Tiantao Cheng

Black carbon in a continental semi‐arid area of Northeast China and its possible sources of fire emission

[1] Surface continuous measurements on black carbon (BC) were performed at Tongyu (44.42°N, 122.87°E) from March to December 2008. Tongyu is an international reference site of semi-arid climate and environment researches, located in a continental semi-arid area of northeastern China. Mass concentrations and potential contributing sources of BC are discussed for the sampling site. Hourly BC concentrations ranged from 77.61 ng m-3 to 59.55 μg m -3 with an average of 2.52 μg m -3 , showing a clear seasonal pattern with high values in spring, fall, and winter and low values in summer. Events of high BC concentrations occurred frequently in spring as a result of long-range transport of polluted air masses from the north, northwest, and south in the atmosphere over the Asian continent. The Yangtse River Delta (YRD) and China Anhui Province, the North China Plain (NCP), Northeast China, the Mongolian boundary near China and Russia, Middle Asia, and some areas of Russian Far East were major potential contribution sources for the observed pollutants. The region between Jiangsu Province and Anhui Province of China and the boundary regions between China and Russian Primorskiy and Khabarovskiy were possible source areas of fire emissions having great contributions to high BC levels at Tongyu. The region between Jiangsu Province and Anhui Province of China was the most important anthropogenic fire source of agricultural residue burning outflows.

Particle number concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai

The aerosol number concentration and size distribution as well as size-resolved particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The number of haze days accounted for 43%, of which 30% was severe (visibility<2km) and moderate (2km≤visibility<3km) haze, mainly distributed in winter and spring. The mean particle number concentration was about 17,000/cm(3) in haze, more than 2 times that in clean days. The greatest increase of particle number concentration was in 0.5-1μm and 1-10μm size fractions during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of particle number concentration was within 50-100nm and 100-200nm fractions during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The particle volume concentration and surface concentration in haze, photochemical smog and clean days were 102, 49, 15μm(3)/cm(3) and 949, 649, 206μm(2)/cm(3), respectively. As haze events got more severe, the number concentration of particles smaller than 50nm decreased, but the particles of 50-200nm and 0.5-1μm increased. The diurnal variation of particle number concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4(+), SO4(2-) and NO3(-) increased greatly, followed by Na(+), K(+), Ca(2+) and Cl(-). These ions were very different in size-resolved particles during haze and photochemical smog episodes.

Characterization of polycyclic aromatic hydrocarbons in fog–rain events

Atmospheric polycyclic aromatic hydrocarbons (PAHs) mainly originate from incomplete combustion or pyrolysis of materials containing carbon and hydrogen. They exist in gas and particle phases, as well as dissolved or suspended in precipitation (fog or rain). Current studies in atmospheric PAHs are predominantly focused on fog and rainwater samples. Some sampling difficulties are associated with fog samples. This study presented the first observation of the characteristics of PAHs in fog samples using a solid phase microextraction (SPME) technique. Eighteen fog samples were collected during ten fog events from March to December 2009 in the Shanghai area. PAHs were extracted by SPME and analyzed by gas chromatography-mass spectrometry (GC-MS). As the compounds were partially soluble in water, with solubility decreasing with increasing molecular weight, low molecular weight (LMW) PAH compounds were universally found in the fog water samples. Naphthalene (NaP), phenanthrene (Phe), anthracene (Ant) and fluoranthene (Flo) were dominant compounds in fog water. The total PAH concentration in fog water ranged from 0.03 to 6.67 μg L(-1) (mean of 1.06 μg L(-1)), and was much higher in winter than in summer. The concentration of PAHs in fog or rain water decreased after undergoing a pre-rain or pre-fog wash. The average concentration of PAHs was higher in fog than in rain. Diagnostic ratio analysis suggested that petroleum and combustion were the dominant contributors to PAHs in urban Shanghai. Backward trajectories were calculated to determine the origin of the air masses, showing that air masses were mostly from the northeast territory.

Interactions between Heterogeneous Uptake and Adsorption of Sulfur Dioxide and Acetaldehyde on Hematite

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.

Distribution and source of alkyl polycyclic aromatic hydrocarbons in dustfall in Shanghai, China: the effect on the coastal area.

Alkyl polycyclic aromatic hydrocarbons (APAHs) are a group of persistent organic pollutants which are widely distributed in the atmospheric environment. To estimate the seasonal and spatial distribution of APAHs in dustfall in Shanghai, supercritical fluid extraction (SFE) followed by gas chromatography/mass spectrometry (GC/MS) were the analytical methods applied to the dustfall samples collected in this area from Dec. 2004 to Oct. 2005. Forty-one APAHs were found and divided into six groups which were alkyl naphthalenes (ANAs), alkyl phenanthrenes (APHs), alkyl anthracenes (AANs), alkyl fluoranthenes (AFLs), alkyl pyrenes (APYs) and alkyl chrysenes (ACHs). ANAs and APHs were two dominant APAHs in the proportion of more than 50%. The concentrations of total APAHs ranged from 1.6 to 9.0 microg g(-1). The ratios of APAHs to TPAHs (PAHs plus APAHs) fell into the range of 28 approximately 50%. The APAH levels were found to be higher in winter and spring than in summer and autumn. In terms of spatial distribution, concentration of APAHs was found to be higher in western Shanghai than eastern Shanghai. The source analysis showed that dustfall APAHs mainly derived from vehicle emissions and used crankcase oil. The annual fluxes of APAHs and PAHs in dustfall in urban Shanghai were 0.53 approximately 2.97 T and 0.96 approximately 5.34 T, respectively.

Analysis of human breath samples of lung cancer patients and healthy controls with solid-phase microextraction (SPME) and flow-modulated comprehensive two-dimensional gas chromatography (GC × GC)

This paper reports the use of chromatographic profiles of breath volatiles to determine disease markers in lung cancer patients and healthy volunteers. The volatile fraction was isolated by headspace solid-phase microextraction (HS-SPME) and analyzed by flow-modulated comprehensive two-dimensional gas chromatography and flame ionization (GC × GC-FID). Following the experiments, collected data were transformed, and partial least-squares discriminant analysis (PLS-DA) as well as Mann–Whitney Test were carried out to model the data and discover breath metabolites with a significant concentration difference between patients and healthy subjects. Using the abovementioned method, lung cancer patients and healthy controls could be correctly distinguished based on metabolic VOCs abnormality in human breath. Five potential target compounds including acetone, isoprene, methanol, pentane and propanol were identified. Lung cancer patients show higher concentrations of propanol (7415.3 ng L−1), acetone (1811.6 ng L−1) and methanol (225 ng L−1) compared with those of healthy volunteers (1975.3 ng L−1, 579.9 ng L−1, 76.8 ng L−1, respectively). In addition, there is no significant relationship between breath VOCs and gender or body mass index (BMI). This approach will facilitate the comparison of complex breath VOC profiles and diseases. These findings may offer valuable and reliable information for the early diagnosis and prognosis of lung cancer.

Chemical characterization of aerosols over the Atlantic Ocean and the Pacific Ocean during two cruises in 2007 and 2008

[1] To help understand the chemical properties of marine aerosols and the long-distance transport of continental aerosols to remote oceanic regions, total suspended particulates (TSP) samples were collected over the Atlantic Ocean and the Pacific Ocean during two cruises in September-December 2007 (cruise I) and March-April 2008 (cruise II) aboard the MN Oceanic II. Data were analyzed and interpreted with the aid of back trajectory, principal component, and multiple linear regression analyses. Compared with the results over the South Pacific from 2 decades ago, the non-sea-salt sulfate (NSS-SO 2- 4 ) concentrations over the South Pacific have increased by a factor of ~1.5, while the NO - 3 concentration has remained constant. On average, NSS-SO 2- 4 accounted for 30-52% of the total SO 2- 4 during the two cruises. Chloride deficit was observed in all samples, with NSS-SO 2- 4 being the preferred species for acid displacement over the South Pacific and the Mediterranean Sea. Persistent clean marine air masses were only observed over the northern Atlantic and South Pacific during cruise I, while more frequent impacts of continental air (dust, biomass burning, and industrial plumes) were observed during cruise II. Combined with the NAAPS aerosol maps, these results indicate that during cruise II, (1) southern Atlantic was influenced by Southern Africa and the interhemisphere transport of biomass burning plumes in Central Africa, (2) northern Atlantic was under the combined pollution plumes of Sahara dust intrusion and biomass burning, and (3) the Mediterranean Sea was affected by the mixed pollution from biomass burning and industrial contamination, as well as Saharan dust.

Evolution of aerosol vertical distribution during particulate pollution events in Shanghai

A set of micro pulse lidar (MPL) systems operating at 532 nm was used for ground-based observation of aerosols in Shanghai in 2011. Three typical particulate pollution events (e.g., haze) were examined to determine the evolution of aerosol vertical distribution and the planetary boundary layer (PBL) during these pollution episodes. The aerosol vertical extinction coefficient (VEC) at any given measured altitude was prominently larger during haze periods than that before or after the associated event. Aerosols originating from various source regions exerted forcing to some extent on aerosol loading and vertical layering, leading to different aerosol vertical distribution structures. Aerosol VECs were always maximized near the surface owing to the potential influence of local pollutant emissions. Several peaks in aerosol VECs were found at altitudes above 1 km during the dust- and bioburning-influenced haze events. Aerosol VECs decreased with increasing altitude during the local-polluted haze event, with a single maximum in the surface atmosphere. PM2.5 increased slowly while PBL and visibility decreased gradually in the early stages of haze events; subsequently, PM2.5 accumulated and was exacerbated until serious pollution bursts occurred in the middle and later stages. The results reveal that aerosols from different sources impact aerosol vertical distributions in the atmosphere and that the relationship between PBL and pollutant loadings may play an important role in the formation of pollution.

Long-range and regional transported size-resolved atmospheric aerosols during summertime in urban Shanghai

In this study, the concentrations of water soluble ions (WSI), organic carbon (OC), and elemental carbon (EC) of size-resolved (0.056-18μm) 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 100.1μgm-3 in July and 7.00, 29.21, and 35.10μgm-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 Shanghais air pollution.

Effect of Formaldehyde on the Heterogeneous Reaction of Nitrogen Dioxide on γ-Alumina

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.