Is it true that an equation written to allow passive soil-gas data to be converted to concentration units is now applicable for vapor-intrusion assessment?
Yes and no. It is true that an equation has been written by a firm providing passive soil-gas services. The analysis of passive soil-gas samplers gives the mass on the passive collector (e.g., micrograms [g] or some other form of relative units), not concentration. Concentration is mass/volume. So, to convert mass to concentration we must know the volume of vapor that comes into contact with the adsorbent during burial. There is no way to know this and no accurate way to measure this volume on a true passive sampler. Therefore passive soil-vapor data cannot be used for quantitative upward vapor-migration assessment, despite what you might be hearing. One could pump a known volume of air through a passive collector, similar to the NIOSH methods or TO-17, but this is far different than simply burying a collector into the ground and is actually a form of active soil-gas surveys.
