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近年来,我国越来越重视臭氧(O3)污染,在多区域范围内O3已取代颗粒物成为首要污染物[1 − 3]. 苏皖鲁豫交界地区位于汾渭平原和长三角之间,已成为继京津冀等区域之后,新的联防联控重点控制区域[4 − 6]. 该地区位于共有22个城市,基础排放量大,空气质量改善进程总体相对滞后,臭氧浓度高且上升趋势明显,光化学污染过程呈现出与周边地区的同步性[7]. 目前针对该区域研究较少,相关监测持续时间较短,无法表征长时间的光化学污染特征变化. 亟需对苏皖鲁豫区域加以重点关注,补齐大气污染防治短板,对于该区域的O3污染治理能力提高和大气光化学污染防治策略制定具有重要的意义.
过氧乙酰硝酸酯(CH3C(O)OONO2,PAN)是光化学烟雾的关键产物[8 − 10]. PAN属于非自然过程排放的污染物,仅通过人类活动排放的前体污染物的光化学反应生成,是光化学污染的重要指示剂[11 − 12]. 大气中挥发性有机物(VOCs)在氧化过程中,可生成PA自由基(Peroxyacetyl Radical),而后PA可与NO2结合生成PAN[13 − 14]. PAN在对流层上部稳定,但在大气对流层下部具有明显的热不稳定性,与O3相比不易远距离输送,能更好地反映本地区域的光化学污染情况[15 − 17]. 在国内,包括城市、郊区、农村和偏远地区,都有PAN的时空变化及其形成机制的相关研究. Yuan等[18]研究表明,在珠三角农村地区,PAN的增加主要受气相化学控制,其次是垂直运输,而其损失主要受水平运输和干沉积的调节. Liu等[19]研究表明,高环境浓度的细颗粒物和气态亚硝酸可以显著促进PAN的形成. Xia等[20]基于稳态模型研究表明,在东南沿海地区生物质燃烧源是PA自由基的重要来源.
淮北市位于苏皖鲁豫交界地区中心位置,地处苏豫皖三省交界,经济发展迅速,近年来光化学污染频发. 本研究于2021年秋季(10月)和2022年夏季(6月)利用PAN在线监测,在淮北市开展PAN污染特征分析与来源研究,对于探究苏皖鲁豫交界地区大气光化学污染及变化规律,加强局地区域光化学污染的理解和防控,将具有积极意义.
苏皖鲁豫典型城市过氧乙酰硝酸酯(PAN)污染特征分析
Analysis of photochemical pollution potential characteristics based on PAN observation in the border area of Jiangsu, Anhui, Shandong and Henan
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摘要: 为探究苏皖鲁豫区域光化学污染特征,于2021年10月和2022年6月在淮北市开展光化学污染产物过氧乙酰硝酸酯(peroxyacetyl nitrate,PAN)的在线监测,分析了PAN浓度特征、空间来源、产生速率和变化趋势. 观测结果表明,观测处2021年10月PAN的浓度范围为(0.08—1.44)×10−9,2022年6月的浓度范围为(0.61—5.72)×10−9;PAN的峰值大部分出现在NO/NO2比值较低的时段. 结合气团后向轨迹,2021年10月观测处PAN的潜在源贡献函数(PSCF)高值区范围出现在南部方向,可能是因为西南方向相近城市较高的前体物排放;2022年6月高值区主要出现在北部和东南部,显示山东省西南部是潜在源贡献地区,东南方向的气团在工业化程度较高的城市群之间存在长距离运输.
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关键词:
- 过氧乙酰硝酸酯(PAN) /
- 光化学污染特征 /
- 苏皖鲁豫 /
- 在线监测.
Abstract: In order to explore the potential of photochemical pollution in the regions of Jiangsu, Anhui, Shandong and Henan, the online monitoring of peroxyacetyl nitrate (PAN), a product of photochemical pollution, was carried out in Huaibei City in October 2021 and June 2022, and the concentration characteristics, spatial sources, production rate and change trend of PAN were analyzed. The observation results show that the concentration range of PAN at the observation site is (0.08—1.44)×10−9 in October 2021 and (0.61—5.72)×10−9 in June 2022. Most of the peak of PAN appeared in the period of low NO/NO2 ratio. In combination with the backward trajectory of the air mass, the high value range of the potential source contribution function (PSCF) of PAN at the observation site in October 2021 appears in the south, which may be due to the higher precursor emissions in the cities near the southwest. In June 2022, the high value areas mainly appeared in the north and southeast, indicating that the southwest of Shandong Province is a potential source contribution area, and the air mass in the southeast has long distance transportation between the urban agglomerations with a high degree of industrialization. -
表 1 国内不同地区PAN浓度均值和最大值对比
Table 1. PAN concentrations in this study and comparison with the other sites in the urban regions
区域
Region城市
City观测时间
Observation time平均值/(×10−9)
Average最大值/(×10−9)
Maximum参考文献 京津冀 北京 2021年7月 0.89 — [23] 北京 2010年1—3月 0.70 3.51 [22] 京津冀 天津 2018年9月 0.93 — [8] 北京 2016年11月—2017年1月 1.1 7.1 [24] 苏皖鲁豫交界地区 淮北 2021年10月 0.42 1.44 本研究 淮北 2022年6月 1.87 5.72 本研究 青岛 2018年10—11月 0.75 5.83 [13] 2019年7—8月 0.81 7.82 [13] 长三角 上海 2017 0.7 7.0 [9] 合肥 2016年8月 1.10 4.65 [25] 浙江 2019年6—10月 0.66 4.35 [26] 珠三角 深圳 2018年9—10月 0.56 3.90 [20] 厦门 2020年3—11月 0.92 — [14] -
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