Volcanoes emit significant amounts of gases into the atmosphere through visible and non-visual degassing manifestations regardless of whether volcanoes are active or quiescent. The latter, also known as diffuse or silent degassing, occurs across the entire volcanic building. Water vapour (H₂O), carbon dioxide (CO₂), and sulfur (S) are the three most abundant magmatic volatiles, with CO₂ being the least soluble in silicate melts. Diffuse volcanic degassing alters the chemical composition of volcanes' ground/soil gas atmosphere, resulting in enrichment of CO₂, He, and other gas species. Over the last 25 years, extensive research on diffuse CO₂ degassing has been conducted at volcanic and geothermal systems, indicating that silent CO₂ degassing is an important mechanism for dissipating energy at volcanoes and contributes significantly to global CO₂ emissions from subaerial volcanism. As a result, diffuse CO₂ degassing studies have been regarded as a powerful tool in geochemical monitoring programs for volcanic surveillance, particularly in volcanic areas lacking visible gas manifestations (plume, fumaroles, hot springs, etc.), a valuable tool for identifying productive geothermal reservoirs, and a potential source of large amounts of CO₂ to the atmosphere via gobal subaerial volcanism.

Diffuse degassing investigations on volcanoes involve primarily in-situ ground CO₂ efflux measurements and the collecting of gases at a certain depth for later chemical and isotopic analysis. CO₂ and He are the two most interesting gas species to investigate in diffuse degassing studies due to their similar low solubility in silicate melts at low pressures and suitability as geochemical tracers of magmatic activity. However, once exsolved from the silicate melts, their journey through the crust to the surface is considerably different. While CO₂, as a reactive gas, is influenced by interfering processes (gas scrubbing by groundwaters and interaction with rocks, decarbonatation processes, biogenic production, and so on), He is chemically inert, radioactively stable, non-biogenic, highly mobile, and relatively insoluble in water. These properties minimize the interaction of this noble gas with the surrounding rocks or fluids during its ascent towards the surface. Their geochemical differences yield higher relative He/CO₂ ratio in the fumarole gases than is actually present in the magma, but it decreases when the magma reservoir reaches enough pressure to generate incipient fracture systems approaching the eruption, thus releasing considerably more of the magma volatiles.

Quantifying global volcanic CO₂ emissions from subaerial volcanism is critical for gaining a better knowledge of the rates and mechanisms of carbon cycling, as well as their effects on the long-term development of Earth's climate across geological timescales. Recent studies show that diffuse degassing contributes 47 to 174 Tg·y^-1 to the atmosphere, although our understanding of the global diffuse CO₂ degassing from subaerial volcanism could be larger.

Several examples of diffuse degassing research on many different volcanic systems around the world performed by our research team and collaborators during the last 25 years will be presented during my award/medal lecture, strongly supporting that diffuse degassing is a useful tool for volcanic surveillance and a significant contributor to the global CO₂ emissions from subaerial volcanism.

How to cite: Pérez, N. M. and the INVOLCAN/ITER Research Team: The silent degassing of volcanoes: a useful tool for volcanic surveillance and a significant contributor to the global CO2 emission from subaerial volcanism , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14781, https://doi.org/10.5194/egusphere-egu24-14781, 2024.

The global impact of diseases and environmental pressures on trees and forests has resulted in the decay and loss of a significant portion of the Earth’s natural heritage. Responding to this challenge, Ground Penetrating Radar (GPR), a well-established and reliable non-destructive testing (NDT) method, emerges as a fundamental assessment technique with vast potential. Its efficacy spans various domains, from Earth sciences to engineering, making GPR uniquely suited for forestry applications and offering a sustainable and non-invasive alternative to destructive methods like coring.

Within forestry applications, GPR assumes a critical role in optimising economic expenditure for tree maintenance while simultaneously enhancing public safety. Swift and reliable detection of subsurface anomalies make GPR essential in safeguarding natural heritage and facilitating early identification of tree decay, ultimately supporting effective tree disease control.

The present work explores the extension of GPR's capabilities to evaluate critical parameters in tree health, focusing on the assessment of root systems and the identification of potential structural weaknesses within tree trunks.

The study introduces a series of recent experimental-based and theoretical models, each contributing to the understanding and enhancement of tree assessment. These models refine the interpretation of intricate reflection patterns, providing a refined understanding of tree trunk conditions. Additionally, models for the early detection of decays and cavities in tree trunks are presented, offering valuable insights into the internal structure of trees and enhancing the sensitivity and precision of GPR for proactive tree health management.

In terms of assessing and monitoring tree roots, the study introduces methodologies designed to enhance the understanding of below-ground ecosystems. Developed algorithms for root detection and tracking, along with methodologies for estimating root mass density, offer insights into growth patterns and contribute to sustainable tree management practices. Furthermore, recent methodologies focus on understanding interconnections within tree root systems and the surrounding environment, identifying buried structures within the root system, addressing unique challenges faced by street trees in urban environments, refining the analysis of tree root systems using frequency spectrum-based processing, and integrating artificial intelligence for automatic recognition to enhance the efficiency of root system assessment.

Finally, unique case studies are presented, showcasing the methodology, survey planning, and site procedures. These case studies add depth to the exploration, reflecting the practical application of the research in diverse and challenging scenarios.

How to cite: Lantini, L. and Tosti, F.: Towards Sustainable Futures in Tree Assessment using Ground Penetrating Radar: Insights, Developments and Novel Perspectives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8419, https://doi.org/10.5194/egusphere-egu24-8419, 2024.