Gasoline vehicle exhaust is an important contributor to secondary organic aerosol (SOA) formation in urban atmosphere. Fuel composition has a potentially considerable impact on gasoline SOA production, but the link between fuel components and SOA production is still poorly understood. Here, we present chamber experiments to investigate the impacts of gasoline aromatic content on SOA production through chamber oxidation approach. A significant amplification factor of 3-6 for SOA productions from gasoline exhausts is observed as gasoline aromatic content rose from 29 to 37 %. Considerably higher emission of aromatic volatile organic compounds (VOCs) using high-aromatic fuel plays an essential role in the enhancement of SOA production, while semi-volatile organic compounds (e.g., gas-phase PAHs) may also contribute to the higher SOA production. Our findings indicate that gasoline aromatics significantly influence ambient PM2.5 concentration in urban areas and emphasize that more stringent regulation of gasoline aromatic content will lead to considerable benefits for urban air quality.

Particulate organonitrates are formed from volatile organic compounds (VOCs) oxidation by radicals. A portion of semi-volatile gas-phase organonitrates can be incorporate into aerosol by oxidation reactions or portioning, and has been an important component of secondary organic aerosol (SOA). Particulate organonitrates study has become one of the important aspects of atmospheric chemistry. Given the large number and variability of chemical constituents, and possible chemical transformations of organonitrates, such characterization presents a key problem for research. Based on recent research progress on particulate organonitrates, this paper summarizes the formation mechanism and quantification method of particulate organonitrates. Profiting from the application of high time resolution techniques, field measurements has become the major approach of particulate organonitrates study. Thermal dissociation-laser induced fluorescence (TD-LIF) and aerosol mass spectrometers (AMS) have been used to quantify and provide the evolution processes of particulate organonirates. Meanwhile, chemical ionization mass spectrometer(CIMS)allows for the determination of molecular ion composition of organonitrates, promising to become the important direction of study of particulate organonirates in future field measurements. To have a deep insight on precursor and atmospheric chemistry processes of particulate organonirates, future research should focus on the combination of field measurement, modeling simulation and laboratory simulation, and these will also lead to a more comprehensive understanding of formation mechanism of particulate organonirates

Although organic compounds in marine atmospheric aerosols have significant effects on climate and marine ecosystems, they have rarely been studied, especially in the coastal regions of East China. To assess the origins of the organic aerosols in the East China coastal atmosphere, PM2.5 samples were collected from the atmospheres of the Yellow Sea, the East China Sea, and Changdao Island during the CAPTAIN (Campaign of Air PolluTion At INshore Areas of Eastern China) field campaign in the spring of 2011. The marine atmospheric aerosol samples that were collected were grouped based on the backward trajectories of their air masses. The organic carbon concentrations in the PM2,5 samples from the marine and Changdao Island atmospheres were 5.5 +/- 3.1 mu gC/m(3) and 6.9 +/- 2.4 mu gC/m(3), respectively, which is higher than in other coastal water atmospheres. The concentration of polycyclic aromatic hydrocarbons (PAHs) in the marine atmospheric PM2.5 samples was 17.0 +/- 20.2 ng/m(3), indicating significant continental anthropogenic influences. The influences of fossil fuels and biomass burning on the composition of organic aerosols in the coastal atmosphere of East China were found to be highly dependent on the origins of the air masses. Diesel combustion had a strong impact on air masses from the Yangtze River Delta (YRD), and gasoline emissions had a more significant impact on the "North China" marine atmospheric samples. The "Northeast China" marine atmospheric samples were most impacted by biomass burning. Coal combustion contributed significantly to the compositions of all of the atmospheric samples. The proportions of secondary compounds increased as samples aged in the marine atmosphere indicating that photochemical oxidation occured during transport. Our results quantified ecosystem effects on marine atmospheric aerosols and highlighted the uncertainties that arise when modeling marine atmospheric PM2.5 without considering high spatial resolution source data and meteorological parameters. (C) 2017 Published by Elsevier Ltd.

The molecular composition of humic-like[GRAPHIC]substances (HULIS) in different aerosol samples was analyzed using an ultrahigh-resolution mass spectrometer to investigate the influence of biomass burning on ambient aerosol composition. HULIS in background aerosols were characterized with numerous molecular formulas similar to biogenic secondary organic aerosols. The abundance of nitrogen-containing organic compounds (NOC), including nitrogen-containing bases (N-bases) and nitroaromatics, increased dramatically in ambient aerosols affected by crop residue burning in the farm field. The molecular distribution of N-bases in these samples exhibited similar patterns to those observed in smoke particles freshly emitted from lab-controlled burning of straw residues but were significantly different with those observed from wood burning. Signal intensity of the major N-bases correlated well with the atmospheric concentrations of potassium and levoglucosan. These N-bases can serve as molecular markers distinguishing HULIS from crop residue burning with from wood burning. More nitroaromatics were detected in ambient aerosols affected by straw burning than in fresh smoke aerosols, indicating that many of them are formed in secondary oxidation processes as smoke plumes evolve in the atmosphere. This study highlights the significant contribution of crop residue burning to atmospheric NOC. Further study is warranted to evaluate the roles of NOC on climate and human health.

Highly time-resolved in situ measurements of airborne particles were conducted at Mt. Yulong (3410 m above sea level) on the southeastern edge of the Tibetan Plateau in China from 22 March to 14 April 2015. The detailed chemical composition was measured by a high-resolution time-of-flight aerosol mass spectrometer together with other online instruments. The average mass concentration of the submicron particles (PM1) was 5.7 +/- 5.4 mu g m(-3) during the field campaign, ranging from 0.1 up to 33.3 mu g m(-3). Organic aerosol (OA) was the dominant component in PM1, with a fraction of 68 %. Three OA factors, i.e., biomass burning organic aerosol (BBOA), biomass-burning-influenced oxygenated organic aerosol (OOA-BB) and oxygenated organic aerosol (OOA), were resolved using positive matrix factorization analysis. The two oxygenated OA factors accounted for 87% of the total OA mass. Three biomass burning events were identified by examining the enhancement of black carbon concentrations and the f(60) (the ratio of the signal at m/z 60 from the mass spectrum to the total signal of OA). Back trajectories of air masses and satellite fire map data were integrated to identify the biomass burning locations and pollutant transport. The western air masses from South Asia with active biomass burning activities transported large amounts of air pollutants, resulting in elevated organic concentrations up to 4-fold higher than those of the background conditions. This study at Mt. Yulong characterizes the tropospheric background aerosols of the Tibetan Plateau during pre-monsoon season and provides clear evidence that the southeastern edge of the Tibetan Plateau was affected by the transport of anthropogenic aerosols from South Asia.

Rapid economic development and urbanization in China has been concentrated in coastal cities, resulting in haze and photochemical smog issues, especially in the densely-populated Yangtze River Delta. In this study, we explore particulate matter (specifically PM2.5) pollution in a city in Zhejiang Province (Ningbo), chosen to represent a typical, densely-populated urban city with residential and industrial sections. PM2.5 samples were collected at five sites in four seasons from Dec. 2012 to Nov. 2013. The annual average PM2.5 mass concentration was 53.2 +/- 30.4 mu g/m(3), with the highest concentration in winter and lowest in summer. Among the five sites, PM2.5 concentration was highest in an urban residential site and lowest in a suburban site, due to effects of urbanization and the anthropogenic influences. The chemical components of PM2.5 show significant seasonal variation. In addition, secondary transformation was high in Ningbo, with the highest proportion of secondary components found at a suburban site and the lowest at the industrial sites. Ningbo is controlled by five major air masses originating from inland China, from the Bohai Sea, offshore from the southeast, the Yellow Sea, and off the east coast of Korea. The relative contributions of these air masses differ, by season, with the Bohai Sea air mass dominating in winter and spring, the maritime southeast air mass in summer, and the YellowSea and coastal Korean air masses dominating in autumn. The continental air mass is associated with a high PM2.5 concentration, indicating that it is primarily transports primary emissions. In contrast, the concentration ratios among secondary formed pollutants were higher in the maritime air masses, which suggests that sea breezes control temporal and spatial variations of air pollution over coastal cities. (C) 2017 Published by Elsevier B.V.