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The adsorption of volatile organic compounds (VOC) onto soils plays an important role in the mobility of these kinds of contaminant through soils. It is therefore of interest to learn more about the mechanisms of interaction between VOC and soil particles. An experimental study has been carried out in order to determine the adsorption isotherms of volatile organic gases of different properties on soil minerals of different characteristics, working in a wide range of compound concentrations. The adsorption of seven organic compounds (n-hexane, n-heptane, n-octane, toluene, xylene, ethylbenzene, and methyl ethyl ketone) and of water vapor on sand, clay, and limestone has been analyzed. The influence of the presence of water on the adsorption of these compounds has also been analyzed, working at levels below the limit of applicability of Henry's law. The levels of relative air humidity used were 20 and 50%. The results show a big difference between the adsorption levels of the three soil minerals and a higher adsorption for polar compounds than for aliphatic and aromatic compounds. The water affects the VOC adsorption by decreasing the retention of these compounds to a greater extent for aromatic and aliphatic compounds than for the polar compound and by linearizing the isotherms. This reduction has been quantified by a simple exponential equation.

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