Study of the aggregation of the surface layer of Technosols from stormwater infiltration basins using grain size analyses with laser diffractometry

To improve understanding of the behavior of contaminants in soils in urban areas, it is vital to characterize the overall material and not only the level of contamination. The present study aims at describing the aggregation state of contaminated materials from the surface of a stormwater infiltration basin and the role of their constituents (microorganisms, organic matter, water and carbonates). Grain size distribution and aggregation state were measured by laser diffractometry before and after sonication. To eliminate each material constituent one by one, 4 kinds of treatment (fumigation, oxidation, drying and acidification) were performed (respectively for microorganisms, organic matter, water and carbonates). Unfortunately, because of methodological shortcomings, the result concerning the role of microorganisms in aggregation was questionable. The roles of material constituents were deduced from the effects of the treatments observed on aggregation states. Organic matter (OM), which is mostly constituted from hydrocarbons, was shown to be the main constituent responsible for the aggregation of the materials studied.