鼎湖山大气颗粒物中OC与EC的浓度特征及粒径分布

Characterization and Size Distribution of Carbonaceous Aerosols at Mountain Dinghu

为了解华南背景区域鼎湖山站碳质气溶胶的浓度水平与来源,采用DRI Model 2001A热/光碳分析仪测定了鼎湖山站大气颗粒物分级样品中的有机碳(OC)与元素碳(EC)浓度水平,并分析了碳质组分的浓度特征和粒径分布.结果表明,在PM1.1、PM2.1和PM9.0中,鼎湖山OC的平均质量浓度分别为(5.6±2.0)、(7.3±2.4)和(12.8±4.0)μg·m^-3,EC的平均质量浓度分别为(2.3±1.4)、(2.7±1.6)和(3.4±1.7)μg·m^-3.PM1.1和PM2.1中OC分别占PM9.0中OC的43.8%和57.0%,EC占67.6%和79.4%.OC和EC主要富集在细粒子中.PM1.1和PM2.1中OC和EC在秋季最高,OC在冬季最低,EC在夏季最低.PM9.0中OC夏季最高.鼎湖山中碳质气溶胶以OC2、EC1、OC3和OC4为主,夏季OC3>EC1,生物排放源增强,冬季EC1质量浓度最高,局地的机动车排放源更强.OC和EC在4个季节都呈现双峰型分布,细粒径段峰值位于0.43~0.65μm,粗粒径段峰值出现在3.3~5.8μm.PM1.1和PM2.1中OC以一次排放为主,二次有机碳(SOC)在春季最高[(3.0±1.4)μg·m^-3],冬季最低[(1.3±1.4)μg·m^-3],春季二次转化更强.鼎湖山大气细粒径段OC主要来自燃煤和机动车排放,粗粒径段主要来自生物源排放,EC主要受到燃煤、机动车排放和扬尘的影响.

To understand the characterization and sources of carbonaceous aerosols at Mountain Dinghu,organic carbon(OC)and elemental carbon(EC)in size-resolved aerosol samples were measured at a regional background site in South China using a DRI Model 2001 A analyzer.The average mass concentrations of organic carbon(OC)are(5.6±2.0)μg·m^-3 in PM1.1,(7.3±2.4)μg·m^-3 in PM2.1,and(12.8±4.0)μg·m^-3 in PM9.0;the average mass concentrations of elemental carbon(EC)are(2.3±1.4)μg·m^-3in PM1.1,(2.7±1.6)μg·m^-3 in PM2.1,and(3.4±1.7)μg·m^-3 in PM9.0.OC concentrations in PM1.1 and PM2.1 account for 43.8%and 57.0%of OC in PM9.0,and EC concentrations in PM1.1 and PM2.1 account for 67.6%and 79.4%,respectively.OC and EC are enriched with fine particles.In PM1.1 and PM2.1,the highest concentrations of OC and EC are measured in autumn,and the lowest concentration of OC is measured in winter and EC in summer.In PM9.0,the highest OC concentration is measured in summer.Carbonaceous aerosols are mainly composed of OC2,EC1,OC3,and OC4.In summer,the concentration of OC3 is higher than that of EC1,suggesting that biogenic sources are dominant during summer.The concentration of EC1 in winter is the highest,indicating that the impacts of motor vehicle emissions are prominent in the local area during winter.OC and EC both show bimodal distributions in four seasons,with peaks in the size ranges of 0.43-0.65μm for fine particles and 3.3-5.8μm for coarse particles.In PM1.1 and PM2.1,the sources of OC are mainly primary emissions.In PM2.1,the highest concentration of SOC is measured in spring at(3.0±1.4)μg·m^-3 and the lowest in winter at(1.3±1.4)μg·m^-3,indicating that the secondary aerosol formation is significant in spring.At the Mountain Dinghu background site,OC is mainly from coal combustion and motor vehicle emissions for fine particles and from biogenic sources for coarse particles.EC is mainly from coal combustion,motor vehicle emissions,and dust.