Suburban Site Research Articles

External particle mixing influences hygroscopicity in a sub-urban area

Abstract. Hygroscopicity strongly influences aerosol properties and multiphase chemistry, which is essential in several atmospheric processes. Although CCN (cloud condensation nuclei) properties are commonly measured, sub-saturated hygroscopicity measurements remain rare. During the ACROSS campaign (Atmospheric ChemistRy Of the Suburban foreSt, conducted in Paris in summer 2022), particles' hygroscopic growth rates at 90 % relative humidity (RH) and chemical composition were measured at the sub-urban site using a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA, scanning at 100, 150, 200, and 250 nm) and an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Growth factor probability density functions (GF-PDFs) revealed two distinct modes, namely hydrophobic and hygroscopic, suggesting a combination of internal and external particle mixing, with the split at GF 1.2. The prevalence of the hygroscopic mode increased with particle size, with mean hygroscopicity (κ) values of 0.23 and 0.38 for 100 and 200 nm particles, respectively. Using the Zdanovskii–Stokes–Robinson (ZSR) mixing rule, the agreement between measured and chemically derived hygroscopicity was approximately 51% for 100 nm particles, which declined for 200 and 250 nm. These emphasise the large effect of external particle mixing and its influence on predicting hygroscopicity. The ZSR approach proves to be unreliable in predicting the wide growth distribution of externally mixed particles. In this measurement, 80 %–90 % of the particles were externally mixed and influenced by fresh emission, which affected the hygroscopicity prediction by a factor of 2. A cluster analysis based on backward trajectories and meteorological conditions gives valuable insights into the chemical composition and variations in the hygroscopicity of different air masses.

Local honey reflects environmental changes in metal concentrations and lead isotope ratios during COVID-19 restrictions in Brussels, Belgium, and Vancouver, Canada.

Effective methods for measuring sudden environmental changes are crucial for understanding how cities respond to shifts in human activity. This study examines atmospheric metal outputs during the COVID-19 restrictions using honey samples collected from three land use types in Brussels Capital Region (BCR), Belgium, and Metro Vancouver Regional District (MVRD), Canada to study changes as the result of restrictions. By comparing these cities with distinct sizes, ages, and structures, we assess how urban environments responded to pandemic-induced restrictions. We present honey samples, analyzed for metal concentration and Pb isotope ratios, to provide insights into the impacts of reduced human activity in different land use types. In BCR, significant increases of Al, Cd, Cr, Cu, Fe, Ni, Pb, Ti, and V were observed in suburban sites, while in MVRD, significant decreases of Cr, Pb, Sb, Ti, and V were observed in suburban sites. The increase in metal concentrations in BCR suburban sites indicates a shift in metal emission patterns due to changes in human activity during the restrictions. Conversely, the decrease in metal concentrations in MVRD suburban areas aligns with expectations of reduced pollution during restrictions. Pb isotope ratios of BCR vary more widely and do not show any spatial trends by land use, suggesting that Pb concentrations in BCR may be more homogenized. In MVRD, significant differences in 208Pb/206Pb were observed during the restrictions, wherein honey sampled from rural sites had more radiogenic (lower 208Pb/206Pb) Pb isotope ratios. This difference suggests that honey may be more sensitive to Pb isotope ratio changes in environments with a less extensive history of metal use, such as rural British Columbia. This research demonstrates the potential of honey as a biomonitor for sudden environmental shifts. This study contributes to a global geochemical honey database, enabling tracking of environmental trends across diverse urban settings worldwide.

Antibiotic-resistant bacteria aerosol in a Caribbean coastal city: Pre- and post- COVID-19 lockdown.

This study assessed the prevalence and spatial distribution of viable ultrafine and fine antibiotic-resistant bacteria aerosols (ARB) in the Metropolitan Area of Barranquilla, Colombia, pre- and post-lockdown (September 2019 to December 2020). Samples were systematically collected from urban, suburban, and rural sites using a six-stage viable cascade impactor. We employed logistic regression and Bayesian Neural Network Classifiers to analyze meteorological variables' influence on antibiotic resistance persistence. The lockdown led to a significant decrease (76%) in overall bacterial aerosol concentrations, likely due to reduced human activity. The most significant reduction (82%) was observed at Peace Square. Bacillus cereus was the most prevalent species, showing high concentrations at all sampling sites. Other species, like Leifsonia aquatica and Staphylococcus lentus, were linked to wastewater effluents and agricultural activities. Despite the overall decrease in bacterial aerosols, antibiotic-resistant bacteria remained high, particularly in highly impacted urban areas like the Barranquilla Riverwalk. Bacillus cereus exhibited resistance to multiple antibiotics, including commonly used ones like Ampicillin and Penicillin G. Resistance to newer antibiotics like Vancomycin was rare. Peace Square, a high-traffic urban area, showed elevated resistance rates in the deeper respiratory regions compared to other locations. Our findings indicate that while overall concentration levels decreased, the threat of antibiotic resistance in bacterial bioaerosols persists, emphasizing the need for continuous monitoring and targeted public health interventions in urban areas.

An insight into recent PM1 aerosol light scattering properties and particle number concentration variabilities at the suburban site ATOLL in Northern France.

Aerosol particles in the PM1 fraction considerably influence the climate-related effects of aerosols and impact human health despite representing very variable fractions of the total aerosol mass concentration. Aerosol optical measurement techniques (aerosol light scattering) may not be sufficiently effective for detecting all particles in the PM1 fraction, particularly regarding number concentration. The present study investigates temporal variations of aerosol light scattering properties and particle number concentration (PNC) at different size modes in the PM1 fraction at the atmospheric site ATOLL (The Atmospheric Observations in Lille), Northern France from January 2018 to February 2023. The total scattering coefficient σsp decreased annually by 6% and 8% at 525 and 635nm, respectively. Maximum annual changes occur in winter and summer seasons with a decrease above 10% per year. Although the backscattering coefficient (σbsp) at 525nm significantly decreased in winter, this did not result in a significant overall decline over time. Despite a decrease in aerosol light scattering, PNC exhibited a notable annual increase in concentration of N20-30 nm and N30-60 nm, which led to an increase in the total N20-800 nm size range. N20-30nm increased by 10% annually, with the highest increase by 37% in spring. Both traffic and photooxidative processes influenced PNCs, underscoring the need for a more comprehensive investigation of the detailed particle number size distribution to assess air quality and the health effects of increased ultrafine PNC at urban/suburban sites in Europe.

Nationwide monitoring of polychlorinated naphthalenes in soils across South Korea: Spatial distribution, source identification, and health risk assessment.

The production and use of polychlorinated naphthalenes (PCNs) were banned several decades ago, but they continue to be detected due to their persistence in surface environments and ongoing emissions from combustion-related sources. This study presents the first nationwide monitoring data for PCNs in soils collected from 61 sites across South Korea. Industrial sites (mean: 127 pg/g, median: 91.4 pg/g) exhibited higher concentrations of Σ63 PCNs than urban (mean: 53.1 pg/g, median: 50.0 pg/g) and suburban (mean: 52.2 pg/g, median: 23.3 pg/g) sites. Tri- and tetra-CNs were the dominant homologues, with CN-14/24 being the most abundant congeners. The majority of PCN contamination at these sites was attributed to combustion sources and historical emissions from Halowax mixtures. Σ63 PCNs and toxic equivalencies (TEQs) were moderately correlated with the number of companies potentially emitting PCNs, industrial electricity usage, and SO2 concentrations, indicating a significant influence of anthropogenic sources on PCN contamination. The 95th percentile cancer risks for both adults and children across all sites were within the acceptable range (< 10-6) set by the US EPA. However, the higher risks observed for children underscore the importance of ongoing PCN monitoring. This study provides valuable insights into the spatial distribution and human exposure to PCNs in soils across South Korea. Based on these initial nationwide findings, comprehensive monitoring of PCNs and other dioxin-like compounds in industrial areas is recommended.

Long-term changes in riparian connectivity and groundwater chemistry in an urban watershed.

Hydrologic alterations associated with urbanization can weaken connections between riparian zones, streams, and uplands, leading to negative effects on the ability of riparian zones to intercept pollutants carried by surface water runoff and groundwater flow such as nitrate (NO3 -) and phosphate (PO4 3-). We analyzed the monthly water table as an indicator of riparian connectivity, along with groundwater NO3 - and PO4 3- concentrations, at four riparian sites within and near the Gwynns Falls Watershed in Baltimore, MD, from 1998 to 2018. The sites included one forested reference site (Oregon Ridge), two suburban riparian sites (Glyndon and Gwynnbrook), and one urban riparian site (Cahill) with at least two locations and four monitoring wells, located 5m from the center of the stream, at each site. Results show an increase in connectivity as indicated by shallower water tables at two of the four sites studied: Glyndon and Cahill. This change in connectivity was associated with decreases in NO3 - at Glyndon and increases in PO4 3- at Glyndon, Gwynnbrook, and Cahill. These changes are consistent with previous studies showing that shallower water table depths increase anaerobic conditions, which increase NO3 - consumption by denitrification and decrease PO4 3- retention. The absence of change in the forested reference site, where climate would be expected to be the key driver, suggests that other drivers, including best management practices and stream restoration projects, could be affecting riparian water tables at the two suburban sites and the one urban site. Further research into the mechanisms behind these changes and site-specific dynamics is needed.

Exploring the Effect of Environmental Conditions on Decay Kinetics of Aerosol Unsaturated Fatty Acids: New Insights Gained from Long-Term Ambient Measurements.

Unsaturated fatty acids (uFAs) are important constituents of atmospheric organic aerosols, undergoing rapid degradation in the atmosphere that significantly influences aerosol's physical and chemical properties. This study quantified the effective pseudo-first order decay rates of three abundant uFAs-oleic, elaidic, and linoleic acids under real atmospheric conditions using continuous bihourly measurement at a suburban site in Hong Kong over a 9-month period from November 2020 to August 2021. The impact of key environmental parameters, including ozone, initial uFA concentration, relative humidity, and temperature, on the decay rates was rigorously examined. Distinct kinetic behaviors were observed across different temperature ranges (TR1: 5-13 °C; TR2: 13-22 °C; TR3: 22-26 °C; TR4: 26-30 °C). Arrhenius plots of the decay rates revealed contrasting effective activation energies under TR2 and TR4, likely due to different phase states of aerosols and reaction mechanisms under varying environmental conditions. This study extends previous laboratory research by incorporating a wider range of ambient conditions, uncovering the complex interactions between environmental factors and the decay kinetics of uFAs. The findings provide critical insights for accurately modeling the fate of ambient organic aerosols and understanding the intricate impacts of atmospheric conditions on aerosol chemistry.

Spatial distributions and source identification of PCDD/Fs and PCBs in soils and pine needles in the multi-industrial city of Ulsan, South Korea

The spatial distribution and contamination patterns of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in soil and pine needles from the multi-industrial city of Ulsan, South Korea were assessed. The mean concentrations of Σ17 PCDD/Fs, Σ12 dl-PCBs, and Σ7 I-PCBs were 78 pg/g dw, 90 pg/g dw, and 453 pg/g dw in the soil and 6 pg/g ww, 31 pg/g ww, and 166 pg/g ww in the pine needles, respectively. The mean concentrations of PCDD/Fs, dl-PCBs, and I-PCBs in the soil at industrial sites (138, 184, and 453 pg/g dw) were significantly higher than those at urban (47, 33, and 186 pg/g dw) and suburban sites (48, 49, and 234 pg/g dw). In the pine needles, although PCDD/F and PCB levels were higher at several industrial sites, mean concentrations at the industrial (6, 31, and 166 pg/g ww), urban (4, 29, and 143 pg/g ww), and suburban (4, 31, and 169 pg/g ww) sites were comparable, indicating that atmospheric transport plays a crucial role in spreading contamination throughout the study area. Higher chlorinated PCBs were predominant in the soils, while PCDFs and lower chlorinated PCBs were more common in the pine needles, reflecting the distinct physicochemical properties and interactions of these chemicals with each medium. Principal Component Analysis (PCA) revealed industrial combustion as the main source of PCDD/Fs and PCBs, with Aroclors identified as an additional source of PCBs. Suburban areas were influenced by both local sources and pollutants transported from urban and industrial areas. This study highlights that industrial activities and atmospheric transport significantly contribute to the widespread contamination of PCDD/Fs and PCBs in Ulsan.

Carbonyl Compounds Observed at a Suburban Site during an Unusual Wintertime Ozone Pollution Event in Guangzhou

Carbonyl compounds are important oxygenated volatile organic compounds (VOCs) that play significant roles in the formation of ozone (O3) and atmospheric chemistry. This study presents comprehensive field observations of carbonyl compounds during an unusual wintertime ozone pollution event at a suburban site in Guangzhou, South China, from 19 to 28 December 2020. The aim was to investigate the characteristics and sources of carbonyls, as well as their contributions to O3 formation. Formaldehyde, acetone, and acetaldehyde were the most abundant carbonyls detected, with average concentrations of 7.11 ± 1.80, 5.21 ± 1.13, and 3.00 ± 0.94 ppbv, respectively, on pollution days, significantly higher than those of 2.57 ± 1.12, 2.73 ± 0.88, and 1.10 ± 0.48 ppbv, respectively, on nonpollution days. The Frame for 0-D Atmospheric Modeling (F0AM) box model simulations revealed that local production accounted for 62–88% of observed O3 concentrations during the pollution days. The calculated ozone formation potentials (OFPs) for various precursors (carbonyls and VOCs) indicated that carbonyl compounds contributed 32.87% of the total OFPs on nonpollution days and 36.71% on pollution days, respectively. Formaldehyde, acetaldehyde, and methylglyoxal were identified as the most reactive carbonyls, and formaldehyde ranked top in OFPs, and it alone contributed 15.92% of total OFPs on nonpollution days and 18.10% of total OFPs on pollution days, respectively. The calculation of relative incremental reactivity (RIR) indicates that ozone sensitivity was a VOC-limited regime, and carbonyls showed greater RIRs than other groups of VOCs. The model simulation showed that secondary formation has a significant impact on formaldehyde production, which is primarily controlled by alkenes and biogenic VOCs. The characteristic ratios and backward trajectory analysis also indicated the indispensable impacts of local primary sources (like industrial emissions and vehicle emissions) and regional sources (like biomass burning) through transportation. This study highlights the important roles of carbonyls, particularly formaldehyde, in forming ozone pollution in megacities like the Pearl River Delta region.

Nest Defense Behavior of Suburban and Rural Red-shouldered Hawks†

ABSTRACT Urban and suburban raptors live in close proximity to humans, and some species defend their nests and young vigorously, even diving at or striking humans walking on the ground. Such raptors may be more defensive of their nests than rural birds. We investigated (1) whether Red-shouldered Hawk (Buteo lineatus) nest defense behavior differs between suburban and rural birds, (2) whether any environmental conditions are associated with aggressive nest defense, and (3) whether nest defense behavior is associated with reproductive rate. First, we used an experimental walk-up protocol to approach nests with incubating or brooding Red-shouldered Hawks at suburban and rural sites, and we scored the hawk’s response to our approach. We measured environmental variables (nest height, distance to the nearest road and nearest house, and habitat proportions within 500 m of the nest) and determined reproductive rate. Second, we used our historical database to retrospectively classify hawks as most aggressive, moderately aggressive, or not aggressive, and we measured the same environmental variables at their nest sites. We found that most birds at both suburban and rural study areas responded to our experimental approach with minimal nest defense, though suburban birds responded with higher levels of nest defense. Environmental variables were unrelated to nest defense intensity in the experimental study. For the retrospective study in the suburban area, nest height was the only environmental factor distinguishing aggressive hawks from non-aggressive ones; aggressive nest defensive behavior was associated with lower nests. Reproductive rate was unrelated to nest defense behavior in both studies. Knowing which environmental factors may contribute to more aggressive behavior may help researchers, managers, and residents better understand bird behavior and predict the circumstances under which problems might develop, particularly in urban/suburban environments.

The Paris low-level jet during PANAME 2022 and its impact on the summertime urban heat island

Abstract. The low-level jet (LLJ) and the urban heat island (UHI) are common nocturnal phenomena. While the UHI has been studied extensively, interactions of the LLJ and the urban atmosphere in general (and the UHI in particular) have received less attention. In the framework of the PANAME (PAris region urbaN Atmospheric observations and models for Multidisciplinary rEsearch) initiative in the Paris region, continuous profiles of horizontal wind speed and vertical velocity were recorded with two Doppler wind lidars (DWLs) – for the first time allowing for a detailed investigation of the summertime LLJ characteristics in the region. Jets are detected for 70 % of the examined nights, often simultaneously at an urban and a suburban site, highlighting the LLJ regional spatial extent. Emerging at around sunset, the mean LLJ duration is ∼ 10 h, the mean wind speed is 9 m s−1, and the average core height is 400 m above the city. The temporal evolution of many events shows signatures that indicate that the inertial oscillation mechanism plays a role in the jet development: a clockwise veering of the wind direction and a rapid acceleration followed by a slower deceleration. The horizontal wind shear below the LLJ core induces variance in the vertical velocity (σw2) above the urban canopy layer. It is shown that σw2 is a powerful predictor for regional contrast in air temperature, as the UHI intensity decreases exponentially with increasing σw2 and strong UHI values only occur when σw2 is very weak. This study demonstrates how DWL observations in cities provide valuable insights into near-surface processes relevant to human and environmental health.

West Nile virus in adults and larvae of Culiseta longiareolata and Culex hortensis (Diptera: Culicidae) captured in Hamedan, western Iran

West Nile virus (WNV) is an emerging arbovirus transmitted by mosquitoes. Although it is considered the most widespread mosquito-borne arbovirus in Iran, vectors of this zoonotic pathogen remain unknown in many regions. This study aimed to assess the presence of WNV in mosquitoes collected in the western city of Hamedan in 2022. Adult mosquitoes were captured using light traps, and mosquito larvae were collected by dipping technique from 45 diverse habitats, including urban, suburban, and rural sites. Specimens were identified and pooled into 69 batches based on their species for viral RNA extraction and Real-Time PCR. In total, 3243 mosquitoes (2209 larvae and 1034 adults) were captured and identified as Culiseta longiareolata, Culex hortensis, Anopheles maculipennis s.l., Culex theileri, Culex pipiens, Anopheles claviger, and Anopheles superpictus s.l. in decreasing order. Molecular screening revealed seven WNV-positive pools of Culiseta longiareolata and Culex hortensis in rural (n = 5) and urban areas (n = 2). Detection of WNV RNA indicates active circulation in mosquitoes and risk of transmission to humans and animals in Hamadan. These findings identify putative vectors in Hamadan, though vectors likely vary regionally in Iran. Further surveillance is needed to elucidate local WNV epidemiology and transmission dynamics fully. Nonetheless, this study provides important baseline evidence of WNV activity to guide prevention strategies in this area.

Causes of the unremitting high ambient levels of PM10 in a suburban background site in NE Spain

Atmospheric PM10 and benzo(a)pyrene (BaP) concentrations in Manlleu (NE Spain) have remained high from 2008 to 2023, frequently exceeding EU limit/target values, and reaching BaP levels up to six times higher than urban averages in Spain. Furthermore, PM speciation campaigns were carried out in 2013, 2014–2015, 2016–2017 and 2021–2022. Chemical mass closure for autumn-winter showed a consistent PM10 composition for the different PM speciation campaigns, comprising 46–53% organic matter (OM), 18–26% secondary inorganic aerosol (SIA), 13–23% mineral matter (MM), and 5–9% elemental carbon (EC). Trend analysis revealed very light decrease and constant concentrations for PM10 and BaP, respectively over the study period, emphasizing the need for compliance with current and forthcoming EU air quality directives, the last aiming to halve PM10 limit values. Source apportionment of samples of the sporadic campaigns identified biomass burning (BB, 17.5 μg m−3, 48%) and MM and industry (16.3 μg m−3, 44%) as the main autumn-winter PM10 contributors, with high SIA concentrations attributed to several factors, including high ammonia (NH3) emissions. Local topography and meteorological conditions contribute to aggravate PM10 pollution. While metal concentrations have decreased since 2013, suggesting reduced industrial emissions, persistently high OM and EC concentrations indicate ongoing issues with BB emissions from domestic, commercial, and agricultural sources. Online analysis of black carbon (BC) and non-refractory PM1 components during winter 2016–2017 confirmed domestic and commercial BB as the primary sources of the BB contributions. These findings highlight the need of the implementation of more effective measures in reducing BB and agricultural/farming NH3 emissions. This study highlights the relevance of these issues for similar towns, the probable unremitting problem over the last decade, and the necessity of enhanced monitoring in small cities and policy actions to meet air quality standards under the new EU directive.

Phantom Writing

In this visual essay I present a body of artistic work done within informal urban and suburban heritage sites in Kyoto. Through the media of text, photography, film and site-specific painting, my works from the cycle Spirit Grounds engage with these sites involving material physical aspects as well as beliefs, fictions, and more-than-human beings. Building upon this, I propose ‘phantom writing’ or ‘phantasmography’ as a situated, multidisciplinary and multisensory approach aimed at understanding and designing contemporary places, landscapes and environments, acknowledging and mediating the agency of diverse phantoms and phantasms.

Investigating the role of photochemistry and impact of regional and local contributions on gaseous pollutant concentrations (NO, NO2, O3, CO, and SO2) at urban and suburban sites

Gaseous pollutant concentrations were monitored for one year in urban (NO, NO2, O3, CO, and SO2) and suburban (NO, NO2, and O3) sites. Common characteristics were identified at both sites, such as higher concentrations during typical winter months for all pollutants except O3. Increased NO, NO2, CO and SO2 concentrations during wintertime were linked to residential heating emissions, with pairwise correlations showing CO as marker for the study site. O3 production was lower in wintertime but higher in summertime at both sites based on its seasonal cycle and the impact of sunlight. Furthermore, diurnal variations showed that traffic emissions during rush hours most profoundly affected CO and NO. Nevertheless, NOx were characteristically higher at the urban site based on the burdened environment, whereas O3 was higher at the suburban site due to the lower destruction rates. O3 was the dominant oxidant at both sites, with a linear regression between OX and NOx revealing a negative relationship. This observation suggested a dominant regional contribution to oxidant concentrations. In addition, abnormally high O3 concentrations in relation to the season were reported for the first time at the study sites. Elevated concentrations were measured in parallel with Sahara dust events indicating noteworthy atmospheric conditions that require further assessment. Other O3 burdened periods were driven by regional transport of polluted plumes from the northeast. Lastly, nocturnal increases in O3 were observed and associated with enhanced vertical mixing.

Role of Organic Vapor Precursors in Secondary Organic Aerosol Formation: Concurrent Observations of IVOCs and VOCs in Guangzhou

AbstractSecondary organic aerosol (SOA) formed through the atmospheric transformation of organic vapors constitutes a significant portion of fine particulate matter or PM2.5. While recent laboratory studies underscore the importance of intermediate‐volatility organic compounds (IVOCs) as key precursors to SOA, field observations that recognize the role of both volatile organic compounds (VOCs) and IVOCs in SOA formation remain scarce. In this study, we conducted concurrent measurements of VOCs and IVOCs in ambient air at urban and suburban sites in Guangzhou during a PM2.5 pollution event in winter 2021. The results reveal that between 12:00–15:00 local time, the photochemically adjusted initial concentrations of VOCs at both sites were approximately 7 times higher than that of IVOCs. However, the SOA formation potential (SOAFP) of primary hydrocarbon IVOCs exceeded that of VOCs by over 3–4 times. Receptor modeling results further indicated that while ship emissions contributed to less than 10% of the C2–C22 primary hydrocarbons concentration (VOCs + primary carbonaceous IVOCs), they accounted for the most significant source (approximately 40%) of SOA formation. This study highlights the substantial role of IVOCs in SOA formation and emphasizes the importance of future PM2.5 pollution control measures targeting major IVOCs contributors, such as ship emissions in harbor cities.

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.

Effect of geographical parameters on PM10 pollution in European landscapes: a machine learning algorithm-based analysis

BackgroundPM10, comprising particles with diameters of 10 µm or less, has been identified as a significant environmental pollutant associated with adverse health outcomes in European cities. Understanding the temporal variation of the relationship between PM10 and geographical parameters is crucial for sustainable land use planning and air quality management in European landscapes. This study utilizes Conditional Inference Forest modeling and partial correlation to examine the impact of geographical factors on monthly average concentrations of PM10 in European suburban and urban landscapes during heating and cooling periods. The investigation focuses on two buffer zones (1000 m and 3000 m circle radiuses) surrounding 1216 European air quality monitoring stations.ResultsResults reveal importance and significant correlations between various geographical variables (soil texture, land use, transportation network, and meteorological) and PM10 quality on a continental scale. In suburban landscapes, soil texture, temperature, roads, and rail density play pivotal roles, while meteorological variables, particularly monthly average temperature and wind speed, dominate in urban landscapes. Urban sites exhibit higher R-squared values during both cooling (0.41) and heating periods (0.61) compared to suburban sites (cooling period R-squared: 0.39; heating period: R-squared: 0.51), indicating better predictive performance likely attributed to the less heterogeneous land use patterns surrounding urban PM10 monitoring sites.ConclusionThe study underscores the importance of investigating spatial and temporal dynamics of geographical factors for accurate PM10 air quality prediction models in European urban and suburban landscapes. These findings provide valuable insights for policymakers, urban planners, and environmental scientists, guiding efforts toward sustainable and healthier urban environments.

A Comparison of Regression Methods for Inferring Near‐Surface NO2 With Satellite Data

AbstractNitrogen dioxide (NO2) is an atmospheric pollutant emitted from anthropogenic and natural sources. Human exposure to high NO2 concentrations causes cardiovascular and respiratory illnesses. The Environmental Protection Agency operates ground monitors across the U.S. which take hourly measurements of NO2 concentrations, providing precise measurements for assessing human pollution exposure but with sparse spatial distribution. Satellite‐based instruments capture NO2 amounts through the atmospheric column with global coverage at regular spatial resolution, but do not directly measure surface NO2. This study compares regression methods using satellite NO2 data from the TROPospheric Ozone Monitoring Instrument (TROPOMI) to estimate annual surface NO2 concentrations in varying geographic and land use settings across the continental U.S. We then apply the best‐performing regression models to estimate surface NO2 at 0.01° by 0.01° resolution, and we term this estimate as quasi‐NO2 (qNO2). qNO2 agrees best with measurements at suburban sites (cross‐validation (CV) R2 = 0.72) and away from major roads (CV R2 = 0.75). Among U.S. regions, qNO2 agrees best with measurements in the Midwest (CV R2 = 0.89) and agrees least in the Southwest (CV R2 = 0.65). To account for the non‐Gaussian distribution of TROPOMI NO2, we apply data transforms, with the Anscombe transform yielding highest agreement across the continental U.S. (CV R2 = 0.77). The interpretability, minimal computational cost, and health relevance of qNO2 facilitates use of satellite data in a wide range of air quality applications.

Characteristics and Influence of Atmospheric VOCs in Ozone Formation Potential in Suburb of Shanghai During Summer

To help promote ozone pollution control and understand the influence of atmospheric volatile organic compounds （VOCs） on O3 during the summer ozone pollution season, the analyses of variation characteristics and ozone formation potentials of VOCs during O3 pollution episodes were carried out based on the online monitoring data of VOCs and O3, as well as the meteorological parameters in the suburban site of Shanghai. The impact of key meteorological factors and regional transport on O3 and VOCs was investigated. The results showed that the mean value of atmospheric φ（VOCs） during summer in the suburban area of Shanghai was （20.91 ± 9.82）×10-9, and the largest proportion of each component was with alkanes and OVOCs, both of which were 30.2%. The mean value of φ（VOCs） on O3 polluted days was （23.84 ± 9.69）×10-9, which was 28.1% higher than that on clean days. The OFP of VOCs on polluted days was 126.92 μg·m-3, which was 31.9% higher than that on clean days. The contribution of olefins to OFP accounted for a significant increase, and species such as propylene and acetone were the most significant compared to on clean days, indicating that these components and species need to be the focus of mitigation. The variation characteristics of the ratio of ethane to acetylene （E/E） and the ratio of m/p-xylene to ethylbenzene（X/E） indicated that there was a significant regional transport influence of the summer air masses in the suburban area of Shanghai, and it occurred mainly in the afternoon and at night. The results of the pollution rose diagram and the backward trajectory of air masses indicated that air masses from the south and southwest directions had the greatest influence on the transport of VOCs in suburban Shanghai. In particular, it is necessary to focus on controlling olefin and OVOCs from southern air masses and aromatic hydrocarbons from southwestern air masses.