“大气气溶胶光学性质”专辑前言

大气气溶胶是悬浮于空气中的固体和液体微小颗粒,其对太阳光的散射和吸收是造成大气能见度降低的主要原因。大气气溶胶还可以通过与太阳光的相互作用影响辐射平衡,从而影响气候。因此,对气溶胶光学性质的深入理解,是了解其气候和环境效应的基础。气溶胶的光学性质与其多种理化性质紧密相关。

大气超细颗粒物来源及其化学组分研究进展

大气超细颗粒物(ultrafine particle, UFP)为粒径小于100 nm的颗粒物,其数浓度主导了大气颗粒物的总数浓度,对人体健康和气候都有显著影响.大气UFP主要来源于污染源烟气和大气中气态前体物的成核和生长.其中,污染源烟气中成核和生长产生的颗粒物排放后构成大气UFP的一次来源,而直接在大气中成核和生长(又称新粒子生成)产生的颗粒物构成大气UFP的二次来源.由于不同来源气态前体物种类的显著差别,所生成UFP的化学组分及其健康和气候效应也会有显著不同.然而,目前对大气UFP的不同来源贡献及其化学组成的相关研究相对较少.本文简要介绍了几种主要污染源排放的一次UFP特征、大气新粒子生成产生的二次UFP特征、以及受多种来源影响的实际大气UFP的化学组分及其来源解析相关研究进展.基于上述分析,建议未来着重开展高时间分辨率和高物种分辨率的大气UFP化学组分观测,加强对大气UFP分子水平上组分及其变化规律的认识.

二次有机气溶胶光学特性研究进展

二次有机气溶胶(SOA)对大气能见度、辐射平衡、气候变化具有重要影响,系统地研究不同环境因素对SOA光学性质的影响是大气科学研究的前沿性方向。外场观测是认知SOA光学性质的重要途径,近年来新的观测仪器和模型的发展使得对SOA光学性质的认识更加深入。而实验室研究通过控制特定变量模拟不同条件下SOA的生成过程,从机制上加深了对SOA光学特性的认知。综述重点关注了近年来有关经气相氧化、多相过程等途径生成的SOA的光学特性研究,并分析了老化过程对SOA光学特性的影响,以及外场和实验室结果的对比和联系。

Environmental chamber study of the photochemical reaction of ethyl methyl sulfide and NO_x

A series of experiments were conducted in a self-made smog chamber at （300 ＋ 1） K and 1.01 × 10^5 Pa to simulate the photochemical reaction of ethyl methyl sulfide （EMS） and NOx. The results showed that the higher the initial concentration of EMS, the more ozone was generated in the simulative reactions. It was found that the light intensity plays a very important role in the evaluation of ozone formation potential for EMS. The parameters of d（Oa-NO） and IR （incremental reactivity） were used to quantify the potential of EMS on ozone formation. The obtained maximum IR values in this article for the five simulative reactions were 1.55 × 10^-2, 0.99 × 10^-2, 1.36 × 10^-2, 2.47 × 10^-2, and 1.65 × 10^-2, respectively. A comparison between the results we obtained here and the results we obtained previously for di-tert-butyl peroxide and acetylene showed that the potential reactivity of EMS on ozone formation was at a relatively low level.

A novel heterogeneous reaction for generating gaseous nitrous acid

The short-lived reactive specimen nitrous acid HONO was generated in the gas phase by the hetero-geneous reaction of gaseous HCl with AgNO2 which can generate higher concentration of HONO than other methods. We investigated the process from generation to dissociation in the gas phase under different controlled temperatures,and discussed the ionization and reaction on the solid surface by combination of the photoelectron spectroscopy and photoionization mass spectroscopy(PES-PIMS) and in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) .

Heterogeneous chemistry of trace atmospheric gases on atmospheric aerosols:An overview

Due to altering the budget of important trace gases and changing the composition of atmospheric aerosols,heterogeneous reactions between trace gases and liquid/solid aerosols have become an important subject of atmospheric science in recent years.However,the kinetics and mechanism of these reactions have not been well-understood yet.In recent years,we have established an integrated method to study a series of atmospheric heterogeneous reactions under control atmospheric conditions.Using on-line techniques,such as Diffuse Reflectance Infrared Fourier Transform spectroscopy,Raman microspectrometry and Knudsen cell,the heterogeneous reactions of a series of trace gases(NO2,SO2,H2O2,DMS,C2H5 I and Monocarboxylic acids)on mineral oxides and black carbon were investigated.The uptake coefficients and mechanisms at different atmospheric conditions(temperature,relative humidity and reactant concentration)were obtained.In addition,a home-made equipment named rotated wetted-wall reactor was designed for the in situinvestigations of the uptake of volatile organic compounds into the H2SO4 solution and H2SO4/H2O2 mixed solution.In this review,we present the main results obtained in our laboratory studies and propose some challenges that still exist in the heterogeneous reaction studies.

Reaction Kinetics and Secondary Organic Aerosol Composition Analysis of 2-Cyclohexen-1-one with NO_(3) Radicals

Unsaturated ketones are typical oxygenated volatile organic compounds(OVOCs)with high reactivity,and are important precursors in air pollution.The sources of OVOCs are complex and include direct emissions and secondary oxidation formation of VOCs in the atmosphere.2-Cyclohexen-1-one is a widespread substance,and is derived from the industrial catalytic oxidation of cyclohexene.In this paper,we investigated the rate constants of the chemical reactions of 2-cyclohexen-1-one with NO_(3) radicals,which is(7.25±0.29)×10^(-15) cm^(3)·molecule^(-1)·s^(-1) at 298 K and under 1 atm(1 atm=101325Pa).It supplemented the kinetics of NO_(3) radicals database,and revealed its effects in the nighttime atmosphere.In addition,the reaction products of 2-cyclohexen-1-one with NO_(3) radicals were detected by Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS),which revealed a series of nitrate esters in the composition of the secondary organic aerosol(SOA),which may reduce atmospheric visibility.Finally,the possible pathways for the generation of the products were developed.

A kinetic study of the reaction of ozone with ethylene in a smog chamber under atmospheric conditions

Ozone is one of the key species in the processes of atmospheric chemistry, which can be taken as an indicator of oxidation capacity in the troposphere. The reaction of ozone with reactive gases is an important process in the troposphere. Experimental simulation equipment of smog chamber for atmospheric reactions is used to study the reaction of ozone with ethylene in real atmospheric environment with ozone concentrations of 100―200 ppb. The concentrations of ozone and ethylene were moni-tored during the reaction with the combination of Model 49C-O_3 Analyzer and GC-FID. A rate constant of 1.01×10^(-18) (cm^3·mol^(-1)·s-(~1)) was obtained at 286.5 K, under condition of which the half-life of ozone was 88 min. The results obtained from our experiments are in excellent agreement with those reported previously by other researchers under extremely low pressure in terms of matrixisolation technology. This demonstrates that our equipment of smog chamber for atmospheric reactions is reliable, which can be used for further research of the processes of atmospheric reactions.

Smog chamber studies of ozone formation potentials for isopentane

The incremental reactivity and ozone formation potential of isopentane have been studied with chamber experiments and computer simulations. The chemical mechanism used in the computer simulations is an isopentane sub-mechanism from the Master Chemical Mechanism (MCM). The results from the chamber experiments suggest that the MCM can well simulate i-C5H12-NOx chamber experiments. The heterogeneous reaction of NO2 and water is an important source for OH radicals in the chamber experiments. The photolysis of HONO is responsible for the initiation of isopentane in photochemical reactions. The reaction rate constant for NO2 → HONO was determined to be 3.9×10-4―5.9×10-3 min-1 by conducting 3 sets of CO-NOx-air irradiations. 5 sets of isopentane-NOx irradiations under different conditions were performed in our chamber. Compared with the experiment with a low relative humidity (RH), an increase in RH can increase the reaction rate of NO2 with H2O, so that the peak ozone occurs earlier. When isopentane is predominant over NOx, the peak ozone concentration is largely dependent on NOx concentrations.

Experimental investigation of incremental reactivity of di-tert-butyl peroxide

Large quantities of di-tert-butyl peroxide (DTBP) have been emitted into the troposphere due to human activities. Its role in the atmospheric photochemical reaction has not been understood. This study presents the results of the photochemical reactions of DTBP and NOx, which have been simulated in a self-made smog chamber under the temperature of (29±1)℃. Both the wall decays of ozone and NO2 could be neglected, compared to the results in simulative experiments. The effective intensity of UV light used in the experiments was 1.28×10-3 s-1, which was expressed by the rate constant of NO2 photolysis in purified air. The reaction mechanism was proposed according to our results and reports of other researchers. The maximum values of incremental reactivity (IR) in the three simulative ex- periments were 9.53×10-2, 5.23×10-2 and 3.78×10-2, respectively. The incremental reactivity decreased with the increase of initial concentrations of DTBP. The IR value of DTBP obtained in this study was comparable to that of acetylene reported in our previous research.

Extinction efficiencies of mixed aerosols measured by aerosol cavity ring down spectrometry

A cavity ring down spectroscopy instrument was introduced and designed for measuring extinction efficiencies of pure and mixing aerosols in this paper.Through averaging 500 individual waveforms,the minimal detectable aerosol extinction coefficient of 8.4 × 10-7 m-1 was achieved.By the test results using the NaCl particles,we concluded that this system could measure the extinction efficiencies of an aerosol with an uncertainty less than 3% under laboratory controlled experimental conditions.The refractive indices of different aerosols were retrieved through comparing the measured extinction efficiencies of each aerosol type with which predicted by Mie theory.Aerosols composed of ammonium sulphate and succinic acid with different weight ratios were used to create a model of mixed aerosols using these two materials,whose extinction efficiencies and complex refractive indices were derived.The refractive indices of the mixed aerosols were also calculated by various optical mixing rules.We found that all the molar refraction/absorption mixing rule,the volume ratio linear rule,and Maxwell-Garnett rule did provide comparable results,of which the volume ratio linear rule gave a slightly worse fit than the others.

Experimental and theoretical studies of the reaction between cationic vanadium oxide clusters and acetylene

The time of flight mass spectrometer coupled with a laser ablation/supersonic expansion cluster source and a fast flow reactor was adopted to study the reactivity of cationic vanadium oxide clusters(VmOn+) toward acetylene(C2H2) molecules under gas phase(P,～ 1.14 kPa),under near room temperature(T,～ 350 K) conditions.Association products,VmOnC2H2+(m,n = 2,4;2,6;3,7―8;4,9―11;5,12―13;6,13―16,and 7,17),are observed.The oxidation of C2H2 by(V2O5)+n(n = 1―3) is experimentally identified.The reactivity of(V2O5)+ n decreases as n increases.Density functional theory(DFT) calculations were carried out to interpret the reaction mechanisms.The DFT results indicate that a terminal oxygen atom from V2O5+ can transfer overall barrierlessly to C2H2 at room temperature,which is in agreement with the experimental observation.Other experimental results such as the observation of V2O6C2H+2 and non-observation of V2O7,8C2H+2 in the experiments are also well interpreted based on the DFT calculations.The reactivity of vanadium oxide clusters toward acetylene and other hydrocarbons may be considered in identifying molecular level mechanisms for related heterogeneous catalysis.

Uptake kinetics of 3-buten-1-ol,4-penten-1-ol and 3-methyl-3-buten-1-ol into sulfuric acid solutions

Unsaturated alcohols are important components in complex mixtures of oxygenated volatile organic compounds,and play a significant role in atmospheric chemistry.The uptake kinetics of 3-buten-1-ol (BO31),4-penten-1-ol (PO41) and 3-methyl3-buten-1-ol (MBO331) into 20 wt%-80 wt% H2SO4 solutions were studied,using a rotated wetted-wall reactor coupled to a differentially pumped single-photon ionization time of flight mass spectrometer (SPI-TOFMS).With increasing acidity,the uptake processes changed from reversible to irreversible (reactive).Reactive uptake was observed in 60 wt%-80 wt%,50 wt%-80 wt% and 30 wt%-80 wt% H2SO4 solutions for BO31,PO41 and MBO331,respectively.Reactive uptake coefficients were acquired and are reported here for the first time.Reactivity order followed the trend:BO31<PO41<MBO331.An electrophilic addition mechanism of H2SO4 to the C==C double bond was used to explain this trend.Atmospheric implications were discussed,based on the reactive uptake coefficients.This heterogeneous reaction with sulfuric acid aerosols may be a potential degradation pathway of unsaturated alcohols,and should not be neglected.

Rate constants for the reaction of ozone with n-butyl, s-butyl and t-butyl methyl sulfides

The rate constants for the ozone reactions with n-butyl methyl sulfide (n-BMS, CH3CH2CH2CH2SCH3), sec-butyl methyl sulfide (s-BMS, CH3CH2(CH3)CHSCH3) and tert-butyl methyl sulfide (t-BMS, (CH3)3CSCH3) were measured using our smog chamber under supposedly pseudo-first-order conditions at 300±2 K and 760 Torr. The experimental determined rate constants for n-butyl, s-butyl and t-butyl methyl sulfide are (1.23 ± 0.06)×10-19, (5.08 ± 0.19)×10?20 and (2.26 ± 0.14)×10?20 cm3·molecule-1·s-1, respectively. The reactivity-structure relationship of the reactions was discussed and used to illustrate the mechanism of the ozone reaction with thioethers. The results enrich the kinetics data of atmospheric chemistry.

Carbazole tricationic salt:A novel potential two-photon fluorescent DNA probe for nucleic imaging of cells

A new carbazole tricationic salt,4,4'-(1E,1'E)-2,2'-(9-(2-(1-(2-hydroxyethyl)pyridinium-4-yl)ethyl)-9H-carbazole-3,6-diyl) bis(ethane-2,1-diyl) bis(1-(2-hydroxyethyl)pyridinium) iodide (THEPC) was synthesized. Photophysical experiments have shown that THEPC has large two-photon excited fluorescence action cross-sections (33 GM in the presence of DNA),which ranks THEPC as a good biological fluorophore. The results from electronic absorption,circle dichroism and single-/two-photon fluorescence emission spectra suggest that THEPC can strongly bind to DNA,with an intrinsic binding constant of 5.79 × 106 L mol-1. THEPC has better photostability under one-or two-photon excitation conditions. Finally,the staining photos from two-photon fluorescence microscopy (TPM) show that THEPC can exclusively label the nucleus with high contrast and without image distortion. These remarkable properties and optimized imaging ability make THEPC an attractive DNA probe in TPM.

Toxicological Effects of Secondary Air Pollutants

Secondary air pollutants,originating from gaseous pollutants and primary particulate matter emitted by natural sources and human activities,undergo complex atmospheric chemical reactions and multiphase processes.Secondary gaseous pollutants represented by ozone and secondary particulate matter,including sulfates,nitrates,ammonium salts,and secondary organic aerosols,are formed in the atmosphere,affecting air quality and human health.This paper summarizes the formation pathways and mechanisms of important atmospheric secondary pollutants.Meanwhile,different secondary pollutants’toxicological effects and corresponding health risks are evaluated.Studies have shown that secondary pollutants are generally more toxic than primary ones.However,due to their diverse source and complex generation mechanism,the study of the toxicological effects of secondary pollutants is still in its early stages.Therefore,this paper first introduces the formation mechanism of secondary gaseous pollutants and focuses mainly on ozone’s toxicological effects.In terms of particulate matter,secondary inorganic and organic particulate matters are summarized separately,then the contribution and toxicological effects of secondary components formed from primary carbonaceous aerosols are discussed.Finally,secondary pollutants generated in the indoor environment are briefly introduced.Overall,a comprehensive review of secondary air pollutants may shed light on the future toxicological and health effects research of secondary air pollutants.

Reaction between sulfur dioxide and iron oxide cationic clusters

The reactivity of sulfur dioxide (SO2) molecules toward iron oxide cationic clusters (FemOn+) is studied by a homemade time-of-flight mass spectrometer coupled with a laser ablation/supersonic expansion cluster source and a fast flow reactor. The association products FemOnSO2+ can be observed for most of the clusters. The interesting result is that the cooperation effect of SO2 and water is in favor of the adsorption of gas phase water on specific scale iron oxide clusters (Fe2O2+ and Fe3O3+ ). The reactivity information obtained may be useful to investigate atmospheric heterogeneous chemistry of related systems.

Temperature dependent kinetics of the gas-phase reaction of OH radicals with EMS

Using an improved smog chamber system,the temperature dependence of OH radical reaction with EMS was investigated over the temperature range of 297-346 K at 1.01×105 Pa pressure of air. The Arrhenius expression of the reaction was obtained for the first time. The mechanism of the reaction was also investigated.

Synthesis, spectra, structure and quantum chemistry study on two novel oxovanadium complexes with hydrotris (pyrazolyl) borate ligands

Two novel oxo-vanadium complexes of VO(HB(pz)3)(pzH)(SCN) (1) and VO(HB(3,5-Me2pz)3) (3,5-Me2pzH)(SCN)(SCNH)2 (2) with tris(pyrazolyl) hydroborate ligands were prepared by the reaction of VOSO4?nH2O, KSCN with Na(HB(pz)3), pyrazole, or Na(HB(3,5-Me2pz)3) and methyl-substituted pyrazole in the solution of MeOH, respectively. The complexes were characterized by element analysis, IR, and UV- vis spectra. In the mean time, the fluorescence spec-trum was studied too, and the result indicates that the luminescence of the complexes is related to the in-teraction between oxovanadium ion and tris(pyra- zolyl) hydroborate ligands. In addition, structures of oxovanadium complexes 1 and 2 were determined by X-ray diffraction. The electronic structures and the bonding characters of the two complexes were ana-lyzed with ab initio calculations.

Synthesis,structure and superoxide dismutase activity of two self-assembly transition metal complexes containing a tridentate amino-Schiff base deviating from salicylaldehyde with glycine

Two new transition metal (Cu, Ni) complexes with amino-Schiff base ligand, (C9H7NO3)Cu(C14H12N2)-H2O (1) and (C9H7NO3)Ni(C3H4N2)3-H2O (2), have been designed and synthesized in ethanol solution at room temperature. Both of the complexes have been characterized by elemental analysis, IR spectra, UV-vis spectroscopy and X-ray single crystal diffraction. For complex 1, the coordination environment of the central copper atom is a distorted square pyramid, and one-dimensional chain is formed through the inter-molecular hydrogen bonds (O4-H2W···O3, O4-H2W···O3#1 (#1: -x+1, y, -z+3/2)) and weak interactions (π-π stacking interaction) between the phenyl rings. For complex 2, the nickel atom is 6-coordinated and in a distorted octahedral environment, and a discrete hydrogen-bond cluster (four molecules are connected by hydrogen bonds into a group) is formed via two types of intra-molecular hydrogen bonds (O-H···O, N-H···O) and inter-molecular hydrogen bonds (O-H···O, N-H···O).