Abstract. In this study, we present real-time measurements of organic aerosol (OA) and biogenic volatile organic compounds (BVOCs) at a pine forest stressed by bark beetles and previous droughts close to a biogas power plant (BPP) in western Germany during June 2020. A proton-transfer-reaction time-of-flight mass spectrometer coupled with a particle inlet (CHARON-PTR-ToF-MS) and a Vocus-PTR-ToF-MS were deployed to measure OA and BVOCs. During the entire measurement period, the average concentration of monoterpenes (2.5 ± 5.3 ppb) was higher than isoprene (0.58 ± 0.54 ppb) and sesquiterpenes (0.01 ± 0.01 ppb). The OA composition mainly consisted of semi-volatile organic compounds formed from monoterpene oxidation. Based on a wind direction analysis, BVOC data were categorized into two groups with main influence from the BPP (WD-BPP) and the forest (WD-forest), respectively. In the WD-BPP group, high concentrations of monoterpenes and sesquiterpenes were attributed to BPP emissions. In the WD-forest group, higher temperatures enhanced the biogenic emissions of isoprene, monoterpenes, and sesquiterpenes especially during daytime, exceeding their photochemical consumption. Positive matrix factorization analysis of VOCs revealed substantial contributions of gaseous organic acids from BVOC oxidation during daytime, while weakly oxidized monoterpene products dominated during nighttime. Moreover, increasing relative humidity promoted the gas-to-particle partitioning of gaseous weakly oxidized monoterpene products, leading to an increase of nighttime OA mass. This study highlights that the variations of BVOCs and their oxidation products are influenced by meteorology, local BPP emissions, and chemical transformation processes at this stressed forest.

中文翻译：

---

沼气发电厂附近松林中生物挥发性有机化合物及其氧化产物的表征


摘要。在这项研究中，我们实时测量了 2020 年 6 月德国西部沼气发电厂 (BPP) 附近一片受到树皮甲虫胁迫和之前干旱的松林中有机气溶胶 (OA) 和生物挥发性有机化合物 (BVOC) 的情况质子转移反应飞行时间质谱仪与粒子入口 (CHARON-PTR-ToF-MS) 和 Vocus-PTR-ToF-MS 相结合来测量 OA 和 BVOC。在整个测量期间，单萜的平均浓度（2.5±5.3ppb）高于异戊二烯（0.58±0.54ppb）和倍半萜（0.01±0.01ppb）。 OA组合物主要由单萜氧化形成的半挥发性有机化合物组成。根据风向分析，BVOC数据分为两组，分别主要受BPP（WD-BPP）和森林（WD-forest）的影响。在 WD-BPP 组中，高浓度的单萜和倍半萜归因于 BPP 排放。在WD森林组中，较高的温度增加了异戊二烯、单萜和倍半萜的生物排放，尤其是在白天，超过了它们的光化学消耗。 VOC 的正矩阵分解分析揭示了白天 BVOC 氧化产生的气态有机酸的大量贡献，而弱氧化的单萜产物在夜间占主导地位。此外，相对湿度的增加促进了气态弱氧化单萜产物的气体到颗粒的分配，导致夜间 OA 质量的增加。这项研究强调，BVOC 及其氧化产物的变化受到气象、当地 BPP 排放和这片压力森​​林的化学转化过程的影响。