化学学报 ›› 2014, Vol. 72 ›› Issue (6): 658-666.DOI: 10.6023/A14040254 上一篇    下一篇

研究论文

二次有机气溶胶估算方法比较研究

郭松, 胡敏, 郭庆丰, 尚冬杰   

  1. 北京大学环境模拟与污染控制国家重点实验室 北京大学环境科学与工程学院 北京 100871
  • 收稿日期:2014-04-14 出版日期:2014-06-14 发布日期:2014-05-11
  • 通讯作者: 胡敏 E-mail:minhu@pku.edu.cn
  • 基金资助:

    项目受国家重点基础研究发展计划(No.2013CB228503)和国家自然科学基金(Nos.21025728,21190052,GZ663,41121004)资助.

Comparison of Secondary Organic Aerosol Estimation Methods

Guo Song, Hu Min, Guo Qingfeng, Shang Dongjie   

  1. State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871
  • Received:2014-04-14 Online:2014-06-14 Published:2014-05-11
  • Supported by:

    Project supported by the National Basic Research Program of China (No.2013CB228503) and the National Natural Science Foundation of China (Nos.21025728, 21190052, GZ663, 41121004).

为研究北京夏季二次有机气溶胶(SOA)浓度,比较多种SOA估算方法的不确定性和在我国的适用性,在CAREBEIJING 2008大型观测期间在城市点北大点和郊区点榆垡点采集大气颗粒物PM2.5样品,利用多种方法对二次有机碳(SOC)的浓度进行了估算,估算方法包括二次有机示踪物产率法、非一次源OC法、非生物质燃烧水溶性有机碳法(WSOC)和元素碳示踪有机碳/元素碳比值法.估算结果表明,二次有机气溶胶已经成为北京颗粒有机物的重要组成部分,夏季SOC可以占总有机碳(OC)的50%甚至更高。通过模拟我国典型的生物质燃烧,实测建立适合我国的获得了非生物质燃烧WSOC方法中的重要参数,即获得方法中重要参数生物质燃烧排放颗粒物中WSOC/OC的比值,我国生物质燃烧颗粒物中该比值平均为0.48±0.04.多种方法结果均表明,SOA已经成为北京颗粒有机物的重要组成部分,所占比例可以达到50%甚至更高.利用化学质量守恒模型(CMB)和示踪物产率法对颗粒有机物来源进行闭合发现,依靠目前的示踪物技术北京大气颗粒有机物中仍然有20%~27%的来源不清楚.通过综合比较了多种SOC估算方法,确定了各方法在我国的适用性: 示踪物产率法、非一次源OC法和EC示踪OC/EC比值法可适用于我国大气中SOC的估算,但是非生物质燃烧WSOC方法仅适用于我国大气中水溶性SOC的估算,但是不同方法之间存在的系统误差.本研究还对这几种方法的不确定性做了初步的分析,为其他研究者选择估算方法提供参考和依据.示踪物产率法仅估算了几种特定VOCs前体物对SOC贡献,因此低估了总的SOC,但是这种方法是目前唯一一种可以估算特定VOCs前体物对SOC贡献的方法;同样地,非生物质燃烧WSOC法仅估算了水溶性的SOC,因此也低估了总的SOC;非一次源OC法高估了SOC,这主要是由于未能解析出的一次源OC造成的.而且这种高估在城市地区更为显著,主要是因为城市地区一次源相对比较复杂造成的;非生物质燃烧WSOC法低估了总的SOC,而且这种方法仅适用于我国水溶性SOC的估算;EC示踪OC/EC比值法的主要不确定性来自于一次源OC/EC比值的确定,由于这个比值造成的单点误差最高可高估54%或低估64%.

关键词: 二次有机气溶胶, 二次有机碳, 估算方法, 方法适用性, 方法比较研究

To investigate the secondary organic aerosol (SOA) formation in Beijing, fine particle (PM2.5) samples were collected at an urban site (Peking University, PKU) and a rural site (Yufa) during CAREBEIJING 2008 summer intensive field campaign.Several approaches were used to estimate ambient secondary organic aerosolsSOA concentrations, including tracer-yield method, non-primary organic carbon method (receptor model, Chemical Mass Balance model), non-biomass burning water soluble organic carbon (WSOC) method and EC tracer OC/EC ratio method.The results indicated secondary formation has become major contributor to organic aerosols in Beijing, accounting for 50% or more of the total OC during the campaign.To develop non-biomass burning WSOC method, simulation of typical Chinese biomass burning was conducted to obtain the important parameters.The average WSOC/OC ratio in Chinese biomass burning is 0.48±0.04.This ratio can be used in non-biomass burning WSOC method to estimate SOC of China.The results from different methods all indicated secondary formation has become major contributor to organic aerosols in Beijing, accounting for 50% or more of the total OC.A closure study was made by combination of CMB model and tracer-yield method.Five primary sources, including vegetative detritus, biomass burning, coal burning, gasoline engines and diesel engines, and four secondary organic aerosols derived from isoprene, α-pinene, β-caryophyllene and toluene were apportioned.To the current knowledge, about 20%~27% of the OC sources still remain unknown.Applicability of these SOC methods in China was tested by comparing the different methods.Tracer-yield method, CMB model and EC tracer OC/EC ratio method can be used to estimate SOC in China.However, non-biomass burning WSOC method can only be used to estimate water-soluble SOC.Uncertainty analysis was conducted to help researchers to choose determine the proper method to estimate SOC in China.Tracer-yield method underestimates total SOC, but it is the only approach thatbecause it can only estimate SOCs from several specific precursors.Similarly, non-biomass burning WSOC method also underestimate SOC.Non-primary OC method overestimates SOC due to unapportioned primary OC, especially in urban area where the particle sources are complicated.Non-biomass burning WSOC method underestimate SOC, and can only be used to estimate water soluble SOC in China.The uncertainty of EC-tracer OC/EC ratio method is mainly from the primary OC/EC ratio.The largest overestimation and underestimation of single point value can be 54% and 64%.

Key words: secondary organic aerosol, secondary organic carbon, estimation method, method applicability, comparison study