Search Results - (Author, Cooperation:P. Alberic)

2013-12-18

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Atmosphere/chemistry ; Brazil ; Carbon Cycle ; Carbon Dioxide/*analysis ; Lakes/chemistry ; Plants/metabolism ; Rivers/*chemistry ; Water Movements ; *Wetlands

1573-1421

Amino acid ; sediment ; porewater ; dissolved organic carbon

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

Abstract Dissolved and particulate fractions extracted from a lake diatom ooze were examined for individual amino acids. The study focused on combined amino acids, the predominant form in the interstitial dissolved pool (〉 90%). An abundance of glycine and β-alanine was observed in porewater samples of sediments both squeezed manually and gathered with in-situ dialysis (“peeper”). Sedimentpress squeezing and leaching of the sediment by water gave higher total quantities and different compositions (with more aliphatic and aromatic protein amino acids, α-alanine being predominant). These two methods modify the original composition, presumably due to the formation of Fe-oxides and dissolution of sediment organic fractions, the alteration being aggravated if squeezing is delayed. Filtration after acidification of porewaters enabled us to distinguish two compartments: a protein-like agglutinated fraction, and a filtrate with a high glycine and β-alanine content. Further division of the filtrate by adsorption on XAD or cation-exchange resins did not reveal additional fractions with different individual amino acid compositions. A link is suggested between the agglutinated fraction and the special composition of the porewaters extracted with sediment-press. Dissolved organic carbon (DOC) and total dissolved hydrolysable amino acids (TDHAA) (≈ 10 mg/l and ≈ 13 μM, respectively) did not increase with depth, as opposed to dissolved inorganic carbon and volatile carbon. Amino acid-C accounted for less than 4% of DOC in porewaters. Individual amino acid compositions in the sediments were similar in all grain size fractions. Chemically extracted fractions had specific compositions: (l) organic fractions (alkali extracts and HF-insoluble residues) have a similar protein amino acid composition; (2) acid extracts have more acidic amino acids (HCI) or more glycine and non protein amino acids (BF). The similarity of amino acid compositions in the sediment HF-soluble fraction and the dissolved pool is discussed with respect to interactions between iron-silicate authigenic phases and porewaters.

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