Improving Gas Permeability Measurements for Environmental Monitoring and Management

Intrinsic permeability is a crucial parameter to interpret soil gas data recorded from monitoring stations in different environmental settings. It is also fundamental for environmental management and pollution remediation. An improved version of a permeameter (PRM3) recently developed for environmental applications is presented and calibrated against a reference instrument (RADON-JOK produced by RADON v.o.s.). The innovations of this prototype are: i) the absence of the flow meter, and ii) a membrane pump in place of a rotary vane device. Proper calculation of the permeability from Darcy's law is provided, as well as a modified formula for permeability determination in volcanic areas. Actually, soil gas viscosity and permeability are affected by changing gas temperature and composition. The effects of these two parameters on soil gas viscosity and permeability are also displayed. The second part of the paper shows the employ of permeability measurements in environmental monitoring. The aim of these field-works was the study of lateral and vertical variability of soil permeability at a very small scale (step of 0.25 m) and the effect of intrinsic permeability on gas transport through the soil and on gas concentration along depth profiles. We chose 2 different test sites: Valle della Caffarella (Roma, Italy) and Solfatara Volcano (Pozzuoli, Italy) areas. A specific protocol, designed to check any interference among permeability measurements carried out at very close distances demonstrated that no disturbance is occurring. Intrinsic permeability profiles resulted to be good proxy indicators for the degassing style of the two areas. In both cases, it gave important hints to interpret environmental data and help in the management of the sites.