Acyclic Lipids in Amazon Shelf Waters

Autor: Bernd R.T. Simoneit, Vladimir O. Elias, Jari N. Cardoso
Rok vydání: 2000
Předmět:
Zdroj: Estuarine, Coastal and Shelf Science. 50:231-243
ISSN: 0272-7714
DOI: 10.1006/ecss.1999.0574
Popis: Acyclic lipids were analysed for dissolved ( 1·2 μm) material from surface water of the Amazon continental shelf to correlate the direct inputs with diagenetic processes of the organic matter and to assess the differences in compound distribution patterns of the samples. The dissolved samples contained n -alkanes with an unusual even-to-odd carbon number predominance 30 and CPIs (carbon-preference index) varying from 0·35 to 1·22 (C 17 –C 22 range) and 0·52 to 1·33 (C 23 –C 28 range). Carbon number maxima (C max ) occurred at C 18 and/or C 22 Pr/Ph ratios varied from 0·28 to 2·62. The n -alkanes in particulate samples ranged from C 15 to C 35 (CPI 17–22 from 0·15 to 0·50 and CPI 23–28 from 0·52 to 1·12) with C max at C 18 and C 20 , while pristane and phytane on the other hand were present in particulate matter only at trace amounts and hence Pr/Ph ratios could not be calculated. Both dissolved and particulate phases showed saturated C 14 , C 16 and C 18 alkanoic acids and an unsaturated C 16:1 acid as major components. The chemical composition of these acyclic lipids indicates an origin from micro-organisms, probably diatoms. Although minor, a contribution of components derived from plant waxes are more abundant in the particulate phase with profiles indicating a remineralized residue. Plant waxes are effectively biodegraded in the shelf waters during downstream transport in the Amazon River. Furthermore, the Pr/Ph ratios calculated for the dissolved samples indicate that the organic matter in the surface of the highly turbid waters passed through an anaerobic stage. The differences in the acyclic hydrocarbon profiles of the dissolved and particulate phases show that organic inputs are preserved differently in smaller and larger particles.
Databáze: OpenAIRE
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