ranged from 0.44 in School 4 to 9.21 in School 2. The highest cumulative cancer risk (CCR × 106) and the total hazard ratio indicator (THRI) values were 126 and 1.58E-01 respectively, in the classroom of School 4. The CCR and THRI values indicated that the exposure of children to the measured concentrations of benzene may have potentially harmful effects.

Fuel-Type Independent Parameterization of Volatile Organic Compound Emissions from Western US Wildfires.

Volatile organic compounds (VOCs) emitted from biomass burning impact air quality and climate. Laboratory studies have shown that the variability in VOC speciation is largely driven by changes in combustion conditions and is only modestly impacted by fuel type. Here, we report that emissions of VOCs measured in ambient smoke emitted from western US wildfires can be parameterized by high- and low-temperature pyrolysis VOC profiles and are consistent with previous observations from laboratory simulated fires. This is demonstrated using positive matrix factorization (PMF) constrained by high- and low-temperature factors using VOC measurements obtained with a proton-transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) on board the NASA DC-8 during the FIREX-AQ (Fire Influence on Regional and Global Environments and Air Quality) project in 2019. A linear combination of high- and low-temperature factors described more than 70% of the variability of VOC emissions of long-lived VOCs in all sampled wildfire plumes. An additional factor attributable to atmospheric aging was required to parameterize short-lived and secondarily produced VOCs. The relative contribution of the PMF-derived high-temperature factor for a given fire plume was strongly correlated with the fire radiative power (FRP) at the estimated time of emission detected by satellite measurements. By combining the FRP with the fraction of the high-temperature PMF factor, the emission ratios (ERs) of VOCs to carbon monoxide (CO) in fresh wildfires were estimated and agree well with measured ERs (r2 = 0.80-0.93).

Atmospheric oxidation capacity and secondary pollutant formation potentials based on photochemical loss of VOCs in a megacity of the Sichuan Basin, China

Volatile organic compounds (VOCs) are significant precursors to photochemical pollution. However, reactive VOC species are easily oxidized during transportation, resulting in a systematic underestimate of the measured concentrations. To address this, we applied an improved calculation method to correct the measured VOC concentrations into photochemical initial concentrations (PICs) in Chengdu, a megacity in the Sichuan Basin, China, which is highly vulnerable to complex pollution. In this study, 56 VOC species on the Photochemical Assessment Monitor Station (PAMS) target list were quantitatively monitored throughout all four seasons. Comparing to directly measured values, photochemically initialized total mixing ratios of VOCs increased by 18.6 % in general. The photochemical loss percentages of alkenes and aromatics were prominent in summer (68.6 %, 28.7 %) and spring (65.9 %, 24.7 %), respectively. Furthermore, we examined contributions of VOCs to atmospheric oxidation capacity (AOC) depending on PICs and found that maximum daily total AOC showed a surge in spring and summer. Besides hydroxyl radicals, daytime O3 in spring and late-afternoon nitrate radicals in summer were essential for AOC with PICs. As expected, alkenes and aromatics dominated PIC-based ozone formation potentials (OFPs). Furthermore, contribution of alkenes to secondary organic aerosol formation potentials reached 15.5 % and 7.6 % in spring and summer, respectively. Using positive matrix factorization model, we identified five VOC sources including vehicular exhaust, industrial emissions, solvent usage, biogenic sources, and liquefied petroleum gas/natural gas use. Based on PICs, biogenic sources were significantly underestimated in spring and summer. Meanwhile, m,p-xylene from solvent usage and isoprene from biogenic sources were the primary contributors to OFPs. Consequently, these results emphasize the significance of photochemically oxidized VOC concentrations, especially for reactive species in typical seasons.