A novel integrated strategy for air quality monitoring in volcanic-hydrothermal, wetland, urban and industrial areas

In the present era, environmental challenges are becoming increasingly prominent, necessitating innovative solutions that facilitate air quality monitoring and mitigation strategies aimed at safeguarding human health, the climate, and ecosystems. This study demonstrates how combining low-cost and high-tech stations (through integrated fixed and mobile monitoring) offers an effective and complementary approach. The strategy was applied in diverse environments (volcanic-hydrothermal areas, a wetland, and a CO₂ production plant), providing high spatial and temporal resolution data. Fixed low-cost stations, calibrated using machine-learning techniques, enabled continuous monitoring of key pollutants (CO₂, CH₄, PM_2.5, PM₁₀), depicting temporal variability linked to atmospheric dynamics, meteorological conditions, and emission strength. Their affordability allowed denser monitoring networks, enhancing spatial resolution and identifying critical areas that require long-term observation. This was especially effective in the wetland, where eutrophic zones emitting higher CH₄ levels were clearly identified. Mobile high-tech monitoring complemented fixed data by extending spatial coverage, with repeated transects allowing partial temporal tracking. An integrated analysis of pollutant concentrations, wind patterns, and isotopic ratios (δ¹³C of CO₂ and CH₄) enabled source apportionment, distinguishing between geogenic-hydrothermal and anthropogenic emissions, particularly in volcanic and industrial contexts. Despite its strengths, some limitations persist in the combination of the two approaches: (i) the drift over time and aging of low-cost sensors were not addressed, despite the necessity of their evaluation to ensure their proper use over longer monitoring periods; (ii) mobile monitoring lacks continuous temporal data and measurements are not simultaneous, limiting its effectiveness for tracking long-term trends and comparing pollutant levels across different areas.