科研成果 by Year: 2003

This article describes recent developments in the synthesis of macrocycles having rigid, monocyclic skeletons composed of arylene and ethynylene units and the studies on their self-assembling behavior.

[1] Waliguan Observatory (WO) is a land-based Global AtmosphereWatch baseline station on the Tibetan Plateau. Size-resolved ionic aerosols (NH4(+), Na+, K+, Ca2+, Mg2+, SO24- , Cl-, NO3- CO32-, formate, acetate and oxalate), organic aerosols, black carbon and gaseous HNO3 and SO2 were measured during an intensive fall-winter field experiment. The observational data were analyzed with a focus on the partitioning of nitrate between the gas and particle phases. Nitrate was found to exist mainly in the particle phase with a typical particulate-to-total nitrate ratio, i.e., NO3-(p)/(NO3-(p) + HNO3(g)), of about 0.9. It was also found that the size distribution pattern of particulate nitrate at WO varied in different samples and the amount of particulate nitrate residing in the fine mode (D-p < 2.0 mu m) was typically larger than or comparable with that in the coarse mode. A gas-particle chemical equilibrium model was used to predict these particulate nitrate size distributions. The size distributions of particulate nitrate were reasonably reproduced with the model within the uncertainties caused by the detection limits. The chemical pathways for the formation of particulate nitrate at WO were analyzed with the size distributions of measured ionic aerosols. It was demonstrated that fine nitrate particles may have been produced by the reaction of gaseous nitric acid with gaseous ammonia, while coarse nitrate particles may have been generated via the condensation of nitric acid on the surface of mineral aerosols. The signature of biomass burning at WO was found to be associated with black carbon as well as the accumulation of potassium and oxalate in the fine particles.

Spatial distribution of traffic-related pollutants within the street canyons in Guangzhou, China was monitored using a self-developed automatic sampling system of vertical section. The wind fields at the roof and street level were also field investigated. The results showed that average horizontal and vertical profiles of traffic-related pollutant concentrations within street canyon depended on wind direction at the roof level, leeward average concentrations were about 1 time higher than those observed at the windward side and there were differences in the daily variation profiles of pollutant concentrations between them; however, these concentration profiles at different heights of each side were similar, with CO, NO, NO2 and NOx concentrations decreasing with height above the ground. For ambient air at roof level, the daily variation profiles of the leeward pollutant concentrations with distinct diurnal fluctuation were different from those at different height level in the street canyon, but daily variation profiles of CO, NO, NO2 and NOx concentrations at windward roof level were consistent with those within the canyon, which corresponded with the traffic volume variation, except for O3. It was deduced from these observed phenomena that pollutants from vehicular exhaust emissions in the urban street canyon were advected by wind vortices that covered most of the canyon from the windward side to the leeward side and ascended to the leeward roof edge with vortex. Then one part of these pollutants became part of circulating pollutants within the canyon by vortex being carried back to the windward side and sinking into the bottom of the street canyon and the rest of them diffused to the windward roof, but ambient air pollutant concentrations at the leeward roof were less affected by pollutants within the street canyon. Additionally, it was observed that O3 daily variation with the concentration level increasing with height at the roof and on windward side of the street showed obvious diurnal fluctuation characteristic, and O3 concentration levels at the roof were higher than those below the roof and there was no clear daily variation or vertical gradient at leeward side below the roof.