Synergetic PM and O control strategy for the Yangtze River Delta, China.

PM concentrations have dramatically reduced in key regions of China during the period 2013-2017, while O has increased. Hence there is an urgent demand to develop a synergetic regional PM and O control strategy. This study develops an emission-to-concentration response surface model and proposes a synergetic pathway for PM and O control in the Yangtze River Delta (YRD) based on the framework of the Air Benefit and Cost and Attainment Assessment System (ABaCAS). Results suggest that the regional emissions of NOx, SO, NH, VOCs (volatile organic compounds) and primary PM should be reduced by 18%, 23%, 14%, 17% and 33% compared with 2017 to achieve 25% and 5% decreases of PM and O in 2025, and that the emission reduction ratios will need to be 50%, 26%, 28%, 28% and 55% to attain the National Ambient Air Quality Standard. To effectively reduce the O pollution in the central and eastern YRD, VOCs controls need to be strengthened to reduce O by 5%, and then NOx reduction should be accelerated for air quality attainment. Meanwhile, control of primary PM emissions shall be prioritized to address the severe PM pollution in the northern YRD. For most cities in the YRD, the VOCs emission reduction ratio should be higher than that for NOx in Spring and Autumn. NOx control should be increased in summer rather than winter when a strong VOC-limited regime occurs. Besides, regarding the emission control of industrial processes, on-road vehicle and residential sources shall be prioritized and the joint control area should be enlarged to include Shandong, Jiangxi and Hubei Province for effective O control.