Detecting industrial ammonia and ethylene point sources with the thermal bands of Landsat 8 and 9

Adriana Valverde , Shanyu Zhou , Javier Roger , Itziar Irakulis-Loitxate , Javier Gorroño , Lulu Si, Luis Guanter

Industrial point sources of ammonia (NH₃) and ethylene (C₂H₄) are poorly constrained in current inventories, in part because satellites tend to offer either fine spatial detail or frequent revisits. We show that the two thermal-infrared bands of the Landsat 8 and 9 Thermal Infrared Sensor (TIRS), though built for land-surface monitoring, can detect and spatially resolve such plumes at 100 m resolution. Using a B10/B11 band-ratio method at five facilities in Iraq, Oman, the United Arab Emirates, and Saudi Arabia, we identified hundreds of plumes over 2021–2025 that recur in most months, pointing to persistent rather than sporadic emission. Because TIRS cannot spectrally separate the two gases, we attribute them from the known source type, corroborated by IASI and hyperspectral cross-checks: Landsat detections agree with morning IASI overpasses on two-thirds to three-quarters of co-observed days, and a near-simultaneous EMIT overpass over the Iraq fertilizer plant confirms that the band-ratio signal follows genuine NH₃ enhancements. Crucially, Landsat resolves individual units that IASI blends into a single column, and its open, multi-decade archive reconstructs facility-level emission histories, with plumes traceable back to 2015, complementing hyperspectral imagers and pointing toward routine, facility-scale monitoring.