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A Tethered balloon-based field campaign was launched for the vertical observation of air pollutants within the lower troposphere of 1000 m for the first time over a Chinese megacity, Shanghai in December of 2013. A custom-designed instrumentation platform for tethered balloon observation and ground-based observation synchronously operated for the measurement of same meteorological parameters and typical air pollutants. One episodic event (December 13) was selected with specific focus on particulate black carbon, a short-lived climate forcer with strong warming effect. Diurnal variation of the mixing layer height showed very shallow boundary of less than 300 m in early morning and night due to nocturnal inversion while extended boundary of more than 1000 m from noon to afternoon. Wind profiles showed relatively stagnant synoptic condition in the morning, frequent shifts between upward and downward motion at noon and in the afternoon, and dominant downward motion with sea breeze in the evening. Characteristics of black carbon vertical profiles during four different periods of a day were analyzed and compared. In the morning, surface BC concentration averaged as high as 20 μg/m 3 due to intense traffic emissions from the morning rush hours and unfavorable meteorological conditions. A strong gradient of BC concentrations with altitude was observed from the ground to the top of boundary layer at around 250–370 m. BC gradients turned much smaller above the boundary layer. BC profiles measured during noon and afternoon were the least dependent on heights. The largely extended boundary layer with strong vertical convection was responsible for a well mixing of BC particles in the whole measured column. BC profiles were similar between the early-evening and late-evening phases. The lower troposphere was divided into two stratified air layers with contrasted BC vertical distributions. Profiles at night showed strong gradients from the relatively high surface concentrations to low concentrations near the top of the boundary layer around 200 m. Above the boundary layer, BC increased with altitudes and reached a maximum at the top of 1000 m. Prevailing sea breeze within the boundary layer was mainly responsible for the quick cleanup of BC in the lower altitudes. In contrast, continental outflow via regional transport was the major cause of the enhanced BC aloft. This study provides a first insight of the black carbon vertical profiles over Eastern China, which will have significant implications for narrowing the gaps between the source emissions and observations as well as improving estimations of BC radiative forcing and regional climate. [ABSTRACT FROM AUTHOR]

The coronavirus (COVID-19) pandemic is disrupting the world from many aspects. In this study, the impact of emission variations on PM 2.5 -bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic. Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown. After the lockdown, they rebounded rapidly, of which V and Ni even exceeded the levels before the lockdown, suggesting the recovery of both inland and shipping activities. Five sources were identified based on receptor modeling. Coal combustion accounted for more than 70% of the measured elemental concentrations before and during the lockdown. Shipping emissions, fugitive/mineral dust, and waste incineration all showed elevated contributions after the lockdown. The total non-carcinogenic risk (HQ) for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ. Whereas, the total carcinogenic risk (TR) for adults was above the acceptable level and much higher than that for children. Waste incineration was the largest contributor to HQ, while manufacture processing and coal combustion were the main sources of TR. Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk. From the perspective of health effects, priorities of control measures should be given to waste incineration, manufacture processing, and coal combustion. A balanced way should be reached between both lowering the levels of air pollutants and their health risks. [Display omitted]. [ABSTRACT FROM AUTHOR]

The heaviest aerosol pollution day in the historical record of the Yangtze River Delta occurred on 19 January 2007, in which the daily concentration of PM10 reached 512μgm−3 in Shanghai, 463μgm−3 in Suzhou, 354μgm−3 in Hangzhou, and 282μgm−3 in Nanjing. The hourly concentrations of PM2.5 and PM10 reached peak values of 466 and 744μgm−3, respectively, in Shanghai. With visibility <0.6km, the regional haze covered nearly the entire Yangtze River Delta. High ratios of PM2.5/PM10 (61%), SO2/PM10 (0.38) and NO2/PM10 (0.24) were observed. The unusual stagnant dispersion conditions before a cold front played the predominant role in this high pollution episode, with relative humidity (RH) of 88%, both surface and upper-level inversions, as well as low wind speed (<1ms−1). The sulfur oxidation rate (SOR) reached 0.67 and the nitrogen oxidation rate (NOR) reached 0.61, signifying that formation of sulfate and nitrate contributed significantly to the high secondary aerosol concentration of PM2.5. The enrichment factors of As, Cd, and Pb reached 4058, 6971, and 3972, which were 4.45–6.68 times higher than those on good/moderate days. It was demonstrated that emissions from anthropogenic sources, especially stationary sources such as power plants, industrial boilers, and furnaces, were the major contributors to the heaviest aerosol pollution in the delta. More attention should be paid to the increases in emissions and the higher occurrence of haze days that have accompanied the rapid development of the economy in the Yangtze River Delta. [Copyright &y& Elsevier]

A cavity attenuated phase shift single scattering albedo monitor was set up on a tethered airship platform to study the vertical profiles of particle light extinction coefficient (b ext) in the lower troposphere (<1000 m) in Shanghai during 12–29 December 2015. Clear transition heights (THs) for vertical profiles of b ext during the polluted days (PM 2.5 > 75 μg m−3) were observed below 1000 m. The vertical differences of b ext were highly dynamic as the vertical variation in b ext was significant by as much as 605 Mm−1. The TH was observed mostly at about 100–200 m, and 450–650 m during night and daytime, respectively, and was in a wide range of ∼50–900 m during 15:00–22:00 due to the low boundary layer and/or the transport of pollutants. In particular, the TH was consistently below 500 m throughout the day during highly polluted haze episodes, highlighting the important role of a stagnant atmosphere situation for high concentrations of PM 2.5. The vertical distribution of b ext did not have a constant rule with respect to relative humidity and wind. Sometimes, peak values of b ext at ∼350 m and 500 m during daytime were caused by enhanced regional transport. During stagnant and highly polluted situations or well-mixed clean days, b ext was usually uniformly distributed below and above the TH, respectively, although b ext was much smaller above the TH. For other situations, local emissions, pollutant transport, and the physical and chemical characteristics of aerosols resulted in highly dynamic vertical profiles of b ext. • The vertical variations of b ext were dynamic within 1000 m. • Transition heights (THs) for b ext were below 1000 m during the polluted days. • b ext was usually uniform below and above the TH during clean and heavy haze episodes. • The TH was consistently below 500 m throughout the day during heavy haze episodes. • Flexible rules were found between b ext and relative humidity/wind within 1000 m. [ABSTRACT FROM AUTHOR]

Abstract Fireworks displays are a traditional form of celebration during the Chinese Spring Festival (Festival). In response to the heavy air pollution caused by fireworks, Shanghai, a megacity in China, has imposed regulatory measures on the use of fireworks in recent years. To investigate air quality trends before and after firework regulation was established and quantify its efficiency, gaseous pollutants, PM 2.5 levels, and PM 2.5 chemical composition were synchronously measured at 1 h time intervals at an urban site and a suburban site in Shanghai in the period during and around the Festival from 2013 to 2017. PM 2.5 concentrations at the urban site during the Festival over the five-year period were 79 (max: 524), 94 (290), 53 (163), 50 (146) and 32 (156) μg/m3, respectively, presenting a decreasing trend at a rate of −13.8 μg/m3/yr (p = 0.05). K+ concentrations, which serve as a tracer of fireworks, were 8.2 (max: 159.4), 2.5 (14.6), 2.2 (10.4), 4.3 (44.2) and 0.8 (4.5) μg/m3 during the Festival from 2013 to 2017, respectively, and thus decreased at a rate of −1.3 μg/m3/yr (p = 0.17). Accordingly, fireworks contributed 41 (51.9%), 38 (36.5%), 6 (10.3%), 21 (35.6%), and 4 μg/m3 (12.1%) to PM 2.5 , respectively, implying the effectiveness of firework regulation in Shanghai. Health effects attributed to PM 2.5 pollution in Shanghai during the Festival were assessed based on Poisson regression. The number of premature deaths related to short-term PM 2.5 exposure in Shanghai during the Festival from 2013 to 2017 was 75 (95% CI: 27, 108), 92 (30, 129), 55 (18, 76), 49 (19, 70), and 31 (12, 45), respectively. Daily mortality due to PM 2.5 exposure during the Festival from 2013 to 2017 accounted for 1.4–3.8% of total daily mortality in Shanghai. This study provides scientific evidence of air quality improvement and the effectiveness of firework regulation in Shanghai. Graphical abstract Unlabelled Image Highlights • Significant air quality improvement was observed in Shanghai during the Festival from 2013 to 2017. • Fireworks contributed 41, 38, 6, 21 and 4 μg/m3 to PM 2.5 in Shanghai during the Festival from 2013 to 2017, respectively. • Health effects related to PM 2.5 exposure during the Festival was calculated based on Poisson regression. [ABSTRACT FROM AUTHOR]

In order to explore the effects of COVID-19 control measures on the concentration and composition of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs), and to better understand the sources of PM2.5-bound PAHs, PM2.5, samples were collected at two sites in urban and suburban areas of Shanghai before the lockdown, during the lockdown, after the lockdown in 2020, and during the same periods in 2019. The mass concentrations of 21 individual PAHs were determined via GC-MS analysis. While the COVID-19 control measures significantly reduced the absolute concentration of PM2.5-bound PAHs, they had no significant effect on their relative abundances, indicating that the significantly reduced traffic emission may not originally be the major source of PAHs in Shanghai. The differences in the composition of PM2.5-bound PAHs at three different lockdown-related periods may be caused by the gas-particle distribution of semi-volatile PAHs. The similarity in the composition of PM2.5-bound PAHs in different functional areas and different periods brings more uncertainties to the identification of PAH sources using the diagnostic ratios. During the lockdown period, the toxic equivalent concentration of PM2.5-bound PAHs in Shanghai was estimated to decrease by about 1/4, which still exhibits substantial carcinogenic risk upon exposure via inhalation. [ABSTRACT FROM AUTHOR]

Traffic-related air pollution (TRAP) was monitored using a mobile sensor network on 125 urban taxis in Shanghai (November 2019/December 2020), which provide real-time patterns of air pollution at high spatial resolution. Each device determined concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), and PM2.5, which characterised spatial and temporal patterns of on-road pollutants. A total of 80% road coverage (motorways, trunk, primary, and secondary roads) required 80–100 taxis, but only 25 on trunk roads. Higher CO concentrations were observed in the urban centre, NO2 higher in motorway concentrations, and PM2.5 lower in the west away from the city centre. During the COVID-19 lockdown, concentrations of CO, NO2, and PM2.5 in Shanghai decreased by 32, 31 and 41%, compared with the previous period. Local contribution related to traffic emissions changed slightly before and after COVID-19 restrictions, while changing background contributions relate to seasonal variation. Mobile networks are a real-time tool for air quality monitoring, with high spatial resolution (~200 m) and robust against the loss of individual devices. [ABSTRACT FROM AUTHOR]

Intensive observations and WRF‐Chem simulations are applied in this study to investigate the adverse impacts of regional transport on the PM2.5 (fine particulate matter; diameter ≤2.5 μm) changes in Shanghai during the Coronavirus Disease 2019 lockdown. As the local atmospheric oxidation capacity was observed to be generally weakened, strong regional transport carried by the frequent westerly winds is suggested to be the main driver of the unexpected pollution episodes, increasing the input of both primary and secondary aerosols. Contributing 40%–80% to the PM2.5, the transport contributed aerosols are simulated to exhibit less decreases (13.2%–21.8%) than the local particles (37.1%–64.8%) in urban Shanghai due to the lockdown, which largely results from the less decreased industrial and residential emissions in surrounding provinces. To reduce the influence of the transport, synergetic emission control, especially synergetic ammonia control, measures are proved to be effective strategies, which need to be considered in future regulations. Plain Language Summary: The anthropogenic emissions were sharply reduced in China due to the lockdown measures during the Coronavirus Disease 2019 pandemic. However, the reduced emissions did not lead to expected decreases in fine particulate matter in Shanghai. To understand why haze pollution still occurred during the lockdown, intensive observations and a variety of simulations using the regional chemical transport model were conducted in this study. Contributing 40−80% to the fine particles in Shanghai, the strong transport of air pollutants carried by the frequent westerly winds is found to be the main driver of the observed pollution episodes, which brings substantial primary and secondary aerosols to the city. Compared to those originated from the local sources, the transport contributed aerosols are simulated to be less affected by the intervention measures, which can be largely attributed to the less decreased industrial and residential emissions in Jiangsu, Zhejiang, and Anhui and enhanced aerosol formation during the transport. Synergetic emission control measures, including reductions in both the traditional regulated emissions and agricultural emissions, in the Yangtze River Delta region are proved to be effective in mitigating the adverse impacts of the transport, which provide practical implications for future pollution control strategies in cities like Shanghai. Key Points: PM2.5 pollution in Shanghai were mostly attributed to the regional transport carried by frequent westerly winds during the COVID‐lockdownThe transport contributed aerosols in Shanghai are less affected by the lockdown measures due to the less decreased surrounding emissionsSynergetic emission control measures, especially those on ammonia emissions, are effective in mitigating the adverse transport impacts [ABSTRACT FROM AUTHOR]

Abstract To reduce air pollution within a 300 km radius from Hangzhou (the capital city of Zhejiang Province in East China) for the 2016 G20 summit (9/4–9/5), the 14-day (8/24–9/6) stringent pollution control measures were implemented in Shanghai. Changes in atmospheric concentrations during the same 14-day period from 2014 to 2016 were examined at two Supersites, i.e., urban Pudong site (PD) and Dianshan Lake regional site (DSL). Up to 50% reductions were found for PM 2.5 , with 13.1% and 9.7% reductions for SO 2 and NO 2 , respectively. No apparent improvements were found for 8-h average O 3 concentrations. Large reductions were also found for SO 4 2− (51.4%), NO 3 − (68.8%), and NH 4 + (84.4%), on average. Elevated coefficient of divergence values (0.52–0.56) suggested that pollutant sources differed at the two sites. Biomass burning, resuspended dust, combustion, iron and steel industry, sea salt, secondary aerosol, and vehicle exhaust were identified at the DSL site by Positive Matrix Factorization (PMF). Secondary aerosol and vehicle exhaust accounted for 45.7% of PM 2.5 mass, followed 11.2%–13.7% each by industry, resuspended dust, and coal and oil combustion. Graphical abstract Unlabelled Image Highlights • Effectiveness of the pollution control measures was evaluated for the G20 summit. • Concentrations of most of criteria air pollutants reduced whereas O 3 elevated. • Impacts of local emissions and regional transport were analyzed at two Supersites. • Secondary aerosols and vehicle exhaust remained the top two sources of PM 2.5. [ABSTRACT FROM AUTHOR]

Atmospheric particulate polycyclic aromatic hydrocarbons (PAHs) have been drawing sustained attention due to their health risk and effects on air pollution. It is essential to determine the main sources and reduce atmospheric levels of PAHs to protect human health. PAHs in PM 2.5 have been detected at five sites located in five districts in Shanghai, a modern metropolitan city in China. Spatial and temporal variations of composition profiles and sources of PAHs at each site in each season were investigated. The results showed that atmospheric particulate PAHs level in Shanghai was the lowest in summer and the highest in winter, dominated by high molecular weight (HMW) PAHs. Analysis with a combination of coefficients of Pearson's correlation and coefficient of divergences indicated heterogeneous spatial and temporal distribution for LMW PAHs and homogenous distribution for HMW PAHs. Diagnostic ratios and positive matrix factorization (PMF) model both identified pyrogenic sources as the main contributor of PAHs in Shanghai, with vehicular source contribution of 32– 43% to the total PAHs annually and around 20% from biomass burning emissions in urban and urban buildup areas. While in winter, coal combustion and biomass burning could act as two major sources of PAHs in suburban areas, which could contribute to > 70% of total PAHs measured in PM 2.5 in Shanghai. [ABSTRACT FROM AUTHOR]

Background Associations of ambient air pollutants with respiratory health are inconsistent. Objectives We analyzed the associations of gestational and early life exposures to air pollutants with doctor-diagnosed asthma, allergic rhinitis, and pneumonia in children. Methods We selected 3358 preschool children who did not alter residences after birth from a cross-sectional study in 2011–2012 in Shanghai, China. Parents reported children's respiratory health history, home environment, and family lifestyle behaviors. We collected daily concentrations of sulphur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM 10 ) during the child's total lifetime (2006–2012) for each district where the children lived. We analyzed the associations using logistic regression models. Results After adjusting for covariates and the other studied pollutants, we found that exposure to NO 2 (increment of 20 μg/m 3 ) during the first year of life was significantly associated with asthma [odds ratio (OR) = 1.77; 95% confidence interval (CI): 1.29–2.43] and allergic rhinitis (OR = 1.67; 95% CI: 1.07–2.61). Exposure to NO 2 during gestation, the first two and three years, and over total lifetimewas all consistently associated with increased odds of allergic rhinitis. Quartiles of NO 2 concentration during different exposure periods showed a slight dose–response relationship with the studied diseases. These diseases had significant associations with pollutant mixtures that included NO 2 , but had no significant association with exposures to SO 2 and PM 10 individually or in mixtures. Conclusions Gestational and early life exposures to ambient NO 2 are risk factors for childhood respiratory diseases. [ABSTRACT FROM AUTHOR]

Modeling air pollutants on a fine spatiotemporal scale is necessary for health studies that focus on critical short-term exposure windows. A unified empirical modeling approach is useful for health studies; however, it is unclear whether this approach can be used in a coastal city for air pollutants driven by local emissions and regional meteorological factors. An advanced empirical modeling approach was used to develop exposure models from October 2012 to December 2019, for particulate matter with aerodynamic diameters less than or equal to 2.5 and 10 μm (PM 2.5 and PM 10) and nitrogen dioxide (NO 2) in the coastal city of Shanghai, China. Air pollutant concentrations were obtained from daily measurements at 55 administrative monitoring sites that were integrated into three-day average concentrations. Data on a large array of geographic variables were collected, and their dimensions were reduced using the partial least squares regression method. A geostatistical model using the land-use regression approach in a universal kriging framework was developed to estimate short-term exposure concentrations. The prediction ability of the models were determined by leave-one (site)-out cross-validation (LOOCV) and external validation (EV). Compared to the LOOCV results, the EV results for PM 2.5 and PM 10 were consistently reliable, but the EV for NO 2 had a larger root mean squared error. The temporal random effects involved in the model structure were interpreted using sensitivity analyses. This affected the short-term PM 2.5 and PM 10 model predictions. This unified empirical modeling approach was successfully used for particulate matter in Shanghai, where air pollution is affected by complex regional and meteorological conditions. These exposure models are going to be applied for making exposure predictions at residential locations for short-term exposure predictions in the "Growth trajectories and air pollution" (GAAP) study in Shanghai that focuses on maternal and early life exposure to air pollutants. [Display omitted] • A unified empirical model development approach for particulate matter and NO 2. •A clear model structure that each part of the model can be interpreted. •Provide fine-scale predictions over both space and time for a health study in Shanghai. [ABSTRACT FROM AUTHOR]

Based on the concentrations of the carbonaceous components and the typical organic tracers in 682 p.m. 2.5 samples collected in Shanghai from 2012 to 2018, the temporal trends of the concentrations and potential sources of the secondary organic aerosols in PM 2.5 in Shanghai were investigated. The annual average concentrations of organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) all showed a decreasing trend along with the PM 2.5 concentration. The annual concentration of total carbon (TC) in 2018 (4.3 μg m−3) was about 34% of that in 2012. Compared with that in 2013, the concentrations of isoprene and sesquiterpene SOA tracers in 2018 decreased by 48% and 43%. Meanwhile, the concentration of monoterpene SOA tracers kept stable in 2 ng m−3 to 3 ng m−3, and the concentration of toluene SOA tracer decreased slightly from 1.3 ng m−3 in 2013 to 1.0 ng m−3 in 2018. Correlation analysis with levoglucosan suggested that biomass burning should be an important source of sesquitertene in Shanghai. It was found that the 2-MGA/2-MTLs ratio of the isoprene tracers was more strongly affected by the ambient temperature but not NOx in Shanghai. The concentration of secondary organic carbon (SOC) estimated with OC/EC-based, WSOC-based and tracer-based methods showed a decreasing trend during the study period, but the contribution of SOC to OC was increasing. Anthropogenic aromatic volatile organic compounds was the increasingly important contributor to the SOC in PM 2.5 , and should be the key pollutants to be controlled to further improve the air quality in Shanghai. • Temporal trend of SOC in PM 2.5 in Shanghai during 2012 and 2018 investigated. • The concentration of SOC decreasing while the contribution to OC increasing in the last decade. • Relative contribution of SOA from toluene was found increased but not decreased. • Biomass burning was the important source of seisquiterpene in Shanghai. • 2-MG/2-MTLs ratio in urban environment strongly affected by ambient temperature. [ABSTRACT FROM AUTHOR]

Tropospheric ozone pollution has been continuously worsening in China during the past decade. Identification of long-term evolution of ozone sensitivity to precursors is essential to evaluating the impact of emission reduction measures on ozone pollution. Traditional observation-based model and 3-d numerical model are not suitable for analyzing long-term variation of ozone sensitivity to precursors. In this study, by transforming the conventional ozone isopleth plot into a VOCR isopleth plot in the functional space of NO x and ozone concentrations, we developed a novel approach to identify ozone sensitivity to precursors by simply using long-term monitoring data of ozone, NO x and temperature. This approach estimated ozone formation regimes (OFR) by ozone sensitivity to NO x and temperature separately, and the convergence of OFR serves as a way of mutual verification. We found that ozone formation was generally in the VOCR-limited or transitional regime in Shanghai, the largest metropolitan area in China. However, OFR was shifted to NO x -limited at Pudong station during 2017–19 due much to the stringent NO x emission control. OFR was also shifted to NO x -limited along with the increasing temperature. When temperature was over 30 °C, Shanghai was mostly in a NO x -limited OFR. This highlights that the NO x emission control measures need to be strengthened to reduce peak ozone levels more efficiently. Jinshan station exhibited a different trend with OFR shifted to VOCR-limited in 2017–19, which proved the effectiveness of VOCs emission control on petrochemical sector. However, OFR was shifted to NO x -limited when temperature was over 30 °C, suggesting more stringent VOCs emissions control should be targeted on days with higher temperature. Unlabelled Image • Long-term changes of OFR is essential to understand reasons for ozone increase in China. • A novel approach was developed to evaluate long-term evolution of ozone sensitivity to precursors. • OFR in Shanghai is shifting from VOCR-limited to NOx-limited along with NOx emission reduction. • OFR shift at JS highlights the effectiveness of VOCs emission control from petrochemical industry. • By only using routine monitoring data, this approach could be applied in most areas worldwide. [ABSTRACT FROM AUTHOR]

Real-time measurements of submicron aerosol species including sulfate, nitrate, ammonium, chloride, organics and black carbon were conducted from a regional site (Dianshan Lake) in the rural area of western Shanghai for 1 year from July 2015 to June 2016. An Aerosol Chemical Speciation Monitor (ACSM) and an Aethalometer were deployed to analyze the seasonal and diurnal variations of aerosol properties at 1-h time resolution. The ACSM and Aethalometer measurements of submicron particulate matter (PM 1) concentration and composition agreed well with collocated measurements of PM 2.5 using a Tapered Element Oscillating Microbalance, a Monitoring Instrument for Aerosols and Gases (MARGA) and a Sunset organic carbon and elemental carbon (OC/EC) analyzer. A rolling-window positive matrix factorization (RW-PMF) algorithm was applied to the ACSM mass spectra to examine organic aerosol (OA) sources and identified three factors representing hydrocarbon-like organic aerosol (HOA), more-oxidized oxygenated organic aerosol (MO-OOA) and less-oxidized oxygenated organic aerosol (LO-OOA), respectively. The annual average mass concentration of PM 1 was 43.6 ± 29.9 μg m−3, with the seasonal average ranging from 32.3 ± 21.0 μg m−3 in summer to 60.3 ± 38.3 μg m−3 in winter. OA contributed the most to PM 1 with a small seasonal difference (29–32%). More seasonal variations were observed in the mass fractions of nitrate (20–26%) and sulfate (18–26%) in PM 1. Nitrate played an important role in PM pollution episodes since its fractional contribution to PM 1 mass increased by approximately a factor of 3 (from ~10% to ~30%) from the lowest to the highest aerosol conditions. Photochemical production and gas-particle partitioning were the main drivers for secondary inorganic aerosol formation, leading to significant diurnal and seasonal cycles. The highest mass fractions of sulfate and nitrate occurred in summer and winter, respectively. Diurnal variation profiles of OA changed significantly between seasons, due to seasonal variations in dominant source contributions and meteorological conditions. HOA showed a predominant morning peak corresponding mainly to traffic emissions. Photochemical production of LO-OOA was observed in the afternoons of summer whereas a relatively flat diurnal cycle of MO-OOA suggested that it was mainly formed on a regional scale. Backtrajectory and potential source contribution function (PSCF) analyses indicated that the most important source region of LO-OOA was located in the coastal areas to the south of Shanghai while MO-OOA had a dominant transport pathway in the northwest direction. Unlabelled Image • Real-time PM 1 measurements were performed at a rural site near Shanghai for 1 year. • Rolling-window PMF algorithm was applied to examine OA sources. • Nitrate increased evidently as a function of PM 1 in all seasons. • OA accounted for the largest part of PM 1 with little seasonal variation. • The coastal area south to Shanghai was an important regional OA source in summer. [ABSTRACT FROM AUTHOR]

Regarding the continuous worsening of tropospheric ozone pollution, the scenario in Shanghai is a microcosm of the entire China. Understanding the ozone formation regimes (OFRs), their variations, and driving factors is a prerequisite for formulating effective ozone control strategies. Traditional OFR estimation by numerical model, which often involves sensitivity analysis on at least tens of scenarios, is labor-intensive and time-consuming; therefore, it is not appropriate to make OFR forecasts to guide ozone contingency control. In this study, by using a localized modeling system consisting of the Weather Research and Forecasting, Sparse Matrix Operator Kernel Emissions, and Community Multiscale Air Quality models and considering the latest emission inventory over the Yangtze River Delta of China, we discovered a strong connection between the variations of large-scale circulation (LSC) and OFRs over Shanghai in July 2017, thereby providing an alternative way to infer OFR. During the northward movement of Western Pacific Subtropical High from South China Sea, the wind field over Shanghai changed from weak westerly to moderate southwesterly and to one without a distinct direction. The local OFR shifted from anthropogenic volatile organic compounds (AVOCs)-limited to NO x -limited and ultimately to the transitional regime. Such a variation in OFR is essentially driven by the spatial heterogeneity of NO x and AVOC emissions in different directions of Shanghai, brought on by the wind under different LSC patterns. With the existing weather forecasting technology, the LSC patterns can be well-predicted 48–72 h in advance. Hence, we propose the adoption of a dynamic ozone control strategy for Shanghai with the priority control target on AVOC or NO x emission sources adjusted according to the LSC pattern and OFR forecasts in a forthcoming O 3 pollution episode. This would serve to maximize the peak ozone reduction under varying pollution conditions. Unlabelled Image • Great spatiotemporal variations of ozone formation regime (OFR) were discovered in Shanghai. • A clear linkage between variations of large-scale circulation (LSC) and OFR was evidenced. • LSC can serve as an indicator for OFR which highlights preferential control target on NO x or VOCs. • A LSC-based OFR forecast leaves enough time for dynamic adjustment of ozone control strategy. [ABSTRACT FROM AUTHOR]

Ground-level ozone (O3) pollution is still one of the priorities and challenges for air pollution control in the Yangtze River Delta (YRD) region of China. Understanding the relationship of O3 with its precursors and contributions of different sources in O3 formation is essential for the development of an O3 control strategy. This study analyzed O3 sensitivity to its precursors using a box model based on online observations of O3, non-methane hydrocarbons (NMHCs), nitrogen oxides (NOx), and carbon monoxide (CO) at an urban site and a suburban site in Shanghai in July 2017. Anthropogenic sources of NMHCs were identified using the positive matrix factorization (PMF) receptor model, and then contributions of different sources in O3 formation were estimated by the observation-based model (OBM). The relative incremental reactivity (RIR) values calculated by the OBM suggest that O3 formation at the urban site was in the NMHC-limited regime, while O3 formation at the suburban site tended between the transition regime and the NMHC-limited regime. Vehicular emission and liquefied petrochemical gas (LPG) use or aged air mass were found to be the two largest contributors at the urban and suburban sites in July, followed by paint and solvent use, and the petrochemical industry. However, from the perspective of O3 formation, vehicular emission and paint and solvent use were the largest two contributors at two sites due to the higher RIR values for paint and solvent use. In addition, the influence of transport on O3 sensitivity was identified by comparing O3 sensitivity at the suburban site across two days with different air mass paths. The result revealed that O3 formation in Shanghai is not only related to local emissions but also influenced by emissions from neighboring provinces. These findings on O3–NMHC–NOX sensitivity, contributions of different sources in O3 formation, and influence of transport could be useful for O3 pollution control in the YRD region. Nevertheless, more quantitative analyses on transport and further evaluation of the uncertainty of the OBM are still needed in future. [ABSTRACT FROM AUTHOR]