soil gas radon concentration and permeability at “valle
TRANSCRIPT
Soil Gas Radon Concentration and PermeabilitySoil Gas Radon Concentration and Permeability
at “Valle dellaat “Valle della Caffarella” Test Site (Roma, Italy). Caffarella” Test Site (Roma, Italy).
Evaluation of Gas Sampling Techniques and Radon MeasurementsEvaluation of Gas Sampling Techniques and Radon Measurements
Using Different ApproachesUsing Different Approaches
Italian teamMauro Castelluccio, Massimo Moroni, Paola Tuccimei
Czech teamMatej Neznal, Martin Neznal
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
1 2
3
4
5
Tevere river
GRA ring road
0 1 2 km
ROMA
N Aniene river
Almone river
Roma (Italy)
Simplified geological map
1 1 PlioPlio--PleistocenePleistocene marine marine tototransitionaltransitional depositsdeposits
2 2 SabatiniSabatini districtdistrict volcanites volcanites
3 Colli Albani 3 Colli Albani districtdistrict ignimbritesignimbrites
4 Colli Albani 4 Colli Albani districtdistrict lavaslavas
5 5 AlluvialAlluvial sedimentssediments ofof Tevere Tevere River and River and itsits tributariestributaries
Valle della Caffarella Test Site
12
3
45
Seasonal Change of Soil Radon Concentration
30 cm 80 cm Rain (mm)
Winter 07 Winter 08 Winter 09
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPING September 22nd – 25th, 2010 - Prague, Czech Republic
PREVIOUS WORK AT VALLE DELLA CAFFARELLA TEST SITE (1)
Monitoring at Permanent Station 1, on Colli Albani ignimbrites
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPING September 22nd – 25th, 2010 - Prague, Czech Republic
SOIL RADON MAPPING
PREVIOUS WORK AT VALLE DELLA CAFFARELLA TEST SITE (2)
PERMANENT STATION 1
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPING September 22nd – 25th, 2010 - Prague, Czech Republic
Soil Radon – Winter Soil Radon - Summer
PREVIOUS WORK AT VALLE DELLA CAFFARELLA TEST SITE (3)
SOIL RADON MAPPING – 80 cm depth
1 2 3 4
Sampling stations Sampling stations December 2009 and June 2010December 2009 and June 2010
Permanent Station
Mobile Station
Inner profile(RAD 7)Outer profile(Radon v.o.s.)
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
THIS WORK
Sampling depths:
Shallow: (~ 30 cm)
Deeper: (~ 80 cm)
Italian Team � Durrridge approachDurridge Probe and alpha counting (RAD 7)
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
Roma, 11 e 12 giugno 2010Il radon: un rischio geologico 8
• ID 7 mm
• OD 11 mm
• Point maximum diameter 13 mm
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
Italian Team � Durrridge approachDurridge Probe with fixed point
Roma, 11 e 12 giugno 2010Il radon: un rischio geologico 9
Special care to tamp down the soil around the probe
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
Main concern : leakage of fresh air down to the sampling point
Roma, 11 e 12 giugno 2010Il radon: un rischio geologico 10
www.radon-vos.cz
www.radon-vos.cz
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
Check Team � Radon v.o.s. approach Radon v.o.s. Probe and Lucas cell + Ionization Chamber
• ID 8 mm
• OD 12 mm
• Point maximum diameter 12 mm
“LOST” TIP
www.radon-vos.cz
SOIL GAS PERMEABILITY MEASUREMENTS
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
)**()*(
tpFVk ∆= µ
(Neznal & Neznal, 2005)
V: air volume in the rubber suck µ: air dynamic viscosity at 10°C F: Shape factor of the probe ∆p: pressure difference between the surface and the s ampling depth t: opening time of the cell
The principle consists of air withdrawal by means of negative pressure driven by a rubber sack, with one or two weights.
Air is pumped out from the soil under constant pressure through the probe with a constant surface of contact between the probe head and the soil.
The gas permeability (k in m2) is calculated using the known air flow through the probe.
SOIL GAS PERMEABILITY USING THE RADON-JOK PERMEAMETE R
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
•Winter campaign
• Total of 60 soil radon measurements including replicates for Lucas Cells and Ionization Chambers
• Soil Radon and Thoron measurements using RAD7
• 21 soil gas permeability determinations
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
Results of the Winter campaign
Deeper depth (~ 80 cm):
� The three methods (alpha counting, Lucas Cell and Ionization Chamber) gave comparable results � Durridge approach up to 15 % lower
�Low permeability � averagely in the range of 10-13 - 10-14 m2
Shallow depth (~ 30 cm):
� Durridge approach gave results 60 % sistematically lower than Radon v.o.s.
� Higher permeability � 2.5 · 10-12 m2
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
100 – 200 kBq / m3
30 – 180 kBq / m3
Roma, 11 e 12 giugno 2010Il radon: un rischio geologico 15
Enhancedeffect at
shallow depth
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
Discussion
Durridge approach gave lower soil radon concentrati ons because of leakage of
fresh air down to the sampling point
DURRIDGE RADON V.O.S.
Atmospheric air
Soil gas radon from shallower
depth
HOLLOW SPACE
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
Summer campaign
� Replication of winter measurements� Increased care to seal the probe hole� Testing a mixed approach at station C:
Radon v.o.s. probe + RAD7 continuous monitor
Results of the Summer campaign
� Lower values of soil radon and higher permeability compared to winter
Deeper depth (80 cm):
� The three methods (alpha counting, Lucas Cell and Ionization Chamber) gave comparable results �Durridge approach just 5 % lower
Shallow depth (30 cm):
� Reduced differences between the two approaches
� The mixed approach gave comparable results with Radon v.o.s. approach
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic
40 – 160 kBq / m3
20 – 50 kBq / m3
Conclusions
•Gas sampling techniques affect soil radon concentration results more than analytical methods
• Fresh air leakage down the sampling hole is is due to the combined effect of the probe tip relative size and the poor sealing of the sampling hole.
• Summer soil radon concentration are lower because of enhanced radon release to the atmosphere when soil is drier, warmer and more permeable.
•Soil gas permeability is a crucial parameter to interpret spatial soil radon variability and seasonal changes
10th INTERNATIONAL WORKSHOP on the GEOLOGICAL ASPECTS OF RADON RISK MAPPINGSeptember 22nd – 25th, 2010 - Prague, Czech Republic