德州市秋冬季大气二次颗粒物污染变化特征

The Change Characterization of Atmospheric Secondary Particulate Matter Pollution during Autumn and Winter in Dezhou City

通过对德州市秋冬季大气二次颗粒物(SPM)污染变化特征进行分析,发现在PM2.5重污染发生时,硝酸盐在PM2.5中的占比显著升高,而有机碳(OC)占比降低,凸显了氮氧化物削减对PM2.5污染防控的重要性;此外,对二次有机碳(SOC)进行分析,发现SOC/OC值随K+/EC (元素碳)值的升高而增加,说明生物质燃烧对二次气溶胶(SOA)生成有一定的贡献;进一步特征分析,发现SOC/OC值随着风速的增加而增加;结合玫瑰图分析,发现区域传输对SOC有一定贡献,并且高大气光化学氧化剂(Ox)或高相对湿度(RH)条件不利于SOC生成,但是高温和高RH条件有利于二次无机盐(包括硫酸盐和硝酸盐)的生成。

In this study, the change characteristics of the atmospheric secondary particulate matter (SPM) pollution in Dezhou city during autumn and winter were analyzed. It is found that the proportion of nitrate in PM2.5 increased significantly when PM2.5 level was high, but the proportion of organic carbon (OC) decreased. The result highlights the importance of controlling nitrogen oxide emission to reduce high PM2.5 episodes. In addition, the analysis of the secondary organic carbon (SOC) showed that the SOC/OC ratio increased with the increase of K+/EC (elemental carbon), indicating that biomass burning has a certain contribution to the formation of secondary aerosols (SOA). It is also found that SOC/OC increased with the increase of wind speed. Combined with wind-rose dia-gram analysis, it implies that regional transport has a certain contribution to SOC. Further analysis showed that high Ox or high RH conditions were unfavorable for SOC formation. In contrast, high temperature and high RH conditions were favorable for the formation of secondary inorganic salts (including sulfate and nitrate).