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Trace metals partitioning among different sedimentary mineral phases and the deposit-feeding polychaete Armandia brevis.

Diaz-de-Alba, Margarita; Huerta-Diaz, Miguel Angel; Delgadillo-Hinojosa, Francisco; Hare, Landis; Galindo-Riano, Dolores M.; Siqueiros-Valencia, Arturo (2016). Trace metals partitioning among different sedimentary mineral phases and the deposit-feeding polychaete Armandia brevis. Science of the Total Environment , vol. 543 , nº Part A. p. 248-266. DOI: 10.1016/j.scitotenv.2015.11.033.

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Résumé

Trace metals (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn) were determined in two operationally defined fractions (HCl and pyrite) in sediments from Ensenada and El Sauzal harbors (Mexico). The HCl fraction had significantly higher metal concentrations relative to the pyrite fraction in both harbors, underlining the weak tendency of most trace metals to associate with pyrite. Exceptionally, Cu was highly pyritized, with degrees of trace metal pyritization (DTMP) >80% in both harbors. Dissolved Fe flux measurements combined with solid phase Fe sulfide data indicated that 98 mt of Fe are precipitated as iron sulfides every year in Ensenada Harbor. These Fe sulfides (and associated trace metals) will remain preserved in the sediments, unless they are perturbed by dredging or sediment resuspension. Calculations indicate that dredging activities could export to the open ocean 0.20 +/- 0.13 to (030 +/- 0.56) x 10(3) mt of Cd and Cu, respectively, creating a potential threat to marine benthic organisms. Degrees of pyritization (DOP) values in Ensenada and El Sauzal harbors were relatively low (<25%) while degrees of sulfidization (DOS) were high (similar to 50%) because of the contribution of acid volatile sulfide. DOP values correlated with DTMP values (p <= 0.001), indicating that metals are gradually incorporated into pyrite as this mineral is formed. Significant correlations were also found between DTMP values and -log(K-sp(Mes)/K-sp(pyr)) for both harbors, indicating that incorporation of trace metals into the pyrite phase is a function of the solubility product of the corresponding metal sulfide. The order in which elements were pyritized in both harbors was Zn approximate to Mn < Fe < Cd approximate to Pb < Ni approximate to Co < < Cu. Lastly, a strong correlation (r(2) = 0.87, p < 0.01) was found between average reactive trace metal concentrations and metal concentrations measured in Armandia brevis (a deposit-feeding Opheliid polychaete), suggesting that these labile sedimentary metals are preferentially accumulated by the polychaete, making it a useful biomonitor of sedimentary metal exposure.

Type de document:
Mots-clés libres: speciation; trace metal; sediment contamination; pyrite; Armandia brevis
Centre: Centre Eau Terre Environnement
Date de dépôt: 20 déc. 2016 15:58
Dernière modification: 20 déc. 2016 15:58
URI: http://espace.inrs.ca/id/eprint/3970

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