Characterization of volatile organic compounds at a roadside environment in Hong Kong: An investigation of influences after air pollution control strategies

Vehicular emission is one of the important anthropogenic pollution sources for volatile organic compounds (VOCs). Four characterization campaigns were conducted at a representative urban roadside environment in Hong Kong between May 2011 and February 2012. Carbon monoxide (CO) and VOCs including methane (CH4), non-methane hydrocarbons (NMHCs), halocarbons, and alkyl nitrates were quantified. Both mixing ratios and compositions of the target VOCs show ignorable seasonal variations. Except CO, liquefied petroleum gas (LPG) tracers of propane, i-butane and n-butane are the three most abundant VOCs, which increased significantly as compared with the data measured at the same location in 2003. Meanwhile, the mixing ratios of diesel- and gasoline tracers such as ethyne, alkenes, aromatics, halogenated, and nitrated hydrocarbons decreased by at least of 37%. The application of advanced multivariate receptor modeling technique of positive matrix factorization (PMF) evidenced that the LPG fuel consumption is the largest pollution source, accounting for 60 ± 5% of the total quantified VOCs at the roadside location. The sum of ozone formation potential (OFP) for the target VOCs was 300.9 μg-O3 m-3, which was 47% lower than the value of 567.3 μg-O3 m-3 measured in 2003. The utilization of LPG as fuel in public transport (i.e., taxis and mini-buses) contributed 51% of the sum of OFP, significantly higher than the contributions from gasoline- (16%) and diesel-fueled (12%) engine emissions. Our results demonstrated the effectiveness of the switch from diesel to LPG-fueled engine for taxis and mini-buses implemented by the Hong Kong Special Administrative Region (HKSAR) Government between the recent ten years, in additional to the execution of substitution to LPG-fueled engine and restrictions of the vehicular emissions in compliance with the updated European emission standards

Dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, fatty acids and benzoic acid in PM2.5 aerosol collected during CAREBeijing-2007: an effect of traffic restriction on air quality

Thirty water-soluble organic species, including dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, fatty acids and benzoic acid were determined as well as organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) in PM2.5 samples collected during the Campaign of Air Quality Research in Beijing 2007 (CAREBeijing-2007) in the urban and suburban areas of Beijing. The objective of this study is to identify the influence of traffic emissions and regional transport to the atmosphere in Beijing during summer. PM2.5 samples collected with or without traffic restriction in Beijing are selected to evaluate the effectiveness of local traffic restriction measures on air pollution reduction. The average concentrations of the total quantified bifunctional organic compounds (TQBOCs), total fatty acids and benzoic acid during the entire sampling period were 1184±241, 597±159 and 1496±511 ng m−3 in Peking University (PKU), and 1050±303, 475±114 and 1278±372 ng m−3 in Yufa, Beijing. Oxalic acid (C2) was found as the most abundant dicarboxylic acid at PKU and Yufa followed by phthalic acid (Ph). A strong even carbon number predominance with the highest level at stearic acid (C18:0), followed by palmitic acid (C16:0) was found for fatty acids. According to the back trajectories modeling results, the air masses were found to originate mainly from the northeast, passing over the southeast or south of Beijing (heavily populated, urbanized and industrialized areas), during heavier pollution events, whereas they are mainly from the north or northwest sector (mountain areas without serious anthropogenic pollution sources) during less pollution events. The data with wind only from the same sector (minimizing the difference from regional contribution) but with and without traffic restriction in Beijing were analyzed to evaluate the effectiveness of local traffic restriction measures on the reduction of local air pollution in Beijing. The results suggested that the traffic restriction measures can reduce the air pollutants, but the decrease of pollutants is generally smaller in Yufa compared to that in PKU. Moreover, an enhancement of EC value indicates more elevated primary emissions in Yufa during restriction periods than in non-restriction periods. This study demonstrates that even when primary exhaust was controlled by traffic restriction, the contribution of secondary organic species formed from photochemical processes was critical with long-range atmospheric transport of pollutants.published_or_final_versio

Subsonic intake duct flows

Here both S-shaped and singly curved (here classified as S-shaped) duct diffusers for intakes in aeronautical propulsion systems are studied. The results are applicable in other situations where similar ducts occur; for example on V/STOL aircraft employing re-direction of thrust, intercomponent ducting in high bypass ratio engines, etc. An open circuit static test rig, capable of mass flow rates of 5 kg/s, and three-dimensional instrumentation were established. Flow measurements were made in S-shaped intake duct diffusers for rear mounted gas turbine engines in both aircraft and air-breathing missiles. These designs are intended for ventral type inlet installation. These ducts possess cross-sectional shape transitions, from oblate to circular, with area increase and annular ducts at the engine face. The work was aimed at both fundamental understanding of the flows and at establishing test data for the prediction methods. Tests were performed at throat Mach numbers of nominally 0.15 and 0.6 and in the unit Reynolds number range of 3x10_6/m - 2x10_7/m for three different ducts each having different upstream bends but common downstream bends. Detailed boundary layer surveys were made to establish plane of symmetry growth of the viscous region and the extent of three-dimensionality away from the plane of symmetry. Data are presented in the form of velocity profiles, streamwise and cross-flow, integral thicknesses and surface pressure fields. Engine face distortion is assessed from full outlet flow surveys. Flow visualization was recorded using surface oil flow techniques. Evidence is presented of a trend towards three-dimensional separation as the upstream bend increases in severity. For the most extreme case large regions of complex three-dimensional separated flow occur and topological analysis of the recorded surface oil flow pattern allows reconstruction of the separating flow. Clear correlations are established between flow visualization results and flow measurements yielding better understanding. Finally, results were compared with a three-dimensional compressible prediction method

Efficacy and effectiveness of inactivated vaccines against symptomatic COVID-19, severe COVID-19, and COVID-19 clinical outcomes in the general population: a systematic review and meta-analysis

BACKGROUND: Inactivated, whole-virion vaccines have been used extensively in the SARS-CoV-2 pandemic. Its efficacy and effectiveness across regions have not been systematically evaluated. Efficacy refers to how well a vaccine performs in a controlled environment. Effectiveness refers to how well it performs in real world settings. METHODS: This systematic review and meta-analysis reviewed published, peer-reviewed evidence on all WHO-approved inactivated vaccines and evaluated their efficacy and effectiveness against SARS-CoV-2 infection, symptomatic infection, severe clinical outcomes, and severe COVID-19. We searched Pubmed (including MEDLINE), EMBASE (via OVID), Web of Science Core Collection, Web of Science Chinese Science Citation Database, and Clinicaltrials.gov. FINDINGS: The final pool included 28 studies representing over 32 million individuals reporting efficacy or effectiveness estimates of complete vaccination using any approved inactivated vaccine between January 1, 2019 and June 27, 2022. Evidence was found for efficacy and effectiveness against symptomatic infection (OR 0.21, 95% CI 0.16–0.27, I2 = 28% and OR 0.32, 95% CI 0.16–0.64, I2 = 98%, respectively) and infection (OR 0.53, 95% CI 0.49–0.57, I2 = 90% and OR 0.31, 95% CI 0.24–0.41, I2 = 0%, respectively) for early SARS-CoV-2 variants of concern (VoCs) (Alpha, Delta), and for waning of vaccine effectiveness with more recent VoCs (Gamma, Omicron). Effectiveness remained robust against COVID-related ICU admission (OR 0.21, 95% CI 0.04–1.08, I2 = 99%) and death (OR 0.08, 95% CI 0.00–2.02, I2 = 96%), although effectiveness estimates against hospitalization (OR 0.44, 95% CI 0.37–0.53, I2 = 0%) were inconsistent. INTERPRETATION: This study showed evidence of efficacy and effectiveness of inactivated vaccines for all outcomes, although inconsistent reporting of key study parameters, high heterogeneity of observational studies, and the small number of studies of particular designs for most outcomes undermined the reliability of the findings. Findings highlight the need for additional research to address these limitations so that more definitive conclusions can be drawn to inform SARS-CoV-2 vaccine development and vaccination policies. FUNDING: Health and Medical Research Fund on COVID-19, Health Bureau of the Government of the Hong Kong SAR

Dicarboxylic acids, ketocarboxylic acids, ∝-dicarbonyls, fatty acids, and benzoic acid in urban aerosols collected during the 2006 campaign of air quality research in Beijing (CAREBeijing-2006)

Author name used in this publication: Lee, S. C.2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Summer and winter variations of dicarboxylic acids, fatty acids and benzoic acid in PM₂.₅ in Pearl Delta River Region, China

Author name used in this publication: Lee, S. C.2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Vehicular emission of volatile organic compounds (VOCs) from a tunnel study in Hong Kong

Author name used in this publication: s. C. LeeAuthor name used in this publication: S. S. H. Ho2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Concentrations of formaldehyde and other carbonyls in environments affected by incense burning

Burning incense to pay homage to deities is common in Chinese homes and temples. Air samples were collected and analyzed for carbonyls from home and temple in Hong Kong where incense burning occurs on daily basis. Carbonyls in the air were trapped on solid sorbent coated with O-(2,3,4,5,6-pentuorobenzyl) hydroxylamine, followed by thermal desorption and subsequent GC/MS analysis. The carbonyls identified include formaldehyde, acetaldehyde, acrolein, 2-furfural, benzaldehyde, glyoxal, and methylglyoxal. The levels of the above carbonyls correlate with the intensity of the incense-burning activities. The total mixing ratios of the carbonyls in the temple exceed those in the ambient air outside the temple by 11-23 times. Formaldehyde is the most abundant species, contributing to approximately 55\% of the total carbonyl mixing ratios in both the temple and the home environments during incense burning. The mixing ratio of formaldehyde ranges from 108 to 346 ppbv in the temple and averages 103 ppbv in the home during incense burning. These values exceed the World Health Organization (WHO) air quality guideline of 100 mug m(-3) (88 ppbv) for formaldehyde. The highest formaldehyde level in the temple exceeds the WHO guideline by 3 times at peak incense burning hours. The mixing ratio of acrolein in the temple ranges from 20 to 99 ppbv, approaching or exceeding the WHO air quality guideline of 50 mug m(-3) (22 ppbv) for acrolein. Our measurements indicate that incense burning significantly elevates the concentrations of number of carbonyls, most notably formaldehyde and acrolein, in the surrounding environments. This study provides preliminary insights on indoor air quality problems created by incense burning