Interstitial Ad - Quality Assessment

Why and when to evaluate the interstitial air quality of soils?

Soil is composed of solid particles, water, and air. These latter two occupy the pore space between the solid particles. 

Naturally, when soil contamination is present and there is contamination by volatile substances, vapors can migrate throughout the soil's gas phase in various directions. These substances, commonly toxic and/or carcinogenic, migrate near the surface, accumulating under a slab or even reaching the surface and/or enclosed indoor spaces. 

Generally, due to the very low concentrations, the odor is not perceived. However, long-term human exposure to soil contamination, whether in the workplace or in a domestic environment, can lead to serious health problems.

An ETP, within its services, conducted a geoenvironmental investigation in an area with historical contamination. Due to the circumstances, it was necessary to assess whether volatile contaminants present in the soil and groundwater had migrated to the surface and consequently accumulated inside an enclosed space. To this end, ETP drilled a bore of approximately 1 meter depth and 10 cm diameter and installed a dedicated vapor point with a shut-off valve at the upper end

To sample the soil's interstitial air, the Wastewater Treatment Plant connected the dedicated vapor probe to a “Summa” Canister (a spherical or cylindrical container made of specially treated stainless steel).

 This container, with a vacuum inside, allowed for the collection of an interstitial soil air sample, in accordance with the research specifications. Once the sampling period was completed, the vapor probe was disconnected from the canister. 

The accredited laboratory proceeded with the analysis of the air sample, allowing conclusions to be drawn about the potential contamination present in the interstitial soil air.

Generally, due to very low concentrations, the odor is not perceived. However, long-term exposure of humans, whether in the workplace or domestic environment, can lead to serious health problems.

The assessment of the quality of interstitial soil air under and/or near buildings in contaminated areas is crucial for human health risk analysis. 

The measures to be taken after the investigation depend on the risks identified for both residents and workers in the area. This entire process culminates in the implementation of a remediation project, as defined by the recommendations from the Portuguese Environment Agency.

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