Hydroxyl radical(.OH)-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber.Four individualseed aerosols such as ammonium sulfate,ammonium nitrate,sodium silicate and calcium chloride,were introduced into the chamberto assess their influence on the growth of secondary organic aerosols(SOA).It was found that the low concentration of seed aerosolsmight lead to high concentration of SOA particles.Seed aerosols would promote rates of SOA formation at the start of the reaction andinhibit its formation rate with prolonging the reaction time.In the case of ca.9000 pt/cm3 seed aerosol load,the addition of sodiumsilicate induced a same effect on the SOA formation as ammonium nitrate.The influence of the four individual seed aerosols on thegeneration of SOA decreased in the order of calcium chloride>sodium silicate and ammonium nitrate>ammonium sulfate.
HAO Li-qing WANG Zhen-ya HUANG Ming-qiang FANG Li ZHANG Wei-jun
Theoretical calculations are performed to study the nature of the hydrogen bonds in complexes HCHO···HNO, HCOOH···HNO, HCHO···NH3, HCOOH···NH3, HCHO···NH2F and HCOOH···NH2F. The geomet- ric structures and vibrational frequencies of these six complexes at the MP2/6-31+G(d,p), MP2/6-311++G(d,p), B3LYP/6-31+G(d,p) and B3LYP/6-311++G(d,p) levels are calculated by standard and counterpoise-corrected methods, respectively. The results indicate that in complexes HCHO···HNO and HCOOH···HNO the N—H bond is strongly contracted and N—H···O blue-shifted hydrogen bonds are observed. While in complexes HCHO···NH3, HCOOH···NH3, HCHO···NH2F and HCOOH···NH2F, the N—H bond is elongated and N—H···O red-shifted hydrogen bonds are found. From the natural bond orbital analysis it can be seen that the X—H bond length in the X—H···Y hydrogen bond is controlled by a balance of four main factors in the opposite directions: hyperconjugation, electron density redistribu- tion, rehybridization and structural reorganization. Among them hyperconjugation has the effect of elongating the X—H bond, and the other three factors belong to the bond shortening effects. In complexes HCHO···HNO and HCOOH···HNO, the shortening effects dominate which lead to the blue shift of the N—H stretching frequencies. In complexes HCHO···NH3, HCOOH···NH3, HCHO···NH2F and HCOOH···NH2F where elongating effects are dominant, the N—H···O hydrogen bonds are red-shifted.
YANG YongZHANG WeiJunPEI ShiXinSHAO JieHUANG WeiGAO XiaoMing
Photooxidation reaction of toluene in smog chamber systems was initiated by the UV radiation of toluene/CH3ONO/NOx mixtures. The products of the photooxidation reaction of toluene and its subsequent reactions were analyzed directly utilizing Fourier transform infrared spectrometer (FTIR). Detailed assignments to FTIR spectrum of gas-phase products were given. The information of some important functional groups in the products, such as, carbonyl groups (C O), hydroxyl groups (—OH), carboxylic acid (—COOH), C C bonding, N—O bonding and C—H bonding (C—H), was got from this analysis. These results were compared to those analyzed by aerosol time of flight mass spectrometer (ATOFMS). It was found that there are some differences between FTIR analysis of gas-phase products and that of particle-phase, for example, the products with carbonyl groups, which were connected to unsaturated chemical bonds, was relatively higher in the gas phase, while ketones, aldehydes, carboxylic acid and organonitrates were the dominant functional groups in the aerosol-phase reaction products. The possible reaction pathways of some important products in the gas phase were also discussed.
