The Estuary of Huelva in southwestern Spain is severely impacted by acid mine drainage (AMD), primarily due to extensive mining activities in the Iberian Pyrite Belt (IPB), and to a lesser extent by industrial sources. The AMD has led to significant contamination of the Odiel and Tinto rivers, which carry high loads of metals into the estuary. In May 2017, an accidental spill occurred at La Zarza mine, releasing approximately 270,000 m