Airborne microplastics are a type of suspended particulate matter less than 100 µm in size. They have drawn attention recently due to their potential impact on human health and the environment. However, knowledge on airborne microplastics in forest and their interaction with plant leaves is limited. Here, we analyzed microplastics on konara oak leaves collected at a small forest in Tokyo. Leaves were water-washed to yield a first extract, sonicated in water to yield a second extract and then extracted with 10%w potassium hydroxide to yield a third extract. We employed micro-Fourier transform infrared spectroscopy with attenuated total reflection imaging to analyze microplastics, identifying polymer materials and quantifying their concentration. Results show that the average number of microplastics in leaf were 0.01 piece/cm² in the water extract (7.6%), 0.05 piece/cm² by sonication (38.4%), and 0.07 piece/cm² in the potassium hydroxide extract (53.8%). Microscopic data reveal that potassium hydroxide extraction allows to remove epicuticular waxes including adhering substances. These findings highlight the need to use a strong basic reagent, potassium hydroxide, to extract most airborne microplastics in leaf. The findings also suggest that canopy leaves could be a long-term sink for airborne microplastics, rather than merely temporary accumulators.

空气中的微塑料是一种尺寸小于 100 微米的悬浮颗粒物。由于它们对人类健康和环境的潜在影响，它们最近引起了人们的关注。然而，关于森林中空气中的微塑料及其与植物叶子的相互作用的知识有限。在这里，我们分析了在东京小森林收集的科纳拉橡树叶上的微塑料。水洗叶子以产生第一提取物，在水中超声处理以产生第二提取物，然后用10%w氢氧化钾提取以产生第三提取物。我们采用微傅里叶变换红外光谱和衰减全反射成像来分析微塑料、识别聚合物材料并量化其浓度。结果表明，叶片中微塑料的平均数量在水提取物中为0.01个/cm ^{2 (7.6%)，在超声处理中为0.05个/cm 2} (38.4%)，在氢氧化钾提取物中为0.07个/cm ² (53.8%)。 %）。显微数据表明，氢氧化钾提取可以去除表皮蜡质，包括粘附物质。这些发现强调需要使用强碱性试剂氢氧化钾来提取叶子中大多数空气中的微塑料。研究结果还表明，树冠叶子可能是空气中微塑料的长期储存库，而不仅仅是暂时的蓄积器。