Insights of Pb isotopic signature into the historical evolution and sources of Pb contamination in a sediment core of the southwestern Iberian Atlantic shelf

Mário Mil-Homens; Carlos Vale; Pedro Brito; Filipa Naughton; Teresa Drago; Joana Raimundo; Bárbara Anes; Sabine Schmidt; Miguel Caetano

doi:10.1016/j.scitotenv.2017.01.204

Insights of Pb isotopic signature into the historical evolution and sources of Pb contamination in a sediment core of the southwestern Iberian Atlantic shelf

Sci Total Environ. 2017 May 15:586:473-484. doi: 10.1016/j.scitotenv.2017.01.204. Epub 2017 Feb 14.

Authors

Mário Mil-Homens¹, Carlos Vale², Pedro Brito³, Filipa Naughton⁴, Teresa Drago⁵, Joana Raimundo³, Bárbara Anes⁶, Sabine Schmidt⁷, Miguel Caetano³

Affiliations

¹ IPMA, Portuguese Institute of Sea and Atmosphere, Rua Alfredo Magalhães Ramalho, 6, 1449-006 Lisboa, Portugal; CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, 289, 4050-123 Porto, Portugal. Electronic address: mario.milhomens@ipma.pt.
² CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, 289, 4050-123 Porto, Portugal.
³ IPMA, Portuguese Institute of Sea and Atmosphere, Rua Alfredo Magalhães Ramalho, 6, 1449-006 Lisboa, Portugal; CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, 289, 4050-123 Porto, Portugal.
⁴ IPMA, Portuguese Institute of Sea and Atmosphere, Rua Alfredo Magalhães Ramalho, 6, 1449-006 Lisboa, Portugal; CCMAR, Center of Marine Sciences, Algarve University, Campus de Gambelas, 8005-139 Faro, Portugal.
⁵ IPMA, Portuguese Institute of Sea and Atmosphere, Rua Alfredo Magalhães Ramalho, 6, 1449-006 Lisboa, Portugal; IDL, Instituto Dom Luiz, Faculty of Sciences, University of Lisbon, Campo Grande, Edifício C1, Piso 1, 1749-016 Lisboa, Portugal.
⁶ IPMA, Portuguese Institute of Sea and Atmosphere, Rua Alfredo Magalhães Ramalho, 6, 1449-006 Lisboa, Portugal; Faculty of Sciences, University of the Lisbon, Centre for Molecular Sciences and Materials, Campo Grande, 1749-016 Lisboa, Portugal.
⁷ UMR 5805 EPOC OASU, University of Bordeaux, 33615 Pessac, France.

PMID: 28209405
DOI: 10.1016/j.scitotenv.2017.01.204

Abstract

Stable Pb isotopic ratios and concentrations of Al, Cu and Pb were measured in a 5m long sediment core (VC2B) retrieved at 96m water depth in the southwestern Iberian Atlantic shelf. Five phases during the last 9.5kyrs were identified, two of them (Roman Period and modern mining) marked by a decrease of ²⁰⁶Pb/²⁰⁷Pb ratios reflecting additional inputs of Pb derived from mining activities. The Roman Period was also characterized by high ²⁰⁸Pb/²⁰⁶Pb ratios suggesting the exploitation of the outcropping portion of the orebody intensely weathered when compared with the other formations later mined. The shift of ²⁰⁸Pb/²⁰⁶Pb ratios towards linearity took approximately 1.0kyrs, which may mirror the time of environmental recovery from the impact of Roman mining activities. The application of a mixing model allowed the quantification of the contribution associated with anthropogenic mining activities to the shelf sediments. The maximum values of Pb contamination occurred in the 20^th century. This study gives direct evidence of Pb and Cu exploitation over the last 2000years. The stable Pb isotopic signatures point to legacy of mining activities that are still the prevailing metal source recorded in the southwestern Iberian Atlantic shelf sediments.

Keywords: Environment recovery; Marine sediments; Pb isotopes; Roman and modern mining activities; Southwestern Iberian shelf; Temporal evolution.