北方沿海城市大气PM2.5和PM10中铁溶解度的分布特征OA北大核心CSCDCSTPCD

Aerosol Fe is a critical component in biogeochemical cycles,simultaneously influencing oceanic primary productivity via atmospheric deposition and significantly impacting air quality and human health.These effects are largely governed by Fe solubility(%Fes).Although particle size is a critical factor influencing aerosol%Fes,the size-dependent distribution characteristics of%Fes remain poorly understood.Therefore,we collected fine particu-late matter 2.5(PM2.5)and 10(PM10)samples under clean and polluted conditions in Qingdao,a coastal city located along a major aerosol-transport pathway from the Asian continent to the northwestern Pacific.Thereafter,we de-termined the mass concentrations of total Fe(FeT),dissolved Fe(Fes),and the resulting%Fes in the samples.The results showed that PM2.5 exhibited FeT and Fes mass concentrations of 876.5±604.4 ng/m3 and 65.5±41.3 ng/m3,respectively,with an average%Fes of 8.3%±2.9%.Conversely,PM10 exhibited higher FeT(3 063.7±2 753.2 ng/m3)and Fes(94.4±107.3 ng/m3),but a lower%Fes(2.9%±1.1%).The variation in%Fes between PM2.5 and PM10 is closely linked to Fe sources and atmospheric acidification processes.Enrichment factor analysis revealed that Fe in PM10 was mainly from natural sources,whereas Fe in PM2.5 was primarily dominated by anthropogenic activities.Single-particle electron microscopy revealed that anthropogenic Fe-rich nanoparticles were mainly concentrated in the fine PM fraction,with an average size of 337±202 nm.Conversely,mineral particles from natural sources ex-hibited significantly larger average particle sizes(1 384±803 nm).Additionally,under clean and polluted condi-tions,%Fes in PM2.5 and PM10 increased with the acidification degree,which was notably higher in PM2.5 than in PM10.