Investigating the large source of particulate mass from nitrophenols observed in Beijing during winter haze events

暴露于恶劣空气质量是全球过早死亡的首要环境风险因素，2015年估计有400万人因长期暴露于当前水平而过早死亡。迄今为止，对健康危害最大的空气污染物是颗粒物（PM）。国际癌症研究机构（International Agency for Cancer Research）最近将空气污染列为一种已知致癌物，其中颗粒污染与癌症发病率上升的关系最为密切。中国大城市，如北京和广州，经常超过直径小于2.5微米（PM2.5）的建议暴露标准。官方数据显示，2016年北京和广州的PM2.5年平均浓度分别比世界卫生组织（who）标准高出近7倍和4倍。一项针对中国272个城市的研究发现，PM2.5的增加可能与死亡率、慢性阻塞性肺病、呼吸系统疾病、中风、冠心病、高血压和心血管疾病的增加有关。因此，中国大城市的人口长期受到有害颗粒物的影响。最近，NERC/MRC资助的中国大城市空气污染与人体健康项目的目标之一是调查PM的来源，并制定策略以减少暴露于有害水平的空气污染。对北京两次野外部署期间收集的气溶胶样本进行了分析，观察到异常高水平的硝基酚类化合物。硝基酚可以对大气产生一系列重要影响。硝基芳香族化合物及其大气和生物反应产物对人类和植物健康具有有害影响。例如，人体在皮肤、口腔或呼吸接触后的毒性作用包括胃肠道、神经系统和生殖障碍、肝硬化、肝炎、白内障、呼吸和皮肤刺激、肾毒性和血液系统缺陷。一些硝基酚具有植物毒性，可能对植物和水生生物有害。在北京观测到的硝基酚含量远高于以往在城市地区的研究，这些化合物的来源尚不清楚。这个雄心勃勃的项目将汇集化学机制开发（Rickard）、模拟室实验（Wang）和详细的气溶胶成分测量（Hamilton）方面的专业知识，以了解在北京城市大气中观测到的条件下，大气中芳烃和酚类物质氧化产生的硝基酚和二次有机气溶胶的来源和形成过程。该项目将解决北京雾霾事件期间颗粒组成测量产生的关键不确定性，并通过将方法应用于中国另一个特大城市广州来扩大结果。我们将改进目前在主化学机制（MCM）中的酚化学表征，该机制广泛用于各种空气质量科学和政策应用。这将用于在广州地球化学研究所设计模拟实验，以研究受控条件下硝基酚的形成。我们将在夏季和冬季测量广州大气中硝基酚的水平，并将其与北京的额外数据相结合，确定控制硝基酚浓度的来源和因素。我们还将启动中国伙伴研究所与EUROCHAMP-2020网络之间的合作，该网络旨在将欧洲最先进的大气模拟室整合到世界一流的研究和创新基础设施中。通过知识交流安置将实现持久的影响，GIG的一名工作人员将在约克度过12周，接受有关MCM和欧洲开发的协议的培训，以便在模拟室中模拟背景化学。

Exposure to poor air quality is the top environmental risk factor of premature mortality globally with an estimated 4 million premature deaths in 2015 from long-term exposure to current levels. By far the most damaging air pollutant to health is particulate matter (PM). The International Agency for Cancer Research has recently classified air pollution as a known carcinogen, with particle pollution being most closely associated with increased cancer rates. Chinese megacities, such as Beijing and Guangzhou, frequently exceed recommended exposure guidelines for particles less than 2.5 microns in diameter (PM2.5). According to official data, the annual mean concentrations of PM2.5 in 2016 in Beijing and Guangzhou were nearly 7 and 4 times higher than World Health Organisation guidelines. A study of 272 Chinese cities found that increases in PM2.5 could be linked to increases in mortality, chronic obstructive pulmonary disease, respiratory diseases, stroke, coronary heart diseases, hypertension and from cardiovascular disease. Therefore the population in Chinese megacities is subjected to damaging levels of particles over extended periods. One of the aims of the recent NERC/MRC funded Air Pollution and Human Health in a Chinese Megacity program was to investigate the sources of PM and develop strategies to reduce exposure to harmful levels of air pollution. Aerosol samples collected during two field deployments in Beijing were analyzed and unusually high levels of nitrophenolic compounds were observed. Nitrophenols can have a range of important atmospheric impacts. Nitro-aromatic compounds, and their atmospheric and biological reaction products, have detrimental effects on human and plant health. For instance, toxic effects in humans after dermal, oral, or respiratory exposure include gastrointestinal, neurological and reproductive disorders, cirrhosis of the liver, hepatitis, cataracts, respiratory and skin irritation, nephrotoxicity, and haematological defects. Some nitrophenols are phytotoxic and may be harmful to plants and aquatic life. The amounts of nitrophenols observed in Beijing were much higher than in previous studies in urban areas and the source of these compounds is unclear. This ambitious project will bring together expertise in chemical mechanism development (Rickard), simulation chamber experiments (Wang) and detailed aerosol composition measurements (Hamilton) to understand the sources and formation processes of nitrophenols and secondary organic aerosol from the atmospheric oxidation of aromatics and phenolic species, under conditions observed in the Beijing urban atmosphere. This project will address key uncertainties arising from the measurements of particle composition during haze events in Beijing and widen the results by applying the methodologies to a different Chinese megacity, Guangzhou. We will improve current representations of phenolic chemistry in the Master Chemical Mechanism (MCM), which is extensively used in a wide variety of air quality science and policy applications. This will be used to design simulation experiments at the Guangzhou Institute of Geochemistry to study the formation of nitrophenols under controlled conditions. We will measure the atmospheric levels of nitrophenols in Guangzhou in summer and winter and combine this with additional data from Beijing to determine the sources and factors that control nitrophenol concentrations.We will also initiate collaboration between the Chinese partner institute and the EUROCHAMP-2020 network, which aims to integrate the most advanced European atmospheric simulation chambers into a world-class infrastructure for research and innovation. Long lasting impact will be achieved through a knowledge exchange placement, where a member of staff from GIG will spend 12 weeks in York to receive training on the MCM and the protocols developed in Europe to model the background chemistry within simulation chambers.