Characterisation of sewage sludge-derived organic matter: lipids and humic acids

International audienc

Characterization of humic substances in highly polluted river sediments by pyrolysis methylation–gas chromatography–mass spectrometry

International audienceHumic substances were extracted from two sediment cores sampled in a river on the outskirts of a large city (Deûle near Lille, France) and in its highly polluted oxbow-lake. Humic acids (HA) were characterized by infrared spectroscopy and in situ pyrolysis/methylation–gas chromatography–mass spectrometry. The main results are the substantial aliphaticity of HA in the oxbow-lake at all depths, mainly due to the presence of a lipid fraction associated with the HA structure. The abundance of sterols in this fraction implies that lipids could originate from the accumulation of sewage in the oxbow-lake. Humic acids of the Deûle sediments show a different trend ; their evolution is characterized by a decrease of the pollutant inputs with increasing depth. The results demonstrate the efficiency of Py–GC–MS in identifying the different organic contributions to HA and in distinguishing natural from anthropogenic sources