The Relevance of Metal Inputs Into Mar Menor Coastal Lagoon (Spain) Through Submarine Groundwater Discharge

  • Gutiérrez Tirado, Raquel (Universidad Nacional Autónoma de México)
  • Gutiérrez Tirado, Raquel (Spanish Institute of Oceanography (IEO-CSIC))
  • Green Ruiz, Carlos Rene (Universidad Nacional Autónoma de México)
  • Rodellas, Valentí (Universitat Autónoma de Barcelona)
  • Rodriguez-Puig, Júlia (Universitat Autònoma de Barcelon, España)
  • Bernardez, Patricia (Spanish Institute of Oceanography)
  • Bravo, Andrea (Institut de Ciències del Mar)
  • Diego-Feliu, Marc (Universidad Politécnica de Cataluña)
  • Alorda-Montiel, Irene (Universitat Autònoma de Barcelona)
  • Santos Echeandía, Juan (Spanish Institute of Oceanography)

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Mar Menor is one of the largest hypersaline (38-51 ppt) coastal lagoons along the Mediterranean coast. The relatively long residence time (months) of water within the lagoon, combined with potential metal inputs from its economic activities (agriculture, tourism, fishing and the historical mining activity) may lead to high concentrations. Although there are previous studies about the presence of metals in Mar Menor sediments or lagoon waters, there is little information on inputs of metals supplied by submarine groundwater discharges (SGD) which is recognize as a potential relevant source of metals. In the present study, samples from groundwater (wells and piezometers) streams and lagoon water were collected during two different contrasting hydrologic seasons (July and November 2021), in order to elucidate both the magnitude of SGD-driven inputs and the spatial and temporal distribution of these metals in the lagoon. Metals studied included Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd and Pb. The results demonstrated higher levels of Fe, Mn and As in groundwater than the concentrations in streams and lagoon water and higher levels of Cr, Cu, Cd and Pb in streams. Furthermore, the metal concentrations were higher in the North and Southeast areas of Mar Menor which could be associated with the agriculture activity at the North and the Cartagena-La Unión mining district located at the Southeast. In terms of fluxes, the predominant pathway transporting Mn, Fe, Co, Ni, Zn and As into the lagoon was through SGD (higher levels for Mn and Fe), nevertheless, Cr, Cu and Pb the had a main flux from the streams. The work done in this research allows a broader picture of all the possible aquatic pathways of metals to the Mar Menor waters, taking into account the relevance of SGD as a conveyor of them.