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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. Source


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


Lu Q.,South China University of Technology | Lu Q.,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 8 more authors.
Atmospheric Environment | Year: 2013

Emission trends and variations in source contributions of SO2, NOx, PM10 and VOCs in the Pearl River Delta (PRD) region from 2000 to 2009 were characterized by using a dynamic methodology, taking into account the economic development, technology penetration, and emission control. The results indicated that SO2 emissions increased rapidly during 2000-2005 but decreased significantly afterward. NOx emissions went up consistently during 2000-2009 except for a break point in 2008. PM10 emissions increased by 76% during 2000-2007 but started to decrease slightly in the following years. VOCs emissions presented continuous increase during the study period. Power plants and industrial sources were consistently the largest SO2 and PM10 emission contributors. The on-road mobile source was the largest emission contributor for VOCs and NOx emissions with decreasing contributions. The NOx contribution from power plants and industrial sources kept increasing. Worthy of mention is that the non-road mobile source is becoming an important SO2 and NOx contributor in this region. Comparisons with satellite data, ground observations and national trends indicated that emission trends developed in this study were reasonable. Implications for future air pollution control policies were discussed. © 2012 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


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 4 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2013

As major air pollutants and key precursors of several secondary air pollutants, nitrogen oxide (NOx) emissions are regulated in many countries. However, NOx control increases ozone concentrations when the ozone formation regime is volatile organic compound (VOC) limited. Although many studies have shown that NOx regulation reduces ozone levels over the long term, it is still of concern that NOx regulation increases short-term ozone levels in metropolitan regions, where ozone formation is found to be predominantly VOC-limited. The Pearl River Delta (PRD) in China is such a region. Our modeling sensitivity study shows that while NOx reduction in the PRD region may raise the mean ozone concentration, it can also decrease peak ozone levels. Similar changes are observed in the NOx and ozone data of the PRD regional air quality monitoring network (2006-2012), lending further credence to our results. In the model, this NOx control effect is a result of the complicated spatial and diurnal variations of the ozone formation regime. In most of the PRD region, the formation regime is VOC-limited in the morning and becomes NOx-limited during peak ozone hours. Although some areas are always VOC-limited, their ozone concentrations are relatively low, and the ozone increases caused by NOx reduction generally do not cause higher ozone levels than the region's original ozone maxima. Several control scenarios are simulated to evaluate the effects of various possible control regulations. Our results show that in addition to VOC control, NOx control can be effective for reducing peak ozone concentrations in the PRD region. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union. Source

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