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Xu B.,Peking University | Xu B.,Zhejiang Province Environmental Monitoring Center | Shang J.,Peking University | Zhu T.,Peking University | Tang X.,Peking University
Atmospheric Environment | Year: 2011

Formaldehyde is one of the most important carbonyl organic compounds. Heterogeneous reactions of formaldehyde on the surface of oxides of crustal elements could be an important sink for formaldehyde in the atmosphere. In this study, the kinetics of the heterogeneous reaction of formaldehyde on the surface of γ-Al2O3 was investigated in situ by diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) combined with ion chromatography (IC), X-ray diffraction (XRD), and field emission environmental scanning electron microscope (ESEM). The adsorbed species, formate, dioxymethylene, polyoxymethylene, and formaldehyde, on γ-Al2O3 particles, were identified by infrared spectroscopy. On the surface of γ-Al2O3 particles, formaldehyde is first oxidized to dioxymethylene, which is further oxidized to formate. The reaction order was determined as 0.74 ± 0.05, and the initial reactive uptake coefficients at room temperature were calculated with the geometric and Brunauer-Emmett-Teller specific surface areas as (3.6 ± 0.8) × 10-4 and (1.4 ± 0.31) × 10-8, respectively. The influences of oxygen concentration, humidity, and temperature on the reaction products and reactive uptake coefficients were studied. The results indicated the reaction is independent of the O2 concentration within the range used in this experiment, and humidity is negatively correlated with the uptake of formaldehyde by the particles. Temperature not only plays a role on the heterogeneous reaction products but also is positively correlated with the uptake rate of formaldehyde by γ-Al2O3 particles in the troposphere. The apparent activation energy of the reaction was determined. © 2011 Elsevier Ltd.

Wu W.,Zhejiang University | Wu W.,University of Massachusetts Amherst | Yang K.,Zhejiang University | Chen W.,Zhejiang University | And 5 more authors.
Water Research | Year: 2016

Adsorption of 22 nonpolar and polar aromatic compounds on 10 carbon nanotubes (CNTs) with various diameters, lengths and surface oxygen-containing group contents was investigated to develop predictive correlations for adsorption, using the isotherm fitting of Polanyi theory-based Dubinin-Ashtakhov (DA) model. Adsorption capacity of aromatic compounds on CNTs is negatively correlated with melting points of aromatic compounds, and surface oxygen-containing group contents and surface area ratios of mesopores to total pores of CNTs, but positively correlated with total surface area of CNTs. Adsorption affinity is positively correlated with solvatochromic parameters of aromatic compounds, independent of tube lengths and surface oxygen-containing group contents of CNTs, but negatively correlated with surface area ratios of mesopores to total pores of CNTs. The correlations of adsorption capacity and adsorption affinity with properties of both aromatic compounds and CNTs clearly have physical significance, can be used successfully with DA model to predict adsorption of aromatic compounds on CNTs from the well-known physiochemical properties of aromatic compounds (i.e., solvatochromic parameters, melting points) and CNTs (i.e., surface area and total acidic group contents), and thus can facilitate the environmental application of CNTs as sorbents and environmental risk assessment of both aromatic contaminants and CNTs. © 2015 Elsevier Ltd.

Jiang F.,Nanjing University | Zhou P.,Meteorological Bureau | Liu Q.,Hong Kong Polytechnic University | Wang T.,Nanjing University | And 2 more authors.
Journal of Atmospheric Chemistry | Year: 2012

In this study, we investigate the springtime O3 formation over East China (April 2008) using the Weather Research and Forecasting Model with Chemistry (WRF/Chem). A simple process analysis scheme is added to WRF/Chem, which could calculate the contributions of photochemical and physical processes to O3 formation. WRF/Chem calculates the hourly 3-D O3 mixing ratios, photochemical O3 production rates (CPR) and physical processes contribution rates (PCR) on a two nested domain system, with inner domain focusing on East China. Model evaluation shows that the modeled results agree relatively well with the observations. On the ground level, the high O3 mixing ratios (>45 ppbv) are located over Fujian and Jiangxi provinces. The O3 levels over the Yangtze River Delta (YRD) and northern Jiangsu are low (<30 ppbv). The distribution patterns of CPR and PCR over East China reveal that the high O3 mixing ratios over Jiangxi and Fujian are caused by both local photochemical generation and regional transport, while the O3 concentrations over the YRD region are transported and diffused from surrounding areas. In addition, the contributions of biogenic and anthropogenic emissions as well as the regional transport from domain's upstream regions are discussed. On average, the biogenic and anthropogenic emissions account for 2.6 and 4.5 ppbv of daytime mean O 3 mixing ratios in East China, respectively. © 2012 Springer Science+Business Media Dordrecht.

Tang Y.-D.,Environmental Engineering Co. | Feng Y.-Q.,Zhejiang Province Environmental Monitoring Center
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2010

Dynamic test signals of a pile with the wavelet method were analyzed. The traditional testing data of stress wave reflection were used. More information about propagating process of stress wave in the pile was obtained by getting ride of errors from the actual measured signals. The results of some examples demonstrated that the proposed method has better accuracy and flexibility.

Li Y.,Peking University | Li Y.,Chinese Academy of Meteorological Sciences | Zhu T.,Peking University | Zhao J.,CAS Institute of Chemistry | Xu B.,Zhejiang Province Environmental Monitoring Center
Environmental Science and Technology | Year: 2012

Quinones are toxicological substances in inhalable particulate matter (PM). The mechanisms by which quinones cause hazardous effects can be complex. Quinones are highly active redox molecules that can go through a redox cycle with their semiquinone radicals, leading to formation of reactive oxygen species. Electron spin resonance spectra have been reported for semiquinone radicals in PM, indicating the importance of ascorbic acid and iron in quinone redox cycling. However, these findings are insufficient for understanding the toxicity associated with quinone exposure. Herein, we investigated the interactions among anthraquinone (AQ), ascorbic acid, and iron in hydroxyl radical (·OH) generation through the AQ redox cycling process in a physiological buffer. We measured ·OH concentration and analyzed the free radical process. Our results showed that AQ, ascorbic acid, and iron have synergistic effects on ·OH generation in quinone redox cycling; i.e., ascorbyl radical oxidized AQ to semiquinone radical and started the redox cycling, iron accelerated this oxidation and enhanced ·OH generation through Fenton reactions, while ascorbic acid and AQ could help iron to release from quartz surface and enhance its bioavailability. Our findings provide direct evidence for the redox cycling hypothesis about airborne particle surface quinone in lung fluid. © 2012 American Chemical Society.

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