Quantified the influence of different synoptic weather patterns on the transport and local production processes of O3 events in Pearl River Delta, China.

Regional ozone (O3) pollution in the Pearl River Delta (PRD) region has become a topic of discussion in recent years. The occurrence of regional O3 pollution are influenced by local emissions and cross-regional transportation. In this study, we identified the predominant synoptic patterns that were associated with regional O3 pollution from August to November in 2015-2021 using the Lamb-Jenkinson classification technique. All synoptic types were divided into four major categories of NE-type, C-type, S-type and A-type, which accounted for 42 %, 25 %, 18 % and 15 % of the total number of regional O3 pollution days, respectively. The weather conditions for each synoptic pattern were described by using MERRA-2 datasets. Then a rapidly method was established to quantify the contribution of cross-regional processes to high O3 concentration in different synoptic patterns over the PRD through the WRF-Flexpart model. The NE-type weather condition was characterized by a relatively large wind speed with a significant cross-regional transport contribution of 35.8 %. The A-type weather condition had moderate surface wind speed with the stable weather condition, resulting in a lower cross-region transport contribution of 27.7 %. Under controlled by C-type, the stagnant weather condition caused by low-pressure systems on its periphery, would suppress diffusion of O3. As a result, the regional O3 pollution in the PRD were mostly attributed to locally (87.9 %) with minimal cross-regional transport (12.1 %). The S-type weather condition was mainly associated with the West Pacific Subtropical High and the surface equalization pressure field, accompanied by low wind speed. Therefore, the considerable (minor) contribution of local production (cross-regional transport) of 83.3 % (16.7 %) to O3 pollution in the PRD is a consequence of the stagnation weather condition.

Potential impact of industrial transfer on PM2.5 and economic development under scenarios oriented by different objectives in Guangdong, China.

For sustainable regional development, industrial transfer is an important trend that will potentially change the spatial and temporal pattern of air pollution and economic development. Aiming to better regulate industrial transfer and guide policy-making, this study proposes an assessment framework for industrial transfer that combines precise enterprise data, GIS technology and a 3-D air quality model. Taking Guangdong Province as an example, this study simulates the redistribution of 4015 high-pollution and high-energy-consumption (double-high) enterprises in the Pearl River Delta (PRD) to surrounding areas, and the potential impact on air quality is further evaluated. Three mutually independent transfer scenarios with different objectives are designed-ENV (ENVironment), ENT (ENTerprise), and GOV (GOVernment)-which aim to maximize benefits from the standpoint of the residents of Guangdong, the enterprises themselves, and local governments, respectively. Results show that Western Guangdong (WG), Northern Guangdong (NG), and Eastern Guangdong (EG) would be the primary transfer-in regions under the ENV, ENT, and GOV scenarios due to different resource endowment. Controlled by the different scenarios, the redistribution of enterprises presented different characteristics regarding the transport of pollutant emissions and economic added value between the PRD and surrounding areas. The average concentration of PM2.5 and the related population-weighted concentrations (PWC) showed a slight decrease over the PRD (-0.75 to -0.62 µg/m3 and -0.35 to -0.49 µg/m3 per person) but increased dramatically in surrounding areas under the three scenarios (0.46-7.68 µg/m3 and 0.07-4.44 µg/m3 per person). The transfer of double-high enterprises could potentially decrease the industrial fossil fuel consumption intensity (fossil energy consumption per unit of industrial GDP) of most of the cities while exacerbating pollution intensity (concentration of PM2.5 per unit of industrial GDP), reflecting the huge gap in the regional industrial development pattern in Guangdong Province at this stage, and illustrating the importance of emission control of these enterprises for improvement of regional air quality in the future. The research perspective on industrial transfer proposed in this study could provide a reference for future studies.

Ozone control strategies for local formation- and regional transport-dominant scenarios in a manufacturing city in southern China.

Given the leveling off of fine particulate matter (PM2.5), ground-level ozone (O3) pollution has become one of the most significant atmospheric pollution issues in the Pearl River Delta (PRD) region in China, especially in the manufacturing city of Dongguan, which faces more severe O3 pollution. The development of strategies to control O3 precursor emissions, including volatile organic compounds (VOCs) and nitrogen oxide (NOx), depends to a large extent on the source region of the O3 pollution. In this study, by combining the Weather Research and Forecasting model coupled with chemistry (WRF-Chem), the Empirical Kinetic Modeling Approach (EKMA), and the Flexible Particle model (FLEXPART), more effective strategies of controlling O3 precursor emissions were identified under two typical types of O3 pollution episodes: local formation (LF)-dominant (8-12 September 2019) and regional transport (RT)-dominant (23-27 October 2017) episodes, distinguished by the WRF-FLEXPART model. During the LF-dominant episode, the EKMA revealed that the O3 formation in Dongguan was in a transitional regime, and the abatement of solvent use-VOCs emissions in the key area of Dongguan was more effective in reducing O3 levels, with an emission reduction benefit 1.7 times that of total VOCs emission sources throughout Dongguan. With respect to the RT-dominant episode, the reduction in VOCs emissions in the local region did not effectively curb O3 pollution, although the photochemical regime of the O3 formation in Dongguan was VOCs-limited. A 50% reduction in NOx emissions in the upwind regions (parts of Guangzhou and Huizhou) effectively decreased the O3 concentration in Dongguan by 17%. The results of this study emphasize the importance of the source region of O3 pollution in the implementation of effective O3 control strategies and provide valuable insights for region-specific precursor emission policy formulation, not only in Dongguan, but also in other regions facing severe O3 pollution.

Five-year observation of aerosol optical properties and its radiative effects to planetary boundary layer during air pollution episodes in North China: Intercomparison of a plain site and a mountainous site in Beijing.

The aerosol microphysical, optical and radiative properties of the whole column and upper planetary boundary layer (PBL) were investigated during 2013 to 2018 based on long-term sun-photometer observations at a surface site (~106 m a.s.l.) and a mountainous site (~1225 m a.s.l.) in Beijing. Raman-Mie lidar data combined with radiosonde data were used to explore the aerosol radiative effects to PBL during dust and haze episodes. The results showed size distribution exhibited mostly bimodal pattern for the whole column and the upper PBL throughout the year, except in July for the upper PBL, when a trimodal distribution occurred due to the coagulation and hygroscopic growth of fine particles. The seasonal mean values of aerosol optical depth at 440 nm for the upper PBL were 0.31 ±â€¯0.34, 0.30 ±â€¯0.37, 0.17 ±â€¯0.30 and 0.14 ±â€¯0.09 in spring, summer, autumn and winter, respectively. The single-scattering albedo at 440 nm of the upper PBL varied oppositely to that of the whole column, with the monthly mean value between 0.91 and 0.96, indicating weakly to slightly strong absorptive ability at visible spectrum. The monthly mean direct aerosol radiative forcing at the Earth's surface and the top of the atmosphere varied from -40 ±â€¯7 to -105 ±â€¯25 and from -18 ±â€¯4 to -49 ±â€¯17 W m-2, respectively, and the maximum atmospheric heating was found in summer (~66 ±â€¯12 W m-2). From a radiative point of view, during dust episode, the presence of mineral dust heated the lower atmosphere, thus promoting vertical turbulence, causing more air pollutants being transported to the upper air by the increasing PBLH. In contrast, during haze episode, a large quantity of absorbing aerosols (such as black carbon) had a cooling effect on the surface and a heating effect on the upper atmosphere, which favored the stabilization of PBL and occurrence of inversion layer, contributing to the depression of the PBLH.