Identification of micro-pollutant sources in urban areas. Advantage of aliphatic hydrocarbons

In urban areas, important amounts of hydrocarbons are released in the environment and a significant part of these pollutants concentrate in the sewage system leading to environmental problems. Many studies are based only on the study of polycyclic aromatic hydrocarbons (PAH) to identify the origin of environmental contamination. This work aims at demonstrating the advantage of aliphatic hydrocarbons (n-alkanes) in the identification of pollutant sources in urban environments. Their specificity and relative distribution allow the identification and follow up of many hydrocarbon generating sources. The analysis of aliphatic hydrocarbon pathways has permitted to build up an important database for the signature of these pollutants. The coarse fraction of the sewage sludges is mainly contaminated by exhaust particulates and lubricating oils, while the organic fraction and the bio-film concentrate the biological and petroleum product contributions. The estimation of the level of degradation of aliphatic hydrocarbons indicates a shorter residence time in the organic and bio-film layer with respect to the coarse deposit. (J.S.)