International audienceSoil vapor migration into house, with subsequent inhalation, is often the main exposure pathway to humans at sites contaminated with Volatile Organic Compounds (VOCs). In the case of VOCs contamination, quantification of indoor gas concentrations is therefore essential while assessing risks for human health. Two approaches are commonly used for quantification of indoor concentrations: indoor gas measurement or transfer modelization from the source (soil, soil vapor phase, groundwater). Model development is relatively well advanced but measurements for model calibration and "validation" hardly exist in the literature. Furthermore, predictions of indoor gas concentrations from different models may vary by several orders of magnitude, depending on the application. Therefore, the validity of the risk calculation obtained through models, and hence of the site management, remains highly uncertain. The research project presented here aims at providing such "validation" data. Long-term goals of the research are improvement of modelization and also development of tools for site-related model-selection. The program consisted in comparing modelization and experimental measurements on a test site. The site was a former factory with a concrete slab, contaminated with chlorinated solvents (trichloroethene and perchloroethylene) in unsaturated soils. Measurements concerned contaminant concentrations and fluxes in different media and at different transfer stages, but also key mode! parameters. The equations of Johnson & Ettinger and VOLASOIL models were used. Air concentrations measured at various times show significant variations, and also differ from model prediction by one or two orders of magnitude. Despite thorough parameter measurements, uncertainty on input values, related to site heterogeneity, induced high uncertainty in the modelization. The preliminary results presented here show intrinsic limitation of some measurements and hence of model validation, but also the need for data on more sites, including very important site instrumentation which would allow to document the impact of site-heterogeneity
