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During the last decade, soil contamination with volatile organic contaminants (VOC) received special attention because of their potential to cause indoor air problems. Moreover, research has shown that people spend 64% to 94% of there time indoors; therefore, the indoor air quality is of a primary importance for exposure to VOC. Human health risks to VOC-in cases of soil contamination-are often dominated by the exposure route 'inhalation of indoor air'. Exposure is often a result of vapour transport from the soil or groundwater to the indoor air of the building. Within human health risk assessments, a variety of algorithms are available that calculate transfer of soil gas to the indoor air. These algorithms suffer from a relatively high uncertainty due to a lack of representation of spatial and temporal variability. For such an application, these algorithms need to be further verified empirically against field observations so that they can be sufficiently reliable for regulatory purposes. This paper presents the accuracy for seven algorithms by using observed and predicted soil and indoor air concentrations from three sites, where the groundwater had been contaminated with aromatic and chlorinated VOC. The algorithms for vapour intrusion that are frequently used in European countries were included in this study and were Vlier-Humaan (Flanders), CSoil (Netherlands), VolaSoil (Netherlands), Johnson & Ettinger (USA), Risc (United Kingdom), and the dilution factor (DF) algorithms from Sweden and Norway. Three sites were investigated in more detail and samples were taken synoptically from the groundwater, soil and indoor air on four occasions. On the petroleum sites, the aromatic hydrocarbons benzene, toluene, ethylbenzene and xylenes were analysed and, on the dry cleaning sites, the chlorinated hydrocarbons tetrachloroethylene, trichloroethylene and cis 1,2-dichloroethene. To increase spatial resolution, measurements in groundwater and soil air were taken in three different zones at each site, in the close proximity of or in the building. During sampling, several relevant soil properties were measured like the bulk density, water and air filled porosity, soil temperature and depth of the groundwater. Also, building properties like the dimensions of the building and the quality of the floor were registered. The seven algorithms were applied to compare that observed with the predicted concentrations in soil and indoor air. The groundwater concentrations were used as a source contamination. The results from the algorithms were compared by using performance criteria to assess the accuracy of each algorithm. All calculations are presented in a box plot that contains the predicted soil or indoor air versus the observed concentrations. Results from the applied criteria are presented for each algorithm. Differences between predictions and observations were up to three orders of magnitude and can be partially related to the amount of parameters included in each algorithm and the mathematical concept used. For example, the ...

Vapour intrusion from the vadose zone-seven algorithms comparedProvoost, J.; Bosman, A.; Reijnders, L.; Bronders, J.; Touchant, K.; Swartjes, F. Published in:Journal of Soils and Sediments DOI:10.1007/s11368-009-0127-4 Link to publication Citation for published version (APA):Provoost, J., Bosman, A., Reijnders, L., Bronders, J., Touchant, K., & Swartjes, F. (2010). Vapour intrusion from the vadose zone-seven algorithms compared. Journal of Soils and Sediments, 10(3), 473-483. DOI: 10.1007/s11368-009-0127-4 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Abstract Background, aim and scope Vapours of volatile organic compounds (VOCs) emanating from contaminated soils may move through the unsaturated zone to the subsurface. VOC in the subsurface can be transported to the indoor air by convective air movement through openings in the foundation and basement. Once they have entered the building, they may cause adverse human health effects. Screening-level algorithms have been developed, which predict indoor air concentrations as a result of soil (vadose zone) contamination. The present study evaluates seven currently used screening-level algorithms, predicting vapour intrusion into buildings as a result of vadose zone contamination, regarding the accuracy of their predictions and their usefulness for screening purpose. Screening aims at identifying contaminated soils that should be further investigated as to the need of remediation and/or the presence of an intolerable human health risk. To be useful in this respect, screening-level algorithms should be sufficiently conservative so that they produce very few false-negative predictions but they should not be overly conservative because they might have insufficient discriminatory power. Materials and methods For this purpose, a comparison is made between observed and predicted soil air and indoor air concentrations from seven reasonably well-documented sites, where the vadose zone was contaminated with aromatic or chlorinated VOCs. The seven screening-level algorithms considered were: Vlier-Humaan (Be), Johnson and Ettinger model (USA), VolaSoil (NL), CSoil (NL), Risc (UK) and the dilution factor models from Norway and Sweden. Calculations are presented in two scatter plots (soil air and indoor air), each containing the predictions versus the observations. Differences between predicted and observed VOCs concentrations were evaluated on the basis of three statistical criteria to establish their accurateness and the usefulness for s...

Background, aim, and scope This paper discusses the variation between generic soil screening values (SSV) from 17 countries for 11 volatile organic contaminants (VOC). The variation between SSV was one to four orders-ofmagnitude (OOM) depending on the SSV and landuse type. What would be the variation if parameter values are harmonized between member states? Main Features The effect of harmonization was visualized by firstly reviewing the technical derivation procedure for SSV for 7 SSV from five countries and collecting all parameter values that are involved in the deviation. The parameters were subdivided in scientific (e.g. algorithm plus its parameter values), political (e.g. toxicological reference) or geographical (e.g. building and soil properties) elements.Secondly, new SSV were calculated with progressively harmonized sets of scientific and/or political parameter values, while the geographical parameters varied. Thirdly, the variation between SSV was compared before and after harmonization.Results Results show that harmonizing algorithms plus other scientific and political parameters are suited for harmonization. The variation decreases to 1 OOM, after scientific and political parameters were harmonized. Geographical parameters seem to have less impact on the differences between SSV. Discussion So, should we harmonize the procedures for deriving SSV between EU member states? The need for discussing harmonization is also raised by the upcoming EU Soil Framework Directive. Conclusions Clearly common generic SSV across all of Europe are not appropriate, since countries are allowed to include member state specific geographical and cultural elements and also political decision making. By harmonizing scientific and/or political parameters differences between SSV can be made more transparent between member states and it will encourage convergence in procedures among member states to ensure neutral conditions of competition and a coherent soil protection regime throughout Europe. Recommendations and perspectives To promote uniformity it is recommended to construct a toolbox for the calculation of human health risk exposure, carried by a European consensus, that includes different model algorithms for which fixed and flexible input parameters are made available. Fixed algorithm parameters are standardized and applied uniformly by all member states, e.g. physicochemical parameters, while flexible input parameters permits member states to include region or country specific parameter values and policy decisions.

In this study, the development and partial validation are presented for an analytical approximation method for prediction of subslab contaminant concentrations in PVI. The method involves combining an analytic approximation to soil vapor transport with a piecewise first-order biodegradation model (together called the analytic approximation method, including biodegradation, AAMB), the result of which calculation provides an estimate of contaminant subslab concentrations, independent of building operation conditions. Comparisons with three-dimensional (3-D) simulations and another PVI screening tool, BioVapor, show that the AAMB is suitable for application in a scenario involving a building with an impermeable foundation surrounded by open ground surface, where the atmosphere is regarded as the primary oxygen source. Predictions from the AAMB can be used to determine the required vertical source-building separation, given a subslab screening concentration, allowing identification of buildings at risk for PVI. This equation shows that the “vertical screening distance” suggested by U.S. EPA is sufficient in most cases, as long as the total petroleum hydrocarbon (TPH) soil gas concentration at the vapor source does not exceed 50–100 mg/L. When the TPH soil gas concentration of the vapor source approaches a typical limit, i.e. 400 mg/L, the “vertical screening distance” required would be much greater.