Evidence for diffuse contamination of river sediments by reed asphalt particles

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 nature organic matter contribution inherited from anthropogenic contaminations, 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 anti 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.