| Popis: |
In a number of dwellings in a residential area in Arnhem, close to a site with heavy industrial pollution, high concentrations of perchloroethylene and trichloroethylene were found in indoor air. It was assumed that the pollutants entered the dwellings through the crawl spaces, located underneath. Isolation of the crawl spaces by two layers of concrete and an damptight film however, did not help to mitigate the indoor concentrations of perchloroethylene and trichloroethylene. An investigation was undertaken to shed some light on the transport mechanisms from soil to crawl space and from crawl space to indoor air. As a first step, the concentrations of 45 volatile organic compounds, among which perchloro- ethylene and trichloroethylene, were assessed in five to six rooms in each of six dwellings. Infiltration and exfiltration was assessed with a freon tracer. However, these tracer measurements proved to be incorrect. In the second stage of the investigation, the concentration of perchloroethylene was measured in the living room and in the crawl space of 28 dwellings. After these measurements it was concluded that in most dwellings the crawl space was still an important source of perchloroethylene, despite the isolation measures mentioned above. It was assumed that a convective flow of polluted air took place from the soil system, along the edges of the damptight film, into the crawl space. The second stage of the investigation led us to assume that there was a clear geographic distinction between houses with and houses without raised concentrations of perchloroethylene. |
