Impact on air quality of carbon and sulfur volatile compounds emitted from hydrothermal discharges: The case study of Pisciarelli (Campi Flegrei, South Italy). (June 2022)

• Record Type: Journal Article
• Authors: Biagi, R.; Tassi, F.; Caliro, S.; Capecchiacci, F.; Venturi, S.
• Is Part Of: Chemosphere. Volume 297(2022)
• Publication Date: 2022-06
• Subjects: Hydrothermal systems -- Air quality -- Carbon and sulfur volatile compounds -- Carbon isotopes -- Natural sources of pollutants.; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.134166
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: 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 (CO2 and CH4 ) and sulfur (H2 S and SO2 ) 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 CO2 and CH4 isotopes revealed that the hydrothermal area acts as a net source of CO2 in air, whilst CH4 originated mainly from anthropogenic sources. Approaching the urban area, anthropogenic sources of CO2 increased and, at distances greater than 800 m from the Pisciarelli field, they prevailed over the hydrothermal signal. While hydrothermal CO2 simply mixed with that in the atmospheric background, H2 S was possibly affected by oxidation processes. Therefore, SO2 measured in the air near the hydrothermal emissions had a secondary origin, i.e. generated by oxidation of hydrothermal H2 S. Anthropogenic SO2 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 H2 S concentrations have reached values up to 3 orders of magnitude higher than the urban background, claiming the attention of the local authorities. Graphical abstract: Image 1 Highlights: CO2, CH4, H2 S, SO2 mole fractions in air, and δ 13 C isotopes, were measured in Pisciarelli. CO2 and H2 S concentrations in air were mainly related to the hydrothermal system emissions. CO2 mixed with both the local background and anthropogenic sources. CH4 emissions were likely governed by anthropogenic sources from the city. SO2 concentrations were governed both from consumption of H2 S and anthropogenic sources.