许昌市典型污染过程VOCs污染特征与臭氧生成敏感性研究

Characteristics of VOCs and Ozone Formation Sensitivity during Typical Pollution Days in Xuchang

关键词:  臭氧污染  挥发性有机物(VOCs)  臭氧生成潜势(OFP)  相对增量反应活性(RIR)  源解析

Key words:  ozone pollution  Volatile Organic Compounds (VOCs)  Ozone Formation Potential (OFP)  Relative Incremental Reactivity (RIR)  source apportionment

摘要:

为有效遏制大气污染，不断提升大气污染防控的科学性与系统性，推动区域环境空气质量持续改善，本研究以污染前、污染中和污染后3个阶段为研究时段，对许昌市大气中的挥发性有机物(Volatile Organic Compounds,VOCs)进行实时监测，以期揭示VOCs污染特征与臭氧生成规律。结果显示，污染前、中、后阶段的VOCs浓度均值分别为33.5×10^-9、39.9×10^-9和28.7×10^-9,占比最大的组分均为含氧挥发性有机物(Oxygenated Volatile Organic Compounds,OVOCs)，其次为烷烃，且污染阶段的乙醛、丙醛与丙酮浓度显著高于非污染阶段。对比3个阶段的VOCs臭氧生成潜势(Ozone Formation Potential,OFP)，污染中阶段的OFP为313.72 μg/m³，分别是污染前、后阶段的1.4倍和1.6倍，表明许昌市在污染中阶段VOCs光化学反应生成臭氧的潜力显著增大。相对增量反应活性(RIR)结果表明，许昌市在污染后阶段处于VOCs控制区，在污染前、中阶段则处于过渡区。采用正交矩阵因子分解法(PMF)进行人为源VOCs解析，研究时段工业源与燃烧源合计贡献54.4%，污染中阶段相较于污染前、后阶段，工业源占比分别增加5.1%和5.5%，燃烧源占比分别增加8.8%和8.7%，说明污染中阶段工业源与燃烧源对许昌市VOCs影响较大。潜在源贡献因子分析法(PSCF)与浓度轨迹权重法(CWT)解析结果表明污染中阶段河南省东部与西北部城市对许昌市VOCs的影响正逐步加剧。

Abstract:

To mitigate air pollution,prevent and control air pollution in a scientific and systematic manner,and promote the continuous improvement of regional ambient air quality,real time monitoring of Volatile Organic Compounds (VOCs) in Xuchang was conducted during three defined periods:pre-pollution,during-pollution,and post-pollution.The pollution characteristics of VOCs and the ozone formation patterns were studied based on the obtained data.The results showed that the average concentrations of VOCs in the pre-pollution,during-pollution and post-pollution periods were 33.5×10^-9,39.9×10^-9 and 28.7×10^-9,respectively.The dominant component was Oxygenated Volatile Organic Compounds (OVOCs),followed by alkanes.The concentrations of acetaldehyde,propionaldehyde,and acetone during the pollution period were significantly higher than those during the non-pollution periods.During the pollution period,the Ozone Formation Potential (OFP) was 313.72 μg/m³,which was 1.4 and 1.6 times of that in the pre-pollution and post-pollution periods,respectively.This indicated that the potential for ozone formation through photochemical reactions of VOCs increased significantly during the ozone pollution period in Xuchang.The Relative Incremental Reactivity (RIR) indicated that Xuchang was in the limited regime of VOCs during the post-pollution period,while it was in the transition regime in the pre-pollution and during-pollution periods.The source apportionment of anthropogenic VOCs by the Positive Matrix Factorization (PMF) model showed that industrial and combustion sources contributed 54.4% to VOCs during the study period.The contributions of industrial sources during the pollution period increased by 5.1% and 5.5% compared with those in the pre-and post-pollution periods,respectively,while the contributions of combustion sources increased by 8.8% and 8.7%,respectively.These findings indicated that industrial and combustion sources were key contributors to elevated concentrations of VOCs during the pollution period.The Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) revealed that cities in eastern and northwestern Henan Province exerted an intensified impact on the concentration of VOCs in Xuchang during the pollution period.