Silver and bismuth as tracers of historical pollution in the Tinto-Odiel estuary (SW Spain)

Abstract

This paper analyzes the vertical evolution of facies and the Ag and Bi contents of a continuous core extracted in the middle estuary of the Tinto river (S.O. Spain). The sedimentological and paleontological analysis allows to define four sedimentary facies, characteristics of alluvial deposits (F1: 6.5-6.2 ka BP), the marine flooding of the sector during the maximum of the Holocene transgression and the period immediately after (F2: 6.2 -5.2 ka BP), the transition to marshes (F3: 5.2-19th century) and an anthropic landfill since the end of the 20th century. The concentrations of Ag and Bi make it possible to specify three main periods of historical contamination: i) the start of mining activities and the exploitation of Ag during the Bronze Age (~ 4.5-3.2 ka BP); ii) the period of maximum intensity of Roman mining (1st-2nd centuries DC); and iii) recent intensive mining (since 1870).