Soil vapour

Consider recent developments in our understanding of vapour intrusion into buildings. A number of soil vapour intrusion models have been developed including ... 

Inhalation of soil vapours Dermal contact with soil... 

For certain substances and conditions, different guideline values have been produced. For example, guideline values for certain metals and metalloids vary according to pFl (which affects the plant uptake pathway), and for organics vary according to the soil organic matter (SOM) content (which affects the plant uptake and inhalation of soil vapours pathways). 

Installation of low permeability barriers to reduce migration of soil vapours and contaminated groundwater Removes VOCs from soil atmosphere by vacuum pumping and encourages further volatilisation from soil particles and groundwater surface... 

Air sparging Groundwater Air is pumped through groundwater to air-strip volatile contaminants which are then removed by soil vapour extraction... 

Figure 1 Schematic of a soil vapour extraction system...

The at least 50% higher vapour pressure of MTBE, ETBE and diisopropyl ether (DIPE) compared to benzene describes the stronger volatilization tendency of these fuel oxygenates. Therefore these substances are amenable to soil vapour extraction. 

Remediation strategies may involve the use of one or more technologies with an increase in overall efficiency (e.g. multi-phase extraction - a combination of soil vapour extraction and groundwater pump-and-treat). From those presented above, an overview of hydrolysis in acidic conditions and adsorption on different media is presented in the following sections. 

Acid hydrolysis Use of solid acid catalysts positively tested at laboratory scale Soil vapour Amenable for ethers used as fuel oxygenates... 

Finally, the term resistance is occasionally used even in the case of only a low-concentration and very short term impact by the chemical. If the amoimt of the chemical and the time period over which the chemical exerts its influence is small compared to the mass of the liner material and the time of the solution process or other material changes, and if die naturally stronger impairment of the initially near-surface range of the material does not have any unfavourable effect on the effectiveness of the whole bulk material, then even a non-resistant material can withstand the impact without imfavourable changes with regard to the performance. Statements about resistance, however, must then describe the respective restriction of quantity of the chemical and exposure time of the liner material, the special impact scenario and the material behaviour under these conditions in detail. In such cases one should only speak about conditional resistance or compatibility, in order to emphasize that the material remains functional only under special conditions (low concentration in the aqueous solution or soil vapour, temporal and quantitative limitation of the e5q)osure). 

Soil vapour this occurs as a result of volatilisation from contamination that has been spilt or been placed in the ground... 

Environment Agency (2004b) Update on estimating vapour intrusion into buildings. CLEA Briefing Note 2. Available on-line at http //www.environment-agency. gov.uk/commondata/105385/soil vapour intrusion 749183.pdf (last accessed 10 June 2004). 

Environment Agency (2005a) Review of building parameters for the development of a soil vapour intrusion model. Environment Agency, Bristol, UK. 

Krylov, V. V. and C. C. Ferguson. 1998. Contamination of indoor air by toxic soil vapours The effects of subfloor ventilation and other protective measures. Building and Environment 33 331-347. 

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