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To combat urban challenges such as air pollution stemming from excessive vehicle use, policy makers have adopted various driving restriction policies (DRPs) worldwide. Although previous studies have extensively justified the effects of citywide DRPs on air quality, little attention has been paid to urban core-focused license-plate-based DRPs (UCLDRPs), which have gained increasing popularity among major cities. To bridge this gap, we carried out an empirical evaluation of the short-run effectiveness of Shanghai's UCLDRPs in improving air quality using difference-in-differences (DID) modeling approaches on high-frequency air quality data. The results show that UCLDRPs did not lead to any reduction of air pollutants including NO 2 , PM 2.5 , and PM 10 during peak hours (the restricted time window) in the inner ring area (the restricted area), while contributing to a 14% increase in the concentration of CO. Moreover, the air quality of surrounding zones (the 5 km buffer area) got worse as the concentration of CO and PM 10 raised by 16% and 8% respectively. Results also justified the temporal-spatial spillover effects in the dynamics: the concentrations of CO and PM 10 got increased by 10%-20% in the 5 km buffer area within time periods right before or after the restricted time windows. [ABSTRACT FROM AUTHOR]

Typhoons could influence air quality via multiple chemical and physical process and has attracted much scientific attention. A typical typhoon, In-Fa, passed through Yangtze River Delta (YRD) and Jing-Jin-Ji (JJJ) after it made a landfall in China. Under such influences, two city clusters both experienced high ozone (O 3) concentrations, with JJJ about 5 days earlier than YRD. Data from several environmental monitoring sites and three regional sites indicated that cross-regional transport and biogenic emissions both played an important role in O 3 formation. During the typhoon process, O 3 precursors were first transported from YRD and its surrounding areas to JJJ due to the summer monsoon. After that, air masses from northern China returned to YRD due to the peripheral winds of the typhoon. High O 3 was concentrated in downwind regions, causing fast secondary formation. The peripheral winds and downdrafts of typhoon led to high temperature and stagnant weather, favorable for biogenic emissions. Observed isoprene concentration was doubled. The ratio of isoprene to VOCs also increased by around 5%. The modeling results showed the contribution of BVOCs to O 3 could reach 10 ppb in JJJ when the typhoon made its landfall in YRD. When the typhoon moved to JJJ, the cross-transport of air masses from northern China to YRD contributed half of biogenic-emission-related O 3. Our research extends the knowledge into the importance of biogenic emissions to O 3 and cross-regional transport during a typhoon process. • High O 3 concentrations occurred in two city clusters, JJJ and YRD, during a typhoon process. • Cross-regional transport connected pollutants and precursors in two city clusters. • Isoprene was enhanced in peripheral areas as the typhoon moved, contributing to O 3 in downwind areas. [ABSTRACT FROM AUTHOR]

Atmospheric new particle formation (NPF) is an important global phenomenon that is nevertheless sensitive to ambient conditions. According to both observation and theoretical arguments, NPF usually requires a relatively high sulfuric acid (H2SO4) concentration to promote the formation of new particles and a low preexisting aerosol loading to minimize the sink of new particles. We investigated NPF in Shanghai and were able to observe both precursor vapors (H2SO4) and initial clusters at a molecular level in a megacity. High NPF rates were observed to coincide with several familiar markers suggestive of H2SO4–dimethylamine (DMA)– water (H2O) nucleation, including sulfuric acid dimers and H2SO4-DMA clusters. In a cluster kinetics simulation, the observed concentration of sulfuric acid was high enough to explain the particle growth to ~3 nanometers under the very high condensation sink, whereas the subsequent higher growth rate beyond this size is believed to result from the added contribution of condensing organic species. These findings will help in understanding urban NPF and its air quality and climate effects, as well as in formulating policies to mitigate secondary particle formation in China. [ABSTRACT FROM AUTHOR]

A lightweight unmanned aerial vehicle (UAV) and a tethered balloon platform were jointly used to investigate three-dimensional distributions of ozone and PM2.5 concentrations within the lower troposphere (1000 m) at a localized coastal area in Shanghai, China. Eight tethered balloon soundings and three UAV flights were conducted on May 25, 2016. Generalized additive models (GAMs) were used to quantitatively describe the relationships between air pollutants and other obtained parameters. Field observations showed that large variations were captured both in the vertical and horizontal distributions of ozone and PM2.5 concentrations. Significant stratified layers of ozone and PM2.5 concentrations as well as wind directions were observed throughout the day. Estimated bulk Richardson numbers indicate that the vertical mixing of air masses within the lower troposphere were heavily suppressed throughout the day, leading to much higher concentrations of ozone and PM2.5 in the planetary boundary layer (PBL). The NO and NO2 concentrations in the experimental field were much lower than that in the urban area of Shanghai and demonstrated totally different vertical distribution patterns from that of ozone and PM2.5. This indicates that aged air masses of different sources were transported to the experimental field at different heights. Results derived from the GAMs showed that the aggregate impact of the selected variables for the vertical variations can explain 94.3% of the variance in ozone and 94.5% in PM2.5. Air temperature, relative humidity and atmospheric pressure had the strongest effects on the variations of ozone and PM2.5. As for the horizontal variations, the GAMs can explain 56.3% of the variance in ozone and 57.6% in PM2.5. The strongest effect on ozone was related to air temperature, while PM2.5 was related to relative humidity. The output of GAMs also implied that fine aerosol particles were in the stage of growth in the experimental field, which is different from ozone (aged air parcels of ozone). Geographical parameters influenced the horizontal variations of ozone and PM2.5 concentrations by changing underlying surface types. The differences of thermodynamic properties between land and sea resulted in quick changes of PBL height, air temperature and dew point over the coastal area, which was linked to the extent of vertical mixing at different locations. The results of GAMs can be used to analyze the sources and formation mechanisms of ozone and PM2.5 pollutions at a localized area. [ABSTRACT FROM AUTHOR]

The accuracy of atmospheric numerical model is important for the prediction of urban air pollution. This study investigated and quantified the uncertainties of meteorological and air quality model during multi-levels air pollution periods. We simulated the air quality of megacity Shanghai, China with WRF/CMAQ (Weather Research and Forecasting model and Community Multiscale Air Quality model) at both non-pollution and heavy-pollution episodes in 2012. The weather prediction model failed to reproduce the surface temperature and wind speed in condition of high aerosol loading. The accuracy of the air quality model showed a clear dropping tendency from good air quality conditions to heavily polluted episodes. The absolute model bias increased significantly from light air pollution to heavy air pollution for SO (from 2 to 14%) and for PM (from 1 to 33%) in both urban and suburban sites, for CO in urban sites (from 8 to 48%) and for NO in suburban sites (from 1 to 58%). A test of applying the Urban Canopy Model scheme to the WRF model showed fairly good improvement on predicting the meteorology field, but less significant effect on the air pollutants (6% for SO and 19% for NO decease in model bias found only in urban sites). This study gave clear evidence to the sensitivities of the model performance on the air pollution levels. It is suggested to consider this impact as a source for model bias in the model assessment and make improvement in the model development in the future. [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]

A tethered balloon-based measurement campaign of particle number concentration (PNC) and particle number size distribution (PNSD) in the size range of 15.7–661.2 nm was conducted within the lower troposphere of 1000 m in Shanghai, a Chinese megacity, during December of 2015. The meteorological conditions, PNC, and PNSD were synchronously measured at the ground-based station as well as by the tethered balloon. On ground level, the 88.2 nm particles were found to have the highest PNC. The Pearson correlation analysis based on the ground level data showed NO 2 had a strong correlation with PNC. The synchronous measurement of PNC and PNSD at the ground station and on the tethered balloon showed that the 15.7–200 nm particles had higher PNC on ground level, but the PNC of 200–661.2 nm particles was higher at 400 m. One haze event (Dec 22nd-Dec 23rd) was selected for detailed discussion on the variation of vertical profiles of PNSD and PNC. The vertical distribution of characteristics of PNC and PNSD were observed and compared. Results indicated that the highest MaxDm (the diameter with the highest PNC) during those three launches all appeared at a high altitude, usually above 300 m. Compared to the clean days, the relatively bigger MaxDm at each height in the haze days also indicated regional transport of pollutants might contribute to more to that haze event. [ABSTRACT FROM AUTHOR]

China has > 400 ports, is home to 7 of 10 biggest ports in the world and its waterway infrastructure construction has been accelerating over the past years. But the increasing number of ports and ships means increasing emissions, and in turn, increasing impact on local and regional air pollution. This paper presents an overview of the broad field of ship emissions in China and their atmospheric impacts, including topics of ship engine emissions and control, ship emission factors and their measurements, developing of ship emission inventories, shipping and port emissions of the main shipping areas in China, and quantitative contribution of shipping emissions to the local and regional air pollution. There have been an increasing number of studies published on all the above aspects, yet, this review identified some critical research gaps, filling of which is necessary for better control of ship emissions, and for lowering their impacts. In particular, there are very few studies on inland ports and river ships, and there are few national scale ship emission inventories available for China. While advanced method to estimate ship emission based on ship AIS activities makes it now possible to develop high spatial- and temporal-resolution emission inventories, the ship emission factors used in Chinese studies have been based mainly on foreign measurements. Further, the contribution of ship emissions to air pollution in coastal cities, the dispersion of pollution plumes emitted by ships, or the chemical evolution process along the transmission path, have so far not been systematically studied in China. [ABSTRACT FROM AUTHOR]

• We build a satellite-driven machine learning model to predict particulate sulfate concentrations across China using atmospheric big data from 2005 to 2018. • Our daily and monthly mean sulfate predictions agree well with ground observations with an out-of-bag cross-validation R2 of 0.68 and 0.93, respectively. • Population-weighted national annual mean sulfate concertation was relatively stable before the enforcement of the Air Pollution Prevention and Control Action Plan in 2013, then significantly decreased by 28.7% from 2013 to 2018. • The national annual mean total non-accidental and cardiopulmonary deaths attributed to sulfate decreased by 40.7% and 42.3% from 2013 to 2018, respectively. Ambient fine particulate matter (PM 2.5) pollution is a major environmental and public health challenge in China. In the recent decade, the PM 2.5 level has decreased mainly driven by reductions in particulate sulfate as a result of large-scale desulfurization efforts in coal-fired power plants and industrial facilities. Emerging evidence also points to the differential toxicity of particulate sulfate affecting human health. However, estimating the long-term spatiotemporal trend of sulfate is difficult because a ground monitoring network of PM 2.5 constituents has not been established in China. Spaceborne sensors such as the Multi-angle Imaging SpectroRadiometer (MISR) instrument can provide complementary information on aerosol size and type. With the help of state-of-the-art machine learning techniques, we developed a sulfate prediction model under support from available ground measurements, MISR-retrieved aerosol microphysical properties, and atmospheric reanalysis data at a spatial resolution of 0.1°. Our sulfate model performed well with an out-of-bag cross-validation R2 of 0.68 at the daily level and 0.93 at the monthly level. We found that the national mean population-weighted sulfate concentration was relatively stable before the Air Pollution Prevention and Control Action Plan was enforced in 2013, ranging from 10.4 to 11.5 µg m−3. But the sulfate level dramatically decreased to 7.7 µg m−3 in 2018, with a change rate of −28.7 % from 2013 to 2018. Correspondingly, the annual mean total non-accidental and cardiopulmonary deaths attributed to sulfate decreased by 40.7 % and 42.3 %, respectively. The long-term, full-coverage sulfate level estimates will support future studies on evaluating air quality policies and understanding the adverse health effect of particulate sulfate. [ABSTRACT FROM AUTHOR]

Since the Action Plan for Air Pollution Prevention and Control (the Action Plan) was implemented at the end of 2013, the ambient air quality in China is significantly improved. However, PM 2.5 (particles with diameter ≤ 2.5 μm) levels in some cities still exhibit clear interannual oscillations. For example, the annual mean PM 2.5 levels in Shanghai decreased by 16.1% in 2014, while increased by 2.2% in 2015 according to year-on-year comparisons. To better understand the corresponding causes, the obliquely rotated T-mode principal component analysis (PCA) method and WRF-Chem model are jointly employed in this study. Results show that the west wind frequency and the accumulative wind (< 1.8 m/s) duration are the key indicators affecting local PM 2.5 transport and dispersion significantly. Moreover, four typical synoptic patterns conductive to PM 2.5 pollution are illustrated as mid-ward path cold (CM), eastward path cold (CE), L-share high (GL) and near high center (GC), in which GL is the most adverse circulation pattern. The year-on-year changes of meteorology have positive effects on PM 2.5 year-on-year variations. The significant decline of PM 2.5 levels in 2014 compared with those in 2013, as well as the obvious increase in 2015 compared with 2014, both well correspond to year-on-year variations of meteorological indicators. Model results present that PM 2.5 interannual variations result from the changes of meteorology during 2013 to 2015, are consistent with measured oscillations. By comparing measured and modeled PM 2.5 year-on-year variabilities, a greater PM 2.5 decreasing at 9.4% is estimated under favorable meteorological conditions, while a less increasing at 6% under unfavorable meteorological conditions due to emission reductions, indicating the initial improvement has been achieved by the Action Plan. Otherwise, since the current Action Plan has difficulties in completely offsetting the PM 2.5 rise attributed to the adverse weather, more stringent program should be drawn up for unfavorable meteorological conditions. [ABSTRACT FROM AUTHOR]

Whether ambient air pollution is associated with childhood atopic eczema is controversial. In this paper, we selected 3358 preschool children who had not altered residences since pregnancy from a cross-sectional study during 2011–2012 in Shanghai, China, and obtained parent-reported data regarding childhood atopic eczema using an improved ISAAC questionnaire. We recorded daily concentrations of SO 2 , NO 2 , and PM 10 throughout the child's lifetime (2006–2012), and calculated period-averaged concentrations for each district where the child lived to represent the child's exposure levels of these pollutants during different periods. In the multiple logistic regression analyses adjusted for potential confounders as well as for the other pollutants in the same periods, childhood atopic eczema was significantly associated with increments of NO 2 in the approximate interquartile range (20 μg/m 3 ) during gestational period (adjusted OR, 95% CI for eczema lifetime-ever: 1.80, 1.29–2.49; for eczema in the year prior to the survey: 2.32, 1.57–3.43) and during the first year of life (2.00, 1.40–2.84; 2.16, 1.43–3.28). Exposure to elevated NO 2 in the first two years, three years and total lifetime, as well as exposure to mixtures containing NO 2 in each of these periods, were consistently associated with increased likelihood of childhood eczema. The highest odds ratios were found between exposure to a mixture of SO 2 and NO 2 during total lifetime (increment: 35 μg/m 3 ) and childhood eczema (adjusted OR, 95% CI: 2.80, 1.75–4.48; 3.50, 1.98–6.19). No significant associations were found between childhood eczema and ambient SO 2 and PM 10 individually or in mixtures. This study indicates that gestational and lifetime exposures to ambient NO 2 are risk factors for atopic eczema in childhood. Exposure to ambient SO 2 and PM 10 may enhance the effect of NO 2 exposure on childhood eczema. [ABSTRACT FROM AUTHOR]

During the Covid-19 outbreak, strict lockdown measures led to notable reductions in transportation-related emissions and significantly altered atmospheric pollution characteristics in urban and suburban areas. In this work, we compare comprehensive online measurements of PM 2.5 major components and organic molecular markers in a suburban location in Shanghai, China before lockdown (Dec. 28, 2019 to Jan. 23, 2020) and during lockdown (Jan. 24 to Feb. 9, 2020). The NO x levels declined sharply by 59% from 44 to 18 ppb during the lockdown, while O 3 rose two times higher to 42 ppb. The PM 2.5 level dropped from 64 to 49 μg m−3 (−24%). The major components all showed reductions, with the reduction of nitrate most prominent at −58%, followed by organics at −19%, and sulfate at −17%. Positive matrix factorization analysis identifies fourteen source factors, including nine primary sources and five secondary sources. The secondary sources consist of sulfate-rich factor, nitrate-rich factor, and three secondary organic aerosol (SOA) factors, with SOA_I being anthropogenic SOA, SOA_II associated with later generation products of organic oxidation, and SOA_III being biogenic SOA. The combined secondary sources contributed to 69% and 63% (40 and 22 μg m−3) of PM 2.5 before and during lockdown, respectively, among which the reductions in the nitrate-rich (−55%) factor was the most prominent. Among primary sources, large reductions (>80%) were observed in contributions from industrial, cooking, and vehicle emissions. Unlike some studies reporting that the restriction during the Covid-19 resulted in enhanced secondary sulfate and SOA formation, we observed decreases in both secondary inorganic and SOA formation despite the overall elevated oxidizing capacity in the suburban site. Our results indicate that the formation change in secondary inorganic and organic compounds in response to substantial reductions in urban primary precursors are different for urban and suburban environments. [Display omitted] • Covid lockdown lowered PM 2.5 and NO x while increased O 3 levels in suburban Shanghai. • Nitrate was the most prominent contributor to PM 2.5 reduction during lockdown. • Lockdown led to reduced PM 2.5 contributions by 8 primary and 5 secondary sources. • Contribution percent drop from industrial and vehicular sources were as high as 87%. • Lockdown effects on SOA formation likely differ in suburban and urban environments. [ABSTRACT FROM AUTHOR]

• An online method with a three-hour time resolution was developed to monitor atmospheric intermediate organic compounds (IVOCs). • Method can monitor both targeted alkanes and PAHS as well as unspeciated complex mixture (UCM). • Method can provide high time resolution IVOCs data needed for SOA formation, source apportionment or other studies. As one of important precursors of secondary organic aerosol (SOA), intermediate volatile organic compounds (IVOCs) have attracted much attention in recent years. Most of the previous studies however largely focused on characteristics of IVOCs from different emission sources, while data from field observations to study their temporal variations was limited for lacking the sufficient time resolution monitoring data. In this study, an online thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) method was developed to generate monitor data with a three-hour time resolution for gaseous atmospheric IVOCs. The method used two multi-sorbent traps that alternated for conducting sample collection and sample analysis. Compounds of C 12 C 22 n-alkanes and 2–4 ring PAHs were chosen as surrogates to evaluate the performance of this method. Regression coefficients of external calibration curves were greater than 0.93 and 0.96 for all individual n-alkanes and PAHs, respectively. Average relative standard deviation (RSD) values among replicate samples spiked at 3 ng for each individual standard were 9% ± 5%. The detection limits of this method for individual n-alkanes and PAHs were 3.1–16.2 ng/m3 and 1.0–2.7 ng/m3, respectively. Atmospheric IVOCs were continuously monitored from September 28 to 30 and October 22 to November 9 in 2018, in an urban area of Shanghai. Besides targeted n-alkanes and PAHs, unspeciated complex mixtures (UCM) of IVOCs as well as total-IVOCs concentrations in the atmosphere were also determined. Measured concentrations and compositions of gaseous IVOCs in the atmosphere in this study were comparable to other similar studies. [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]

Both PM 2.5 and TSP over Yulin, a rural site near the Asian dust source region, were collected from 2007 to 2009. Characteristics, sources, and formation mechanisms of sulfate and nitrate were investigated. SO 4 2 − displayed a distinct seasonal variation with the highest average concentration observed in summer when SO 4 2 − accounted for an average of 14.1% and 13.7% of the PM 2.5 and PM coarse mass concentrations, respectively. Ambient temperature and relative humidity were two important factors influencing the formation processes of SO 4 2 − and NO 3 − . In summer, the high concentrations of SO 4 2 − in PM 2.5 were probably from the gas phase oxidation of SO 2 , while the low concentrations of NO 3 − in PM 2.5 were attributed to the high temperature that was not favorable for the formation of NH 4 NO 3 . In spring, autumn, and winter, SO 4 2 − and NO 3 − were significantly enhanced in those days with high relative humidity, implying that in-cloud/aqueous processing dominated the formations of SO 4 2 − and NO 3 − . Different from PM 2.5 in which NH 4 + acted as the dominant neutralizer for acids, alkaline species such as Ca 2 + and Mg 2 + played an important role in the formation of sulfate and nitrate salts in coarse particles throughout the whole year. During the dust event days, SO 4 2 − in coarse particles significantly increased, while black carbon and NO 3 − largely decreased, suggesting that the primary mineral dust could be one of the major sources of SO 4 2 − . By comparing the mass ratio of SO 4 2 − /3/S in the dust aerosols of Yulin with different dust source regions (i.e., Taklimakan Desert and Gobi Desert) and the application of air mass backward trajectory analysis, it was found the long-range transported dust from the Taklimakan Desert, which was rich in primary sulfate due to its paleo-ocean characteristics, was a non-negligible source of SO 4 2 − over Yulin. In spring and winter, the prevailing northerlies and northwesterlies promoted chemical interaction between alkaline mineral dust and acid gaseous precursors from local and/or regional emissions. While in summer, regional transport facilitated by the southerlies and southeasterlies may contribute to the high secondary aerosol concentrations over Yulin. This study demonstrated that a considerable portion of aerosol over a Chinese rural area could be derived from complex chemical reactions via long-range/regional transport. [ABSTRACT FROM AUTHOR]

Joint field observations were conducted from October to November in 2011 to observe haze pollution in the Yangtze River Delta (YRD), China. Samples of particulate matter with diameter less than 2.5 μm (PM 2.5 ) and less than 10 μm (PM 10 ), gaseous pollutants and meteorology data were collected in five cities – Shanghai, Suzhou, Nanjing, Ningbo and Hangzhou – in the YRD. The chemical composition of PM 2.5 was analyzed and the light extinction resulting from each chemical species was calculated using the IMPROVE algorithm. A typical heavy haze episode was selected and the chemical mass balance (CMB) model was applied to identify the sources of PM 2.5 . The average PM 2.5 and PM 10 mass concentrations during the haze episode were 100 ± 24 μg/m 3 and 164 ± 19 μg/m 3 , respectively; visibility decreased to 1 km. Organic matter (OM), sulfate, nitrate, and ammonium were the dominant components of PM 2.5 , accounting for 33%, 19%, 17% and 11% of PM 2.5 mass, respectively. Sulfate, OM and nitrate had the highest impact on light extinction, contributing 30%, 28% and 19%, respectively. The source apportionment indicate that PM 2.5 is primarily from secondary pollutants and primary emissions from vehicles and biomass burning. A polluted air mass from north Jiangsu Province and stagnant meteorology further aggravated the haze pollution. The five cities had similar characteristics and pollution sources. [ABSTRACT FROM AUTHOR]

PM 2.5 with its major chemical components were measured and analyzed during a concurrent haze in Jan. 1–19, 2013 at three sites (Shanghai, Beijing, and Huaniao, a remote isle over the East China Sea) to probe the sources and formation process of such a severe haze over three typical regions in China. The mean PM 2.5 concentrations during the severely polluted days reached 180.8 μg m −3 , 299.2 μg m −3 , and 131.1 μg m −3 in Shanghai, Beijing, and the Huaniao Isle, respectively. The mass ratio of the sum of SO 4 2 − , NO 3 − , and NH 4 + to PM 2.5 were over 1/3 during the polluted days at all the three sites. Promoted gas-to-particle transformations from acidic SO 2 and NO x to SO 4 2 − and NO 3 − under high relative humidity conditions played a major role in the formation of this severe haze. Significant contribution of traffic emissions to the haze formation over China was suggested to be one of the major sources in triggering the heavy haze over China. Specifically, there was a more contribution from traffic in Shanghai than in Beijing as indicated by the higher NO 3 − / SO 4 2− ratio in Shanghai. In Beijing, the enhanced coal combustion for winter heating along with the traffic emission was suggested to be the major two sources of this haze episode. Typical pollution elements such as As, Cd, and Pb as well as Cl − and K + were substantially enhanced in the severely polluted days. Although the Huaniao Isle is located in the remote oceanic area as a background site, pollution elements, secondary ions, and K + all increased substantially during the polluted days. As visualized by the backward air mass trajectories associated with the potential source region identification technique, air masses that passed over Northern China and Yangtze River Delta evidently invaded the offshore areas of Eastern China. The ratios of As, Cd, Cu, Zn, and K + to Al at the Huaniao Isle were closer to those of Beijing rather than Shanghai, indicating that the marine aerosol over the East China Sea had been significantly polluted via the long-range transport of anthropogenic pollutants originating from Northern China. [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]

The source profiles of VOCs in the industry are closely related to the raw and auxiliary materials, process characteristics and waste gas treatment of the enterprise, as well as the number of VOCs that can be identified by analytical methods. In the process of industry transformation, it is necessary to update the source profiles. This study selects the coating industry as a case study as it is in a transitional stage and has high volatile organic compounds (VOCs) production and odor complaints. The VOCs emissions in seven coating enterprises in 2019 were studied using a broad-spectrum and high species identification rate analysis method to identify many new species of VOCs, which increased the total emissions by 6.4 times compared with previous studies. A total of 26 new types of VOCs pollutants were identified, especially the number of oxygenated VOCs species increased by 3.1 times, and proved that butyl acetate replaced the benzene series to become was the new dominant species in the coating industry. And the average ozone formation potential (OFP) of coating industry was 2.6 times the measurement result of the classic method of PAMs and TO15. The source reactivity increased on average by 366.7%. [Display omitted] • The content of 30% new species discovered in coatings industry increased by 50%. • OVOC in sources profile accounted for 99.7%, and acetate is dominant odor pollutant. • Redefined VOCs dominant species, OFP and SR have multiplied in coatings industry. • New acetate/benzene series ratio determine the production type in coating industry. [ABSTRACT FROM AUTHOR]

Source apportionment of fine particulate matter (PM 2.5) components is crucial for air pollution control. Prediction accuracies by the chemical transport model (CTM) significantly affect source apportionment results. Many efforts have been made to improve source apportionment results based on the CTM using mathematical algorithms, but the reasons for uncertainties in source apportionment results are less concerned. Here, an integrated optimization methodology is developed to quantify deviations from emission inventory and chemical mechanism in the model for improving prediction and source apportionment accuracies. Emission deviations of primary aerosols and gaseous pollutants are firstly calculated by an optimization algorithm with observation and receptor model constraints. Emission inventory is then adjusted for a new CTM simulation. Deviations from chemical mechanism for secondary conversions are evaluated by biases between observations and new predictions. Source apportionment results are adjusted according to both emission and chemical mechanism deviations. A winter month in 2016 at the Qingpu supersite in eastern China is selected as a case study. Results show that our integrated optimization methodology can successfully adjust emissions to pull original predictions towards observations. Total deviations of emissions for elemental carbon, organic carbon, primary sulfate, primary nitrate, primary ammonium, sulfur dioxide (SO 2), nitrogen oxides (NO x) and ammonia (NH 3) are estimated +59.6%, +95.9%, +72.9%, +82.2%, +75.9%, −6.4%, +67.6% and −17.6%, respectively. Also, major directions of deviations from chemical mechanisms can be captured. Deviations from SO 2 to secondary sulfate, nitrogen dioxide (NO 2) to secondary nitrate and NH 3 to secondary ammonium conversions are estimated −77.3%, +27.1% and −38.8%, respectively. Consequently, source apportionment results are significantly improved. This developed methodology provides an efficient way to quantify deviations from emissions and chemical mechanisms to improve source apportionment for air pollution management. [Display omitted] • An integrated methodology is developed to improve source apportionment results of CTM. • Deviations of regional emission inventory can be quantified through the methodology. • The methodology was also able to adjust the bias of implemented chemical mechanisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Detecting O 3 -precursor sensitivity (OPS) is key for building O 3 control strategies. • We analyze the relationship between the HO 2 /OH indicator and OPS in the YRD. • WRF-CAMx and ensemble diagnostic tools reveal the mechanisms of this relationship. • HO 2 /OH can be used to identify OPS and quantify O 3 sensitivity to its precursors. Continued exacerbation of ozone (O 3) pollution in China has driven the urgent need for an emission control strategy that efficiently reduces O 3 levels. Determining O 3 precursor sensitivity (OPS) and its driving factors is a prerequisite for formulating effective O 3 control strategies. In this study, we proposed an atmospheric oxidative capacity-based indicator, HO 2 /OH, and demonstrated its effectiveness in indicating OPS over the Yangtze River Delta (YRD) of China by applying a localized comprehensive air quality model with extensions (CAMx) coupled with the Weather Research and Forecasting (WRF) model. A strong correlation was discovered between HO 2 /OH and OPS, and HO 2 /OH showed the best performance in separating NO x - and VOC-limited regimes in comparison with other commonly used indicators. A comprehensive analysis with ensemble diagnostic tools revealed the spatial heterogeneity of NO x and VOC emissions and the impact of regional transport controlling the relationship between OPS variations and the HO 2 /OH indicator over the YRD. The process analysis results show that days with higher contributions from horizontal advection favored OPS transitions in Shanghai, Nanjing, Hefei, Suzhou, and Wuhu, while vertical advection caused OPS transitions in Hangzhou and Ningbo. O 3 source apportionment technology analysis indicated that the regional contributions from Zhejiang and Jiangsu/Anhui corresponded well to the NO x -limited and VOC-limited regimes, respectively. Our results provide a better understanding of the underlying mechanisms of the relationship between OPS and the HO 2 /OH indicator and can help guide contingency control measures for O 3 despiking over the YRD and other photochemically active regions worldwide. [ABSTRACT FROM AUTHOR]

Abstract: A multi-year (2004–2008) study of horizontal visibility and factors controlling its variations was conducted in Shanghai. The seasonal average visibility in spring, summer, autumn, and winter was 7.7 km, 8.4 km, 8.1 km, and 6.5 km, respectively, significantly exceeding the haze criteria of 10 km throughout all four seasons. Although SO2 and NO2 concentrations gradually shifted to lower levels on an annual basis, no distinct improvement of the annual mean visibility was noticed. Via a grouping method, it was found that the water soluble ions and black carbon were the major contributors to haze formation while the role of mineral aerosol was negligible. Of the ions, SO4 2−, NO3 −, NH4 +, K+, and C2O4 2− were most associated with the formation of heavy haze. SO4 2− and NO3 − were both found to have significant decreasing trends with annual decreasing rates of 0.96 and 0.56 μg/m3/yr, respectively. Conversely, NH4 + showed a significant increasing trend with the annual increasing rate of 0.52 μg/m3/yr. Based on a quantitative correlation analysis, the roles of NH4 + and Ca2+ on the acids neutralization were almost equivalent in the earlier years of 2004–2005. While the role of Ca2+ had tremendously dropped to less than 23% in the later years of 2006–2008. Intense control measures on the emissions of construction works and roadside dust were the main driving force for the evident decreasing trend of annual Ca2+ concentrations. This study found that the gradual replacement of CaSO4 and Ca(NO3)2 by (NH4)2SO4 and NH4NO3 in aerosol was the major cause of no improvement of the visibility impairment in Shanghai during recent years. [Copyright &y& Elsevier]

[Display omitted] • OBM and EBM can produce significant discrepancies in ozone-precursor sensitivity. • Input data, simulation period, domain size and other factors lead to OPS discrepancies. • Combining OBM and EBM improved OPS accuracy markedly in Shanghai, China. • Our methodology has clear applicability to other photochemically active regions worldwide. Ground-level O 3 pollution has been continuously worsening in China despite gradual improvement in other major pollutant levels. Understanding the sensitivity of O 3 production to its precursors (OPS) is a prerequisite for formulating effective O 3 control measures, but this has been hampered by significant discrepancies in OPS produced by traditional identification approaches using observation-based models (OBM) and emission-based models (EBM). In this study, by applying OBM and EBM in parallel within a month having significant O 3 pollution in Shanghai, China, we demonstrated that a lack of carbonyl input, overestimation in NO 2 monitoring data, and differences in simulation period and emission reduction area were the core factors leading to OPS discrepancies, and that a reliable OPS cannot be obtained unless these factors are reconciled. By collectively addressing these factors, the number of days with a consistent OPS from both models increased from 6–7 to 20–21 in a month, and the R value defined to quantify the discrepancy decreased by ∼55%. The contributions of these factors to OPS discrepancy differed greatly in urban and suburban settings, mainly caused by differences in pollutant emission and transport characteristics. Overall, OPS identified solely by OBM or EBM is associated with great uncertainty, while reliable OPS estimation can be achieved by a collective application of OBM and EBM with consensus on the above factors. The method demonstrated here could be applied to other photo-chemically active regions worldwide as part of efforts to address ozone pollution. [ABSTRACT FROM AUTHOR]

High levels of formaldehyde (HCHO) have been frequently detected during spring-summertime in the densely populated and rapidly developing Yangtze River Delta (YRD) region, China. However, the detailed formation mechanism of HCHO pollution remains unclear. Based on a comprehensive field campaign conducted at Dianshan Lake (DSL) station, a supersite located in the suburban YRD region, the influence of VOCs on HCHO formation, as well as the role of HCHO in the RO x radical recycling was analyzed. Results indicate that the maximum atmospheric oxidation capability (AOC) during HCHO pollution episodes varies from 0.65 × 108 to 1.29 × 108 molecules cm−3 s−1, and high AOC value favors the secondary formation of HCHO. Meanwhile, the photolysis of HCHO accounts for 21.2% of the primary RO x , suggesting the significant role of HCHO in RO x recycling. Isoprene was identified to be a key precursor of HCHO, and the RO from isoprene contributed ∼15% to the total daytime HCHO production rate (P HCHO). Sensitivity analysis reveal that when isoprene, xylene or ethylene was cut off, the simulated HCHO concentration could be reduced by 50%, 15%, or 13%, respectively. Based on the isopleth of HCHO under different VOCs/NO x reduction ratios, we found that the VOCs/NO x reduction ratio should be above 1.03 to mitigate the HCHO pollution. Reactive VOCs (such as isoprene, xylene and alkenes) should be reduced to suppress HCHO pollution in the YRD region. [Display omitted] • Photolysis of HCHO is a significant source of RO x. • Isoprene was found as a key precursor of HCHO. • More active VOCs should be reduced to mitigate HCHO pollution in the YRD region. [ABSTRACT FROM AUTHOR]

Abstract: To characterize the air pollutants in Shanghai Port and identify the contribution from ship traffic emission, field measurements have been conducted in 2011. The trace gases SO2, NO2 and O3 were monitored and aerosol samples of TSP, PM2.5 and size-segregated particles were collected in a working area of Shanghai Port. Elements including V, Ni, Al, Fe, Si, Ca, Na, Mg, Mn, Zn, Co, Cr in aerosol samples and heavy fuel oil samples were analyzed. The results revealed that average hourly SO2 and NO2 concentrations in Shanghai Port were respectively 29.4 and 63.7 μg m−3, average daily concentrations of TSP and PM2.5 were 114.39 and 62.60 μg m−3, comparable with the ones in Shanghai land area. Ni and V were found enriched in fine particles with averaged concentrations of 80.0 and 14.8 ng m−3 in PM2.5 respectively. Also ratio of V/Ni in aerosol under summertime airflow was 3.4, very close to the ratio of averaged V and Ni content in international heavy fuel oils used in Shanghai Port. The backward trajectory analysis further revealed that SO2, NO2, and V under coastal airflows were mainly from ship traffic emission. The mean concentration of V was 15.84 ng m−3 under hybrid coastal airflows, much higher than that of 9.84 ng m−3 under continental airflows. Furthermore, V was found to be highly correlated with ship fluxes, and was selected as an indicator of ship traffic emission in Shanghai. The estimated primary PM2.5 contribution from ship traffic ranged from 0.63 to 3.58 μg m−3, with an average of 1.96 μg m−3. This PM2.5 fraction accounted for 4.23% of the total PM2.5 in an average level, and reached to a maximum of 12.8%. Furthermore, there could be 64% of primary PM2.5 contributed by ships in Shanghai Port transported to inland region. Our results suggest that ship traffic has a non-negligible contribution on ambient levels of fine particles and secondary contribution of SO2 and NO2 emitted by ships need to be estimated on local and regional scale in future. [Copyright &y& Elsevier]

Odor pollutants from a landfill can have serious impacts on the surrounding environment and nearby residents. Moreover, the variety and complexity of volatile organic compounds (VOCs) along with the landfill odor makes sampling and identifying compounds challenging. In this study, the authors monitored municipal solid waste (MSW)-related areas, sludge-related areas and waste coverage with the most malodorous compounds. In terms of all 120 VOCs, 67 malodorous VOCs with significant variations were categorized into six classes of compounds under all test conditions. Among the concentration characteristics, Site B concentrations were the highest. For the odor index (OI), the OI values of Site B were higher than those on other sites. The organic sulfides, organic acids and amine were the major malodorous pollutants emitted from landfill and influenced the residential area. Through a coefficient of divergence analysis, the CD jk values of Sites A (0.66) and B (0.69) were lower than others, indicating the effects of odor emission on the surrounding residential area were slightly more severe than on the other sites because of the meteorological condition during the study period. The results of this study can provide essential information to enhance understanding the actual odor emission intensity and characteristics of landfill and the migration, transportation and influence of odorant emissions on the working surface of the landfill. [Display omitted] • Various VOCs from a typical landfill were monitored and distinguished. • The most abundant odorous contributors to total odors were calculated. • Malodorous landfill gases had a slightly effect on residential areas. [ABSTRACT FROM AUTHOR]

Scarce evidence is available on the health effects of various chemical constituents of PM 2.5 on hospital visits in China. To examine the short-term associations between a wide range of PM 2.5 constituents and hospital outpatient and emergency room visits in Shanghai. We obtained daily concentrations of PM 2.5 total mass, organic carbon (OC), elemental carbon (EC), eight water-soluble ions and thirteen elemental constituents between January 1, 2014 and December 31, 2015. We analyzed the data using over dispersed generalized additive models with Poisson regression. Single-constituent, PM 2.5 -adjusted and constituent-residual models were built respectively to assess the associations. Exposure-response curves for the PM 2.5 constituents with robust effects were graphed. The average daily mean PM 2.5 concentration was 63.3 μg/m3 in Shanghai during the study period. An interquartile range (IQR) increase in PM 2.5 was associated with a 2.57% (95% confidence interval [CI]: 1.28%, 3.87%) increase in outpatient visits, and a 3.60% (95% CI: 2.16%, 5.03%) increase in emergency room visits. We observed robust and positive associations between Mg2+, Ca2+, six elemental components (Ca, Mn, Fe, Zn, Ga and Se) and outpatient visits. OC, EC, Cl−, Mg2+, Ca2+ and ten elemental components (Ca, Cr, Mn, Fe, Zn, Ga, As, Se, Pb, and Ni) were significantly and positively associated with emergency room visits. The exposure-response relationships were positive and generally linear for the above constituents. This time-series study in Shanghai demonstrated significant associations between various carbonaceous, water-soluble and elemental constituents of PM 2.5 and hospital visits, providing evidence for source-specific control of particulate air pollution. [Display omitted] • Scarce evidence on the health effects of PM 2.5 constituents on hospital visits. • Mg2+, Ca2+ and six elemental constituents linked with outpatient visits. • Carbonaceous and ten elemental constituents associated with emergency room visits. • Positive and linear exposure-response relationship curves for these constituents. [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]

To investigate the potential public health impact of ambient air pollution under various energy scenarios in Shanghai, we estimated the air pollution exposure level of the general population under various planned energy scenarios, and assessed the potential public health impact using the concentration–response functions derived from available epidemiologic studies. The results show that ambient air pollution in relation to various energy scenarios could have significant impact on the health status of Shanghai residents. Compared with base case scenario, implementation of various energy scenarios could prevent 608–5144 and 1189–10,462 PM10-related avoidable deaths (mid-value) in 2010 and 2020, respectively; and it could also decrease substantial cases of relevant diseases. These findings illustrate that an effective energy and environmental policy will play an active role in reduction of air pollutant emissions, improvement of air quality, and public health. [Copyright &y& Elsevier]

The accurate source tracing of volatile organic compounds (VOCs) in complicated source environments is challenging to perform, as similar pollutants may be emitted from different chemical processes. An emission profile-based source tracing method, based on comparing similarities between source profiles and ambient air profiles, was evaluated, and was found to improve the tracing efficiency. Emission profiles were acquired from a typical chemical industrial park in the Yangtze River Delta, China. A total of 30 process-based emission profiles comprising 107 VOC species were investigated and similarities among them were calculated. This analysis demonstrated that the similarities between emissions from various chemical processes are universal. Source tracing was then conducted for six air pollution episodes, based on the emission profile-based source tracing method combined with wind speed and direction data. The results showed that the proposed approach represents an efficient method for source tracing. This study enriches the database of source profiles for petroleum-related industries. The emission profiles from references and the air pollution episodes augment the emission profile database, especially under abnormal emission conditions. The database will more effectively serve future source-tracing cases, creating a virtuous circle that improves source tracing efficiency. Unlabelled Image • Emission profiles were acquired from a typical chemical industrial park. • The similarities between profiles were quantified and compared. • Emissions from particular chemical processes were proven to be similar. • Source tracing was performed using an emission profile-based method. • The database of source profiles for petroleum-related industries was augmented. [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]

• PID-type sensor have superiority over other VOC sensor types and the potential to provide information in networks. • Pollution alarm and pollution distribution analysis are two feasible and highly dependable applications in an industrial area. • Humidity physical control and algorithm modification are necessary in long-term high humidity climates. With low-cost sensors getting more attention in network monitoring, whether volatile organic compounds (VOCs) sensors are easily serviceable in ambient air monitoring is debatable. Evaluations of performance are necessary to provide a comprehensive understanding of commercially available sensor devices at present. In this paper, 17 photo-ionization detectors (PID) based VOC sensor devices have been evaluated through both laboratory and field tests, sensor were primarily from Alphasense and Baseline. The results exhibited the average level of all participating devices and the influence of the humidity on the results has been discussed in detail. Good linearity (R2>0.93), repeatability (<10 %), and quick response time (T 80 <1 min) over the target gases in the laboratory have been revealed. The average of intra-best two devices correlation (R) is 0.68 and correlations (R2) with reference data are 0.5∼0.8 for one third of devices in the field tests. However, the accuracy is not as robust as flame ionization detector (FID). In summary, PID-type VOC sensor devices are capable of providing useful information in some application scenarios. The features of quick response and good accuracy at high concentrations are recognized as pollution indicators. Devices with good consistency, correlation and stability are appropriate for investigating the regional VOCs pollution distribution using network monitoring. [ABSTRACT FROM AUTHOR]

China's lockdown to control COVID-19 brought significant declines in air pollutant emissions, but haze was still a serious problem in North China Plain (NCP) during late-January to mid-February of 2020. We seek the potential causes for the poor air quality in NCP combining satellite data, ground measurements and model analyses. Efforts to constrain COVID-19 result in a drop-off of primary gaseous pollutants, e.g., −42.4% for surface nitrogen dioxide (NO 2) and −38.9% for tropospheric NO 2 column, but fine particulate matter (PM 25) still remains high and ozone (O 3) even increases sharply (+84.1%). Stagnant weather during COVID-19 outbreak, e.g., persistent low wind speed, frequent temperature inversion and wind convergence, is one of the major drivers for the poor air quality in NCP. The surface PM 2.5 levels vary between −12.9~+15.1% in NCP driven by the varying climate conditions between the years 2000 and 2020. Besides, the persistent PM 2.5 pollution might be maintained by the still intensive industrial and residential emissions (primary PM 2.5), and increased atmospheric oxidants (+26.1% for ozone and +29.4% for hydroxyl radical) in response to the NO 2 decline (secondary PM 2.5). Further understanding the nonlinear response between atmospheric secondary aerosols and NO x emissions is meaningful to cope with the emerging air pollution problems in China. Image 1 • Both satellite data and ground measurements confirm improved NO 2 air quality. • PM 2.5 varies between −12.9~+15.1% driven by climate conditions. • High PM 2.5 is maintained by intensive primary emission and increased oxidants. [ABSTRACT FROM AUTHOR]

One vertical observation field campaign based on a tethered mega-balloon (with onboard instruments over 200 kg) was conducted at a campus site in rural Shanghai in order to investigate the vertical distributions of key air pollutants (PM 2.5 , SO 2 , black carbon (BC) and O 3) and regional transport characteristics during a severe air pollution episode in mid-December 2015. Vertical patterns of measured air pollutants show relatively even profiles within the planetary boundary layer (PBL) while declined sharply above PBL during the daytime. Specifically, high concentrations of SO 2 were observed near the top of the boundary layer. Lagrangian particle dispersion modeling showed air pollutants within the boundary layer mainly derived from local sources (i.e. Shanghai) and regional transport within the Yangtze River Delta (YRD) region in the morning before the development of boundary layer. Aerosol chemical components measured at a ground site (about 60 km northwest of the balloon site) showed that regional transport brought a large amount of aged sulfate and nitrate. This study provides new insights in the vertical distribution and transport of haze associated with the PBL development and long-range transport. • A vertical observation from 0 to 1000 m based on a tethered mega-balloon was conducted in winter of 2015, Shanghai. • Vertical profiles of key air pollutants (PM 2.5 , SO 2 , O 3 and black carbon) with high spatiotemporal resolution were revealed. • PM 2.5 in Shanghai was mainly derived from transport within the YRD based on a synergy of measurement techniques. • Nitrate contributed most to the increase of PM 2.5 with high SO 2 during regional transport. [ABSTRACT FROM AUTHOR]

Findings for impacts of outdoor air pollutants on birth outcomes were controversial. We performed a retrospective observational study in 2527 preschoolers of Shanghai, China and investigated associations of duration-averaged concentrations of outdoor sulphur dioxide (SO 2), nitrogen dioxide (NO 2), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM 10) in different months and trimesters of gestation, with preterm birth (PB), low birth weight (LBW), term low birth weight (T-LBW), and small for gestational age (SGA). Daily concentrations of outdoor air pollutants were collected in each residence-located district. Parents reported health information. In the multivariate logistic regression analyses, exposures to outdoor NO 2 were consistently associated with the higher odds of LBW and T-LBW. These associations were generally stronger for early months than for later months of the gestation. Adjusted odds ratios generally were larger in multi-pollutant model than in single-pollutant model. Exposure to NO 2 in the first month of the gestation was significantly associated with T-LBW (adjusted OR, 95%CI: 1.91, 1.02–3.58 for increment of interquartile range (18.5 μg/m3); p -value = 0.044) in multi-pollutant model. This association was stronger in girls, renters, and children whose mothers ≥30 years-old, with household dampness-related exposures, and with parental smoking during pregnancy. Our results indicate that exposure to NO 2 during gestation perhaps is a risk factor for LBW and T-LBW, and effects of NO 2 exposures could be greater during early periods than during later periods of gestation. • A retrospective observational study in 2527 preschoolers was conducted. • Exposures to outdoor NO 2 consistently associated with LBW and T-LBW. • These associations were stronger for early months than for later months. • Adjusted ORs were larger in multi-pollutant than single-pollutant model. • No significant associations were found of SO 2 and PM 10 with all outcomes. [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]

Pollutants from navigation sector are key contributors to emission inventories of most coastal cities with heavy port activities. The use of high fuel sulfur content (FSC) bunker oil by ocean going vessels (OGVs) has been identified as a major source of sulfur dioxide (SO 2). Government authorities all over the world, including Hong Kong government, have implemented air pollution control regulations to cap FSC of fuel used by OGVs to 0.5%, from the existing 3.5%, to reduce SO 2 emissions. However, the lack of efficient screening tools to identify non-compliant OGVs has prevented effective enforcement. This study developed and evaluated an unmanned aerial vehicle (UAV)-borne lightweight (750 g) microsensor system (MSS), which is capable of measuring ship plume SO 2 , NO 2 , NO, CO 2 , CO, and particulate matter in real-time. Extensive experiments were conducted on the sensor system to evaluate its performance during laboratory and field operations. The effects of cross-sensitivity and meteorological conditions were studied and incorporated to account for the measurement conditions in dispersed ship plumes. The SO 2 to CO 2 concentration ratio-based FSC expression was formulated as per the 2016 European Union Directive and Regulations. Furthermore, the impact of plume dilution on the accuracy of FSC measurement was investigated at different stages using the MSS, with and without the UAV in both simulated conditions and real-world scenarios, maintaining a safe distance from the OGV exhaust stacks. The study demonstrates the robustness of using UAV-borne sensor system for ship emission sniffing and FSC determination. The results will assist in development of a technological framework for effective enforcement of ship emission control regulations. Unlabelled Image • Studied impacts of cross-sensitivity and meteorological changes on MSS performance. • Plume dilutions showed nominal effects on FSC estimation while using UAV-borne MSS. • FSC estimation accuracy of MSS validated by measuring predefined FSC emissions. • Airborne MSS emerges as an efficient tool for remotely screening non-compliant OGVs. • Useful in pollutant concentration ratio based assessment of varied emission sources. [ABSTRACT FROM AUTHOR]

Nitrate became the most significant component of secondary inorganic aerosols (SNA, the sum of sulfate, nitrate and ammonium ions) as the emissions of sulfur dioxide (SO 2) have been greatly reduced in China in recent years. In the Yangtze River Delta (YRD), nitrate could contribute 56% of SNA and 34% of total PM 2.5 during haze episodes. In this study, a modified Community Multiscale Air Quality (CMAQ) model was used to provide a comprehensive understanding of nitrate source and formation under severe pollution during winter 2015 and 2016. Three haze episodes (HEP1, HEP2 and HEP3) and one clean episode (CEP) were selected to investigate the emission sector and regional contributions to nitrate at six environmental monitoring sites in the YRD. Source apportionment results showed that industry (35%), transportation (32%) and power (28%) sectors were the important sources of nitrate during haze episodes. Regional transport (60–98%) was responsible for the high nitrate concentrations in the YRD. During haze episodes, the high ozone production (PO 3) rate (up to 700 ppb/h) and hydroxyl radicals (OH) removal rate (up to 9 ppb/h) were observed in the daytime indicating the important atmospheric oxidation capacity in the YRD. Also, the nitrogen oxidation ratio (NOR) analysis elucidated that daytime photochemistry played an important role in nitrate formation and the heterogeneous chemistry enhanced the high nitrate at night. Results from emission scenario analysis demonstrated that averaged nitrate concentration in Shanghai decreased by 18% during haze episodes under emission reductions of 20% NO x , NH 3 and VOC in the YRD, and Shandong, Shanxi, Henan and Hebei provinces. Emission reduction on the regional scale (one city and its surrounding areas) is an efficient strategy to reduce nitrate concentration in the YRD. Unlabelled Image • Regional transport is the main origin of nitrate during haze episodes in the YRD. • Photochemistry is important in nitrate formation during the daytime in the YRD. • Emission reduction on a regional scale (one city and its surrounding areas) is effective to control nitrate. [ABSTRACT FROM AUTHOR]

Ambient fine particulate matter (PM 2.5) can cause adverse health effects through the generation of reactive oxygen species (ROS) after inhalation. Humic-like substances (HULIS) are major constituents contributing to the ROS-generation potential in organic aerosols. In this study, PM 2.5 samples in urban Shanghai during autumn and winter (2018–2019) were collected. Mass-normalized ·OH generation rate in surrogate lung fluid (SLF) was used to denote the intrinsic ROS-generation potential of PM 2.5 or of the HULIS isolated from PM 2.5. In this study, ROS-generation potential of PM 2.5 decreased with increasing ambient PM 2.5 concentration due to higher percentage of inorganic components in high PM 2.5 event. Same trend was observed for the ROS-generation potential of unit mass of HULIS, which was higher when HULIS and PM 2.5 concentrations were both relatively lower. The HULIS with high ROS-generation potential but low concentration (High-ROS/Low-Conc HULIS) were likely produced by the atmospheric aqueous-phase reactions during nighttime or under high relative humidity conditions, not from biomass burning emissions or the photochemical pollution products. The association between ROS-generation potential and light absorption properties of HULIS was studied as well. The High-ROS/Low-Conc HULIS also showed stronger light absorbance than the other HULIS. Our results implied the potentially important roles that HULIS species might play in atmospheric environment and human health even when the PM 2.5 pollution is low. • HULIS with high ROS-generation potential were observed at low PM 2.5 concentration. • High-ROS/Low-Conc HULIS were likely formed via aqueous-phase reactions. • HULIS with higher ROS-generation potential showed stronger light absorbance. [ABSTRACT FROM AUTHOR]

• We surveyed 3177 preschoolers who did not change residences after birth. • We studied associations of early exposures to NO 2 , SO 2 , PM 10 with airway diseases. • Prenatal and Postnatal exposures to NO 2 were associated with airway diseases. • Associations of NO 2 were generally stronger than in the early than later trimesters. It's inconsistent about associations of early exposures to outdoor air pollutants with allergies and airway diseases in childhood. Here, we investigated associations of prenatal and postnatal exposures to outdoor nitrogen dioxide (NO 2), sulphur dioxide (SO 2), and PM 10 (particulate matter with an aerodynamic diameter ≤ 10 μm) with asthma, wheeze, hay fever, rhinitis, pneumonia, and eczema in childhood. We surveyed 3,177 preschoolers who never change residences since birth in Shanghai, China. Parents reported information regarding children's health status. Daily-averaged concentrations of these pollutants in the children's gestation and in the first year of lifetime for district where children lived were collected by Shanghai Environmental Monitoring Center. After adjusting for covariates, exposures to higher level of NO 2 during different trimesters of gestation and of the first year of lifetime had significant associations with the increased odds of asthma, hay fever, rhinitis, pneumonia, and eczema in childhood. Associations of NO 2 exposures in the early trimesters of gestation and of the first year of lifetime with pneumonia were stronger than in the later trimesters, whereas associations of NO 2 exposures in the early trimesters with hay fever and eczema were weaker than in the later trimesters. Our results indicated that prenatal and postnatal exposures to outdoor NO 2 could be risk factors for allergies and airway diseases in childhood. Both dose and duration were related with the influence degree of early NO 2 exposure on childhood allergies and airway diseases. [ABSTRACT FROM AUTHOR]

Ambient heavy fine particulate matter (PM 2.5) pollution events occur frequently during winter seasons in eastern China. Investigating the evolution of source contributions during heavy pollution episodes is critical for strategies of pollution relief. In this study, a two-month field campaign was conducted in the winters of 2015 and 2016 at a regional supersite in eastern China and over one thousand hourly online measurements for twenty PM 2.5 species were obtained. Hourly source apportionment for the total mass of PM 2.5 , and its major species (primary organic carbon, elemental carbon, nitrate, sulfate and ammonium), were then performed by Positive Matrix Factorization (PMF) and Multilinear Engine-2 (ME2) models. Three PM 2.5 heavy pollution episodes including ten high concentration peaks were identified for further analysis. Results showed that ME2 performed better than PMF by fixing source profiles of secondary nitrate, secondary sulfate and sea salt, although they have dominant consistencies. Two types of pollution sources were identified from high PM 2.5 mass peaks: coal combustion-oriented responsible for four peaks and secondary inorganic aerosol-oriented responsible for the remaining six peaks. Low wind speed and planetary boundary layer favorited the coal combustion-oriented peaks, but also weakened the secondary inorganic formation due to low temperature and accumulated nitric oxide. Primary emissions from coal combustion can contribute 18% to ammonium in addition to 72% from secondary inorganic aerosol. Secondary organic aerosol would contribute 20% of PM 2.5 mass during the heaviest episodes. Findings in this study provide insights into the causes of heavy pollution episodes and support implementing effective control strategies to mitigate heavy pollution events in eastern China. • Distinct source characteristics during heavy pollution evolution could be identified based on high time resolution. • Coal combustion and secondary inorganic aerosol were responsible for the highest PM 2.5 mass peaks separately. • ME2 fixing known source profiles could obtain more reasonable apportionment results than PMF. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are important precursors of photochemical smog and secondary organic aerosol (SOA). Quantitatively assessing the impact of VOCs on ozone (O 3) formation could provide valuable information for the management of emission reduction and photochemical pollution control. In this study, we first figured out the ozone pollution episodes during 2018 at Dianshan Lake (DSL), which is located in the suburban area of Shanghai and is adjacent to three provinces of the YRD region. Then we analyzed continuous variation of O 3 precursors and meteorological parameters. The online measurements show that the average volume mixing ratio of total VOCs (TVOC) was 15.41 ± 11.39 ppbv during the ozone pollution episodes, with the largest contribution from alkanes. To further identify the sources of VOCs, VOC concentration-weighted trajectories (CWT) were analyzed, and the results suggested that Zhejiang province could be the most important source region of VOCs at DSL. Analysis using an observation-base model showed that NO x and alkenes exhibited the most significant negative and positive influences on O 3 formation, respectively. As for individual species, toluene and isoprene, whose S-weighted concentrations were 6.67 × 10−2 and 5.94 × 10−2 ppbv, respectively, were the key factors promoting the formation of O 3 at DSL. To control the increase of O 3 , considering the policy feasibility, the abatement ratio of VOCs/NO x should be no less than 0.72. The findings advanced our knowledge of VOCs and their impact on O 3 formation and will be helpful in formulating emission control strategies for coping with O 3 pollution in YRD region. • Characteristics of ambient VOCs and their influences on O 3 formation in a rural area downwind Shanghai were investigated. • Strong photochemical losses of VOCs, especially alkenes, were found under high O x concentrations situations. • Abatement ratio of VOCs/NOx should be no less than 0.72 to effectively control O 3. [ABSTRACT FROM AUTHOR]

Aircraft engine emissions during landing and take-off cycle are commonly estimated on the basis of the International Civil Aviation Organization (ICAO) promulgated calculation model and emission parameters; however, the ICAO certified parameters are generally not applicable for an individual airport. In this study, the operation times, fuel and emission parameters of 8 aircraft models during taxi phase at Shanghai Hongqiao International Airport (SHA) are analyzed with the Aircraft Communication Addressing and Reporting System (ACARS) data, and compared with corresponding values referenced by the ICAO. The results show perceptible discrepancies between the SHA-specific and ICAO certified values. The taxi-out times at SHA are considerably overestimated (up to 35.3%) by ICAO for all the analyzed aircraft models, whereas the taxi-in durations are highly close to the ICAO referenced value with a variation within −6.3% to 9.7%. In the majority of cases, the localized fuel flows and emission indices (EIs) are overvalued by ICAO, and the extent of overestimation can be as large as 21.6% and 28.3%, respectively. Variabilities in operation times, fuel and emission parameters are also characterized depending on aircraft types. Additionally, as a novel attempt, the effect of engine aging on EIs is explored and no significant correlation has been detected, indicating that other factors may affect the EIs dominantly over engine age. The resulting SHA-specific emission parameters are significant towards a precise emission quantification and modeling of impacts on air quality and health. Unlabelled Image • ICAO overestimates the SHA-specific taxi-out operation times by up to 35%. • Overvaluation in fuel flows and NO x EIs can be as high as 22% and 28%, respectively. • Correlation of engine age and NO x EIs is not evident in aging effect examination. [ABSTRACT FROM AUTHOR]