左旋葡聚糖大气传输损失量的校正及其对生物质燃烧源排放定量的改进

生物质燃烧是大气颗粒物和气体的重要来源。为了研究生物质燃烧对气候、空气质量及人体健康的影响，需对生物质燃烧排放的颗粒物进行准确定量。以左旋葡聚糖为示踪物定量生物质燃烧排放是目前最可靠的方法。该方法的一个基本假设是左旋葡聚糖在大气中可稳定存在，然而近年来研究发现左旋葡聚糖在大气中可降解，以至该方法会低估生物质燃烧排放量，目前此问题尚未得到解决；针对此问题，本研究提出以左旋葡聚糖降解产物为依据计算左旋葡聚糖的降解量，从而校正生物质燃烧源排放量。本研究拟通过实验室烟雾箱模拟左旋葡聚糖降解过程建立左旋葡聚糖降解量和特定降解产物之间的数学方程，然后通过外场观测验证该数学方程，最后将该方程用于珠三角地区定量生物质燃烧源排放，并初步表征珠三角地区左旋葡聚糖的降解特征。该方法的建立预计可提高大气颗粒物源解析中生物质燃烧源贡献量的准确性，为政府决策提供更加准确的基础数据，有重要的科学意义和应用价值。

Emissions of particulate matters (PM) and gases from biomass burning (BMB) impose significant impacts on climate, air quality and human health. To understand the local, regional and global impacts of BMB, it will be necessary to quantify the contribution of BMB emission to PM and gases. Levoglucosan is considered as the most reliable tracer to quantify the contribution of BMB emission to PM and gases in source apportionment since (1) the concentration of levoglucosan from BMB is high and (2) the source of levoglucosan is unique (only from BMB emission). Levoglucosan is also considered to be stable in the atmosphere in recent years, which is an important assumption of the chemical tracer method for source quantification. However, levoglucosan has been found degradable in the atmosphere resulting in the underestimation of the contribution of BMB when levoglucosan is employed as the tracer. Currently there is no alternative tracer better than levoglucosan. To correct the underestimation of BMB emission in source apportionment, this study proposes a degradation-product-based method to estimate the amount of degraded levoglucosan in the atmosphere. A correlation equation of degraded levoglucosan and the selected degradation products will be established based on a smog chamber study of degradation of levoglucosan. The established equation will be then verified with filed PM2.5 samples. The method will be applied to correct the quantification of BMB emission in the field PM2.5 samples in Pearl River Delta (PRD) region. It is expected that the accuracy of quantification of BMB emission in source apportionment can be improved and more reliable data can be provided to the policy makers.