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Since volatile organic compounds (VOCs) are important precursors of ozone (O3), identification and quantification of their emission sources are prerequisite for the formulation and implementation of O3 pollution control policies. In this study, seven major sources of VOCs were identified and their contributions to photochemical O3 formation were evaluated at an urban site (TW) in Hong Kong by the combined application of the positive matrix factorization (PMF) model and the observation based model (OBM). The relative incremental reactivity (RIR)-weighted values, which considered both the reactivity and abundance of VOCs, suggested that paint and sealant solvents, diesel exhaust and liquefied petroleum gas (LPG) usage were the key contributors to O3 formation. Among the identified sources, xylenes and ethylbenzene in paint and sealant solvents, toluene in gasoline exhaust, butanes, ethene, propene and propane in LPG usage and n-butane and ethene in diesel exhaust made significant contributions. Sensitivity analysis on the basis of relative O3 reduction efficiency (RORE), using the reduction of VOCs from 10% to 90% as input, indicated that the O3 reduction was the most effective when the identified VOC sources and the major species from these sources were cut by specific percentages. The findings provide valuable insights into the formulation and implementation of VOCs and O3 control strategies in Hong Kong.

Two models (the Positive Matrix Factorization (PMF) model and a photochemical box model with Master Chemical Mechanism (PBM-MCM)) were applied to analyze the formaldehyde (HCHO) data collected in July 2006 at an urban site (GPEMC) in the Pearl River Delta (PRD), southern China. Three major HCHO sources (secondary formation, vehicular exhaust, and solvent usage) were identified and they were found to contribute in average 53%, 31% and 16% respectively to the total HCHO loading at GPEMC. Alkenes was the most important group contributing to the secondary formation of HCHO, followed by aromatics and alkanes. Among them, trans-2-butene had the largest contribution to secondary HCHO formation, with the average percentage of 16 ± 4%, followed by i-butene, cis-2-butene, propene, isoprene and m,p-xylene. Secondary HCHO and HCHO emitted from vehicular emissions contributed comparably to ground-based measured O

Alkyl nitrates (RONO2) were measured concurrently at a mountain site (TMS) and an urban site (TW) at the foot of the same mountain in Hong Kong from September to November 2010, when high O3 mixing ratios were frequently observed. The abundance and temporal patterns of five C1–C4 RONO2 and their parent hydrocarbons (RH), the RONO2/RH ratios and photochemical age of air masses at TMS differed from those at TW, reflecting different contributions of direct emissions and secondary formation of RONO2 at the two sites. Relative to 2-BuONO2/n-butane, the measured ratios of C1–C2 RONO2/RH at the two sites exhibited significant positive deviations from pure photochemical (PP) curves and background initial ratio (BIR) curves obtained from laboratory kinetic data, suggesting that background mixing ratios had a significant influence on the RONO2 and RH distributions. In contrast to the C1–C2 RONO2/RH ratios, the evolution for the measured ratios of C3 RONO2/RH to 2-BuONO2/n-butane agreed well with the ratio distributions in the PP and BIR curves at the two sites. Furthermore, the ratios of 1-/2-PrONO2 and yields of 1- and 2-PrONO2 suggested that the C3 RONO2 were mainly from secondary formation at TMS, whereas secondary formation and other additional sources had a significant influence on C3 RONO2 mixing ratios at TW. The source apportionment results confirmed that secondary formation was the dominant contributor to all the RONO2 at TMS, while most of the RONO2 at TW were from secondary formation and biomass burning. The findings of the source apportionments and photochemical evolution of RONO2 are helpful to evaluate photochemical processing in Hong Kong using RONO2 as an indicator.

To advance our understanding on the factors that affect photochemical pollution at different elevations in mountainous areas, concurrent systematic field measurements (September to November 2010) were conducted at a mountain site and at an urban site at the foot of the mountain in Hong Kong. The mixing ratios of air pollutants were greater at the foot of the mountain (i.e. Tsuen Wan urban site, TW) than near the summit (i.e. Tai Mao Shan mountain site, TMS), except for ozone. In total, only 1 O3 episode day was observed at TW, whereas 21 O3 episode days were observed at TMS. The discrepancy of O3 at the two sites was attributed to the mixed effects of NO titration, vertical meteorological conditions, regional transport and mesoscale circulations. The lower NO levels at TMS and the smaller differences of "oxidant" Ox (O3 + NO2) than O3 between the two sites suggested that variations of O3 at the two sites were partly attributed to different degree of NO titration. In addition, analysis of vertical structure of meteorological variables revealed that the inversion layer at the range of altitudes of 500–1000 m might be another factor that caused the high O3 levels at TMS. Furthermore, analyses of the wind fields and the levels of air pollutants in different air flows indicated that high O3 concentrations at TMS were somewhat influenced by regional air masses from the highly polluted Pearl River Delta (PRD) region. In particular, the analysis of diurnal profiles and correlations of gaseous pollutants suggested influence of mesoscale circulations which was further confirmed using the Master Chemical Mechanism moving box model (Mbox) and the Weather Research and Forecasting (WRF) model. By investigating the correlations of observed O3 and NOx*, as well as the ratios of VOC/NOx, it was concluded that photochemical O3 formation was VOC-sensitive or both NOx and VOC-sensitive at TMS, while it was VOC-sensitive at TW.

We have investigated the polarization dependence of FT-IR of the stretching of CD2 in chiral alkyl chain of TFMHxPOCBC-D2(4-(trifluoromethylhexy-3-d2 carbonyl) phenyl 4′-octyloxybiphenyl caboxylate) with a homeotropically aligned cell.It is found that the polarization dependence of Sm-C and that of Sm-CA are different.Simulation calculation indicates that the rotation of CD2 around the alkyl chain is hindered.

A simple structure for a Fresnel phase zone plate is proposed using the techniques of polymer-network stabilized liquid crystals. This kind of structure can give a high value of diffraction efficiency and the diffraction light intensities can be controlled electrically. The detail fabrication process and experimental results will be given.

The Cooperative Medical System (CMS) and its barefoot doctors have been in decline in rural China for nearly a decade. In order to explore the reasons for this, in 1987 we carried out a survey of villagers, barefoot doctors, and local administrators in Fengxian, Shanggoa, and Loaan counties, where incomes are good, fair, and low, respectively. The state of the CMS in these counties was contrasted and the situations which prevailed in 1978, 1982, and 1985, when the system was, respectively, at its peak, had begun to decline, and had declined markedly, were compared. A random sample of villages was selected and all the barefoot doctors and administrators as well as a random sample of households were surveyed. The results indicate that health status (as measured by infant mortality, immunization coverage, and rate of infectious diseases) has decreased in areas where the CMS has declined, while per capita incomes increased. Concomitantly, villager's expenditures on health care have increased. Barefoot doctors and their patients were, however, reasonably happy with the system, and in its absence the doctors are no longer able to obtain ongoing training. The CMS was fiscally sound, and did not decline to the same extent in all areas--it continues to thrive in Fengxian, which is relatively affluent. It is concluded that the system probably declined because many local administrators perceived that it no longer enjoyed the backing of the central government.