中国东部城市群氨减排对PM2.5质量浓度及健康风险的综合影响OA

With the continued advancement of air pollution control in China,reducing ammonia(NH3)emissions has emerged as a critical pathway for further mitigating PM2.5 pollution.The latest Air Quality Continu-ous Improvement Action Plan issued by the State Council emphasizes the progressive control of atmospheric am-monia pollution.However,previous studies have primarily focused on the nonlinear effects of NH3 emissions on PM2.5 mass concentrations at individual regional scales,lacking a comprehensive assessment of regional differences in mitigation effectiveness,associated health risks,and economic losses.Moreover,although the health impacts of PM2.5 have been extensively studied,the specific contribution of NH3 emissions to PM2.5-related health burdens and economic costs in China remains insufficiently quantified.Given that secondary inorganic aerosols(SIAs)account for 30%—50%of PM2.5 mass in eastern China,with ammonium as a key component,quantifying the role of NH3 emissions is essential for developing effective control strategies. To address these gaps,this study employs the GEOS-Chem chemical transport model and the GEMM to sys-tematically evaluate the impacts of NH3 emission reductions on PM2.5 mass concentrations,health risks,and eco-nomic losses across three major urban agglomerations in eastern China—the Beijing-Tianjin-Hebei(BTH),Yan-gtze River Delta(YRD),and Pearl River Delta(PRD)regions—during 2020.A series of sensitivity experiments with NH3 emission reduction rates ranging from 20%to 100%were conducted to characterize the nonlinear re-sponses of PM2.5 and its inorganic components. The results show that PM2.5mass concentrations exhibit a pronounced nonlinear response to NH3emission re-ductions.As the reduction rate increases from 20%to 100%,the annual mean PM2.5 mass concentration in eastern China decreases by 3.55%—35.50%.This nonlinearity is primarily driven by substantial decreases in ammonium and nitrate,while sulfate showsrelatively limited variation due to ammonia availability and gas-aerosol partitioning processes.Sulfate formation is generally not ammonia-limited except under extremely ammonia-poor conditions,whereas nitrate formation is highly sensitive to NH3 levels. The effectiveness of NH3 emission reductions varies significantly across regions and seasons.In winter(Janu-ary),under ammonia-rich conditions,PM2.5 reductions are initially limited.However,once critical thresholds are exceeded(greater than 60%reduction in the YRD and PRD,and greater than 80%in the BTH),substantial de-creases in PM2.5 are achieved,reflectinga transition from ammonia-rich to ammonia-limited regimes.In contrast,during summer(July),the PRD exhibitsa weak PM2.5 response even under high reduction scenarios,due to lower baseline SIA mass concentrations,higher temperatures favoring gas-phase partitioning,and differing meteorological conditions.Seasonal analysis further indicates that northern regions are more sensitive to NH3 re-ductions in winter,while southern regions show greater sensitivity in spring and autumn. Health risk assessments indicate that PM2.5 exposure was associated with approximately 178.03-539.38 thousand premature deaths across the three regions in 2020,of which 22%—38%were attributable to NH3 emis-sions.The YRD region experiences the highest health burden,at approximately 1.3-1.5 times that of the BTH,due to its dense population and higher baseline PM2.5 levels.Corresponding economic losses are estimated at 151.6-813.7 billion CNY,accounting for 1.37%—4.06%of regional GDP.Moreover,health benefits increase nonlinearly with increasing emission reductions,with substantial gains observed beyond the 60%reduction thresh-old.This nonlinear response highlights the importance of achievingdeep emission reductions to maximize public health benefits. Thesefindings provide scientific support for developing region-specific NH3 emission control strategies and offer insights into balancing environmental protection with socioeconomic development.Continuous year-round NH3 control is recommended for ammonia-sensitive regions such as the YRD;for the BTH,deep reductions ex-ceeding 80%in winter or integrated multi-pollutant control strategies are necessary;and for the PRD,priority should be given to wintertime pollution control.Future studies should expand spatial coverage,consider multi-pol-lutant interactions,and incorporate cost-benefit analyses to inform more targeted and feasible ammonia mitigation policies.