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As one of the largest agglomerations of cities in the world, the infrastructure and living conditions of the residents in the Pearl River Delta (PRD) have significantly improved since the late 1970s. However, as a two-sided sword, the boosting of economic growth has inevitably exerted adverse effects on the environment in this region. To further understand the current fine particulate matter (PM2.5) pollution sources in this region and formulate an effective future air pollution control strategy for it, a hybrid source apportionment method was applied to adjust source estimates of secondary inorganic aerosols (SIAs) [particulate sulfate (SO42−), nitrate (NO3−), and ammonium (NH4+)] by combining Comprehensive Air Quality Model Extensions and measurement data from 19 sampling sites covering the PRD region in 2015. After correction by the hybrid method, the normalized mean errors for the three major species SO42−, NO3−, and NH4+ in PM2.5 simulated by the model decreased from 0.412, 1.261, and 0.401 to 0.321, 0.565, and 0.130, respectively. Tianhu, Taishan, Taipa Grande, whose secondary inorganic aerosol concentration variations are −48.33%, −40.59%, and 39.10% after adjustment, respectively, are the three top sites with the most substantial modification. Our study revealed that the emissions outside the PRD region are still the most important contributor to the three components after the correction. In most Hong Kong sites, the adjusted mobile source is subordinate to the cross-boundary transport and became the largest endogenous source. In contrast to that in Hong Kong, preceded only by super-regional sources, the outstanding contributor to SIAs in Guangdong and Macao is the area source. Our results indicated that besides collaborative control measures, the Hong Kong and Guangdong government should emphasize the emissions from motor vehicles and residential sources, respectively. Overall, this hybrid source apportionment approach can narrow down the discrepancy betwee

As one of the largest agglomerations of cities in the world, the infrastructure and living conditions of the residents in the Pearl River Delta (PRD) have significantly improved since the late 1970s. However, as a two-sided sword, the boosting of economic growth has inevitably exerted adverse effects on the environment in this region. To further understand the current fine particulate matter (PM2.5) pollution sources in this region and formulate an effective future air pollution control strategy for it, a hybrid source apportionment method was applied to adjust source estimates of secondary inorganic aerosols (SIAs) [particulate sulfate (SO42−), nitrate (NO3−), and ammonium (NH4+)] by combining Comprehensive Air Quality Model Extensions and measurement data from 19 sampling sites covering the PRD region in 2015. After correction by the hybrid method, the normalized mean errors for the three major species SO42−, NO3−, and NH4+ in PM2.5 simulated by the model decreased from 0.412, 1.261, and 0.401 to 0.321, 0.565, and 0.130, respectively. Tianhu, Taishan, Taipa Grande, whose secondary inorganic aerosol concentration variations are −48.33%, −40.59%, and 39.10% after adjustment, respectively, are the three top sites with the most substantial modification. Our study revealed that the emissions outside the PRD region are still the most important contributor to the three components after the correction. In most Hong Kong sites, the adjusted mobile source is subordinate to the cross-boundary transport and became the largest endogenous source. In contrast to that in Hong Kong, preceded only by super-regional sources, the outstanding contributor to SIAs in Guangdong and Macao is the area source. Our results indicated that besides collaborative control measures, the Hong Kong and Guangdong government should emphasize the emissions from motor vehicles and residential sources, respectively. Overall, this hybrid source apportionment approach can narrow down the discrepancy betwee

Accurate and gridded VOC emission inventories are important for improving regional air quality model performance. In this study, a four-level VOC emission source categorization system was proposed. A 2010-based gridded Pearl River Delta (PRD) regional VOC emission inventory was developed with more comprehensive source coverage, latest emission factors, and updated activity data. The total anthropogenic VOC emission was estimated to be about 117.4 x 104 t, in which on-road mobile source shared the largest contribution, followed by industrial solvent use and industrial processes sources. Among the industrial solvent use source, furniture manufacturing and shoemaking were major VOC emission contributors. The spatial surrogates of VOC emission were updated for major VOC sources such as industrial sectors and gas stations. Subsector-based temporal characteristics were investigated and their temporal variations were characterized. The impacts of updated VOC emission estimates and spatial surrogates were evaluated by modeling O3 concentration in the PRD region in the July and October of 2010, respectively. The results indicated that both updated emission estimates and spatial allocations can effectively reduce model bias on O3 simulation. Further efforts should be made on the refinement of source classification, comprehensive collection of activity data, and spatial-temporal surrogates in order to reduce uncertainty in emission inventory and improve model performance. (C) 2015 Elsevier B.V. All rights reserved.

Accurate and gridded VOC emission inventories are important for improving regional air quality model performance. In this study, a four-level VOC emission source categorization system was proposed. A 2010-based gridded Pearl River Delta (PRD) regional VOC emission inventory was developed with more comprehensive source coverage, latest emission factors, and updated activity data. The total anthropogenic VOC emission was estimated to be about 117.4 x 104 t, in which on-road mobile source shared the largest contribution, followed by industrial solvent use and industrial processes sources. Among the industrial solvent use source, furniture manufacturing and shoemaking were major VOC emission contributors. The spatial surrogates of VOC emission were updated for major VOC sources such as industrial sectors and gas stations. Subsector-based temporal characteristics were investigated and their temporal variations were characterized. The impacts of updated VOC emission estimates and spatial surrogates were evaluated by modeling O3 concentration in the PRD region in the July and October of 2010, respectively. The results indicated that both updated emission estimates and spatial allocations can effectively reduce model bias on O3 simulation. Further efforts should be made on the refinement of source classification, comprehensive collection of activity data, and spatial-temporal surrogates in order to reduce uncertainty in emission inventory and improve model performance. (C) 2015 Elsevier B.V. All rights reserved.

Accurate and gridded VOC emission inventories are important for improving regional air quality model performance. In this study, a four-level VOC emission source categorization system was proposed. A 2010-based gridded Pearl River Delta (PRD) regional VOC emission inventory was developed with more comprehensive source coverage, latest emission factors, and updated activity data. The total anthropogenic VOC emission was estimated to be about 117.4 x 104 t, in which on-road mobile source shared the largest contribution, followed by industrial solvent use and industrial processes sources. Among the industrial solvent use source, furniture manufacturing and shoemaking were major VOC emission contributors. The spatial surrogates of VOC emission were updated for major VOC sources such as industrial sectors and gas stations. Subsector-based temporal characteristics were investigated and their temporal variations were characterized. The impacts of updated VOC emission estimates and spatial surrogates were evaluated by modeling O3 concentration in the PRD region in the July and October of 2010, respectively. The results indicated that both updated emission estimates and spatial allocations can effectively reduce model bias on O3 simulation. Further efforts should be made on the refinement of source classification, comprehensive collection of activity data, and spatial-temporal surrogates in order to reduce uncertainty in emission inventory and improve model performance. (C) 2015 Elsevier B.V. All rights reserved.

In November 2005 the Guangdong and Hong Kong governments established the Pearl River Delta regional air quality monitoring network (

For the purpose of systematically characterizing the ambient volatile organic compound (VOC) levels and their emission sources in the Pearl River Delta (PRD) of China, a grid study with VOC samples simultaneously taken at 84 sites over the PRD was conducted in summer and winter of 2008 and 2009. Positive Matrix Factorization (PMF) model was applied to identify the major VOC contributing sources and their temporal and spatial variations. Nine sources were identified, with gasoline exhaust, industrial emission and LPG leakage 82 propellant emission the top three significant sources. They accounted for 23%, 16% and 13% of the ambient VOC levels, respectively. Control measures should be therefore targeted on mitigating the VOC emissions from the traffic-related and industrial-related sources. The total VOC level did not show strong increase from 5 a.m. to 10 a.m. during all the four sampling campaigns, which may result from stronger wind and higher mixing height at 10 a.m. Three hotspot areas with significant VOC contributions were identified by source apportionment analysis: (1) the Pearl River Estuary; (2) an area from Central Dongguan to North Shenzhen; and (3) the Zhuhai-Zhongshan-Jiangmen area. For better characterizing the roles of VOC and NO, in producing the secondary pollutants and to identify specific sources emitting excessive concentrations of precursors, the emission-oriented Photochemical Assessment Monitoring Station (PAMS) network is recommended to be established in the PRD. Three PAMS networks are suggested in correspondence to the three identified hotspot areas. (C) 2012 Elsevier Ltd. All rights reserved.

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 OFF 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. (C) 2012 Elsevier Ltd. All rights reserved.

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

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

In November 2005 the Guangdong and Hong Kong governments established the Pearl River Delta regional air quality monitoring network (

For the purpose of systematically characterizing the ambient volatile organic compound (VOC) levels and their emission sources in the Pearl River Delta (PRD) of China, a grid study with VOC samples simultaneously taken at 84 sites over the PRD was conducted in summer and winter of 2008 and 2009. Positive Matrix Factorization (PMF) model was applied to identify the major VOC contributing sources and their temporal and spatial variations. Nine sources were identified, with gasoline exhaust, industrial emission and LPG leakage 82 propellant emission the top three significant sources. They accounted for 23%, 16% and 13% of the ambient VOC levels, respectively. Control measures should be therefore targeted on mitigating the VOC emissions from the traffic-related and industrial-related sources. The total VOC level did not show strong increase from 5 a.m. to 10 a.m. during all the four sampling campaigns, which may result from stronger wind and higher mixing height at 10 a.m. Three hotspot areas with significant VOC contributions were identified by source apportionment analysis: (1) the Pearl River Estuary; (2) an area from Central Dongguan to North Shenzhen; and (3) the Zhuhai-Zhongshan-Jiangmen area. For better characterizing the roles of VOC and NO, in producing the secondary pollutants and to identify specific sources emitting excessive concentrations of precursors, the emission-oriented Photochemical Assessment Monitoring Station (PAMS) network is recommended to be established in the PRD. Three PAMS networks are suggested in correspondence to the three identified hotspot areas. (C) 2012 Elsevier Ltd. All rights reserved.

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 OFF 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. (C) 2012 Elsevier Ltd. All rights reserved.

In November 2005 the Guangdong and Hong Kong governments established the Pearl River Delta regional air quality monitoring network (

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

For the purpose of systematically characterizing the ambient volatile organic compound (VOC) levels and their emission sources in the Pearl River Delta (PRD) of China, a grid study with VOC samples simultaneously taken at 84 sites over the PRD was conducted in summer and winter of 2008 and 2009. Positive Matrix Factorization (PMF) model was applied to identify the major VOC contributing sources and their temporal and spatial variations. Nine sources were identified, with gasoline exhaust, industrial emission and LPG leakage 82 propellant emission the top three significant sources. They accounted for 23%, 16% and 13% of the ambient VOC levels, respectively. Control measures should be therefore targeted on mitigating the VOC emissions from the traffic-related and industrial-related sources. The total VOC level did not show strong increase from 5 a.m. to 10 a.m. during all the four sampling campaigns, which may result from stronger wind and higher mixing height at 10 a.m. Three hotspot areas with significant VOC contributions were identified by source apportionment analysis: (1) the Pearl River Estuary; (2) an area from Central Dongguan to North Shenzhen; and (3) the Zhuhai-Zhongshan-Jiangmen area. For better characterizing the roles of VOC and NO, in producing the secondary pollutants and to identify specific sources emitting excessive concentrations of precursors, the emission-oriented Photochemical Assessment Monitoring Station (PAMS) network is recommended to be established in the PRD. Three PAMS networks are suggested in correspondence to the three identified hotspot areas. (C) 2012 Elsevier Ltd. All rights reserved.

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 OFF 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. (C) 2012 Elsevier Ltd. All rights reserved.

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.

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.

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.

In recent decades, the Pearl River Delta (PRO) 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 PRO 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 11.7 ppbV and 21.3 mu g m(-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 PRO 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. (C) 2011 Elsevier Ltd. All rights reserved.

In recent decades, the Pearl River Delta (PRO) 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 PRO 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 11.7 ppbV and 21.3 mu g m(-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 PRO 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. (C) 2011 Elsevier Ltd. All rights reserved.

The Pearl River Delta (PRD) is one of the largest fast-developing economic zones in China. Hong Kong and the mainland part of the PRD differed in socio-economic development history and chemical management policies. Polyurethane foam (PUF)-passive air sampling (PAS) was deployed at 21 regional air quality monitoring stations across the PRD in summer and winter, respectively. Dichloro-diphenyl-trichloroethane (DDT), chlordane and hexachlorobenzene (HCB) were analyzed with GC-MS. High total DDT (240–3700 pg m–3) and chlordane (100–2600 pg m–3) concentrations were observed. Concentrations of DDTs and chlordane were higher in summer than winter; HCB vice versa. Spatially, the mainland part of the PRD generally displayed higher DDT concentrations than Hong Kong. Antifouling paint for fishing ships in coastal China was suggested to be an important current DDT source in the coast. The reason is unknown for the very low trans-/cis-chlordane (TC/CC) ratios (0.27) found in the mainland in winter. HCB concentrations were relatively uniform across the PRD, and long range transport of HCB from inland/North China to the PRD in winter was suggested.