Sustainable Solutions for Air Quality Improvement in China: Evidence from PM2.5 and Nitrogen Deposition (Invited Presentation)

The effectiveness of national policies on air pollutants control has been demonstrated on a global scale. Here, we use reactive nitrogen (Nr) and PM_2.5 pollution as indicators to reveal the political logic of short-term measures operation and the new challenges of air quality improvement after long-term policy implementation. Short-term and aggressive abatement policies for important international events (i.e. the 2008 Beijing Olympics, the APEC Blue, etc.) substantially reduced gaseous precursors and PM_2.5 concentrations; however, air quality rebounded to pre-event levels shortly after the measures ceased. Long-term adherence to sustained and strict emissions reduction policies has led to successful decreases (up to 23%) in atmospheric nitrogen (N) deposition over a decade; meanwhile the dominant forms and components of N deposition have changed as well. Atmospheric ammonia (NH₃) concentration and dry deposition have increased by about 1/3, and the bulk NO₃^--N deposition has remained almost the same; while concentrations and deposition of other Nr species (NO₂, HNO₃, particulates NH₄⁺ and NO₃^-) have decreased substantially (by 22-60%). These results suggest that the emissions of major atmospheric Nr species have been controlled effectively after long-term strict emission mitigation policies over China but agricultural NH₃ emissions need further control. Over the past 10 years, a clear decoupling of Nr pollution and economic development has been observed in North China, inspired by the "blue sky" achieved by short-term policies. The different variations in Nr pollution within the region and the spatial spillover effects of pollutant emissions between regions, strongly point to the fact that region-specific emission reduction targets and inter-regional joint prevention and control pathways should be formulated. Under the influence of climate change and the requirements of Carbon Neutrality, a shift from pollutants emission end-of-pipe control to energy structure reformation and low-carbon/low-nitrogen technology innovation should be considered in industries, transportations, residents, and agricultural sectors.