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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.


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.


Louie P.K.K.,33 F Revenue Tower | Ho J.W.K.,33 F Revenue Tower | Tsang R.C.W.,33 F Revenue Tower | Blake D.R.,University of California at Irvine | And 6 more authors.
Atmospheric Environment | Year: 2013

Ambient air measurements of volatile organic compounds (VOCs) and oxygenated volatile organic compounds (OVOCs) were conducted and characterised during a two-year grid study in the Pearl River Delta (PRD) region of southern China. The present grid study pioneered the systematic investigation of the nature and characteristics of complex VOC and OVOC sources at a regional scale. The largest contributing VOCs, accounting over 80% of the total VOCs mixing ratio, were toluene, ethane, ethyne, propane, ethene, butane, benzene, pentane, ethylbenzene, and xylenes. Sub-regional VOC spatial characteristics were identified, namely: i) relatively fresh pollutants, consistent with elevated vehicular and industrial activities, around the PRD estuary; and ii) a concentration gradient with higher mixing ratios of VOCs in the west as compared with the eastern part of PRD. Based on alkyl nitrate aging determination, a high hydroxyl radical (OH) concentration favoured fast hydrocarbon reactions and formation of locally produced ozone. The photochemical reactivity analysis showed aromatic hydrocarbons and alkenes together consisted of around 80% of the ozone formation potential (OFP) among the key VOCs. We also found that the OFP from OVOCs should not be neglected since their OFP contribution was more than one-third of that from VOCs alone. These findings support the choice of current air pollution control policy which focuses on vehicular sources but warrants further controls. Industrial emissions and VOCs emitted by solvents should be the next targets for ground-level ozone abatement. © 2012 Elsevier Ltd.


Wang X.,Peking University | Zhang Y.,Peking University | Hu Y.,Georgia Institute of Technology | Zhou W.,Peking University | And 7 more authors.
Atmospheric Chemistry and Physics | Year: 2010

In this study, the Community Multiscale Air Quality (CMAQ) modeling system is used to simulate the ozone (O3) episodes during the Program of Regional Integrated Experiments of Air Quality over the Pearl River Delta, China, in October 2004 (PRIDE-PRD2004). The simulation suggests that O 3 pollution is a regional phenomenon in the Pearl River Delta (PRD). Elevated O3 levels often occurred in the southwestern inland PRD, Pearl River estuary (PRE), and southern coastal areas during the 1-month field campaign. Three evolution patterns of simulated surface O3 are summarized based on different near-ground flow conditions. More than 75% of days featured interactions between weak synoptic forcing and local sea-land circulation. Integrated process rate (IPR) analysis shows that photochemical production is a dominant contributor to O3 enhancement from 09:00 to 15:00 local standard time in the atmospheric boundary layer over most areas with elevated O3 occurrence in the mid-afternoon. The simulated ozone production efficiency is 2-8 O3 molecules per NOx molecule oxidized in areas with high O3 chemical production. Precursors of O3 originating from different source regions in the central PRD are mixed during the course of transport to downwind rural areas during nighttime and early morning, where they then contribute to the daytime O3 photochemical production. The sea-land circulation plays an important role on the regional O3 formation and distribution over PRD. Sensitivity studies suggest that O3 formation is volatile-organic-compound- limited in the central inland PRD, PRE, and surrounding coastal areas with less chemical aging (NOx/NOy≥0.6), but is NO x-limited in the rural southwestern PRD with aged air (NO x/NOy<0.3). © Author(s) 2010.


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.


Zhong L.,Guangdong Provincial Environmental Monitoring Center | Louie P.K.K.,33 F Revenue Tower | Zheng J.,South China University of Technology | Yuan Z.,Hong Kong University of Science and Technology | And 3 more authors.
Atmospheric Environment | Year: 2013

The information provided by the scientific studies and control measures implemented in the Pearl River Delta (PRD) region of China reveals that tremendous progress has been made in the understanding of regional air pollution issues and the deployment of mitigation measures for alleviating these problems. Given the unparalleled rapid economic growth in the PRD over the past two decades, such progress was only made possible by strong, science-based support and the partnerships between government and research institutions in the region and overseas. Researchers from these partnership programs and related studies have deployed cutting-edge expertise and experience in various crucial mainland China and mainland China/Hong Kong-level projects. China recognizes the importance of protecting the environment and cleaning up the air in the pursuit of sustainable growth and economic development. To avoid falling into a cycle of event-driven clean-up efforts, China has recently taken a major step and updated the national ambient air quality standards. Clearly, China is implementing an increasing number of evidence-based policies to address air pollution problems. Thus, to bring a fresh impetus at a national level, the PRD must maintain and augment the Hong Kong-mainland collaborative momentum, inducing a "whole-China" effort to clean up air pollution. To strengthen the science-based support system and ensure continuous and concerted effort in implementing the regional multi-pollutant control strategy, there must be an overarching and integral Hong Kong-Guangdong science consortium framework supporting the formulation of regional policy and control measures built on common goals under the "one country, two systems" principle. The "PRD Approach" of the air quality management regime reflected regional cooperative efforts in synchronous air pollutant control, catalyzed the crucial role of information disclosure and subtly transformed the air quality management approach to overcome the nation's new air pollution challenges. © 2013 Elsevier Ltd.


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.


Zheng J.,South China University of Technology | Zhong L.,Guangdong Provincial Environmental Monitoring Center | Wang T.,Hong Kong Polytechnic University | Louie P.K.K.,HKSAR | Li Z.,South China University of Technology
Atmospheric Environment | Year: 2010

The ambient air quality monitoring data of 2006 and 2007 from a recently established Pearl River Delta (PRD) regional air quality monitoring network are analyzed to investigate the characteristics of ground-level ozone in the region. Four sites covering urban, suburban, rural and coastal areas are selected as representatives for detailed analysis in this paper. The results show that there are distinct seasonal and diurnal cycles in ground-level ozone across the PRD region. Low ozone concentrations are generally observed in summer, while high O3 levels are typically found in autumn. The O3 diurnal variations in the urban areas are larger than those at the rural sites. The O3 concentrations showed no statistically significant difference between weekend and weekdays in contrast to the findings in many other urban areas in the world. The average ozone concentrations are lower in urban areas compared to the sites outside urban centers. Back trajectories are used to show the major air-mass transport patterns and to examine the changes in ozone from the respective upwind sites to a site in the center of the PRD (Wanqingsha). The results show higher average ozone concentrations at the upwind sites in the continental and coastal air masses, but higher 1 h-max O3 concentrations (by 8-16 ppbv) at the center PRD site under each of air-mass category, suggesting that the ozone pollution in the PRD region exhibits both regional and super-regional characteristics. © 2009 Elsevier Ltd. All rights reserved.


Zheng J.Y.,South China University of Technology | Zheng J.Y.,Pearl River Delta Atmospheric Environment Research Joint Laboratory | Yin S.S.,South China University of Technology | Yin S.S.,Pearl River Delta Atmospheric Environment Research Joint Laboratory | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2012

Detailed NH3 emission inventories are important to understand various atmospheric processes, air quality modeling studies, air pollution management, and related environmental and ecological issues. A high-resolution NH3 emission inventory was developed based on state-of-the-science techniques, up-to-date information, and advanced expert knowledge for the Pearl River Delta region, China. To provide model-ready emissions input, this NH 3 emissions inventory was spatially allocated to 3 km × 3 km grid cells using source-based spatial surrogates with geographical information system (GIS) technology. For NH3 emissions, 9 source categories and 45 subcategories were identified in this region, and detailed spatial and temporal characteristics were investigated. Results show that livestock is by far the most important NH3 emission source by contributing about 61.7% of the total NH3 emissions in this region, followed by nitrogen fertilizer applications (∼23.7%) and non-agricultural sources (∼14.6%). Uncertainty analysis reveals that the uncertainties associated with different sources vary from source to source and the magnitude of the uncertainty associated with a specific source mainly depends on the degree of accuracy of the emission factors and activity data as well as the technique used to perform the estimate. Further studies should give priority to the hog, broiler, goose subsectors of the livestock source and N fertilizer application source in order to reduce uncertainties of ammonia emission estimates in this region. The validity of the NH3 emissions inventory is justified by the trend analysis of local precipitation compositions, such as pH values, the Ca 2++NH4+/SO4 -2+ NO- 3 ratios, and NH4 + concentrations which are directly or indirectly related to NH3 emissions. © 2012 Author(s).


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.

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