title: Enrichment of rare earth elements as environmental tracers of contamination by acid mine drainage in salt marshes: a new perspective.
abstract: Rare earth elements (REE) were analyzed in surface sediments from the Guadiana Estuary (SW Iberian Pyrite Belt). NASC (North American Shale Composite) normalized REE patterns show clearly convex curvatures in middle-REE (MREE) with respect to light- and heavy-REE, indicating acid-mixing processes between fluvial waters affected by acid mine drainage (AMD) and seawater. However, REE distributions in the mouth (closer to the coastal area) show slightly LREE-enriched and flat patterns, indicating saline-mixing processes typical of the coastal zone. NASC-normalized ratios (La/Gd and La/Yb) do not discriminate between both mixing processes in the estuary. Instead, a new parameter (E(MREE)) has been applied to measure the curvature in the MREE segment. The values of E(MREE)>0 are indicative of acid signatures and their spatial distribution reveal the existence of two decantation zones from flocculation processes related to drought periods and flood events. Studying REE fractionation through the E(MREE) may serve as a good proxy for AMD-pollution in estuarine environments in relation to the traditional methods.
authors: Department of Geology, University of Huelva, Campus 'El Carmen', 21071 Huelva, Spain. joaquin.delgado@dgeo.uhu.es
authors: Joaquín
authors: J
authors: Delgado
authors: Rafael
authors: R
authors: Pérez-López
authors: Laura
authors: L
authors: Galván
authors: José Miguel
authors: JM
authors: Nieto
authors: Tomasz
authors: T
authors: Boski
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D008674:Metals, Rare Earth / Q000032:analysis*; D008906:Mining; D012623:Seawater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
chemical_list: D008674:Metals, Rare Earth; D014874:Water Pollutants, Chemical