Saturated hydrocarbons analysis was carried out on
different river sediments from Alsace-Lorraine in order to
detect possible contaminations by petroleum byproducts.
The distributions of n-alkanes from all studied samples are
very similar and are characterized by an odd-over-even
carbon number predominance, underlining the higher plant
contributions. On the other hand, pentacyclic triterpanes
and steranes occur in all river sediments and display similar
signatures that are characteristic of a mature organic
matter contribution inherited from anthropogenic contamina
tions. Among the different possible pollutants origins,
point industrial sources seem unlikely because of the highly
homogeneous biomarker signatures and the geographical
repartition of the studied rivers. Because of the intense
road traffic in Alsace-Lorraine, main vehicle fuels and exhausts
have been investigated. Unleaded and diesel fuels, used
engine oils, and engine exhausts cannot account for the
biomarker distributions observed in river sediments. On the
contrary, saturated hydrocarbons extracted from road
asphalts are chiefly composed of polycyclic biomarkers
with chromatographic signatures very close to those of river
sediments. Moreover, microscopic investigations of river
sediments allow us to identify asphalt particles and to confirm
that the different rivers studied are contaminated by
road asphalts. Such contaminations may distort biomarker
signatures and GC−MS data and overprint the possible
pollution by other petroleum byproducts.
Thirty-three samples of shales from the Lodeve Permian uranium deposit were examined by different analytical techniques. Samples were analyzed by Rock-Eval pyrolysis and by gas chromatography-mass spectrometry after extraction and fractionation. The determination of uranium content was carried out by atomic emission spectrometry. The composition of the organic extracts allows two groups of shales to be distinguished: the first one is marked by a high proportion of aliphatic hydrocarbons and the second by the predominance of aromatic compounds. These two groups exhibit distinctive biomarker characteristics. One group is characterized by (1) pristane/phytane ratios higher than 1, (2) distributions of terpanes dominated by the tricyclic terpanes and (3) the predominance of C 29 and C 28 steranes. The second group is marked by (1) pristane/phytane ratios lower than 1, (2) the predominance of the pentacyclic terpanes over the tricyclic terpanes and (3) the predominance of C 27 and C 29 steranes. It is suggested that the differences observed are mainly related to different depositional environments, although the uranium content may also influence some parameters such as the hydrogen index and the extraction yield.
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