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Che W.,South China University of Technology | Che W.,Pearl River Delta Atmospheric Environmental Research Joint Laboratory | Zheng J.,South China University of Technology | Zheng J.,Pearl River Delta Atmospheric Environmental Research Joint Laboratory | And 5 more authors.
Atmospheric Environment | Year: 2011

In recent decades, the Pearl River Delta (PRD) region located in south China has been experiencing severe air pollution, arising from the rapid increase in industry and motor vehicles. As a major contributing source to VOCs and NO x emissions, control of vehicular emissions plays a very important role in improving regional air quality. By taking 2015 as a target year, this paper assessed the impacts of five possible motor vehicle emission control measures and a combined policy scenario on ambient air quality in the PRD region, with the use of the Model-3/CMAQ (Community Multi-scale Air Quality) model. The results show: (1) an overall decreasing pattern in SO 2, NO 2 and PM 10 concentrations was found in central-south metropolitan areas of the PRD region for all measures, but increased O 3 concentrations may occur in these areas as well. The exception to this is that a slight decrease was observed for the cases of motorcycle restriction and introduction of HEV; (2) upgrading to National IV emission standards is the most effective individual measure and can reduce daily averaged NO 2 and PM 10 concentrations by 11.7ppbV and 21.3μgm -3, respectively; but involves an increase (at maximum) of 10.3ppbV in O 3 concentration. Evaluation of the combined scenario indicates that solely controlling motor vehicle emissions is not sufficient to improve PRD regional air quality significantly. O 3 and PM 10 concentrations under the same VOC/NO x reduction ratios exhibit differently at different locations, suggesting that integrated and location-specific pollution control strategies, considering co-control of multi-pollutants, are needed in this region in order to decrease primary and secondary pollutant concentrations simultaneously. © 2011 Elsevier Ltd. Source

Zheng J.,South China University of Technology | Zheng J.,Pearl River Delta Atmospheric Environmental Research Joint Laboratory | Che W.,South China University of Technology | Che W.,Pearl River Delta Atmospheric Environmental Research Joint Laboratory | And 4 more authors.
Aerosol and Air Quality Research | Year: 2013

Characterizing spatial and temporal variations of PM pollution is critical for a thorough understanding of its formation, transport and accumulation in the atmosphere. In this study, Aerosol Optical Thickness (AOT) data retrieved from a Moderate Resolution Imaging Spectroradiometer (MODIS) were used to investigate the spatial and temporal variations of PM10 (particles with aerodynamic diameters of less than 10 μm) pollution in the Pearl River Delta (PRD) region. Seasonal linear regression models between 1-km retrieved MODIS AOT data and ground PM10 measurements were developed for the PRD region with meteorological corrections, and were subjected to a validation against observations from the regional air monitoring network in this region from 2006 to 2008, with an overall error of less than 50%. Consistent with ground observations, the estimated PM10 concentrations from the regression models appeared to be highest in winter, lower in autumn and spring, and lowest in summer. A high PM10 concentration band was detected over the inner part of the PRD region, where heavy industries and dense populations are located. The shape and concentration levels of this band exhibit significant seasonal variations, which shift with synoptic wind direction, indicating different source regions and their contributions to the PM10 pollution in the PRD region. Several discrete "hot spots" were found in the southwest of the PRD region during spring and other seasons, where no ground measurements are available. The reasons for the formation of these hot spots are unclear, and further investigations are needed. Despite the limitations of this work, the results demonstrate the effectiveness of retrieving remote sensing data for characterizing regional aerosol pollution, together with ground measurements. The combination of satellite data and ground monitoring presented in this work can help in better understanding the sources, formation mechanisms and transport process of particulate matters on a regional scale. © Taiwan Association for Aerosol Research. Source

Zheng J.,South China University of Technology | Zheng Z.,South China University of Technology | Yu Y.,South China University of Technology | Zhong L.,Guangdong Provincial Environmental Monitoring Center
Atmospheric Environment | Year: 2010

Using the Global Biosphere Emissions and Interactions System model (GloBEIS), 3 × 3 km gridded and hourly biogenic volatile organic compound (BVOC) emissions in the Pearl River Delta (PRD) were estimated for the year 2006. The study used newly available land cover database, observed meteorological data, and recent measurements of emission rates for tree species in China. The results show that the total BVOC emission in the PRD region in 2006 was 296 kt (2.2 × 10 11 gC), of which isoprene contributes about 25% (73 kt, 6.4 × 10 10 gC), monoterpenes about 34% (102 kt, 8.9 × 10 10 gC), and other VOCs (OVOC) about 41% (121 kt, 6.8 × 10 10 gC). BVOC emissions in the PRD region exhibit a marked seasonal pattern with the peak emission in July and the lowest emission in January, and are mainly distributed over the outlying areas of the PRD region, where the economy and land use are less developed. The uncertainties in BVOC emission estimates were quantified using Monte Carlo simulation; the results indicate high uncertainties in isoprene emission estimates, with a relative error of -82 to +177%, ranging from 12.4 to 186.4 kt; -41 to +58% uncertainty for monoterpenes emissions, ranging from 67.7 to 181.9 kt; and -26 to +30% uncertainty in OVOC emissions, ranging from 88.8 to 156.2 kt on the 95% confidence intervals. The key uncertainty sources include emission factors and the model empirical coefficients α, C T1, C L, and E opt for estimating isoprene emission, and emission factors and foliar density for estimating monoterpenes and OVOC emissions. This implies that determining these empirical coefficient values properly and conducting more field measurements of emission rates of tree species are key approaches for reducing uncertainties in BVOC emission estimates. Improving future BVOC emission inventory work in the PRD region requires giving priority to research on shrub land, coniferous forests, and irrigated cropland and pasture. © 2010 Elsevier Ltd. Source

Li Y.,Hong Kong University of Science and Technology | Lau A.K.-H.,Hong Kong University of Science and Technology | Lau A.K.-H.,Pearl River Delta Atmospheric Environmental Research Joint Laboratory | Fung J.C.-H.,Hong Kong University of Science and Technology | And 5 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2012

It is well-known that ground-level ozone is not just a local or regional air quality problem; emission sources from super-regional (sources outside the PRD region) scales are known to contribute significantly to local ozone concentrations. However, source apportionment studies differentiating the relative contributions of local, regional, and super-regional ozone precursors are still limited. In this paper, using the Pearl River Delta (PRD) as an example, we have conducted a detailed apportionment (by source categories and by source regions) study of surface ozone using photochemical model source apportionment tools. Our results show that, while the super-regional contribution is dominant under mean ozone conditions, elevated local and regional sources are the causative factor for the formation of high ozone episodes. In particular, the local and PRD regional contributions increase from about 30% during non-episode days to about 50% during high ozone episode days in the autumn (November 2006) and even up to about 70% during high ozone episodes in the summer (July 2006). These results suggest that local and regional controls of ozone precursors are still very important for ozone reduction, particularly for episodic events. Furthermore, our results show that mobile emission is by far the highest contributing source category to ozone levels in the PRD for episodic ozone events. Moreover, we find substantial seasonal variations in the way ozone precursors from neighboring areas affect ozone levels in any particular city, suggesting that regional collaborations are important for developing effective long-term strategies to reduce ozone over the PRD region. © 2012. American Geophysical Union. All Rights Reserved. Source

Tao Y.,Peking University | Huang W.,Peking University | Huang X.,Consensus Information Center | Zhong L.,Guangdong Provincial Environmental Monitoring Center | And 5 more authors.
Environmental Health Perspectives | Year: 2012

Background and objectives: Epidemiologic studies have attributed adverse health effects to air pollution; however, controversy remains regarding the relationship between ambient oxidants [ozone (O 3) and nitrogen dioxide (NO 2)] and mortality, especially in Asia. We conducted a four-city time-series study to investigate acute effects of O 3 and NO 2 in the Pearl River Delta (PRD) of southern China, using data from 2006 through 2008. Methods: We used generalized linear models with Poisson regression incorporating natural spline functions to analyze acute mortality in association with O 3 and NO 2, with PM 10 (particulate matter ≤ 10 μm in diameter) included as a major confounder. Effect estimates were determined for individual cities and for the four cities as a whole. We stratified the analysis according to high- and low- exposure periods for O 3. Results: We found consistent positive associations between ambient oxidants and daily mortality across the PRD cities. Overall, 10-μg/m 3 increases in average O 3 and NO 2 concentrations over the previous 2 days were associated with 0.81% [95% confidence interval (CI): 0.63%, 1.00%] and 1.95% (95% CI: 1.62%, 2.29%) increases in total mortality, respectively, with stronger estimated effects for cardiovascular and respiratory mortality. After adjusting for PM 10, estimated effects of O 3 on total and cardiovascular mortality were stronger for exposure during high-exposure months (September through November), whereas respiratory mortality was associated with O 3 exposure during nonpeak exposure months only. Conclusions: Our findings suggest significant acute mortality effects of O 3 and NO 2 in the PRD and strengthen the rationale for further limiting the ambient pollution levels in the area. Source

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