Air Pollution in Megacities and Surrounding Regions

Author:admin | published date:2013-11-30 | click:1056

The North China Plain is the largest territory covering many different provincial areas in China, and the region is facing increasing severe air pollution which is of global importance. The coordinated provincial air pollution control thus becomes one of critical strategy options. Based on the understanding of the formation mechanism of the air pollution in Beijing and North China Plain, we developed strategies and methodologies for regional coordinated air pollution controlling. Our work successfully ensured the air quality during the 2008 Beijing Olympic Games by implementing coordinating emission control in six provinces and cities, and fostered the start and application of the regionally-coordinated air pollution control in the state-level air pollution control strategy.

Characterization of the temporal and spatial distributions of air pollutants and the chemical transformations with an integrated observation technology. Within the framework of Campaigns of Air Quality Research in Beijing and surrounding regions (CAREBeijing), we conducted field measurements in North China Plain in an area of about 500 km x 600 km. We developed a comprehensive and multi-dimensional measurement network (Figure 3) to characterize both horizontal (ground based observation sties, mobile vans, and remote sensing by satellite) and vertical (tower, balloons, LIDAR and aircraft) distributions of the air pollutants. These multi-dimensional measurements are particularly useful for the validation of air quality models and improvement of emission inventories. By using data assimilation techniques, better accuracy of air quality forecast can be achieved. We developed several advanced in-situ and on-line monitoring systems for the detection of primary and secondary pollutants including reactive intermediates. Super sites for investigation of the chemical transformation and formation mechanism of the secondary pollutants were also established. We designed and manufactured the first mobile monitoring platform in China for on road air pollutants measurements with comprehensive measurement instruments on-board. This mobile monitoring platform was successfully deployed during the air quality assurance projects of 2008 Beijing Olympic Games and 2010 Shanghai World Exposition.

By understanding the non-linear coupling mechanisms between the emission of primary air pollutants and the formation of secondary air pollutants, we developed the supporting technologies for the regionally coordinated control of multi-air pollutants. (1) the new particle formation event was observed under pollution episodes, and we suggested the strong oxidizing capacity overcome its condensational sink should be the explanation; (2) we revealed that the local chemical transformations of primary pollutants (SO2, NOx, VOCs, PM) and inter-provincial/city transport of secondary pollutants (O3, fine particle) are the major causes of heavy pollution episodes in Beijing; (3) By combining the observational based model (OBM) and air quality model (CAMx), we elucidated the relative source contribution budgets from Beijing and its surrounding areas toward the O3 and fine particle in Beijing; (4) we proposed a framework for regionally-coordinated control of primary and secondary air pollutants, and this framework was further used as a policy supporting tool in formulating regional controlling strategies for the ambient precursors of O3 and fine particles.

By combining the mobile observations and the meteorological models, we developed a method to quantify the inter-provincial air pollutant transport and impacts. (1) based on the ground mobile platforms and the aircraft measurements, transport fluxes of air pollutants were experimentally measured; (2) based on the long-term measurements and meteorological models, the footprint technique is further used to calculate the source contributions from different air masses for certain receptor sites. The air pollution transport of different provinces in North China Plain was successfully unveiled.

We developed a model to quantify the impact on the economy of various pollution controlling measures, and formulated a regionally coordinated air pollution control scheme for multi-provinces. (1) a comprehensive diagnostic model is developed to describe the key economic factors for air pollution control such as emission - control technology and measures - benefit so that the regional air pollution control scenarios are conceived and the reduction potential can be predicted; (2) an extended cost-benefit model for regional control and environmental gains was constructed and accordingly we deduced the regional air pollution control strategy and measures; (3) we proposed a roadmap for reforming the current air pollution controlling scheme by optimizing the resource allocations and the sharing of responsibilities and benefits.

Overall, we published over 40 papers in Journal of Geophysical Research-Atmosphere and Atmospheric Chemistry and Physics as two special issues, 3 articles as IGAC (International Global Atmospheric Chemistry) newsletter. In addition, faculty members were also invited to give invited oral presentations in several international conferences. As the lead author, Prof. ZHU, Tong edited a report - “Impacts of Megacities on Air Pollution and Climate” with contributions from worldwide renowned scientists in this field, and part of the report was also published in Science as a perspective article - “Clean Air for Megacities” as an effort of drafting a general framework of air pollution control for megacities.

Figure 3 Schematic View of Three Dimensional Observation Network in North China Plain Based on Ground, Aircraft and Satellite Platforms with In-Situ and Remote Sensing Techniques

Figure 4 Three Dimensional Distributions of the Aloft O3 Concentrations over Beijing Measured by Aircraft