A Numerical Study Of PM_2.5 Source Apportionment In Guangdong Province,china

As one of the most populous and developed provinces in China,Guangdong province（GD）has been experiencing regional haze problems characterized by high concentrations of fine particulate.Thanks to the continuous emissions control efforts implemented in the past few years,the number of haze days and ambient PM_2.5 concentrations were in decline trends,but ambient PM_2.5 concentrations in some cities were still high and frequently violated the new air quality standard.To further reduce ambient PM_2.5 concentrations,control strategies on more comprehensive sources should be considered,thus a full understanding of the relationship between ambient PM_2.5 and emission sources is needed.In this study,using the most up-to-date emission inventory and the Comprehensive Air Quality Model with Extension（CAMx）,source contributions to ambient PM_2.5 in GD in 2012 from eight emission source sectors（agriculture,biogenic,dust,industry,power plant,residential,mobile and others）and regional transport were quantified.Results showed that super ? regional transport dominates the ambient PM_2.5 in GD with notable seasonal differences(about 19.8³9.8 μg·m^-3 in winter and autumn,7.6¹1.1 μg·m^-3 in spring and summer).Among sources in GD,contributions to ambient PM_2.5 from high to low are industry,mobile,agriculture,power plant,residential,biogenic,dust and others which are 30.8%、16.4%、13.7%、11.0%、10.7%、9.4%、6.3% and 1.7%.Mobile sources contribute 20.1% of the ambient PM_2.5 to the Pearl River Delta（PRD）region,the central and most developed area of GD,higher than the outside PRD regions.Contributions from agriculture sources to the outside PRD regions are largely higher than PRD.In addition,agriculture sources are responsible for 13.7% to ambient PM_2.5 in GD,indicating the importance of regulations on agricultural activities,which has been largely ignored in the current air quality management.To understand the relationship between emission changes and source contributions to ambient PM_2.5 in GD in recent years,a source apportionment of PM_2.5 in GD in 2006 was conducted.Emissions of SO2,PM10,PM_2.5 and NH₃ were in decline trends from 2006 to 2012 while NO_X,CO and VOCs were increased.Contributions from power plant to ambient PM_2.5 concentrations were declined.Contributions from industry sources to PRD were declined from 2006 to 2012,while those to the outside PRD regions were increased,indicating the importance of emission control on industry sources in the outside PRD regions.Preliminary evaluation of super-regional transport with observed PM_2.5 concentrations at a national background monitoring station shows that super-regional transport might be overestimated.Boundary conditions and transport process might be accounting for the overestimation of super-regional impacts.