北京大气细颗粒物中硝基多环芳烃类污染物的来源研究

Nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) belong to a group of important airborne toxic pollutants that threaten public health. This pollution arises from both the primary emission of combustion sources and the secondary formation through nitration reactions in the atmosphere, while the later source provides an important evidence on the adverse health effects of atmospheric transformations. Therefore, to reveal the sources in particular the secondary one is the key issue in the research filed of nitro-PAHs. Focusing on this scientific issue, we propose to carry out a long-term observation, covering at least 8 years, to investigate the temporal variation of particle-bound nitro-PAHs. Based on a systemic measurement of nitro-PAHs and related species, contributions from different sources could be apportioned. Meanwhile monitoring with ultra-fast online mass spectrometers will be taken during representative polluted days to track the formation process of nitro-PAHs and related species. Through the proposed on-line monitoring and long-term observation, we could get further knowledge on the formation mechanism of nitro-PAHs in the atmosphere. In conclusion, this proposed study will take the advantage of the rapidly changed pollution condition in Beijing nowadays and explore the influence of atmospheric reaction processes on the toxicity of airborne pollutants, therefore it could help in devising mitigation strategies and regulations on this pollution.

硝基多环芳烃是大气中重要的健康危害物种，它来源于一次排放，亦可通过大气硝基化反应二次生成，后者是大气化学反应影响污染物健康效应的重要证据；识别其来源尤其是二次源是系统认识大气中硝基多环芳烃类污染物的关键。针对这一科学问题，拟在北京开展八年以上大气采样观测，通过以硝基多环芳烃为核心的系统分析，揭示目标污染物的长期变化规律，识别各来源贡献及影响因素；在典型污染时段开展高时间分辨率的在线监测，追踪污染物的二次形成过程，与长期监测结合以完善对于污染物生成和来源的认识。项目利用中国当前大气污染快速变化的契机，以硝基多环芳烃类污染物为切入点揭示大气化学过程对于污染物健康危害的影响，从而一方面从这一类污染物角度评价当前污染物控制政策的有效性，同时为进一步的针对性控制措施提供理论依据。

硝基芳香组分（NACs，包括NPAHs）是重要的健康危害物种，二次生成是重要的来源，对其进行研究能提供大气化学反应影响污染组分健康危害的关键证据。项目利用2012至2021在北京地区采集的时长104个月的细颗粒物样品开展研究；同时开展时间分辨率2小时的加强观测。针对细颗粒物基质极其复杂、NACs浓度极低但组成复杂（尤其是未知组分）的难题，由硝基的亲电特性切入，开发基于电子捕获负电离的高分辨和串联质谱技术，识别出超过5000种NACs：①基于全组分表征，发现昼夜变化趋势差异的典型物质，分别代表白昼OH·反应生成和夜间N2O5相关非均相生成机制；发现硝基水杨酸的NO2·非均相生成机制，这一过程可显著增强颗粒物的吸光性；②发现新污染物有机硝酸酯主要来自于白昼OH·与人为源烯烃发生的自由基加成反应，贡献占70%；碘代间苯二酚则主要由颗粒相亲电取代反应生成；③发现随着大气污染控制的深入，夜间NO3·反应的重要性逐年上升，对2-硝基荧蒽的贡献上升了80%，已取代9-硝基蒽成为丰度最高的NPAHs，是影响有效控制NPAHs的关键因素；④开发NACs的人体暴露标志物，发现其与人体硝化应激的显著关联，这将有助于揭示大气硝基转化过程的人体健康效应。发表标注资助的SCI论文21篇，其中第一标注10篇（包括5篇ES&T）/第二标注9篇；另有数篇论文已投稿或在准备中。