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Abstract A two-year gaseous elementary mercury (GEM) measurement was implemented at an iron–steel plant in Yangtze River Delta, China, which provided an excellent opportunity to investigate their dynamic cycling. The hourly GEM concentrations ranged between 0.78 and 113.8 ng m−3, with a mean value of 3.83 ± 2.53 ng m−3. Temporally, seasonal GEM contents decreased as winter ≈ spring > summer > autumn, while diurnal cycling was observed with a steady decrease at 14:00–17:00. GEM variations were found to be related to source emissions, meteorology and regional transportation. Three major oxidants (O 3 , Br and OH radicals) were used to evaluate GEM oxidation in the daytime, and the estimated GEM depletion rate was 70.8 ± 52.5 molecule cm−3 s−1 (0.09 ± 0.06 ng m−3 h−1). The GEM oxidized by Br radicals accounted for 83.4% of the total GEM oxidation rate, followed by O 3 (13.8%). The estimated atmospheric lifetime of GEM was 22.9 to 345.2 days, which implies a major contribution of Br radicals to the GEM sink. These findings highlight the ability of iron–steel industry emissions and in–situ oxidation to affect daily local GEM cycling significantly. Graphical abstract Simplified mechanisms of GEM oxidization by atmospheric oxidant radicals in the iron-steel industry. Unlabelled Image Highlights • A two-year-time hourly measurement of gaseous elemental mercury was implemented in an iron-steel plant in China. • The observed hourly GEM concentrations ranged between 0.78 to 113.8 ng m-3, with a mean value of 3.83 ± 2.53 ng m-3. • The GEM oxidation rate initiated by three major oxidants (O 3 , Br· and OH· radicals) were evaluated. • The calculated GEM lifetime against oxidation ranged from 22.9 to 345.2 days. [ABSTRACT FROM AUTHOR]

High pollution episodes of PM 2.5 and O 3 were frequently observed at a rural site (N31.0935º, E120.978°) in eastern Yangtze River Delta (YRD) in summer. To study the impacts of photochemical reactions on secondary aerosol formation in this region, we performed real-time measurements of the mass concentration and composition of PM 2.5 , particle size distribution (13.6 ~ 736.5 nm), concentrations of gas pollutants including O 3 , SO 2 , NO 2 , CO, non-methane hydrocarbons (NMHC)), and nitrate radical in 2013. During the sampling period, the average concentration of PM 2.5 was 76.1 (± 16.5) μg/m 3 , in which secondary aerosol species including sulfate, nitrate, ammonium, and secondary organic aerosol (SOA) accounted for ~ 62%. Gas-phase oxidation of SO 2 was mainly responsible for a fast increase of sulfate (at 1.70 μg/m 3 /h) in the morning. Photochemical production of nitric acid was intense during daytime, but particulate nitrate concentration was low in the afternoon due to high temperature. At night, nitrate was mainly formed through the hydrolysis of NO 3 and/or N 2 O 5 . The correlations among NMHC, O x (= O 3 + NO 2 ), and SOA suggested that a combination of high emission of hydrocarbons and active photochemical reactions led to the rapid formation of SOA. In addition, several new particle formation and fast growth events were observed despite high ambient aerosol loading. Since the onset of new particle events was accompanied by a rapid increase of H 2 SO 4 and SOA, enhanced formation of sulfate and SOA driven by photochemical oxidation likely promoted the formation and growth of new particles. Together, our results demonstrated that strong atmospheric photochemical reactions enhanced secondary aerosols formation and led to the synchronous occurrence of high concentrations of PM 2.5 and O 3 in a regional scale. These findings are important for better understanding the air pollution in summer in YRD. [ABSTRACT FROM AUTHOR]

The COVID-19 epidemic broke out in Wuhan, Hubei in December 2019 and in January 2020 and was later transmitted to the entire country. Quarantine measures during Chinese New Year effectively alleviated the spread of the epidemic, but they simultaneously resulted in a decline in anthropogenic emissions from industry, transportation, and import and export of goods. Herein, we present the major chemical composition of non-refractory PM 2.5 (NR-PM 2.5) and the concentrations of gaseous pollutants in an urban site in Shanghai before and during the quarantine period of the COVID-19 epidemic, which was Jan. 8―23 and Jan. 24―Feb. 8, respectively. The observed results show that the reduction in PM 2.5 can be mainly attributed to decreasing concentrations of nitrate and primary aerosols. Nitrate accounted for 37% of NR-PM 2.5 before the quarantine period when there was no emission reduction. During the quarantine period, the nitrate concentration decreased by approximately 60%, which is attributed to a reduction in the NO x concentration. Ammonium, as the main balancing cation, showed an approximately 45% simultaneous decrease in concentration. The concentrations of chloride and hydrocarbon-like organic aerosols from primary emissions also declined due to limited human activities. By contrast, sulphate and oxygenated organic aerosols showed a slight decrease in concentration, with their contributions increasing to 27% and 18%, respectively, during the quarantine period, which resulted in two pollution episodes with PM 2.5 exceeding 100 μg/m3. This study provides a better understanding of the impact of quarantine measures on variations of the PM 2.5 concentration and chemical compositions. Atmospheric oxidation capacities based on the oxidant (O x = O 3 + NO 2) and oxidation ratios have been discussed for elucidating the source and formation of haze in an environment with lower anthropogenic emissions. With increasing contribution of secondary aerosols, lower NO x and nitrate concentrations did not completely avoid haze in Shanghai during the epidemic. Unlabelled Image • Quarantine measures led to a reduction in the concentrations of PM 2.5 , SO 2 , NO x , and CO in Shanghai. • Reduction in NO x led to increasing O 3 and decreasing nitrate. • Reduction in PM 2.5 is attributed to the decreasing concentrations of primary aerosols and nitrate. • The increasing contribution of sulphate and OOA inhibited further PM 2.5 reduction. [ABSTRACT FROM AUTHOR]

At the end of 2019, a novel coronavirus, designated as SARS-CoV-2, emerged in Wuhan, China and was identified as the causal pathogen of COVID-19. The epidemic scale of COVID-19 has increased dramatically, with confirmed cases increasing across China and globally. Understanding the potential affecting factors involved in COVID-19 transmission will be of great significance in containing the spread of the epidemic. Environmental and meteorological factors might impact the occurrence of COVID-19, as these have been linked to various diseases, including severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), whose causative pathogens belong to the same virus family as SARS-CoV-2. We collected daily data of COVID-19 confirmed cases, air quality and meteorological variables of 33 locations in China for the outbreak period of 29 January 2020 to 15 February 2020. The association between air quality index (AQI) and confirmed cases was estimated through a Poisson regression model, and the effects of temperature and humidity on the AQI-confirmed cases association were analyzed. The results show that the effect of AQI on confirmed cases associated with an increase in each unit of AQI was statistically significant in several cities. The lag effect of AQI on the confirmed cases was statistically significant on lag day 1 (relative risk (RR) = 1.0009, 95% confidence interval (CI): 1.0004, 1.0013), day 2 (RR = 1.0007, 95% CI: 1.0003, 1.0012) and day 3 (RR = 1.0008, 95% CI: 1.0003, 1.0012). The AQI effect on the confirmed cases might be stronger in the temperature range of 10 °C ≤ T < 20 °C than in other temperature ranges, while the RR of COVID-19 transmission associated with AQI was higher in the relative humidity (RH) range of 10% ≤ RH < 20%. Results may suggest an enhanced impact of AQI on the COVID-19 spread under low RH. Unlabelled Image • AQI - COVID-19-confirmed cases association is statistically significant in some cities. • Lag effect of AQI on confirmed cases is statistically significant on lag 1–3 days. • AQI effect on the confirmed cases in temperature range of 10–20 °C may be stronger. • Impact of AQI on the spread of COVID-19 may be enhanced under low relative humidity. [ABSTRACT FROM AUTHOR]

Shanghai, a metropolitan city in China, has suffered from severe air pollution, especially PM 2.5 , in the last few years. Up to now the contribution of local emission and regional transport to the formation of haze in Shanghai remains unclear. With an aim to characterize the mechanism of haze formation in Shanghai, the present paper attempted to provide an overview of a tethered balloon-based field campaign. According to the backward trajectories, the air mass traveling slowly from Jiangsu province accounted for the highest PM 2.5 concentration (66 ± 20 μg/m3). Seventy vertical profiles of PM 2.5 , NO, NO 2 , SO 2 and O 3 within 1000 m were obtained, through which a comparison study on the characteristics of the vertical distributions of air pollutants on clean days and haze days was conducted. When altitude increased, clearly decreasing pattern of PM 2.5 , NO, and NO 2 was observed during the field campaign. Due to the low atmospheric boundary layer, the diffusion of air pollutants was suppressed, which favored the formation of haze. The results of the generalized additive model revealed NO 2 could the most significant factor influencing the vertical distribution of PM 2.5 in both clean and haze days. This study provides new insight into the sources and vertical distribution of PM 2.5 , which could offer references for air pollution modeling. Unlabelled Image • NO 2 was the most significant factor influencing the vertical distribution of PM 2.5. • Polluted air mass from neighboring provinces could influence the air in Shanghai. • Low ABL favored the accumulation of air pollutants in haze days. [ABSTRACT FROM AUTHOR]

With the implementation of the ultra-low emission policy in China, emission factors (EFs) of power plant pollutants are constantly changing. Emission inventories developed using the recommended EFs contain high levels of uncertainty and it is difficult to achieve a high temporal resolution. Detailed sulfur dioxide (SO 2), nitrogen oxides (NOx), and particulate matter (PM) emission data based on a continuous emission monitoring system (CEMS) were obtained from 33 units at 13 power plants in Shanghai in 2017. The data were used to develop an hourly unit-based emission inventory and to devise updated EFs for coal-fired power plants. Emissions of SO 2 , NOx, and PM typically met the ultra-low emission limit, with total emissions of SO 2 , NOx, and PM of 2895.0, 5348.3, and 503.8 tons, respectively. Emission proportions of SO 2 and NOx for 300–600, 600–1000, and above 1000 MW units were similar, while the emission proportion of PM decreased with an increase in unit capacity. Emissions of SO 2 , NOx, and PM displayed similar monthly variations, peaking in winter and summer. Diurnal hourly variations of SO 2 , NOx, and PM emissions displayed a bimodal trend, with higher emissions at night on weekends than on weekdays. EFs based on CEMS (EF C) of SO 2 , NOx, and PM were 0.10, 0.36, and 0.04 g kg−1 of coal, respectively, which were one or two orders of magnitude lower than the widely-used EFs and 4–30 times lower than EFs based on the mass balance approach. After replacing the recommended fixed decontamination efficiencies with individually fitted values, the calculated EFs were consistent with the corresponding EF C and discrepancies were further reduced. The new inventory and updated EFs will enable a better understanding of the temporal variations of power plant emissions and reduce the uncertainty caused by the overestimation of EFs after the implementation of ultra-low emissions technology. Unlabelled Image • An hourly-resolution unit-based emission inventory and updated emission factors in coal-fired power plants were developed. • There was a significant difference in the diurnal emission trend between workdays and non-weekdays • The EFs of SO 2 , NO x , and PM were one or two orders of magnitude lower than previously reported. [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]

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]

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]

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]

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]

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]

Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations were performed from 27 December 2018 to 16 January 2019 in Changshou, one of subdistricts of Chongqing, China. Primary atmospheric pollutant in Changshou during wintertime was PM 2.5 , whose contribution averaged about 70.15% ± 9.5% of PM 10. The ratio of PM 2.5 /PM 10 decreased when PM 2.5 pollution became worse, and it should attribute to biomass burning and the contribution of hygroscopic growth and enhanced heterogeneous chemistry under high relative humidity condition. Moreover, nitrogen dioxide (NO 2), formaldehyde (HCHO) and glyoxal (CHOCHO) vertical profiles during the campaign period were retrieved separately. TROPOMI HCHO vertical column densities (VCDs) and MAX-DOAS HCHO VCDs were correlated well (R = 0.93). In order to identify the sources of volatile organic compound (VOC) in Changshou, the ratio of CHOCHO to HCHO (R GF) in five different layers were estimated. The estimated daily averaged R GF were 0.0205 ± 0.0077, 0.0727 ± 0.0286, 0.0864 ± 0.0296, 0.0770 ± 0.0275 and 0.0746 ± 0.0263 in 0–100 m, 100–200 m, 300–400 m, 500–600 m and 700–800 m layers, respectively. The estimated R GF will increase when biomass burnings were dominated. Using NO 2 as a tracer of anthropogenic emissions, we found the R GF values gradually decrease with the increase of NO 2 levels. R GF values in 0–100 m layer and all the other upper layers are 0.015–0.025 and 0.06–0.14, and that means the dominant sources of VOCs in 0–100 m layer and all the other upper layers are biogenic emission and anthropogenic emission (especially biomass burning), respectively. In addition, we found that R GF has site dependence which is in compliance with several previous studies. Unlabelled Image • The ratio of PM 2.5 /PM 10 decreased when PM 2.5 pollution became worse • HCHO and CHCOHO mainly distributed in 0-100 m and 100-200 m, respectively. • The sources of VOCs above 100 m are mainly from biomass burning. [ABSTRACT FROM AUTHOR]

Since the concentrations of primary particles and secondary inorganic aerosol components have been reduced significantly due to stringent emission controls, quantifying the source contributions and regional transport of secondary organic aerosol (SOA) is critical to further improve air quality in eastern China. In this study, the Community Multiscale Air Quality (CMAQ) model coupled with the updated SAPRC-11 photochemical mechanism and a revised SOA module was applied to investigate the emission sector and regional contributions to SOA in winter 2015 (January 5–26, 2015) and 2016 (December 20, 2015–January 20, 2016) in the Yangtze River Delta (YRD). The model is generally capable of reproducing the observed SOA concentrations at the Qingpu Supersite in Shanghai. The observed and predicted SOA concentrations are 6.4 μg/m3 and 6.9 μg/m3 in winter 2015, and 5.7 μg/m3 and 9.6 μg/m3 in winter 2016. The mean fraction bias (MFB) of the hourly SOA predictions is 0.22 and 0.32, respectively. High SOA concentrations in the wintertime of YRD are mainly due to aromatic compounds and dicarbonyls (glyoxal and methylglyoxal), which, on average, account for 43% and 53% of total SOA, respectively. The average contributions of industrial, residential, and transportation sectors in the YRD region during the entire simulation periods are 61%, 22%, and 17%, respectively. At the Qingpu Supersite in Shanghai, the industrial sector contributes to as much as 65% of total SOA in the heavy pollution episode of 2016. The contributions from transportation and residential sectors are 16% and 17%, respectively, during the same episode. The industry emissions from the Jiangsu, Zhejiang, and Shanghai are major contributors to the SOA at the Qingpu supersite during the heavy-polluted episodes, accounting for 31%, 19%, and 14% of the total predicted SOA. This study represents the first detailed regional modeling study of source region contributions to SOA in the YRD region and the detailed analyses of SOA in two winters months complement the previous SOA source apportionment studies focusing on seasonal average contributions. Unlabelled Image • Formation path and source region contributions to SOA in the YRD region were investigated. • Industry source in the YRD region dominates total SOA during the heavy polluted episodes. • Reginal control policy should be considered in the VOCs and SOA reduction in YRD. [ABSTRACT FROM AUTHOR]

Systemic inflammation is considered one of the key mechanisms in the development of cardiovascular diseases induced by fine particulate matter (PM 2.5) air pollution. However, evidence concerning the effects of various PM 2.5 constituents on circulating inflammatory biomarkers were limited and inconsistent. To evaluate the associations of short-term exposure to a variety of PM 2.5 constituents with circulating inflammatory biomarkers. We conducted a panel study from May to October 2016 among 40 healthy adults in Shanghai, China. We monitored the concentrations of 27 constituents of PM 2.5. We applied linear mixed-effect models to analyze the associations of PM 2.5 and its constituents with 7 inflammatory biomarkers, and further assessed the robustness of the associations by fitting models adjusting for PM 2.5 mass and/or their collinearity. Benjamini-Hochberg false discovery rate was used to correct for multiple comparisons. The associations of PM 2.5 were strongest at lag 0 d with tumor necrosis factor- α (TNF-α), at lag 1 d with interleukin-6, interleukin-8, and interleukin-17A, at lag 02 d with monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule-1 (ICAM-1). After correcting for multiple comparisons in all models, Cl−, K+, Si, K, As, and Pb were significantly associated with interleukin-8; SO 4 2− and Se were marginally significantly associated with interleukin-8; SO 4 2−, As, and Se were marginally significantly associated with TNF- α ; and Si, K, Zn, As, Se, and Pb were marginally significantly associated with MCP-1. Our results suggested that some constituents (SO 4 2−, Cl−, K+, and some elements) might be mainly responsible for systemic inflammation triggered by short-term PM 2.5 exposure. Unlabelled Image • It remains unclear how PM 2.5 constituents affect systemic inflammation differently. • 27 constituents and 7 inflammatory biomarkers were evaluated in Shanghai, China. • SO 4 2−, Cl−, K+ and some elements may be responsible for inflammation. [ABSTRACT FROM AUTHOR]

The identification of constituents of fine particulate matter (PM 2.5) air pollution that had key impacts of ischemic stroke (the predominant subtype of stroke) is important to understand the underlying biological mechanisms and develop air pollution control policies. To explore the associations between PM 2.5 constituents and hospitalization for ischemic stroke in Shanghai, China. We conducted a time-series study to explore the associations between 27 constituents of PM 2.5 and hospitalization for ischemic stroke in Shanghai, China from 2014 to 2016. The over-dispersed generalized additive models with adjustment for time, day of week, holidays, and weather conditions were used to estimate the associations. We also evaluated the robustness of the effect estimates for each constituent after adjusting for the confounding effects of PM 2.5 total mass and gaseous pollutants and the collinearity (the residual) between this constituent and PM 2.5 total mass. We also compared the associations between seasons. In total, we identified 4186 ischemic stroke hospitalizations during the study period. The associations of ischemic stroke were consistently significant with elemental carbon and several elemental constituents (Chromium, Iron, Copper, Zinc, Arsenic, Selenium, and Lead) at lag 1 day in single-constituent models, models adjusting for PM 2.5 total mass or gaseous pollutants and models adjusting for collinearity. The associations were much stronger in cool season than in warm season. The current study provides suggestive evidence that elemental carbon and some metallic elements may be mainly responsible for the risks of ischemic stroke hospitalization induced by short-term PM 2.5 exposure. Unlabelled Image • Few evidence on the associations between PM 2.5 constituents and ischemic stroke • The effects of PM 2.5 on ischemic stroke hospitalizations varied by constituents. • Elemental carbon and some trace elements might be mainly responsible. [ABSTRACT FROM AUTHOR]