•Spatial source distributions of size-resolved particles were studied.•Potential pollution sources of inorganic and carbonaceous aerosols in PM1.8-associated particles were studied.•Important role of ship emission in the air quality of Shanghai in summer.•Significant contribution of particulate pollutants from long-range transported air masses to PM levels of Shanghai in summer.In this study, the concentrations of water soluble ions (WSI), organic carbon (OC), and elemental carbon (EC) of size-resolved (0.056–18 μm) atmospheric aerosols were measured in July and August 2015 in Shanghai, China. Backward trajectory model and potential source contribution function (PSCF) model were used to identify the potential source distributions of size-resolved particles and PM1.8-associated atmospheric inorganic and carbonaceous aerosols. The results showed that the average mass concentrations of PM0.1, PM1, and PM1.8 were 21.21, 82.90, and 100.1 μg m− 3 in July and 7.00, 29.21, and 35.10 μg m− 3 in August, respectively, indicating that the particulate matter pollution was more serious in July than in August in this study due to the strong dependence of the aerosol species on the air mass origins. The trajectory cluster analysis revealed that the air masses originated from heavily industrialized areas including the Pearl River Delta (PRD) region, the Yangtze River Delta (YRD) region and the Beijing-Tianjin region were characterised with high OC and SO42 − loadings. The results of PSCF showed that the pollution in July was mainly influenced by long-range transport while it was mainly associated to local and intra-regional transport in August. Besides the contributions of anthropogenic sources from YRD and PRD region, ship emissions from the East China Sea also made a great contribution to the high loadings of PM1.8 and PM1.8-associated NO3−, NH4+, and EC in July. SO42 − in Shanghai was dominantly ascribed to anthropogenic sources and the high PSCF values for PM1.8-associated SO42 − observed in August was mainly due to the ship emissions of Shanghai port, such as Wusong port and Yangshan deep-water port. These results indicated that the particulate pollutants from long-range transported air masses and shipping made a significant contribution to Shanghai's air pollution.Download high-res image (268KB)Download full-size image

•Atmospheric ultrafine and fine particle pollution in Shanghai were very serious.•Air pollution had close links with NO3− and NH4+ in condensation and droplet mode.•Great contribution of SOC in droplet mode to OC and PM pollution.•Possible connections between the formation of SOC and SNA were revealed by PSCF.Size-segregated aerosol particles were collected with a 10-stage Micro-Orifice Uniform Deposit Impactor (MOUDI) at an urban site in Shanghai, China for four non-consecutive months representing four seasons from 2015 to 2016. Chemical composition, including water-soluble ions as well as organic carbon (OC), elemental carbon (EC) and secondary organic carbon (SOC) of size-resolved (0.056–18 μm) atmospheric aerosols in four seasons and in different polluted cases were studied. The size distributions of sulfate, nitrate and ammonium (SNA) and carbonaceous aerosol (OC, EC and SOC) were discussed and the potential sources of PM1.8-associated secondary species (SO42−, NO3−, SNA and SOC) in different seasons were identified by potential source contribution function (PSCF) model. Results showed that atmospheric ultrafine and fine particle pollution in Shanghai were very serious during the study period. Most of the water-soluble ions tended to be enriched in fine particles, especially being abundant in the droplet mode in polluted cases. Compared with sulfate, size distributions of nitrate and ammonium presented more significant seasonal variations and showed distinctive characteristics in polluted days. Abundant nitrate was concentrated in fine particles in cold seasons (spring and winter), whereas it was enriched in coarse mode during summer and autumn. The droplet mode sulfate with high concentration did not result in the aggravation of air pollution, while the nucleation mode sulfate may have made a great contribution to the air pollution in urban Shanghai. It was also found that the formation of air pollution in urban Shanghai had a significant link with nitrate and ammonium, especially with nitrate and ammonium in condensation mode and droplet mode, and the contribution of sulfate to the pollution formation in Shanghai would somehow be surpassed by the increasing nitrate and ammonium. OC and EC concentrations from spring to winter were found to be 11.10, 7.10, 12.30, 20.16, and 3.73, 2.84, 4.63, 7.10 μg m−3, respectively, distinctly presenting the summer minima and winter maxima in this study. The maximum OC/EC was in the droplet mode and the minimum was in the nucleation mode for both clean and polluted days. The great contribution of SOC to OC in droplet mode and the occurrence of PM pollution necessarily had an important bearing on the SOC formation in droplet mode particles. Particle acidity may play a key role in secondary organic aerosol formation and the particles with the size of 0.056–0.1 μm was the most sensitive particles to acid catalysis in SOA formation. The similar PSCF results of PM1.8-associated SOC to those of SO42−, NO3− and SNA indicated possible connections between the formation of SOC and secondary inorganic species in PM.Download high-res image (369KB)Download full-size image

Heterogeneous reactions of nitrogen oxides on the surface of aluminium oxide result in the formation of adsorbed nitrite and nitrate. However, little is known about the effects of other species on these heterogeneous reactions and their products. In this study, diffuse reflectance infrared spectroscopy (DRIFTS) was used to analyze the process of the heterogeneous reaction of NO2 on the surface of aluminium oxide particles in the presence of pre-adsorbed organic species (acetaldehyde, glyoxal and acetic acid) at 298 K and reveal the influence of these organic species on the formation of adsorbed nitrite and nitrate. It was found that the pre-adsorption of organic species (acetaldehyde, glyoxal and acetic acid) on γ-Al2O3 could suppress the formation of nitrate to different extents. Under the same experimental conditions, the suppression of the formation of nitrate by the pre-adsorption of acetic acid is much stronger than that by pre-adsorption of acetaldehyde and glyoxal, indicating that the influence of acetic acid on the heterogeneous reaction of NO2 is different from that of acetaldehyde and glyoxal. Surface nitrite is formed and identified to be an intermediate product. For the heterogeneous reaction of NO2 on the surface of γ-Al2O3 with and without the pre-adsorption of acetaldehyde and glyoxal, it is firstly formed and then gradually disappears as the reaction proceeds, but for the reaction with the pre-adsorption of acetic acid, it is the final main product besides nitrate. This indicates that the pre-adsorption of acetic acid would promote the formation of nitrite, while the others would not change the trend of the formation of nitrite. The possible influence mechanisms of the pre-adsorption of acetaldehyde, glyoxal and acetic acid on the heterogeneous conversion of NO2 on γ-Al2O3 are proposed and atmospheric implications based on these results are discussed.

Sulfur dioxide and organic aldehydes in the atmosphere are ubiquitous and often correlated with mineral dust aerosols. Heterogeneous uptake and adsorption of one of these species on mineral aerosols can potentially change the properties of the particles and further affect the subsequent heterogeneous reactions of the other species on the coating particles. In this study, the interactions between heterogeneous uptake and adsorption of sulfur dioxide and acetaldehyde on hematite are investigated by using in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) at room temperature. It is found that the preadsorption of SO2 on α-Fe2O3 can significantly hinder the subsequent heterogeneous oxidation of CH3CHO to acetate, while the preadsorption of CH3CHO significantly suppresses the heterogeneous reaction of large amounts of SO2 on the surface of α-Fe2O3 and has a little influence on the uptake of small amount of SO2. The heterogeneous reactions of SO2 on α-Fe2O3 preadsorbed by CH3CHO change the existing acetate on the particle surface into chemisorbed acetic acid, for the enhancement of surface acidity after the uptake of SO2. During these processes, different surface hydroxyl groups showed different reactivities. Atmospheric implications of this study are discussed.

Heterogeneous reactions of NO2 on various mineral aerosol particles have been investigated in many previous studies, but a fundamental understanding of how the adsorption of formaldehyde influences the heterogeneous reactions of NO2 remains unclear. In this work, the effect of formaldehyde preadsorption on heterogeneous reaction of NO2 on the surface of γ-Al2O3 at 298 K and ambient pressure was investigated by using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS). It was found that the preadsorption of HCHO on γ-Al2O3 could suppress the formation of nitrate, and the rate of nitrate formation decreased with increasing amount of preadsorbed HCHO, whereas the following heterogeneous uptake of NO2 could suppress the hydration reaction of HCHO and promote the production of HCOO– during the reaction. Surface nitrite was formed and identified to be an intermediate product and gradually disappeared as the reaction proceeded. The amount of the formed nitrite decreased when the amount of HCHO increased. Uptake coefficients of heterogeneous reactions were calculated and found to be sensitive to the adsorption of HCHO. A possible mechanism for the influence of HCHO adsorption on the heterogeneous conversion of NO2 on γ-Al2O3 was proposed, and atmospheric implications based on these results were discussed.

Small crystal zeolite Beta with SiO2/Al2O3 ratios ranging from 30 to 400 has been synthesized in a biphasic H2O–CTAB–Alcohol system using colloidal precursor which contains secondary building units of zeolite Beta as the silica and aluminum sources. The experimental results evidenced that the synthesis system employed here resulted in readily the formation of small crystal size zeolite Beta, and the crystallite aggregates consisting of many small particles with size close to the range of nanometer were obtained. The obtained zeolite Beta samples synthesized in the biphasic system displayed higher catalytic activity for n-hexane hydrocracking than that synthesized in single aqueous system.

Heterogeneous reactions of nitrogen oxides on the surface of aluminium oxide result in the formation of adsorbed nitrite and nitrate. However, little is known about the effects of other species on these heterogeneous reactions and their products. In this study, diffuse reflectance infrared spectroscopy (DRIFTS) was used to analyze the process of the heterogeneous reaction of NO2 on the surface of aluminium oxide particles in the presence of pre-adsorbed organic species (acetaldehyde, glyoxal and acetic acid) at 298 K and reveal the influence of these organic species on the formation of adsorbed nitrite and nitrate. It was found that the pre-adsorption of organic species (acetaldehyde, glyoxal and acetic acid) on γ-Al2O3 could suppress the formation of nitrate to different extents. Under the same experimental conditions, the suppression of the formation of nitrate by the pre-adsorption of acetic acid is much stronger than that by pre-adsorption of acetaldehyde and glyoxal, indicating that the influence of acetic acid on the heterogeneous reaction of NO2 is different from that of acetaldehyde and glyoxal. Surface nitrite is formed and identified to be an intermediate product. For the heterogeneous reaction of NO2 on the surface of γ-Al2O3 with and without the pre-adsorption of acetaldehyde and glyoxal, it is firstly formed and then gradually disappears as the reaction proceeds, but for the reaction with the pre-adsorption of acetic acid, it is the final main product besides nitrate. This indicates that the pre-adsorption of acetic acid would promote the formation of nitrite, while the others would not change the trend of the formation of nitrite. The possible influence mechanisms of the pre-adsorption of acetaldehyde, glyoxal and acetic acid on the heterogeneous conversion of NO2 on γ-Al2O3 are proposed and atmospheric implications based on these results are discussed.