Contribution of anthropogenic emission changes to the evolution of PM2.5 concentrations and composition in the Pearl River Delta during the period of 2006–2020

Abstract

Over the last decade, the Pearl River Delta (PRD) region has seen substantial improvements in PM2.5 concentrations, which can be attributed to both local emission reductions and nationwide efforts. To formulate effective strategies for long-term PM2.5 mitigation in the PRD, it is essential to understand the benefits derived from emission reductions in various regions. In this study, we employed a simulation-based decomposition analysis to evaluate the impact of national and local emission changes on PM2.5 and its composition in the PRD region from 2006 to 2020. The downturn in annual average PM2.5 concentrations in the PRD region from 2006 to 2020 primarily stems from local emission reductions, constituting 41–55% of the overall improvement, and nationwide emission reductions (excluding those within the PRD), which add another 10–28% to the improvement. The PM2.5 improvement associated with local emission reduction primarily originates from industrial sources, power plants, and vehicles. Both local and nationwide emission reductions significantly curtail sulfate concentrations, but their impact on nitrate concentrations are relatively moderate, impeded by the ozone rebound due to the inappropriate reduction ratio of NOx/VOCs emissions, particularly in regions with VOCs-limited regime. Since 2013, as a result of China's accelerated efforts to reduce air pollution, national emission reductions have played a larger role in reducing PM2.5 concentrations in the PRD region, especially in the autumn and winter seasons when their contributions to PM2.5 decline can reach 44% and 54%, respectively. Therefore, comprehensive ozone control as well as coordinated regional emission reductions will be crucial for the long-term improvement of PM2.5 in the PRD. Furthermore, stricter measures remain imperative to reduce emissions from local sources such as vehicles, agricultural sources, non-road sources, and dust sources.