| The PRD（Pearl River Delta）region is one of the typical regions with high atmospheric heavy metal emission and deposition in China,which is facing ecological risks that cannot be ignored.In this study,the deposition fluxes of six heavy metals,As,Cd,Cr,Cu,Pb and Zn,were observed for a long time（2016-2020）at two sites,GZ（Guangzhou）and DHS（Dinghushan）,which respectively represent the characteristics of urban and suburban underlying surface,and their variation characteristics were analyzed.The main sources,transport pathways and potential source regions of heavy metals with significant ecological risks（Cd,As,Cu,Pb）were identified.Based on the superimposed PM2.5emission inventory（MEIC）of the identified potential source regions,the spatial pattern of relative contributions of each emission industry corresponding to ecological risks in the region near the observation site was obtained.The results of this study provide an important scientific basis for establishing accurate prevention and control policies based on maximization of ecological benefits.The results showed that:（1）In the PRD region,the average annual flux of total heavy metal deposition was Zn>Cu>Pb>Cr>As>Cd,while the ecological risk grade was Cd>As>Cu>Pb>Zn>Cr.The total deposition flux was mainly contributed by wet deposition（54%～73%）.In recent years,the total deposition flux in this region changed insignificantly,while the contribution of dry deposition increased.（2）The primarly influencing factors of heavy metals wet deposition at GZ and DHS sites were vehicles/smelting industries/coal combustion.For dry deposition,the most important influencing factor at GZ site was the coal combustion/ceramic industry/vehicles（84%～100%）,while the vehicles/smelting industries at DHS site contributed64%～94%of heavy metals.The most significant impact factors of heavy metals identified by PMF and PCA methods were mixed sources.（3）In the key source region at GZ site,area within the PRD region contributed the majority（68%-81%）of the heavy metal wet deposition flux.While at DHS site,the area contribution within the PRD region was similar（37%～52%）.The heavy metal flux of dry deposition was more easily affected by transport sources.The total deposition flux of heavy metals with high ecological risk was primarily contributed by the industrial and residential sectors outside the PRD region in the key source region of the dry deposition.And the total deposition flux was closed to the total emissions within the key potential source regions.Although the PM2.5emission inventory has not fully considered the contribution of non-fossil combustion and marine source to heavy metal emissions and deposition,it could still help create effective and precise policy to control heavy metal emissions with higher ecological risks,thus reducing the ecological risks of heavy metals. |
