Volcanic CO is widely acknowledged as an important geochemical precursor for volcanic activity; however, obtaining observations through remote sensing remains a challenge. It is well established that volcanic CO diffusely degases during magma ascent, and the volatiles interact with the ecosystem on the surface through CO fertilization, which can improve vegetation health. A normalized difference vegetation index (NDVI) is a remote sensing method that quantifies vegetation health. This study compared NDVI signals from Landsat 8, MODIS, Sentinel 2, and VIIRS to soil CO flux signals from 5 ground-based EtnaGas stations on Mt. Etna from 2011 to 2018. Due to variances in sensor and spectral characteristics, the NDVI values were calibrated across all 4 sensors. The 2nd derivatives of NDVI and soil CO flux highlight the timeframes of the increase/decrease cycles of CO degassing, which in turn, correspond to the change in storage levels as magma rises from an intermediate chamber to a shallow one. Between 2017 and 2018, the 2nd derivative spikes showed 16 magma recharge events in both NDVI and soil CO signals. A flank analysis of homogenous trees across Mt. Etna showed the same 2nd derivative spike pattern for NDVI when compared to individual EtnaGas stations, indicating that trees do not have to be located within 30 m of volcano-tectonic structures to be affected by diffusely escaping volcanic CO. This study highlights the potential of NDVI as a remote sensing method for monitoring volcanic CO emissions, paving the way for innovative approaches to volcanic surveillance.

中文翻译：

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通过遥感意大利埃特纳火山植被监测火山二氧化碳通量


火山二氧化碳被广泛认为是火山活动的重要地球化学前体；然而，通过遥感获得观测结果仍然是一个挑战。众所周知，火山二氧化碳在岩浆上升过程中广泛脱气，挥发物通过二氧化碳施肥与地表生态系统相互作用，这可以改善植被健康。归一化植被指数（NDVI）是一种量化植被健康状况的遥感方法。本研究将 2011 年至 2018 年来自 Landsat 8、MODIS、Sentinel 2 和 VIIRS 的 NDVI 信号与来自埃特纳火山 5 个地面 EtnaGas 站的土壤 CO 通量信号进行了比较。由于传感器和光谱特性的差异，NDVI 值为所有 4 个传感器均经过校准。 NDVI 和土壤 CO 通量的二阶导数突出了 CO 脱气循环增加/减少的时间范围，这反过来又对应于岩浆从中间室上升到浅室时储存水平的变化。 2017 年至 2018 年间，NDVI 和土壤 CO 信号中的二阶导数峰值显示了 16 个岩浆补给事件。对埃特纳火山上同质树木的侧面分析显示，与各个埃特纳天然气站相比，NDVI 具有相同的二阶导数尖峰模式，这表明树木不必位于火山构造结构 30 m 范围内，才会受到扩散逃逸火山的影响这项研究强调了 NDVI 作为监测火山二氧化碳排放遥感方法的潜力，为火山监测的创新方法铺平了道路。