• 关键词：硝酸气体  亚硝酸气体  氨气  denuder  PM_2.5  气-粒平衡

• 基金项目：国家自然科学基金(No.41176097);国家重点基础研究发展计划(973)项目(No.2011CB409802)

• 李丽平
• 中国海洋大学环境科学与工程学院, 青岛 266100

• 石金辉
• 1. 中国海洋大学海洋环境与生态教育部重点实验室, 青岛 266100;2. 中国海洋大学环境科学与工程学院, 青岛 266100

• 李非非
• 中国海洋大学环境科学与工程学院, 青岛 266100

• 姚小红
• 1. 中国海洋大学海洋环境与生态教育部重点实验室, 青岛 266100;2. 中国海洋大学环境科学与工程学院, 青岛 266100

• 高会旺
• 1. 中国海洋大学海洋环境与生态教育部重点实验室, 青岛 266100;2. 中国海洋大学环境科学与工程学院, 青岛 266100

• 摘要：研究PM_2.5中NO₃^-、NO₂^-、NH₄⁺及其气态前体物HNO₃、HNO₂、NH₃的浓度特征和气-粒平衡关系,对深入认识PM_2.5的来源及控制因素具有重要意义.因此,本文利用2012年6—7月在青岛采集的denuder和PM_2.5大气样品,分析了其中气态和颗粒态氮组分的浓度.结果发现,青岛大气中HNO₃、HNO₂和NH₃浓度分别为(0.80±0.79) μg·m^-3、(0.49±0.59) μg·m^-3和(4.71±4.03) μg·m^-3,PM_2.5中NO₃^-、NO₂^-和NH₄⁺的浓度分别为(7.50±9.00) μg·m^-3、(0.07± 0.02) μg·m^-3和(8.23±5.57) μg·m^-3.HNO₃气体浓度的昼夜变化具有统计意义上的显著差异,白天平均为1.16 μg·m^-3,高于夜晚的0.44 μg·m^-3,但其他氮组分无显著昼夜差异.观测期间,青岛大气为富氨环境,PM_2.5中NH₄⁺主要以(NH₄)₂SO₄的形式存在,NO₃^-生成主要受HNO₃的限制.利用ISORROPIA II热力学平衡模型探讨了青岛PM_2.5中氮组分的控制因子,通过敏感性实验发现,颗粒态NO₃^-和NH₄⁺分别对总HNO₃(TN)和总H₂SO₄(TS)的变化响应敏感,而对总NH₃(TA)的变化响应不敏感,这暗示了减少大气中TN和TS而不是TA对降低青岛PM_2.5浓度更有效.

• Abstract：Reactive nitrogen compounds consist of an important part of PM_2.5 and their gas-particle partitioning are usually associated with thermodynamic equilibrium. Characterization of NO₃^-, NO₂^- and NH₄⁺ concentrations in PM_2.5 and their partners (HNO₃, HNO₂ and NH₃) in gas phase are important in improving understanding of source apportionment of PM_2.5 and determining factors controlling their partitioning in PM_2.5. In this study, these gas and particulate species were collected in Qingdao from June to July 2012 using a PM_2.5 sampler equipped with two denuders. The averaged concentrations of HNO₃, HNO₂ and NH₃ were (0.80±0.79) μg·m^-3, (0.49±0.59) μg·m^-3 and (4.71±4.03) μg·m^-3, respectively while they were (7.50±9.00) μg·m^-3, (0.07±0.02) μg·m^-3 and (8.23±5.57) μg·m^-3 for NO₃^-, NO₂^- and NH₄⁺ in PM_2.5. We also found that HNO₃ showed statistically significant diurnal variation with higher concentration (1.16 μg·m^-3) during daytime and low concentration (0.44 μg·m^-3) at night, but there were no significant difference for other species between daytime and nighttime samples. During the study period, NH₃ was rich and NH₄⁺ in PM_2.5 was mainly present in the form of (NH₄)₂SO₄. The analysis results suggested that formation of NO₃^- were likely determined by availability of HNO₃. To further explore the control factors of these species in PM_2.5, the thermodynamic equilibrium model of ISORROPIA II was used. Through sensitivity analysis of single component, we found that formation of NO₃^- and NH₄⁺ was sensitive to the changes in total HNO₃ (TN) and total H₂SO₄ (TS) respectively, and less sensitive to the change in total NH₃ (TA). This implies that reducing TN and TS rather than TA appears to be more effective in lowering mass concentrations of PM_2.5 in Qingdao.

• Key words：nitric acid gas  nitrous acid gas  ammonia  denuder  PM_2.5  gas-particle partitioning

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