大气颗粒物源解析中左旋葡聚糖标记生物质燃烧源分担率的缺陷与校正

Biomass burning source (BBS) is an important source of atmospheric particulate matter (PM) and levoglucosan is an ideal marker indicating BBS. Recent studies have found that levoglucosan can not only partition between gas and PM phases, but also suffer chemical degradation in the atmosphere. These will lead to serious underestimate of the contribution of BBS only using measured concentration of levoglucosan in PM (CPMM) for source apportionment. This project aims to emendate CPMM into its original value from emission sources (CATV, CATV=CPMM+CG+CD). Different scenarios will be considered by selecting typical cities and seasons with various meteorological conditions. On the one hand, the partitioning of levoglucosan will not only be measured with primary influencing factors confirmed, but also be simulated in different fashions, such as building multiple linear regression model, applying or revising existing models. The simulated and measured results will be compared and the optimal model will be selected to estimate the gaseous concentration of levoglucosan (CG). On the other hand, two methods will be applied to estimate the amount of levoglucosan due to atmospheric chemical degradation (CD). One method is applying the Spectral Aerosol Cloud Chemistry Interaction Model (SPACCIM) or a chemical kinetics model, and the other is establishing equation between elemental carbon (ECbb) and levoglucosan from biomass burning by 14C technology. At last, the research achievements will be applied to some projects from local governments for source apportionment. The results of source apportionment will be compared when levoglucosan values are corrected or uncorrected. These research achievements have important theoretical significance and practical application value.

生物质燃烧源（BBS）是大气颗粒物（PM）的重要源之一，左旋葡聚糖（Lev）是指示BBS的理想标志物。最新研究表明，Lev不仅能在气、颗粒两相间分配，还能发生大气降解反应，使用PM的Lev“观测值”进行源解析可能大大低估BBS的分担率。本项目旨在将Lev“观测值”校正为“实际源排放值”，拟在南北选取不同的典型城市和典型季节进行研究。一方面，实测Lev的气、颗粒两相分配并确定其主要影响因素；针对不同气象条件情景，通过构建多元线性回归模型、运用或修订现有不同气-颗粒两相分配模型进行多情景模拟，并与实测结果拟合，筛选模型用于估算气相中的Lev。另一方面，使用两种方法估算大气降解的Lev，其一是利用大气气溶胶云化学模型或化学动力学模型；其二是利用14C技术，建立源于BBS的元素碳与Lev间的关系方程。后将研究成果应用于地方源解析项目，对比是否校正Lev时对PM源解析结果的影响。

项目背景：生物质燃烧源（BBS）是大气颗粒物的重要源之一，左旋葡聚糖（Lev）是BBS的理想标志物。由于Lev能在气-颗粒两相间分配，导致只以颗粒相中Lev（CLev颗粒）进行颗粒物源解析时可能低估BBS的分担率。.主要研究内容与成果：（1）通过方法比选，建立了滤膜+PXP采样、超声提取、HPAEC-PAD分析的分析方法。测定了南方和北方典型代表城市广州和太原大气中糖类物质的含量水平和季节差异，并解释了原因。（2）利用PMF模型解析表明太原市糖类物质主要来源于生物质燃烧，植物花粉和碎屑、真菌释放、土壤颗粒的再悬浮也有一定贡献。识别出太原市生物质燃烧主要为硬木和作物残渣的混合贡献。（3）秋季Lev的两相分配系数（Kp）变化明显大于夏季，广州的Kp值明显大于太原。lgKp和1/T间呈良好的正相关；Kp与颗粒相含水率间在太原有良好正相关，而在广州正相关相对较弱。CLev颗粒与WSOC间呈现较强的正相关，与OC呈现一定的正相关，而与EC之间相关性在两个城市则明显不同，暗示存在明显不同的影响机制。气象条件、颗粒物组成是明显影响因素。建立了估算两个城市CLev气的多元线性回归方程，预测值接近实测值。（4）对比CLev颗粒、（CLev颗粒+CLev气）对颗粒物源解析结果的影响，在广州和太原校正前后BBS分担率变化均不显著，但其它源的贡献变化明显。.科学意义：项目建立了大气气、颗粒两相中糖类物质的分析方法，识别了糖类物质的来源，探讨了影响Lev气-颗粒分配的影响因素，评估了只考虑CLev颗粒对评估BBS分担率的影响。研究成果可进一步完善大气颗粒物来源解析方法。