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The roles of heterogeneous chemical processes in the formation of an air pollution complex and gray haze

Science China Chemistry 2011年第1期54卷 145-153页

作者： zhu tong,shang Jing & {2. defeng state key joint laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering,Peking University,Beijing 100871,China 1. state key {2. laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering Peking University Beijing 100871 China

Urban and regional air pollutions are characterized by high concentrations of secondary pollutants such as photo-oxidants （mainly ozone） and fine particulate matter, which are formed through chemical reactions of the primary pollutants emitted from various sources. The accumulation of these pollutants under stagnant meteorological conditions results in the formation of gray haze, reducing visibility and causing major impacts on human health and climate. In an air pollution complex, the co- existence of high concentrations of primary and secondary gaseous and particulate pollutants provides a large amount of reac- tants for heterogeneous reactions on the surface of fine particles; these reactions change the oxidizing capacity of the atmos- phere, as well as chemical compositions along with the physicochemical and optical properties of particulate matter, thereby accelerating formation of the air pollution complex and gray haze. Using in situ technologies, such as diffuse reflectance infra- red Fourier-transform spectroscopy and single-particle Raman spectroscopy, we systematically investigated the reaction kinet- ics and mechanisms of gaseous pollutants （i.e., NO2. SO2. 03, and formaldehyde） on the surfaces of the major components of atmospheric particles such as CaCO3, kaolinite, montmorillonite, NaC1, sea salt, A12.3, and Tit2. We found that the main re- action products were sulfate, nitrate, or formate, which can change the hygroscopicity and light extinction parameters of those particles significantly. By analyzing the reaction kinetics of these heterogeneous reactions, we identified synergetic mechanisms of the three ternary reaction systems, ,i.e., NOE-particles-H2., SO2.particles-O3, and organics/SO2.particles-UV illumination. These synergetic mechanisms can provide experimental and theoretical bases for understanding the feedback mechanisms and nonlinear processes in the formation of an air pollution complex and gray haze.

关键词： fine particles secondary pollutants oxidizing capacity ternary reaction nonlinear processes

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Photocatalytic degradation of rhodamine B by dye-sensitized TiO_2.under visible-light irradiation

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Science China Chemistry 2011年第1期54卷 167-172页

作者： shang Jing,zhao FengWei,{2. & LI Jia state key joint laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering,Peking University,Beijing 100871,China 1. state key {2. laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering Peking University Beijing 100871 China

Perylene tetracarboxylic diimide (PTCDI),widely used in organic photovoltaic devices,is an n-type semiconductor with strong absorption in the visible-light *** has been almost no study of the PTCDI-sensitized TiO2.composite used to photocatalytically degrade *** this study,PTCDIand copper phthalocyanine tetrasulfonic acid (CuPcTs)-sensitized TiO2.composites were prepared using a hydrothermal *** morphologies and structures of the two composites were characterized by X-ray diffraction,transmission electron microscopy,ultraviolet-visible spectroscopy,and fluorescence *** visible-light photocatalytic activities of the composites were evaluated using the degradation of rhodamine B as a model *** showed that dye-sensitized TiO2.samples had a wider absorption spectrum range and higher visiblelight photocatalytic activity compared to TiO2.*** double dye-sensitized (or co-sensitized) TiO2.composite with efficient electron collection exhibited higher photocatalytic activity than did the single dye-sensitized TiO2.*** electron transfer processes of single and double dye-sensitized TiO2.composites were illustrated according to band theory.

关键词： copper phthalocyanine tetrasulfonic acid dye sensitization perylene tetracarboxylic diimide rhodamine B visible-lightphotocatalysis

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Raman micro-spectrometry as a technique for investigating heterogeneous reactions on individual atmospheric particles

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Science China Chemistry 2011年第1期54卷 154-160页

作者： zhao defeng,{2.,CHEN Qi,LIU YingJun & ZHANG ZeFeng state key joint laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering,Peking University,Beijing 100871,China 1. state key {2. laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering Peking University Beijing 100871 China

Investigating the heterogeneous reaction on individual atmospheric particles is important because it approximates actual atmospheric conditions and can aid in reducing artifacts in elucidating real mechanisms and processes,and determining real kinetic parameters of the atmosphere *** study developed a Raman microspectrometry method to investigate heterogeneous reactions on individual *** method was applied to the reaction of NO2.with individual CaCO3 *** was demonstrated that Raman microspectrometry can obtain information on both chemical composition and microscopic morphology at the same time,as well as information on chemical characteristics,such as the phase,which is useful for studying reaction *** spectra of individual particles deposited on a substrate showed no interference by morphological resonance,which is helpful for obtaining high-quality ***,Raman microspectrometry was compared with other methods for investigating heterogeneous reactions on individual particles and was found to have several advantageous characteristics.

关键词： Raman microspectrometry individual atmospheric particle heterogeneous reaction

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Heterogeneous reaction of NO_2.with sea salt particles

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Science China Chemistry 2010年第12期53卷 2652-2656页

作者： YE ChunXiang 1,LI HongJun 1,zhu tong 1,shang Jing 1,ZHANG ZeFeng 1,2.& {2. defeng 1 1 state key joint laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering,Peking University,Beijing 100871,China 2.College of Atmospheric Physics,Nanjing University of Information Science and Technology,Nanjing 2.0044,China 1. state key {2. laboratory of environmental simulation and pollution control College of environmental Sciences and Engineering Peking University Beijing 100871 China2. College of Atmospheric Physics Nanjing University of Information Science and Technology Nanjing 210044 China

To understand how NO2.reacts with sea salt particles in the atmosphere of Mega-cities in coastal zones,the heterogeneous reaction of NO2.on the surface of wet sea salt was investigated with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC).Kinetic measurements indicated that nitrate formation on sea salt was second order in NO 2.concentration and reactive uptake coefficients were (5.51 ± 0.19) × 10-7 and 1.2. × 10-6 respectively under 0% and 2.% relative humidity (RH) at NO 2.molecular concentration of 1.96 × 1015 mol/*** results showed that liquid water was formed at the site of MgCl2.6H2.,CaCl2.2.2. on the surface of sea salt and made the reaction more sustainable by releasing hydrated water and absorbing water from air even under a low RH (30%).Therefore,pure NaCl particles should not be used to represent sea salt in studies of the heterogeneous reaction with NO2.

关键词： sea salt particles diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) hydrated water absorbed water reactive uptake coefficient

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Heterogeneous reaction of NO_2.on the surface of montmorillonite particles

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Journal of environmental Sciences 2012年第10期24卷 1753-1758页

作者： Zefeng Zhang Jing shang tong {2. Hongjun Li defeng zhao Yingju Liu Chunxiang Ye College of environmental Sciences and Engineering Peking UniversityBeijing 100871China CMA key laboratory for Atmospheric Physics and Environment Nanjing University of Information Science and TechnologyNanjing 210044China

The studies on heterogeneous reactions over montmorillonite, which is a typical 2.1 layered aluminosilicate, will benefit to the Understanding of heterogeneous reactions on clay minerals. Montmorillonite can be classified as sodium montmorillonite or calcium montmorillonite depending on the cation presented between the different layers. Using diffuse reflectance infrared Fourier transform spectroscopy （DRIFTS）, the heterogeneous reaction mechanism of NO2.on the surface of montmorillonite was firstly investigated. Results showed that the reaction of NO2.on the surface of sodium and calcium montmorillonite fit a first-order kinetics, and the reaction duration of calcium montmorillonite was longer than that of sodium montmorillonite under the dry condition. For either sodium or calcium montmorillonite, the uptake coefficient decreased as humidity increased.

关键词： heterogeneous reaction uptake coefficient DRIFTS montmorillonite NO2

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