Characteristics and sources of non-methane hydrocarbons and halocarbons in wintertime urban atmosphere of Shanghai, China.

The characteristics and sources of major hydrocarbons and halocarbons in the wintertime ambient air of urban center of Shanghai, a mega city of China, were investigated. Propane, toluene, ethyl acetate, and benzene were the most abundant hydrocarbons. The majority of species showed significant variability in mixing ratios with occasional episodic increases. The more common use of liquefied petroleum gas fuel for taxis and light motorcycles was believed to lead to high levels of ambient propane over the urban center of Shanghai. Correlating with toluene, dichloromethane, and 1,2-dichloroethane (1,2-DCE), abundant chloromethane (up to a daily mean of 1.61 ± 0.99 ppbv and a maximum of 5.34 ppbv) was mainly associated with industrial emissions, although biomass burnings exist widely in east China. The Chinese New Year (CNY) holiday period with no industrial activity over China provides a platform for the study of industrial emissions over the urban atmosphere of Shanghai. The normal weekly cycles were characterized by higher and more variable mixing ratios during weekdays which dropped during weekends. Enhanced mixing ratios were observed in the fortnight before the CNY holidays due to increased industrial emissions as a result of overtime production to make up for the holiday losses. During the CNY holidays, lower level and less variable mixing ratios were observed. A benzene/toluene (B/T) ratio of 0.6 ± 0.4 (mean ± std.) for the morning rush hour samples was identified to be the characteristic ratio of vehicular emissions. However, a B/T ratio of 0.4 ± 0.2 from vehicles and other sources was derived for the ambient air.

Analysis of carbon monoxide budget in North China.

A global chemical transport model (MOZART-2; model of ozone and related tracers, version 2) was used to assess physical and chemical processes that control the budget of tropospheric carbon monoxide (CO) in North China. Satellite observations of CO from the measurements of pollution in the troposphere (MOPITT) instrument are combined with model results for the analysis. The comparison between the model simulations and the satellite observations of total column CO (TCO) shows that the model can reproduce the spatial and temporal distributions. However, the model results underestimate TCO by 23% in North China. This underestimation of TCO may be caused by the uncertainties of emissions. The tropospheric CO budget analysis suggests that in North China, surface emission is the largest source of tropospheric CO. The main sinks of tropospheric CO in this region are chemical reaction and stratosphere_and_troposphere exchange. The analysis also shows that most of inflow CO to Pacific regions comes from the upwind regions of North China. This transport of CO is significant during Winter and Spring time.

Characterizing driving patterns for Zhuhai for traffic emissions estimation.

Zhuhai, a relatively less developed city on the western coast of the Pearl River Delta (PRD) of China, is planning to undergo major development in coming years. A Hong Kong-Zhuhai-Macao Bridge project has been approved by the Central Government of China. The project will have great impact on the driving pattern and vehicular emissions to the city. This baseline study collected speed-time data of two instrumented private cars in morning and evening periods, as well as a daytime nonpeak period of >10 consecutive days in the spring and winter of 2003. The authors used the microwave speed sensor and global positioning system installed in the instrumented cars and used car-chasing technique to perform the data collection. They used the statistical package SPSS to assess the consistency, as well as to evaluate the variability of the data. Nine parameters, namely, average speed, average running speed, average acceleration rate, average deceleration rate, mean length of a driving period, time proportions of driving modes, average number of acceleration-deceleration changes, root mean square acceleration, and positive acceleration kinetic energy are calculated to represent the driving characteristics. A driving cycle for private cars was developed. If emission tests were conducted using the Zhuhai driving cycle, the level of vehicle emissions measured is likely to be in between that of the Federal Test Procedure (FTP) cycle and the Melbourne Peak cycle.

Commuter exposure to aromatic VOCs in public transportation modes in Hong Kong.

This study investigated commuter exposure to aromatic volatile organic compounds (VOCs) in different commuting microenvironments. In Hong Kong, more than 90% of the local citizens rely on public transport facilities in their daily commutes. During five winter months in late 2001 and early 2002, in-vehicle monitoring was performed in nine popular public transportation modes: tram, public light bus, air-conditioned bus, non-air-conditioned bus, taxi, ferry and three railway systems (Mass Transit Railway-MTR, Kowloon-Canton Railway-KCR and Light Rail Transit-LRT). These transports were grouped into three categories: railway transport, roadway transport and marine transport. Air samples of benzene, toluene, ethylbenzene and m/p/o-xylene were collected by canisters and analysed by gas chromatography and mass selective detector technique. Results indicated that the in-vehicle VOC exposure levels were greatly influenced by the mode of transport. For benzene, mean concentration ranged from 4.8 to 6.1 microg x m(-3) in roadway transports, 3.0-3.8 microg x m(-3) in railway transports and it was 2.1 microg x m(-3) in ferry. Regardless of the results in MTR and air-conditioned buses, the VOC levels in roadway transport were the highest and was followed by railway transport. The exposure levels in marine transport were the lowest. The TEX concentrations were found to be substantially higher in air-conditioned buses and MTR trains than in other transports, suggesting the existence of additional solvent-related sources in their vehicle interiors. Measurements in non-air-conditioned double deck vehicles indicate that there was slightly higher VOC levels in the lower deck than in the upper deck microenvironment. The average upper to lower deck exposure ratio ranged from 0.79 to 0.87 in trams and 0.78-0.83 in non-air-conditioned buses, depending on the compound of concern. The VOC exposure levels of public transport commuters in Hong Kong are far lower than those in most oversea cities. The experimental concentrations obtained in this study are within the relevant health-protecting limits as stated in the Hong Kong Indoor Air Quality Objective. Influences of recent VOC pollution control measures and local traffic characteristics on in-vehicle level are discussed.