A comparison of in situ vs. ex situ filtration methods on the assessment of dissolved and particulate metals at hydrothermal vents
|Author(s)||Cotte Laura1, 2, 3, Waeles Mathieu1, 2, Pernet-Coudrier Benoit1, 2, Sarradin Pierre-Marie3, Cathalot Cecile4, Riso Ricardo D.1, 2|
|Affiliation(s)||1 : Univ Europeenne Bretagne, Brest, France.
2 : Univ Bretagne Occidentale, Grp Chim Marine, CNRS, IUEM,LEMAR,UMR 6539, F-29280 Plouzane, France.
3 : IFREMER Ctr Brest, Lab Environm Profond LEP DEEP REM, F-29280 Plouzane, France.
4 : IFREMER Ctr Brest, Lab Geochim & Metallogenie LGM GM REM, F-29280 Plouzane, France.
|Source||Deep-sea Research Part I-oceanographic Research Papers (0967-0637) (Pergamon-elsevier Science Ltd), 2015-11 , Vol. 105 , P. 186-194|
|WOS© Times Cited||15|
|Keyword(s)||Metal, Hydrothermal vent, Dissolved, Particulate, Filtration method|
|Abstract||The objective of this study was to assess the impact of the filtration method (in situ vs. ex situ) on the dissolved/particulate partitioning of 12 elements in hydrothermal samples collected from the Lucky Strike vent field (Mid-Atlantic Ridge; MAR). To do so, dissolved ( <0.45 mu m) and particulate Mg, Li, Mn, U, V, As, Ba, Fe, Zn, Cd, Pb and Cu were measured using different techniques (HR-ICP-MS, ICP-AES and CCSA). Using in situ filtration as a baseline, we showed that ex situ filtration (on-board and on shore after freezing) resulted in an underestimation of the dissolved pool, which was counterbalanced by an overestimation of the particulate pool for almost all the elements studied. We also showed that on-board filtration was acceptable for the assessment of dissolved and particulate Mn, Mg, Li and U for which the measurement bias for the dissolved fraction did not exceed 3%. However, in situ filtration appeared necessary for the accurate assessment of the dissolved and particulate concentrations of V, As, Fe, Zn, Ba, Cd, Pb and Cu. In the case of Fe, on-board filtration underestimated the dissolved pool by up to 96%. Laboratory filtration (after freezing) resulted in a large bias in the dissolved and particulate concentrations, unambiguously discounting this filtration method for deep-sea chemical speciation studies. We discuss our results in light of the precipitation processes that can potentially affect the accuracy of ex situ filtration methods.|