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Volatile organic compounds effective diffusion coefficients and fluxes estimation through two types of construction material.

UNLABELLED
Accumulation of volatile organic compounds (VOCs) that migrate inside buildings from underlying contaminated soils and groundwater poses human health risks. VOCs intrusion into buildings driven only by diffusion was reproduced by a laboratory-scale experiment. Effective diffusion coefficients and fluxes of a group of selected chlorinated solvents and BTEX through two types of isolation material - that is, concrete (anhydrite screed) and geo-membrane - were estimated. The laboratory experiment indicated that the diffusive transfer of pollutants through sediments into indoor air of buildings cannot be prevented by building sealing material, but it could be attenuated to a certain degree by concrete and up to non-detectable levels by the geo-membrane. Effective diffusion coefficients through concrete and geo-membrane ranged from 3.17 × 10(-2) to 5.90 × 10(-5) cm(2) /s and from 5.47 × 10(-6) to 5.50 × 10(-8) cm(2) /s, respectively.


PRACTICAL IMPLICATIONS
The vapor intrusion of volatile organic compounds (VOCs) into buildings has special relevance in human health risk assessment. Prediction of indoor air VOCs concentration by applying numerical or analytical models eventually fails due to the lack of input parameters, such as the VOCs effective diffusion coefficient through building material used as foundation or isolation material. Passive migration of VOCs from contaminated sites into indoor air through construction and isolation materials has not been extensively investigated. Our findings showed that the mass flux through building material is not negligible, but it could be reduced partly, and to a minimum, with the utilization of concrete and geo-membranes, respectively. As a result of our investigation, effective diffusion coefficients of BTEX and chlorinated solvents, as well as the correlation between specific compounds’ parameters and the estimated effective diffusion coefficient, are provided.