Hazardous volcanic CO2 diffuse degassing areas - A systematic review on environmental impacts, health, and mitigation strategies.

Volcanic CO2 diffuse degassing can impact infrastructure, soils, vegetation, microbiota, fauna, and human health. These impacts include acidification of soils, leading to sparse or absent vegetation and changes in microbiota types. Most of the study sites in this review are areas of quiescent volcanism, where soil CO2 emissions is a permanent and silent hazard. Lethal indoor and outdoor CO2 concentrations measured in different regions of the world (Azores, Aeolian and Canary Islands, Colli Albani, Methana, Massif Central, Mammoth Mountain, Nyiragongo, Nyamulagira, and Rotorua volcanoes) are associated with the asphyxia and death of humans and other fauna (e.g., birds, reptiles, cows, elephants, and dogs). To address the hazard posed by volcanic CO2 diffuse degassing, we suggest mitigation measures including mandatory CO2 hazard maps for land-use planning, "gas-resistant" construction codes, ventilation mechanisms, monitoring and early warning systems, along with educational campaigns to reduce the gas exposure risks.