Natural, anthropogenic and fossil organic matter in river sediments and suspended particulate matter: A multi-molecular marker approach

Author(s)

Thilo Hofmann, Vesna Micic Batka, Michael Kruge, Jürgen Köster

Abstract

Different classes of organic matter (OM) have been systematically investigated in sediments and suspended

particulate matter (SPM) along the Danube River in order to understand causes of compositional changes.

Analytical pyrolysis revealed the dominance of natural organic matter (NOM) in most of the samples. The

predominance of aquatic biomass is evident mainly from the abundance of organonitrogen compounds and

phenol distributions. As the river enters a forested gorge, the terrestrial component of the NOM in sediments

is more significant. This is reflected in abundant methoxyphenols and a very high carbon preference index.

SPM sample from a tributary shows a unique geochemical signature. It contains abundant carboxylic acids,

amines, isoprenoids in the pyrolyzate, and is dominated by phytol and 24-methyl-cholesta-5,24(28)-dien-3β-

ol in the extract, produced by a diatom bloom. Wax esters with a relatively high proportion of short, methylbranched

alkyl-chains appear together with abundant phytadienes and n-C17 alkane in some samples,

suggesting a microbial origin. Anthropogenic OM from runoff and atmospheric deposition was evident from a

minor input of polycyclic aromatic hydrocarbons (PAHs) originating from mixed combustion sources.

Multivariate analysis using PAH data led us to define simple molecular ratios to distinguish the PAH

composition in sand and silty sediments. The newly defined ratios are the alkylated phenanthrenes

and anthracenes ratio (APA; C1-C3/C0–C3 phenanthrenes and anthracenes) and the PAH ring number ratio

(RN; 5–6 ring parent PAHs/all parent PAHs). This demonstrates that alkylated, as well as 5–6 ring PAHs are

better preserved in the finer than in coarser grained sediments. A ubiquitous, but minor input of petroleumrelated

contamination with a uniform composition was evident in all samples as revealed by the analysis

of petroleum biomarkers. This study demonstrates that the investigation of different classes of riverine

OM requires a detailed molecular analysis, applying a series of analytical techniques and adequate statistical

data treatment.

Organisation(s)

External organisation(s)

Montclair State University, Carl von Ossietzky Universität Oldenburg

Journal

Science of the Total Environment

Volume

409

Pages

905-919

No. of pages

15

ISSN

0048-9697

Publication date

2011

Peer reviewed

Yes

Austrian Fields of Science 2012

105303 Hydrogeology, 104023 Environmental chemistry, 105105 Geochemistry, 105904 Environmental research

Sustainable Development Goals

SDG 15 - Life on Land

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