Abandoned mine tailings in cultural itineraries: Don Quixote Route (Spain)

Metallic mining wastes are a crucial environmental concern because of the accumulation and emission of toxic elements. The abandoned San Quintín mine tailings, from the exploitation of galena and sphalerite (Puertollano mining district, Spain), are surrounded by farmland and are crossed by the European Cultural Itinerary known as the “Don Quixote Route”. Geophysical, mineralogical and geochemical techniques have been applied to determine the geometry and composition of mine ponds and the possible occurrence of AMD that could entail ecosystem and human risks. Seven electrical resistivity tomography profiles were surveyed, and re-worked tailing samples of two ponds, five soil samples, nine water samples and gaseous mercury emissions were analyzed. Both mine ponds are ~ 8 m deep and overlie Quaternary colluvial sediments deposited over Precambrian metasediments. The pond infilling is mainly composed of quartz and clay minerals, and minor amounts of gypsum and sulfides, with significant As, Cd, Hg, Pb, Sb and Zn contents. This metal emission source affects the underlying colluvial sediments and high Hg and Pb contents have also been found in nearby agricultural soils. AMD has been identified, but metal contamination in the stream that borders the tailings is below the USEPA's recommended limits. Although gaseous mercury emissions from a cinnabar stockpile increase in summer, the measured levels do not reach the WHO's recommended limit. The Enrichment Factor and Igeo indexes for As, Cd, Hg, Pb, Sb and Zn indicate strong to extreme contamination in the mine ponds and moderate contamination in the colluvial sediments/metasediments. Aeolian dispersion is the most important contaminant agent. The surrounding soils show strong to extreme levels of Hg and moderate to extreme levels of As, Cd, Pb and Sb. Restoration of these abandoned wastes is recommended to reduce the health risks for residents and tourists due to this aeolian contaminant dispersion.