基于气溶胶质谱的二次有机气溶胶识别

二次有机气溶胶(SOA)是大气气溶胶十分重要的组成部分,也是目前人们认识最为薄弱的气溶胶组分.由于有机气溶胶化学组成的复杂性,对SOA进行有效的识别和估算一直是国际气溶胶研究领域的热点和难点问题.本研究尝试使用一种新方法来定量识别深圳冬季大气中的SOA:利用气溶胶质谱仪在线观测的高时间分辨率优势和质谱中的特征碎片离子,应用正定矩阵因子解析(PMF)模型对细粒子组分的主要来源进行解析,识别出其中的二次有机物.结果表明:深圳冬季大气细粒子中SOA浓度平均为9.41±6.33μg/m3,占总有机物质量的39.9±21.8%;相比于一次有机气溶胶(POA),SOA浓度水平变化较为平缓,体现了区域性二次污染物的特征.SOA/BC比值具有鲜明的日变化规律,且与Ox(O3+NO2)的日变化规律相似,说明SOA的生成过程显著地受控于大气光化学活性.深圳冬季大气SOA生成最活跃的时段约为9～15时,期间SOA/BC比值增长了122%.本文为研究我国大气二次有机气溶胶提供了一种新的技术方法和思路.

Identification of secondary organic aerosol based on aerosol mass spectrometry

Secondary organic aerosol （SOA） is one of the major components of aerosols in the atmosphere and has not been well understood so far. Due to the complex chemical composition of organic aerosols,the identification of SOA has been a hotspot and difficult issue in the field of aerosol study. This study attempts to quantitatively identify SOA in winter,Shenzhen based on positive matrix factorization （PMF） analysis. Major sources were resolved and SOA were identified subsequently according to the characteristic ion fragments measured by highly time-resolved Aerosol Mass Spectrometer measurement. It showed that in the winter of Shenzhen the average SOA concentration was 9.41±6.33 μg/m3,accounting for 39.9±21.8% of the total organic mass. Compared with primary organic aerosol （POA）,the SOA concentrations had no large variation,suggestive of characteristics of regional secondary pollutants. The ratio of SOA/BC had pronounced diurnal variation,similar to that of Ox （O3 ＋ NO2）,indicating SOA formation was significantly controlled by activity of photochemistry in the atmosphere. The most effective period for SOA formation was from 9 am–3 pm since the SOA/BC ratio increased by 122% during this period. This study provides a new technical method and a new idea for SOA investigation.