Radon geochemistry of groundwater and soil gas is useful for detecting, quantifying and
monitoring contamination by Non Aqueous Phase Liquids (NAPL).
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Radon is present in readily detectable concentrations in nearly all subsurface environments.
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Radon has an affinity for organic liquids, and in the presence of NAPL the radon concentration
in groundwater or soil gas is reduced due to partitioning into the organic NAPL phase.
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Thus, by measuring radon it is often possible to identify those locations where NAPL is likely
present, and to
limit the use of more costly procedures when searching for hydrocarbon contamination.
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The reduction in radon concentration in groundwater can sometimes be quantitatively correlated
with the amount of NAPL present, and it is sometimes possible to obtain
quantitative estimates for NAPL saturation.
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Semprini et al. (see below) propose the use
of radon in groundwater "for monitoring changes in NAPL quantities resulting from remediation activities".
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In the case of soil gas, radon:thoron ratios are more sensitive still.
These ratios have proven successful in uranium exploration
Link
and should prove useful in NAPL searches as well.
We have a formula to resolve radon from thoron giving on-the-spot results with our field
instruments.
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INSTRUMENTS
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We measure: radon - radium - thoron - radon daughters - alpha radiation.
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The
Lucas cell
is recognized as the most sensitive and reliable method for these elements.
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Our instruments are used around the world in exploration for uranium, oil & gas, groundwater and hydrothermal,
and in environmental protection, health physics, earthquake prediction, and evaluation of hydrocarbon and NAPL contamination.
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In the radon business since 1968, our latest major instrument update was 2015.
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Modern, low-power, field-rugged electronics. Some earlier versions still working after 35 years.
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Continuous real-time monitoring and data recording.
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Winter and summer, from the Sahara Desert to the Canadian Shield, our instruments have faced up to severe field conditions.
- Intrinsically safe functions.
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Sensitive to geochemical trace levels necessary for radon in lake water and for radon-thoron isotope ratios.
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Can work in a tent without electricity or be carried from point to point in the field.
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50 readings per day. Results available immediately.
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Rechargeable battery pack good for a long day in the field and recharges in a few hours.
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Can be operated by junior personnel if carefully supervised.
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Same instruments used for radon and radium in soil, sediment,
plant parts, rocks, water, soil gas, air, and snow, and for radon daughters in air.
- EPA compliant.
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Click here for more details of instruments.
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Click here for or other instruments, components and
accessories we provide
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Technical specification sheets and pictures of our instruments provided on request.
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Multilingual consulting and training (if required).
For instruments contact
R.H. Morse & Associates Ltd.
1-416-269-9979
morse@finderschoice.com
skype: robert.morse.toronto |
Robert H. Morse, Ph.D., P.Eng.
July 20, 2010
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ANNOTATED BIBLIOGRAPHY
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Dyck, W. and J.R.Jonason, 2000. Geochemical Remote Sensing of the Sub-Surface. Edited by: Hale, M. © 2000 Elsevier,
Chapter 11 on radon.
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An extensive scientific discussion of the geochemistry of radon
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K. Fan, T. Kuo, Y. Han, C. Chen, C. Lin and C. Lee, 2007
Radon distribution in a gasoline-contaminated aquifer.
Radiation Measurements
Volume 42, Issue 3, Pages 479-485
Link
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Abstract: "Naturally occurring radon-222 gas in groundwater was investigated as a partitioning tracer to detect non-aqueous phase liquid
(NAPL) in a gasoline-contaminated aquifer. The radon-222 activity of groundwater decreased significantly from an average
of 7.38 +/- 1.68 Bq/L measured in monitoring wells located upgradient in the uncontaminated zone to an average of
2.30 +/- 0.60 Bq/L measured in monitoring wells inside the NAPL source zone.
Meanwhile, the radium-226 concentrations measured in aquifer matrix were virtually homogeneous at several locations
both upgradient of and inside the NAPL source zone. Furthermore, the NAPL concentration obtained from the
Radon Deficit Factor agrees reasonably with the results derived from direct sampling and chemical analysis of soil samples
taken from the residual NAPL source zone.
The field results of this study confirmed the general applicability of groundwater radon to detect residual NAPL source zone."
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J.E. Garcia-Gonzalez, M.F. Ortega, E. Chacon, LF. Mazadiego, E. De Miguel, 2008
Crupo de Ceoquimica Ambiental, Universidad Politecnica de Madrid,
E.T.S. Ingenieros de Minas, Alenza 4, 28003 Madrid, Spain
Field validation of radon monitoring as a screening methodology
for NAPL-contaminated sites.
Applied Geochemistry, Volume 23, Issue 9, September 2008, Pages 2753-2758
Link
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Measured radon-222 in soil gas.
If a non aqueous phase liquid (NAPL) is present,
radon is enriched in the NAPL and depleted in the gas phase.
There is less radon free to enter our sampling tool and we should find low radon values over
hydrocarbon enrichments.
Based on a field study of 67 station, the authors conclude:
"...as was
theoretically predicted, reductions of Rn concentration in
soil air above subsurface accumulations of hydrocarbons
can be deterministically differentiated from background
values (the former being between 5 and 10 times lower
than the latter) under real field conditions."
"Emanometry has the advantage that it can locate
and determine the boundaries of free-phase plumes of
contaminants even when the amount of organic vapors
reaching the surface is very low or non-existent."
The paper cites a number of studies which gave similar results.
Note: It is likely that if the authors had used our formula to distinguish between
radon and thoron,
and plotted both the radon and radon/thoron ratios, results would have been better.
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Michael Schubert , Klaus Freyer, Hans-Christian Treutler and Holger Weiss, 2001
UFZ Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany.
Using the soil gas radon as an indicator for ground contamination by non-aqueous phase-liquids.
Journal of Soils and Sediments, Volume 1, Number 4 / December, 2001
.
Link
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Quote from abstract:
"Both the results of the lab experiments and the on-site findings demonstrate that the soil-gas radon concentration can be used
as an indicator for subsurface NAPL contamination. The investigation showed that NAPL-contaminated soil volumes give rise
to anomalous low soil-gas radon concentrations in the close vicinity of the contamination. The reason for this decrease in the
soil-gas radon concentration is the good solubility of radon in NAPLs, which enables the NAPLs to accumulate and ‘trap’
part of the radon available in the soil pores."
Note: It is likely that if the authors had used our formula to distinguish between
radon and thoron,
and plotted both the radon and radon/thoron ratios, results would have been better.
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Michael Schubert, Albrecht Paschke, Steffen Lau, Wolfgang Geyer and Kay Knoller, 2006.
UFZ Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany.
Radon as a naturally occurring tracer for the assessment of residual NAPL contamination of
aquifers. Environmental Pollution, February 2007, Pages 920-927.
Link
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Abstract: "The noble gas radon has a strong affinity to non-aqueous phase-liquids (NAPLs). That property makes it
applicable as naturally occurring partitioning tracer for assessing residual NAPL contamination of aquifers. In a NAPL
contaminated aquifer, radon dissolved in the groundwater partitions preferably into the NAPL. The magnitude of the resulting
radon deficit in the groundwater depends on the NAPL-specific radon partition coefficient and on the NAPL saturation of the
pore space. Hence, if the partition coefficient is known, the NAPL saturation is attainable by determination of the radon deficit.
After a concise discussion of theoretical aspects regarding radon partitioning into NAPL, related experimental data and results
of a field investigation are presented. Aim of the laboratory experiments was the determination of radon partition coefficients of
multi-component NAPLs of environmental concern. The on-site activities were carried out in order to confirm the applicability
of the "radon method" under field conditions.
The paper presents the theoretical concept and experimental results which confirm the applicability of naturally occurring radon
for assessing residual NAPL contamination of aquifers."
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M. Schubert, P. Pena, M. Balcazar, R. Meissner, A. Lopez and J.H. Flores, 2005
UFZ Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany.
Determination of radon distribution patterns in the upper soil as a tool for the localization of subsurface NAPL contamination
Radiation Measurements, Volume 40, Issues 2-6 , November 2005, Pages 633-637
Link
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Abstract: "A radon survey was carried out at an abandoned military airfield, heavily contaminated with non-aqueous
phase-liquids (NAPLs). Geo-statistical analysis of the data was used to confirm the validity of the chosen soil gas sampling
pattern. The survey revealed a non-uniform distribution of the soil gas radon concentration in the upper soil in spite of a
virtually homogenous geological situation. The radon distribution pattern showed minimum zones with radon concentrations
decreased by up to 90% with regard to the local background level. The determined radon minimum anomalies could be
explicitly associated with the NAPL subsurface contamination. The observed effect is due to the strong partitioning of radon
into NAPLs from soil gas or groundwater. Corresponding partitioning coefficients were determined in the laboratory for some
NAPL. As result of the study, it was shown that naturally occurring soil gas radon has the potential to be used as an indicator
for the localization of subsurface NAPL contamination."
Note: It is likely that if the authors had used our formula to distinguish between
radon and thoron,
and plotted both the radon and radon/thoron ratios, results would have been better.
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Semprini, 1992.
Stanford University (Partially Supported by the U. S. Department of Energy)
Radon-222 Method for Locating and Quantifying Contamination by Residual Non-
Aqueous Phase Liquids in the Subsurface:
Link (page 30)
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Measured radon-222 in solution in groundwater.
Refers to some work commenced in 1989 at CFB Borden in Ontario, in cooperation with
University of Waterloo.
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Semprini, Lewis ; Istok, Jack, 2008.
OREGON STATE UNIV CORVALLIS DEPT OF CIVIL CONSTRUCTION AND ENVIRONMENTAL ENGINEERING
Radon-222 as Natural Tracer for Monitoring the Remediation of NAPL Contamination in the Subsurface.
Technology Certification Program,
U.S. Department of Defense
Link
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Measured radon-222 in solution in groundwater.
"This Cost and Performance Report describes the use of naturally occurring radon-222 (Rn) as a partitioning tracer for
locating and quantifying NAPL contamination in the subsurface and for monitoring changes in NAPL quantities resulting from
remediation activities."
"...it is an easy method to implement and apply with other
methods, such as monitoring the chlorinated solvents concentration in groundwater samples. The
best use of the method would be as a monitoring method where changes in radon concentration
in groundwater samples could be tracked over time as a means of monitoring the progress of
remediation."
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