Biagi R, Tassi F, Caliro S, Capecchiacci F, Venturi S
Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121, Firenze, Italy.
Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121, Firenze, Italy; Institute of Geosciences and Earth Resources (IGG), National Research Council of Italy (CNR), Via G. La Pira 4, 50121, Firenze, Italy.
Chemosphere. 2022 Jun;297:134166. doi: 10.1016/j.chemosphere.2022.134166. Epub 2022 Mar 1.
Volcanoes are currently to be regarded as natural sources of air pollutants. Climatic and environmental forcing of large volcanic eruptions are well known, although gases emitted through passive degassing during periods of quiescence or hydrothermal activity can also be highly dangerous for the environment and public health. Based on compositional and isotopic data, a survey on the spatial distribution in air of the main volatile compounds of carbon (CO and CH) and sulfur (HS and SO) emitted from the fumarolic field of Pisciarelli (Campi Flegrei, Pozzuoli, Naples), a hydrothermal area where degassing activity has visibly increased since 2009, was carried out. The main goals of this study were (i) to evaluate the impact on air quality of these natural manifestations and (ii) inquire into the behavior of the selected chemical species once released in air, and their possible use as tracers to distinguish natural and anthropogenic sources. Keeling plot analysis of CO and CH isotopes revealed that the hydrothermal area acts as a net source of CO in air, whilst CH originated mainly from anthropogenic sources. Approaching the urban area, anthropogenic sources of CO increased and, at distances greater than 800 m from the Pisciarelli field, they prevailed over the hydrothermal signal. While hydrothermal CO simply mixed with that in the atmospheric background, HS was possibly affected by oxidation processes. Therefore, SO measured in the air near the hydrothermal emissions had a secondary origin, i.e. generated by oxidation of hydrothermal HS. Anthropogenic SO was recognized only in the furthest measurement site from Pisciarelli. Finally, in the proximity of a geothermal well, whose drilling was in progress during our field campaign, the HS concentrations have reached values up to 3 orders of magnitude higher than the urban background, claiming the attention of the local authorities.
目前，火山被视为空气污染物的天然来源。大型火山喷发对气候和环境的影响是众所周知的，尽管在静止期或热液活动期间通过被动脱气释放的气体对环境和公众健康也可能极具危险性。基于成分和同位素数据，对皮斯恰雷利（坎皮弗莱格雷、波佐利、那不勒斯）喷气孔场排放的主要挥发性碳化合物（一氧化碳和甲烷）和硫化合物（硫化氢和二氧化硫）在空气中的空间分布进行了调查，皮斯恰雷利是一个热液区，自2009年以来脱气活动明显增加。本研究的主要目标是：（i）评估这些自然现象对空气质量的影响；（ii）探究所选化学物质一旦释放到空气中的行为，以及它们作为区分自然源和人为源示踪剂的可能性。一氧化碳和甲烷同位素的基林曲线分析表明，热液区是空气中一氧化碳的净源，而甲烷主要源自人为源。靠近市区时，一氧化碳的人为源增加，在距离皮斯恰雷利场大于800米处，人为源超过了热液信号。热液一氧化碳只是简单地与大气背景中的一氧化碳混合，而硫化氢可能受到氧化过程的影响。因此，在热液排放源附近空气中测得的二氧化硫有二次来源，即由热液硫化氢氧化产生。仅在距离皮斯恰雷利最远的测量点识别出了人为源二氧化硫。最后，在一口地热井附近，在我们进行实地考察期间该井正在钻探，硫化氢浓度达到的值比城市背景值高出多达3个数量级，引起了当地当局的关注。
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