Abstract. Climate extremes are projected to cause unprecedented deviations in the emission and transformation of volatile organic compounds (VOCs), which trigger feedback mechanisms that will impact the atmospheric oxidation and formation of aerosols and clouds. However, the response of VOCs to future conditions such as extreme heat and wildfire events is still uncertain. This study explored the modification of the mixing ratio and distribution of several anthropogenic and biogenic VOCs in a temperate oak–hickory–juniper forest as a response to increased temperature and transported biomass burning plumes. A chemical ionization mass spectrometer was deployed on a tower at a height of 32 m in rural central Missouri, United States, for the continuous and in situ measurement of VOCs from June to August of 2023. The maximum observed temperature in the region was 38 °C, and during multiple episodes the temperature remained above 32 °C for several hours. Biogenic VOCs such as isoprene and monoterpene followed closely the temperature daily profile but at varying rates, whereas anthropogenic VOCs were insensitive to elevated temperature. During the measurement period, wildfire emissions were transported to the site and substantially increased the mixing ratios of acetonitrile and benzene, which are produced from burning of biomass. An in-depth analysis of the mass spectra revealed more than 250 minor compounds, such as formamide and methylglyoxal. The overall volatility, O:C, and H:C ratios of the extended list of VOCs responded to the changes in extreme heat and the presence of combustion plumes. Multivariate analysis also clustered the compounds into five factors, which highlighted the sources of the unaccounted-for VOCs. Overall, results here underscore the imminent effect of extreme heat and wildfire on VOC variability, which is important in understanding future interactions between climate and atmospheric chemistry.

中文翻译：

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极端高温和野火排放增加了挥发性有机化合物：对未来气候的见解


摘要。极端气候预计将导致挥发性有机化合物（VOC）的排放和转化发生前所未有的偏差，从而触发反馈机制，影响大气氧化以及气溶胶和云的形成。然而，挥发性有机化合物对未来极端高温和野火事件等条件的反应仍不确定。本研究探讨了温带橡树-山核桃-杜松林中几种人为和生物挥发性有机化合物的混合比例和分布的变化，以响应温度升高和运输的生物质燃烧羽流。美国密苏里州中部农村地区的一座32 m高的塔上部署了化学电离质谱仪，用于2023年6月至8月连续原位测量VOCs。该地区观测到的最高温度为38° C，并且在多次发作期间，体温在数小时内保持在 32°C 以上。异戊二烯和单萜等生物源挥发性有机化合物密切关注每日温度变化，但变化率不同，而人为挥发性有机化合物对温度升高不敏感。测量期间，野火排放物被输送到现场，大大增加了生物质燃烧产生的乙腈和苯的混合比例。对质谱的深入分析揭示了 250 多种微量化合物，例如甲酰胺和甲基乙二醛。扩展的 VOC 列表的总体挥发性、O:C 和 H:C 比率响应极热的变化和燃烧羽流的存在。多变量分析还将这些化合物分为五个因素，突出了未解释的挥发性有机化合物的来源。 总的来说，这里的结果强调了极端高温和野火对挥发性有机化合物变化的迫在眉睫的影响，这对于理解未来气候和大气化学之间的相互作用非常重要。