Monitoring air pollutants in urbanized hydrothermal areas: challenges and benefits of traditional measurement strategies

TL;DR

This study examines air pollution in Tivoli Terme, Italy, from natural hydrothermal sources and human activities, highlighting limitations of traditional monitoring methods.

Contribution

The paper introduces an integrated monitoring strategy combining mobile and low-cost instruments to better track pollution sources.

Findings

Hydrothermal and anthropogenic emissions both contribute to air contamination, but levels remain below outdoor thresholds.

H2S concentrations near sulfur-rich pools indicate a significant hydrothermal impact.

Traditional fixed monitoring fails to reliably distinguish pollution sources due to weather and ambiguous geochemical data.

Abstract

Carbon- and sulfur-bearing gases are emitted at relevant amounts from hydrothermal manifestations at Tivoli Terme (Latium, central Italy), where different potential anthropogenic contaminant sources also occur. This study presents a geochemical dataset including CO2, CH4, SO2, and H2S concentrations and δ13C-CO2 and δ13C-CH4 values measured in air at the center of Tivoli town. The main aim was to evaluate the impact on air quality of hydrothermal manifestations and anthropogenic activities employing a traditional stationary monitoring strategy. The analytical results reveal significant air contamination from both natural and anthropogenic emissions, although gas levels were below outdoor air quality thresholds. Carbon dioxide and CH4 were primarily linked to anthropogenic sources, while hydrothermal emissions played a secondary role. However, H2S concentrations up to 282 ppb highlighted a notable impact from hydrothermal emissions surrounding the measurement station, where SO4-rich pools are located. Nevertheless, the geochemical data did not provide a reliable estimate of the specific contributions from each source. The study identifies key limitations in relying on a single fixed monitoring station, as weather conditions highly influence it and cannot reliably capture the relative impacts of various sources across a broad area. Additionally, compositional and isotopic geochemical parameters often produce ambiguous results, complicating the differentiation of pollution sources. An integrated approach is recommended, combining mobile stations for periodic pollutant mapping with low-cost instruments deployed at strategic locations near potential sources and progressively farther away. This strategy could better track the spatial and temporal evolution of contaminant concentrations, addressing the shortcomings of current monitoring systems and enhancing mitigation efforts.

The online version contains supplementary material available at 10.1007/s10653-025-02422-y.

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