An experimental study of the reactive tracing method to determine the polycyclic aromatic hydrocarbon dynamics in a refinery wasteland soil
Résumé
The quantitative analysis of a small sample size of soil may not provide an adequate representation of the overall field composition due to its significant heterogeneity. In other words, measuring the organic carbon content of a few grams of soil is not representative of the whole field. The aim of this experimental study is to carry out a global assessment of these types of parameters and investigate the relevance of reactive tracing methods. Reactive tracing consists of injecting into a porous medium a (non-inert) weakly retained tracer whose interaction with the medium is well characterized. Thus, by injecting a solution containing a low-mass organic solute, a breakthrough curve reflecting the distribution of the retention times is obtained. Its delay compared to that of a tracer of water makes it possible to determine the organic carbon fraction in the soil. This approach was applied with two types of organic solutes tracers: the phenol and the toluene in order to measure the organic carbon fraction. In parallel, soil samples were analyzed and characterized by different techniques of chromatography (HPLC), X-ray fluorescence and infrared. The results showed that toluene was not suitable for such measurements because of its high retention time compared to the average residence time of the fluid in the column. Regardless, it yields an organic carbon fraction value of 11%, which is close to the one determined analytically in the soil sample 15%. Phenol has a lower retention time and would therefore be more suitable for field measurements. However, it gives an organic carbon fraction that is five times lower.