title: Early diagenesis and clay mineral adsorption as driving factors of metal pollution in sediments: the case of Aveiro Lagoon (Portugal).
abstract: This work aims to define the factors driving the accumulation of metals in the sediment of the lagoon of Aveiro (Portugal). The role of initial diagenetic processes in controlling trace metal retention in surface sediment is traced by mineralogy, magnetic susceptibility and geochemical analyses. Although several studies have focused on the metal distribution in this polihaline and anthropized coastal lagoon, most of them have been solely focused on the total metal concentrations. This study instead represents the first attempt to evaluate in a vast area of the Aveiro Lagoon the role of biogeochemical processes in metal availability and distribution in three extracted phases: exchangeable cations adsorbed by clay and elements co-precipitated with carbonates (S1), organic matter (S2) and amorphous Mn hydroxides (S3). According to the sediment guideline values, the sediment is polluted by, for instance, As and Hg in the inner area of the Murtosa Channel, Pb in the Espinheiro Channel, Aveiro City canals and Aveiro Harbour, and Zn in the northern area of the Ovar Channel. These sites are located near the source areas of pollutants and have the highest total available concentrations in each extracted phase. The total available concentrations of all toxic metals are however associated, firstly, with the production of amorphous Mn hydroxides in most of the areas and, secondly, with adsorption by organic compounds. The interplay of the different processes implies that not all of the sites near pollution sources have polluted surface sediment. The accumulation of metals depends on not only the pollution source but also the changing in the redox state of the sediments that may cause alterations in the sediment retention or releasing of redox-sensitive metals. Results of this work suggest that the biogeochemical processes may play a significant role in the increase of the pollutants in the sediment of the Aveiro Lagoon.
authors: Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, Av. São Francisco Xavier, 524, Maracanã, 20550-013, Rio de Janeiro, RJ, Brazil, virginia.martins@ua.pt.
authors: Maria Virgínia Alves
authors: MV
authors: Martins
authors: Miguel Ângelo
authors: MÂ
authors: Mane
authors: Fabrizio
authors: F
authors: Frontalini
authors: José Francisco
authors: JF
authors: Santos
authors: Frederico Sobrinho
authors: FS
authors: da Silva
authors: Denise
authors: D
authors: Terroso
authors: Paulo
authors: P
authors: Miranda
authors: Rubens
authors: R
authors: Figueira
authors: Lazaro Luiz Mattos
authors: LL
authors: Laut
authors: Cristina
authors: C
authors: Bernardes
authors: João Graciano Mendonça
authors: JG
authors: Filho
authors: Rodolfo
authors: R
authors: Coccioni
authors: João M Alveirinho
authors: JM
authors: Dias
authors: Fernando
authors: F
authors: Rocha
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry; D000077215:Clay; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D008628:Mercury / Q000032:analysis; D008670:Metals / Q000032:analysis*; D008903:Minerals / Q000032:analysis; D011174:Portugal; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D000538:Aluminum Silicates; D008670:Metals; D008903:Minerals; D014874:Water Pollutants, Chemical; D008628:Mercury; D000077215:Clay