Relevance and Reliability of Outdoor SO 2 Monitoring in Low-Income Countries Using Low-Cost Sensors.

In the Western world, the SO₂ concentration in ambient air dropped to low levels, but some emission sources (e.g., merchant ships) and some regions (e.g., low-income countries) still emit substantial amounts of SO₂. At those locations, SO₂ monitoring is critical. However, low-income countries do not have much access to expensive reference instruments. Low-cost gas sensors might be an alternative, but it is unclear how reliable such measurements are. To evaluate the performance of the low-cost alternative, the same SO₂ gas sensor has been subjected to three different calibration methods: (1) low-cost calibration performed in the tropical climate of Cuba; (2) high-end calibration performed in Belgium; (3) a field calibration at an air quality measuring station in Belgium. The first two methods showed similar trends, suggesting that the gas sensor can be calibrated with a low-cost method. The field calibration was hampered by the low SO₂ concentrations. For the monitoring campaign in Cienfuegos, Cuba, the low-cost SO₂ sensor calibrated by the low-cost method appeared to be sufficiently reliable. The reliability of the sensor increases with the increase in SO₂ concentration, so it can be used in Cuba instead of Belgium. [ABSTRACT FROM AUTHOR]