News | 12 June 2024

Scientists warn about the effects of mining and accidental toxic spills in the Iberian pyritic belt


A new ICM-CSIC study has revealed a significant increase of heavy metals in the sediments of the northwestern Alboran Sea coinciding with the rise of mining concessions in the region heavy rainfall events and accidental spills.

To carry out the study, researchers analysed heavy metals in sediment cores accumulated in the northwestern Alboran Sea over the last two centuries / ICM-CSIC.
To carry out the study, researchers analysed heavy metals in sediment cores accumulated in the northwestern Alboran Sea over the last two centuries / ICM-CSIC.

A new study led by the Institut de Ciències del Mar (ICM-CSIC) has warned of the effects of mining activity in the Iberian pyritic belt. The work also examines the impact of accidental spills of toxic mining waste, such as the spill that occurred in the Aznalcóllar mine (Seville) 26 years ago, considered one of the biggest environmental disasters in the history of Spain. 

The study, recently published in Marine Pollution Bulletin, analyses the role of Atlantic inflow in the transport and accumulation of polluted sediments from the Gulf of Cadiz to the northwest Alboran Sea. That is, the transport of Atlantic water entering the Alboran Sea through the Strait of Gibraltar from the Gulf of Cadiz.

To carry out the study, researchers analyzed the heavy metals in sediments accumulated in the northwest Alboran Sea over the last two centuries. They found that the levels of zinc (Zn), copper (Cu) and lead (Pb) increased significantly from the second half of the 19th century, coinciding with the increase in mining concessions in the pyrite belt in the southwest of the Iberian Peninsula. 

The team also used sediment traps to monitor the sediment descending in the water column continuously. This allowed them to detect increased contaminants in the sediments transported by the Atlantic inflow during the months following the Aznalcóllar accident in 1998 and during episodes of flooding in the rivers that flow into the Gulf of Cádiz.

"This study suggests that the effects of mining in the Iberian pyritic belt and potential accidents in the tailings ponds not only have a major impact on the fluvial and marine environments of the Gulf of Cadiz, but can also reach the Alboran Sea. This must be considered in the risk assessment of mining operations in the Gulf of Cadiz basins and is crucial when considering the reactivation of mines such as Aznalcollar or Riotinto," insists Albert Palanques (ICM-CSIC), the lead author of the paper.

The environmental catastrophe of Aznalcóllar

This year marks the 26th anniversary of the rupture of the tailings pond at the Aznalcóllar mine, an incident that left the Guadalquivir estuary with high concentrations of metals and metalloids. Among others, this had major implications for the fishing and agricultural sectors, which, together with scientists and environmental organisations, now oppose the resumption of mining activity in the area.

In contrast to the previous model, the company that now manages the mine has tried to differentiate itself from the previous model by designing an underground mine without a tailings pond, but with a 30-kilometer pipeline through which it intends to transport the heavy metals from the mining activity diluted in water to the Guadalquivir estuary. 

According to the scientific community, this model is no better than the previous one, as it does not take into account either the hydrodynamics or the physical-chemistry of the waters of the estuary and the Gulf of Cadiz, nor does it consider the impact on coastal and marine ecosystems. However, the project is now in the final phase of processing, pending the granting of the Unified Environmental Authorisation by the Junta de Andalucía, which is the gateway to receiving other necessary permits.