Both chemical and isotopic compositions of volcanic plumes are highly useful in evaluating the present status of active volcanoes. Monitoring their temporal changes can facilitate the forecasts of volcanic activity as well. In the present study, we developed a drone-borne automatic sampler for volcanic plumes in which an output signal from a sulfur dioxide (SO₂) sensor triggered a pump to collect samples when its SO₂ concentration exceeded a predefined threshold. First, we tested the automatic sampler while holding the device by hand at Iwo-yama volcano, Kirishima volcanic complex, Japan, where the fumaroles were accessible. Second, we fitted the sampler on a drone at Nakadake central cone, Aso volcano, Japan, where only the crater rim was accessible. In both sampling campaigns, good consistency in isotope ratios (²H/¹H) of molecular hydrogen (H₂) between samples collected by the automatic sampler and those collected directly into pre-evacuated flasks was obtained. Furthermore, by using the drone-borne sampler at Aso volcano, we obtained plume samples with higher concentrations of H₂ and carbon dioxide than those taken directly into flasks at the crater rim. Our sampler can be utilized to collect volcanic plume samples for the determination of stable isotopic compositions in general by subsequent laboratory analysis and the remote establishment of fumarole outlet temperature based on the ²H/¹H ratios of hydrogen, including their temporal changes.

火山羽的化学和同位素组成在评估活火山的现状方面都非常有用。监测它们的时间变化也可以促进火山活动的预测。在本研究中，我们开发了一种用于火山羽的无人机自动采样器，其中二氧化硫（SO ₂）传感器的输出信号触发了泵，当其SO ₂收集样品时浓度超过预定阈值。首先，我们在日本雾岛火山群硫磺山火山易得的地方，用手拿着设备测试了自动采样器。其次，我们将采样器安装在日本麻生火山中枝岳中央锥体的一架无人驾驶飞机上，那里只有火山口边缘是可及的。在这两个采样活动中，在自动采样器收集的样品和直接收集到预抽空烧瓶中的样品之间，分子氢（H ₂）的同位素比（² H / ¹ H）都具有良好的一致性。此外，通过使用阿苏火山上的无人机采样器，我们获得了H ₂浓度更高的羽状样品。和二氧化碳相比，直接进入火山口边缘的烧瓶中的二氧化碳要少得多。一般而言，我们的采样器可用于收集火山羽流样品，以便通过随后的实验室分析和基于² H / ¹ H氢比（包括其时间变化）远程确定富马酚出口温度来确定稳定的同位素组成。