Using Bayesian optimization method and FLEXPART tracer model to evaluate CO emission in East China in springtime.

Carbon monoxide (CO) is of great interest as a restriction factor for pollutants related to incomplete combustions. This study attempted to evaluate CO emission in East China using the analytical Bayesian inverse method and observations at Mount Hua in springtime. The mixing ratio of CO at the receptor was calculated using 5-day source-receptor relationship (SRR) simulated by a Lagrangian Particle Dispersion Model (FLEXPART) and CO emission flux. The stability of the inversion solution was evaluated on the basis of repeated random sampling simulations. The inversion results demonstrated that there were two city cluster regions (the Beijing-Tianjin-Hebei region and the low reaches of the Yangtze River Delta) where the difference between a priori (Intercontinental Chemical Transport Experiment-Phase B, INTEX-B) and a posteriori was statistically significant and the a priori might underestimate the CO emission flux by 37 %. A correction factor (a posteriori/a priori) of 1.26 was suggested for CO emission in China in spring. The spatial distribution and magnitude of the CO emission flux were comparable to the latest regional emission inventory in Asia (REAS2.0). Nevertheless, further evaluation is still necessary in view of the larger uncertainties for both the analytical inversion and the bottom-up statistical approaches.

A kinetics and mechanistic study of the OH and NO2 initiated oxidation of cyclohexa-1,3-diene in the gas phase.

The kinetics and products of the OH and NO2-initiated oxidation of cyclohexa-1,3-diene have been investigated at 296 K and 700 Torr using long path FTIR spectroscopy. Relative rate methods were employed using the photolysis of cyclohexa-1,3-diene/CH3ONO/NO/air mixtures to measure kappa(OH + cyclohexa-1,3-diene) = (1.68 +/- 0.43) x 10(-10) cm3 molecule(-1) s(-1). From the pseudo-first order decay of cyclohexa-1,3-diene in the presence of excess NO2, a value of kappa(NO2 + cyclohexa-1,3-diene) = (1.75 +/- 0.15) x 10(-18) cm3 molecule)-1) s(-1) was derived. An upper limit of kappa < or = 7 x 10(-21) cm3 molecule(-1) s(-1) was established for the reaction of NO with cyclohexa-1,3-diene. Benzene was observed as a product of both the OH and NO2 initiated oxidation, providing evidence of H atom abstraction in both reactions. Assuming the reaction of cyclohexadienyl radicals (C6H7) with O2 produces benzene as the sole organic product, the results are consistent with abstraction channel branching ratios of (8.1 +/- 0.2)% and (1.5 +/- 0.4)%, respectively. The results also indicate that C6H7 reacts with NO2, with a relative rate coefficient kappa(C6H7 + NO2)/kappa(C6H7 +O2) = (1.8 +/- 0.5) x 10(5), and that this partially forms benzene, with a branching ratio of (27 +/- 7)%. The stoichiometry and products of the NO2 reaction were investigated in the absence of O2, in the presence of O2, and in the presence of O2 and NO. Reaction mechanisms consistent with the observations are presented. In the presence of NO and O2, the NO2-initiated chemistry leads to NO-to-NO2 conversion, and the formation of HOx radicals in significant yield, (0.79 +/- 0.05), such that cyclohexa-1,3-diene removal occurs by reaction with both NO2 and OH. HCOOH was detected as a product in this system, providing evidence for significant formation of stabilised C6 alpha-hydroxyperoxy radicals from the OH-initiated chemistry, and their subsequent reaction with NO. An estimate of ca. 500-1000 s(-1) is made for their decomposition rate, based on the [NO]-dependence of the HCOOH yields. The implications of the results are discussed within the context of the atmospheric chemistry of conjugated dienes.

[Biocompatibility of polyvinylalcohol gel as a vitreous substitute].

Polyvinylacohol (PVA) gel cross linked by gamma irradiation was assessed as a possible vitreous substitute. In our previous, reports, elevation of intraocular pressure and inflammatory changes in the vitreous cavity after operation were observed in some of the experimental animals. Four types of PVA gel (sol) were produced by a newly refined method. We improved the gel systhesis process to remove the monomer and contamination. Colored rabbits were used for this experiment. Vitreous replacement was performed after vitrectomy. This was followed clinically by ophthalmoscopy, tonometry, fundus photography, electroretinogram, chemotaxis, and laser-flare-cell-metering. Histopathological examination by light microscopy was performed after 3 months. PVA gel has good biocompatibility in the vitreous cavity, and gel with a network similar to that of the vitreous body showed the best biocompatibility. Although it is necessary to investigate the biocompatibility over the long term and to evaluate the tamponade effect, PVA gel will be a bood candidate for a vitreous substitute.