Consumer volatile chemical products (VCPs) are widely used indoors, yet their formulation-specific volatile organic compound (VOC) emissions remain poorly characterized. Here, we quantified formulation-resolved 119 VOC emission factors for four representative consumer VCPs, including cleaning products, air fresheners, hairsprays, and insecticides in Hong Kong, using dynamic chamber experiments and applied these experimentally derived emission factors to identify key species contributing to 1-h acute inhalation risk and secondary organic aerosol (SOA) formation potential. Oxygenated VOCs, monoterpenes, and liquefied petroleum gas-derived alkanes dominated emission profiles, with pronounced formulation-dependent variability. Emission factors of hairsprays and insecticides (350-641 g VOC kg-1 VCP) were significantly higher than those of cleaning products and air fresheners (3.8-52 g VOC kg-1 VCP), with nonwater-based formulations consistently showing emission factors 1.4-14 times higher than their water-based counterparts. Acetaldehyde and acrolein were identified as the primary drivers of 1-h acute inhalation risks, whereas monoterpenes and sesquiterpenes were identified as the key precursors driving SOA formation. Scenario analyses in Hong Kong indicated that consumer VCP use is unlikely to pose unacceptable 1-h acute inhalation risks under regulatory minimum living-condition standards. However, nonwater-based hairsprays may exceed acceptable 1-h acute inhalation risk thresholds in a typical indoor environment under poor ventilation due to elevated acetaldehyde emissions; increased ventilation substantially reduced these risks. Overall, this study provides formulation-resolved emission data and identifies key species contributing to acute inhalation risk and SOA formation potential from consumer VCPs.

Climate change is driving more frequent and severe dry and wet heatwaves, yet a clear picture of how each type influences ozone (O3) production in areas characterized by intricate industry and geography are still lacking. This study examines O3 formation during heatwaves, focusing on interactions among meteorological factors, atmospheric chemistry, and pollutant emissions in a unique industrial area at the junction of Jiangsu, Shandong, Henan, and Anhui provinces of northern China in summer 2022 and 2023. This study integrates hourly data of temperature, relative humidity (RH), solar radiation (SF), 115 VOCs, and other atmospheric pollutants, and quantifies the contribution of each factor using machine learning models combined with SHAP. Results show that SF is the main driver influencing O3, contributing 13.7 mu g/m3 during dry heatwaves and 5.0 mu g/m3 during wet heatwaves. RH and atmospheric diffusion conditions are distinct between the dry and wet heatwaves. PMF indicates that industrial emissions dominate O3 formation during dry heatwaves while biogenic VOCs dominate during wet heatwaves. For VOCs, during dry heatwaves the SHAP values for styrene, propene and isoprene were 9.1, 4.4 and 3.8 mu g/m3, respectively, significantly affecting O3 formation; In wet heatwaves, styrene, propene and acetaldehyde dominate, with SHAP values of 6.7, 4.3 and 2.5 mu g/m3 respectively. Diurnal analysis indicates that while styrene and propene boost O3 during daytime (9:00-17:00), their effects reverse in the early morning (6:00-8:00). In contrast, isoprene contributes positively (2.85 mu g/m3) during dry heatwaves and negatively (-2.92 mu g/m3) during wet ones. Overall, the study offers an efficient framework for understanding O3 formation in extreme weather and informs targeted pollution control strategies.

While proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) is widely used for ambient volatile organic compounds (VOCs) quantification, its accuracy is limited by isomeric speciation and ionization byproducts. Here, gas chromatography (GC) coupled with PTR-ToF-MS was deployed at a suburban site in Hong Kong to resolve isomers and quantify interferences for ambient VOCs measurement. We identified 48 compounds using GC-PTR and resolved their isomer profiles in direct-PTR data. Our analysis revealed that direct-PTR measurements substantially underestimated long-chain aldehydes (C5-C8) due to extensive fragmentation, while overestimating isoprene, benzene, styrene, and phenol by ∼14-60% because of interference from other species. The biogenic VOCs' OH reactivity was overestimated by up to 31% for monoterpenes and 241% for isoprene, depending on the seasonality of biogenic emissions. Propagating these biases into the photochemical model resulted in a 46% overestimation in daytime net O3 production under VOC-limited and low-isoprene conditions, whereas the overestimation decreased to 19% under VOC-saturated, high-isoprene conditions. Correcting isomer distributions and interference effects reduced modeled ozone production rates and altered precursor sensitivities, revealing a larger role for oxygenated VOCs in ozone formation than previously recognized. Our results highlight the necessity for isomer-resolved measurements and interference-aware calibration to improve VOC-based assessments of photochemical air pollution.

Water vapor plays a critical role in weather and climate, and high-temporal resolution satellite observations are essential for characterizing its variability. The geostationary meteorological satellite Fengyun-4B (FY-4B) carries the Geostationary Interferometric Infrared Sounder (GIIRS), the first operational geostationary hyperspectral thermal infrared sounder, which provides continuous observations over East Asia. We evaluate water vapor profiles and total column water vapor (TCWV) retrieved from FY-4B/GIIRS using the Optimal Sequential Physical Retrieval System (OSPRS) against ERA5 reanalysis, polar-orbiting JPSS-1/CrIS TROPESS retrievals, and IGRA radiosonde and AERONET sun-photometer measurements. OSPRS TCWV reproduces the spatial patterns and seasonal cycle of ERA5 and TROPESS, with differences concentrated in warm, moist monsoon and oceanic regions, while absolute differences remain small over cold, dry mid-high latitudes and the Tibetan Plateau. OSPRS TCWV is highly correlated with IGRA and AERONET in all seasons, with correlation coefficients of 0.94-0.99 and 0.93-0.98, respectively, and mean absolute errors of 1.69-3.33 and 1.65-3.85 kg m-2, respectively. Vertically, OSPRS water vapor profiles show smaller differences with the averaging kernel-smoothed IGRA than TROPESS, especially in the lower troposphere and in summer. The Super Typhoon Doksuri case further shows that OSPRS produces sharper local moisture gradients than ERA5, while localized 2-hr fluctuations in cloud-affected regions require cautious interpretation, as variable cloud cover and associated retrieval gaps may also contribute to these fluctuations. These results demonstrate that OSPRS provides a reliable FY-4B/GIIRS water vapor product for characterizing spatial, temporal, and vertical variations and is valuable for monitoring extreme events, though further optimization is needed.

Architectural paints represent an important source of volatile organic compounds (VOCs) in urban environments. The ongoing shift from solvent-based to water-based formulations can substantially alter VOC composition, emission factors, and associated secondary formation potentials; however, these effects remain poorly quantified and may introduce biases in current emission inventories. In this study, dynamic-chamber evaporation experiments were performed on selected architectural paint products spanning water-based and solvent-based formulations to obtain their VOC composition profiles and emission factors and to estimate their ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP). The selected water-based paints were dominated by oxygenated VOCs (OVOCs) and alkenes, with an average total emission factor of 56 g VOC kg-1 paint. In contrast, the solvent-based products contained abundant alkanes, OVOCs, and aromatics, resulting in a higher total emission factor of 228 g VOC kg-1 paint. For the water-based products, the emission-factor-derived OFP was 90 g O3 kg-1 paint, mainly contributed by acetaldehyde and limonene, while the SOAP was 0.8 g SOA kg-1 paint and was also dominated by limonene. In solvent-based products, the emission-factor-derived OFP and SOAP were 482 g O3 kg-1 paint and 5.3 g SOA kg-1 paint, respectively, with aromatics (e.g., toluene and ethylbenzene) and alkanes (e.g., n-octane) being the major contributors to both. Comparison between the mass-fraction- and emission-factor-based calculations showed distinct OFP and SOAP estimates, indicating that apportioning total emissions according to VOC composition may affect the accuracy of assessments of secondary pollution formation potentials. This study provides compound-specific and formulation-resolved emission factors for the selected architectural paint products and suggests that emission-factor-based characterization offers a more reliable assessment of their secondary formation potentials.

Initial success has been achieved in Hong Kong in controlling primary air pollutants, but ambient ozone levels kept increasing during the past three decades. Volatile organic compounds (VOCs) are important for mitigating ozone pollution as its major precursors. This study analyzed VOC characteristics of roadside, suburban, and rural sites in Hong Kong to investigate their compositions, concentrations, and source contributions. Here we show that the TVOC concentrations were 23.05 ± 13.24, 12.68 ± 15.36, and 5.16 ± 5.48 ppbv for roadside, suburban, and rural sites between May 2015 to June 2019, respectively. By using Positive Matrix Factorization (PMF) model, six sources were identified at the roadside site over five years: Liquefied petroleum gas (LPG) usage (33–46%), gasoline evaporation (8–31%), aged air mass (11–28%), gasoline exhaust (5–16%), diesel exhaust (2–16%) and fuel filling (7–9%). Similarly, six sources were distinguished at the suburban site, including LPG usage (30–33%), solvent usage (20–26%), diesel exhaust (14–26%), gasoline evaporation (8–16%), aged air mass (4–11%), and biogenic emissions (2–5%). At the rural site, four sources were identified, including aged air mass (33–51%), solvent usage (25–30%), vehicular emissions (11–28%), and biogenic emissions (6–12%). The analysis further revealed that fuel filling and LPG usage were the primary contributors to OFP and OH reactivity at the roadside site, while solvent usage and biogenic emissions accounted for almost half of OFP and OH reactivity at the suburban and rural sites, respectively. These findings highlight the importance of identifying and characterizing VOC sources at different sites to help policymakers develop targeted measures for pollution mitigation in specific areas.

Volatile organic compounds (VOCs) play a significant role in air quality and climate change, and certain VOCs are harmful to the respiratory system and pose risks of cancer to individuals. In this study, regular monthly samples were collected at two urban stations and one suburban station in Hong Kong from August 2020 to July 2022, and thirty-two hazardous VOC species were measured using GC-MS/FID/ECD analytical instruments. The total health risk of observed VOCs was evaluated based on their ozone formation potential (OFP), secondary organic aerosol potential (SOAFP), and toxicity grades. The contributions from distinct sources to public health risks were investigated by applying Positive Matrix Factorization (PMF) technique at different monitoring sites. The results revealed toluene consistently emerged as the most significant VOC species during integrated health risk assessment and solvent usage was the largest health risk contributor at all monitoring sites. In addition, the suburban site also needs to consider the risks from combustion sources, while risks from vehicular exhausts were more important at urban sites. Currently, heightened vigilance is warranted for cancer risks in Hong Kong. Short-lived hydrocarbons, like chloroform, benzene, and trichloroethylene, contributed a lot to cancer risks, and further monitoring is necessary for these non-regulated VOCs.

Carbonyl compounds are critical air pollutants with adverse impacts on regional air quality and human health. This study presents a pioneering analysis of spatiotemporal distribution, source appointment, and health risk assessments of carbonyl compounds in the coastal marine atmosphere. By combining ship-borne and groundbased sampling followed with enhanced chemical analysis, 39 carbonyls were identified and quantified in the coastal Hong Kong. Carbonyl concentrations were generally higher in late summer/autumn with lower levels in winter, correlating with their secondary formation rates from precursors. Most species exhibited higher concentrations in open waters than in the fairway and sea channels, due to prominent photochemical formation from regional outflows in the Pearl River Estuary. In contrast, alpha, beta-unsaturated aliphatic aldehydes and acetone were elevated in harbor areas, highlighting the influence of ship emissions on these compounds. Source analysis further indicated a notable contribution from ocean emissions to long-chain aldehydes (C >= 6), acetone and dialdehydes. Health risk assessment demonstrated that carbonyl compounds pose substantial carcinogenic and non-carcinogenic risks to maritime workers and other exposed populations, even exceeding risks faced by road workers. These findings underscore the necessity of considering carbonyl compounds in occupational exposure risk assessments. Overall, this study provides a comprehensive overview of carbonyl compounds in the coastal marine atmosphere, shedding light on the interactions among ship emissions, ocean activities and coastal urban emissions on airborne carbonyls and emphasizing the associated health implications.

The spatial representativeness (SR) of air quality monitoring sites is critical for ensuring that gathered data accurately reflect the broader area's air quality. Evaluating the SR of sites at a national scale and its long‐term trends is particularly important for countries like China, where both air quality and monitoring networks have changed dramatically over time. Here, we used 1‐km daily air pollutant concentrations from the China High Air Pollutants dataset to assess the yearly SR of state‐controlled sites in China from 2013 to 2022 for multiple pollutants. With the number of sites increasing from 460 in 2013 to 1,590 in 2022, our results showed that the total SR area of sites increased by 89% for PM 2.5 , 149% for PM 10 , and 2,190% for O 3 . While the number of sites mainly drove these increases, its impact varied at different phases. Interestingly, the rise in sites from 2020 to 2022 actually led to a decrease in the total SR area for PM 2.5 (−18,300 km 2 ) and PM 10 (−14,200 km 2 ). Additionally, we found that applying SR to pollution exposure assessments did not improve their accuracy at national and city levels when compared to the official method, which involves exposure calculation using arithmetic mean aggregation of monitoring sites. This was related to poor SR performance, with more than half of the population being uncovered by SR areas in more than 85% of Chinese cities. Nevertheless, we demonstrated the benefits of applying SR for city‐level air quality attainment.

The Geostationary Interferometric Infrared Sounder (GIIRS) onboard the FY-4B satellite is the world's first and currently the only operational hyperspectral thermal infrared sounder in geostationary orbit, with the unique advantage of continuously scanning the atmosphere over East Asia on an hourly basis during both daytime and nighttime. Compared to previously established low-Earth orbit satellite sounders, developing and applying Level 2 atmospheric products from FY-4B/GIIRS are still in the exploratory stage. In this study, we present an optimal sequential physical retrieval system (OSPRS) for retrieving high-accuracy atmospheric strong absorbers, including water (H2O), ozone (O3) and carbon monoxide (CO) from FY-4B/GIIRS. OSPRS first selects a subset of sensitive spectral channels for each variable based on column- and pressure-related sensitivity. It then determines the optimal retrieval sequence consisting of multiple retrieval steps, aiming to reduce the nonlinearity of each inversion problem and the influence of interfering variables on the primary retrieval targets. Finally, OSPRS employs the optimal estimation method as the retrieval operator to perform the retrieval at each step, outputting the profiles of the primary retrieval targets and critical scientific diagnostic information. We confirm the improved accuracy of OSPRS through Observing System Simulation Experiments (OSSE). We compare OSPRS with existing products and evaluate them based on high-quality in situ data from the Integrated Global Radiosonde Archive H2O, the ground-based Pandonia Global Network O3, and solar absorption Fourier transform infrared CO measurements. The results show that the mean absolute error, linear fitting slope, and correlation coefficient between OSPRS's H2O, O3 and CO and in-situ or ground-based measurements are superior to those of existing products. This study is dedicated to providing the community with high-quality atmospheric products retrieved from FY-4B/GIIRS and promoting the research and application of GIIRS in numerical weather forecasting, atmospheric environment, and other related fields.

Isoprene emissions, primarily of biogenic origin, play an important role in atmospheric chemistry and climate. However, the atmospheric implications of marine isoprene emissions remain underexplored due to sparse in situ measurements and the intricate mechanisms governing isoprene in the upper ocean. This study uses 20 years of MODIS satellite observations to upscale isoprene production and loss rates derived from laboratory experiments, enabling global modeling of aqueous isoprene concentrations and emissions. Earth system model simulations with integrated marine isoprene emissions demonstrate substantial alterations in atmospheric composition over global oceanic regions. Our investigation uncovers diurnal variations in the vertical profiles of atmospheric isoprene, indicating that surface isoprene can ascend to the mid-to-upper troposphere, where nitrogen monoxide (NO) influences isoprene epoxydiol (IEPOX) production differently over selected oceanic and terrestrial regions. These findings pave the way for future studies on the role of marine isoprene in climate models and advance our understanding of its broader implications for atmospheric chemistry under a changing climate.

The COVID-19 outbreak and the Beijing Winter Olympics provided an opportunity to study the impact of human activities on volatile organic compounds (VOCs) in the atmosphere. Continuous measurements of 117 VOC species were conducted in urban Ji'nan, the capital city of Shandong Province, North China Plain, from 2019 to 2024. The total volatile organic compound concentrations ranged from 30.7 ppbv to 41.7 ppbv, and the seasonal characteristics of VOCs were generally high in autumn and winter and low in spring and summer, with alkanes as the component with the highest percentage. The average VOC volume fraction increased by 24.8% after the COVID-19 outbreak compared to that before the outbreak, among which the concentrations of aromatics increased most markedly (334.7%), and those of alkanes increased by 95.2%. Alkenes, alkynes, halocarbons, and oxygenated VOCs showed decreasing trends. The volume fraction of each VOC species showed a decreasing trend during the Beijing Winter Olympics air quality guarantee period compared with the pre-Beijing Winter Olympics period, with a 16.7%-36.3% reduction rate. The positive matrix factorization model identified six sources: vehicle emission, industrial mixing sources, solvent use, oil and gas volatilization, biogenic and secondary sources, and combustion sources. Influenced by the resumption of work and production by enterprises after the COVID-19 pandemic, solvent use increased by 26.7% after the pandemic, and the contribution of diesel vehicle emissions was significant. After the pandemic, the contribution of industrial mixing sources decreased by 28.6%, whereas coal combustion sources increased by 5.3% compared to the pre-COVID-19 period. During the Beijing Winter Olympics air quality guarantee period, coal combustion sources and vehicle emission sources decreased by 11.6% and 6.5%, respectively, and contributions from industrial sources and biogenic and secondary sources increased by 13.2% and 6.4%, respectively, compared with those during the pre-Beijing Winter Olympics period. During the Beijing Winter Olympics air quality guarantee period, the results of the backward airflow trajectory, and potential source area analysis, showed a strong influence of air mass transmission in the southwest direction, and VOCs emissions from industrial sources had higher values in the southwest region. Before the COVID-19 outbreak, there were obvious ship sources from the long-range transmission of the near-coastal region in the Yellow Sea. However, in post-COVID-19, long-range transport contributions from ship sources vanished due to the upgrading of marine oils after implementing the DECA 2.0.

Sixteen sites in the coastal city of Qingdao, including eight national control sites, seven provincial control sites, and one background site, were selected. By coupling the extreme gradient boosting （XGBoost） model with the interpretability SHapley Additive exPlanations （SHAP） module, the impact of meteorological elements and atmospheric pollutant emissions on ozone （O3） pollution was investigated. The results indicated that from 2019 to 2023, meteorological factors contributed 67.7% to O3 formation, whereas emissions from atmospheric pollutants accounted for 32.3%. Surface solar radiation significantly affected O3 formation from 10：00 to 17：00. A positive correlation existed between temperature and O3 concentration, peaking at 14：00. A relative humidity below 70% was conducive to O3 formation and a relative humidity above 70% had a 94% probability of negatively contributing to O3 production. Particularly between 12：00 and 16：00, relative humidity significantly and positively contributed to O3 formation. When the boundary layer height was below 500 meters, it positively affected O3 concentration, whereas above this height, its impact weakened. In the morning and late afternoon, boundary layer height promoted the formation of O3 concentration. Easterly （E） to southwesterly （SW） winds had a positive effect on O3 concentrations in Qingdao. NO2 showed a negative response in the morning （06：00-11：00） and a positive response in the afternoon （12：00-15：00）. PM2.5 had a nonlinear positive correlation with O3, positively affecting O3 concentration from 07：00 to 14：00 PM and suppressing it from 15：00 to 18：00. Significant differences existed in the dominant factors of O3 concentration across different areas and seasons. In the western Laoshan District, Yangkou, the western site of the Shinan District, and eastern and western parts of the West Coast New Area, surface solar radiation had a noticeably lower impact on O3 than in other locations. The effect of NO2 was most significant in the eastern parts of the West Coast New Area, western Laoshan District, and Yangkou. PM2.5 affected O3 formation more in these sites than in others of Qingdao. In spring, the impact of NO2 was more significant in the western Laoshan and Shinan Districts. In summer, surface solar radiation was more influential in Yangkou, the eastern and western parts of the West Coast New Area, the western Laoshan District, and the Shibei District, whereas, relative humidity was the key factor in other locations. In autumn, temperature and surface solar radiation were the main factors affecting O3. In winter, the contribution of NO2 was higher than that in different seasons, with anthropogenic emissions playing a more important role in O3 formation. The analysis of days exceeding O3 standards showed that surface solar radiation and NO2 were the main drivers of exceeding O3 concentrations. For all sites, the total SHAP values of PM2.5 and PM10 on days exceeding O3 standards ranged between 6.1 μg·m-3 and 12.4 μg·m-3.

Zaozhuang, located at the center of the boundary between Jiangsu, Shandong, Henan, and Anhui, contains coal and heavy industries. Zaozhuang has experienced severe O3 pollution in recent years and it is crucial to identify the key drivers. This study aims to deeply excavate and analyze the formation mechanism of O3 in Zaozhuang based on hourly measured volatile organic compound (VOC) concentration data for the year 2023, combined with meteorological factors and other atmospheric pollutants, using a machine learning model in combination with the SHapley Additive Properties Interpretation method and Positive Matrix Factorization model. The results show the important contributions of meteorological factors to O3 production, especially solar radiation and temperature. Among atmospheric pollutants, VOCs are the main contributors, with significant effects from alkene and oxygenated VOCs, whereas propene and acetone have the most critical individual impacts on local O3 production. O3 peaked in June and August, with June seeing added contributions from temperature, and a higher chemical variable contribution than meteorological factors in August, led by NO2, OVOCs, and alkenes. The effects of the six emission sources on O3 formation in Zaozhuang showed that chemical emission sources (5.98 mu g/m3), combustion sources (3.75 mu g/m3), and solvent use sources (3.06 mu g/m3) were the main drivers. The solvent source exhibited the most significant change on the O3 polluted day, with a relative increase of 115%. This relative increase was significantly higher than that of the other sources. During persistent pollution events with the highest levels of O3, the use of solvents made the greatest contribution to the emission sources, representing 23% of the total impact of the emission sources. Therefore, an integrated approach using machine learning, SHapley Additive Properties Interpretation, and Positive Matrix Factorization rapidly diagnoses the causes of O3 pollution at different timescales and provides a basis for targeted control measures.

This study investigates the seasonal variations in O-3 levels in Qingdao, a typical coastal city, and quantifies the effects of key photolysis rate constants (J[(OD)-D-1] and J[NO2]), meteorological parameters (RH, TEMP, and SF), and pollutants (Delta CO, PM2.5, and NO2) on O-3 levels across different seasons using machine learning. Additionally, the summer months, when photochemical reactions are most active, were analyzed in detail. The results indicate that the factors contributing to summer O-3 levels in order of importance, were RH, Delta CO, SF, PM2.5, J[(OD)-D-1], NO2, TEMP, WS, and J[NO2]. RH was the most significant factor, with high humidity levels (>75%) inhibiting O-3 formation. Delta CO, representing regional transport, was the second most influential, suggesting that direct O-3 transport and the delivery of high concentrations of precursors significantly promoted local O-3 production and accumulation. While J[(OD)-D-1] and J[NO2] had different roles in O-3 promotion and depletion, J[(OD)-D-1] had a greater impact overall. The temperature in the range of 26 degrees C-32 degrees C inhibits O-3 production, When RH exceeded 90%, J[(OD)-D-1] accelerates while other photolysis rate constants decline, further suppressing the production of O-3. For comparison, multiple linear regression models were used to develop empirical equations for calculating hourly O-3 concentrations across the four seasons. The results showed that these factors explained 50%, 64%, 61%, and 63% of the O-3 sources in Qingdao for spring, summer, autumn, and winter, respectively. Sensitivity tests on factors influencing summer O-3 concentrations found that MLR could not quantify their contributions to O-3 levels.

Land-cover understanding in remote sensing increasingly demands class-agnostic systems that generalize across datasets while remaining spatially precise and interpretable. We study a geometry-first discovery-and-interpretation setting under domain shift, where candidate regions are delineated class-agnostically and supervision avoids lexical class names via anonymized identifiers. Complementary to open-set recognition and open-world learning, we focus on coupling class-agnostic mask evidence with taxonomy-grounded scene interpretation, rather than unknown rejection or continual class expansion. We propose MVT, a three-stage framework that (i) extracts boundary-faithful region masks using SAM2 with domain adaptation, (ii) performs mask-grounded semantic tagging and scene description generation via dual-step LoRA fine-tuning of multimodal LLMs, and (iii) evaluates outputs with LLM-as-judge scoring calibrated by stratified expert ratings. On cross-dataset segmentation transfer (train on OpenEarthMap, evaluate on LoveDA), domain-adapted SAM2 improves mask quality; meanwhile, dual-step MLLM fine-tuning yields more accurate taxonomy-aligned tags and more informative mask-grounded scene descriptions.

Weakly absorbing reactive trace gases play important roles in the atmospheric environment and usually have short lifetimes ranging from seconds to days. HIRAS-II, the second hyperspectral infrared atmospheric sounder aboard the world's first civilian meteorological satellite in dawn-dusk orbit, FengYun-3E (FY-3E), can theoretically detect more than a dozen weakly absorbing reactive trace gases and make important contributions to global trace gas mapping by filling the gap for diurnal variation. This study uses state-of-the-art weak absorber thermal infrared spectral feature quantification and identification methods to detect weak absorbers from FY-3E/HIRAS-II and successfully capture 14 species from 35.4 million FY-3E/HIRAS-II clear-sky measurements in July 2023. We map the reliable global distribution of spectral features from nine routine reactive gases and find that these gases originate from scenes that are usually of special concern, including densely populated areas, vegetation, and biomass burning. This study confirms the capability of FY-3E/HIRAS-II in detecting weak absorbers and serves as a stepping stone for subsequent research in concentration retrieval. The case of the ammonia column over wildfires retrieved using neural network technology initially demonstrates that FY-3E/HIRAS-II can improve our understanding of the diurnal variation of trace gases by complementing measurements at dawn and dusk.

Photochemical ozone (O3) pollution remains a persistent environmental challenge, and growing evidence highlights the critical role of oxygenated volatile organic compounds (OVOCs) in photochemical processes. However, comprehensive and quantitative measurements of OVOCs remain limited. This study investigates the impact of OVOCs on O3 formation mechanisms and radical budgets by intergrating high-resolution field measurements from a subtropical coastal region in South China with observation-based photochemical modeling. 63 OVOC species were measured by a proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS), and accounted for 72 %-77 % of total VOC concentrations. The O3-precusor relationship analysis revealed a transition regime for O3 formation and high sensitivity to OVOCs. OVOC-related reactions, including OVOC photolysis, OVOC oxidation by OH and NO3 radicals, contributed approximately 36 %-73 % to daytime production rates of HO2 and RO2 radicals. Model simulations without comprehensive consideration of OVOCs would significantly underestimate daytime production rates of O3 and ROx radicals by 41 %-48 %, and shift the diagnosis of O3 formation from a transition regime to a VOC-limited regime, leading to biased policy recommendations and potentially ineffective control strategies. These findings underscore the critical role of OVOCs in atmospheric photochemistry and highlight the urgent need for comprehensive OVOC quantification to improve OVOC-inclusive model frameworks. Such improvements are essential for accurately characterizing O3-precursor relationships and for developing effective and sustainable strategies to mitigate regional O3 pollution.