Geochemical processes controlling the distribution and concentration of metals in soils from a Patagonian (Argentina) salt marsh affected by mining residues

IDASZKIN Y; CAROL E; ALVAREZ M P

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 596 p. 230 - 235

0048-9697

Heavy metal pollution that affects salt marshes is a major environmental concern due to its toxic nature, persistence, andpotential risk to organisms and to human health. Mining waste deposits originated four decades ago, by the metallurgicalextraction of heavy metals, are found near to the San Antonio salt marsh in Patagonia. The aim of the work was todetermine the geochemical processes that control the distribution and concentration of Cu, Fe, Pb and Zn in the soils ofthis Patagonian salt marsh. A survey of the mining waste deposits was carried out where three dumps were identified.Samples were collected to determine soil texture, Eh pH, Organic matter and metal contents and the soil mineralogicalcomposition. The results shows that the soils developed over the mining waste deposits are predominantly reddish constitutedmainly by iron oxide, hydroxide and highly soluble minerals such as Zn and Cu sulphates. The drainage fromthese deposits tends to move towards the salt marsh. Within the salt marsh, the highest concentrations of Cu, Pb and Znoccur in the sectors closest to the mining wastes deposits. The sulphide oxidation and the dissolution of the Cu, Pb andZn sulphates could be the mainly source of these metals in the drainage water. The metals in solution that reach the saltmarsh, are adsorbed by the organic matter and the fine fraction of the soils. These adsorbed metals are then remobilizedby tides in the lower sectors of the marsh by desorption from the cations present in the tidal flow. On the other hand, Fetends to form non soluble oxides, hydroxides and sulphates which remain as altering material within the mining wastedeposit. Finally, the heavy metal pollutants recorded in the San Antonio salt marsh shows that the mining waste depositsthat were abandoned four decades ago are still a source metal contamination.