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

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

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

The vertical distribution of SO2, NO, NO2, O3, CO, PM2.5, black carbon, particle sizedistribution, species of PM1 within 0-1000m as well as meteorological parameters weremeasured simultaneously on tethered balloon at Wangdu County, Baoding City, NorthChina Plain, as part of the winter field campaign which hold during December2018.During December 18 to 21, the ground monitoring data demonstrated sharp increase of NO,CO and PM2.5 concentration during the nighttime and decrease in the daytime,while the diurnal variation of ozone concentration was the opposite. The increasedconcentrations of pollutants at night mostly due to the much lower boundary layerduring nights, which could be as low as 100 meters. Except for the worse verticaldiffusion at night, the low wind speed also contributed to the increase of pollutantsconcentrations.The organic component accounted for up to 60% of PM2.5 at night, which was the maincontribution to the increased PM2.5. The significant increase of NO, CO and organic may dueto the emission from home heating at night.The vertical detection demonstrated very low boundary layer and inversion layer during theobservation period. The vertical distribution of pollutant in the boundary layer and upper theboundary layer are quite different at night. The concentrations of gaseous pollutants (CO,SO2, NO and NO2) and PM2.5 were higher in the nocturnal boundary layer, and theproportion of organic component, black carbon and chloride were significantly higher thanthat upper the boundary layer. During the daytime, with the development of the boundarylayer, the favorable horizontal and vertical diffusion condition lead to the decreased pollutantsconcentrations. In addition, pollutants with high concentrations were found at high altitudes,where the proportion of secondary components such as nitrates, sulfates and ammoniumwere higher than that of the ground. It may attributed to air mass from regionaltransport. [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]

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]

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]

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]

Carbonaceous aerosols have adverse effects on both human health and the climate. To understand the temporal variations and sources of carbonaceous aerosols, organic carbon (OC) and elemental carbon (EC) were measured hourly in suburban Shanghai in 2015–2017 during winter. The average OC concentrations were 7.34 ± 4.51 μgC/m3 in 2015, 7.16 ± 4.43 μgC/m3 in 2016, and 6.4 ± 3.22 μgC/m3 in 2017. The EC concentrations decreased significantly each year, with average concentrations of 3.82 ± 2.43, 2.91 ± 2.28, and 2.46 ± 1.88 μgC/m3, respectively, which caused the OC/EC ratio to increase from 2015 to 2017. Although the meteorological conditions differed each winter, there was a similar pattern of OC and EC diurnal variations, with concentrations peaking at 08:00 and 20:00, largely due to rush-hour vehicle emissions. A downward trend of EC/CO and EC/NO 2 (mass ratios) but steady CO and NO 2 concentrations from 2015 to 2017 revealed that the characteristics of primary vehicle emissions changed, and that less EC was emitted. Secondary organic carbon (SOC) and primary organic carbon (POC) were estimated with the minimum R 2 (MRS) method. The hiemal SOC/OC values in suburban Shanghai were 19.2 ± 18.6% in 2015, 31.1 ± 18.6% in 2016, and 51.0 ± 21.4% in 2017, exhibiting an increasing trend. As the PM 2.5 concentration increased (from 0 to 50 μg/m3 to 100–300 μg/m3), a decreasing SOC/OC ratio (from 43.6 ± 23.9% to 21.8 ± 17.7%) was observed over the three years, showing that primary emissions were the main contributors to carbonaceous aerosols on haze days. Case analysis of haze events further demonstrated that the primary sources of OC and EC were vehicle emissions. The contributions of biomass burning and coal combustion to carbonaceous aerosols became less important over the study period. This study highlights the importance of controlling vehicle emissions to reduce carbonaceous aerosol concentrations in the suburbs of the Chinese megacity, Shanghai. Image 1 • Hourly OC and EC were analyzed at suburban Shanghai in winter 2015 to 2017. • SOC/OC decreased with increased PM 2.5 pollution. • Biomass burning and coal combustion contribution to OC and EC decreased. • Vehicle emissions are the dominant source of carbonaceous aeorosols. [ABSTRACT FROM AUTHOR]