DURRIDGE RAD7 User manual

WATER PROBE
Passive, Slow Response Radon in Water Accessory for the RAD7
User Manual!
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TABLE OF CONTENTS
INTRODUCTION 4
Fig. 1 Assembled Water Probe 4
1 WATER PROBE SETUP 5
1.1 Connections 5
1.1.1 Air Loop 5
Fig. 2 RAD7 Water Probe Standard Setup 5
1.1.2 DRYSTIK 5
1.1.3 RAD7 and Exchanger Location 5
1.1.4 Temperature Probe 6
1.2 Water Flow and Source 6
1.3 Air Flow and Pump Setting 6
1.4 Protocol 6
1.4.1 RAD7 Protocol, Mode and Cycle 6
1.4.2 Water Probe Protocol 6
1.4.3 User Protocol 6
2 MEASUREMENT PROCEDURE 7
2.1 Start Up 7
2.1.1 Temperature Probe 7
2.1.2 Start Measurement 7
2.2 Speed of Response 7
2.2.1 Measurement in Progress 7
2.2.2 In!uencing Factors 7
2.2.3 Air Flow Rate 7
2.2.4 RAD7 Mode 8
2.3 Long Term Measurement 8
2.3.1 Desiccant 8
2.3.2 Memory 8
3 DATA 9
3.1 Data Handling 9
3.1.1 Infrared Printer 9
3.1.2 RAD7 Memory 9
3.1.3 CAPTURE Software for Windows and macOS 9
3.1.4 Temperature Data 9
3.1.5 Time Relationship 9
3.2 Data Conversion Formulas 10
3.2.1 Fritz Weigel Formula 10
Table of Contents
2

3.2.2 Schubert Et. Al. Formula 10
Fig. 3 The CAPTURE Run Parameters Window 10
4 DRYSTIK 11
4.1 Passive DRYSTIK 11
4.2 DRYSTIK ADS-3 and ADS-3R 11
4.3 Effect on Response Time 11
4.4 Custom DRYSTIK Settings 11
Fig. 4 Water Probe con#guration with Active DRYSTIK 12
5 CARE, MAINTENANCE, AND TROUBLESHOOTING 13
5.1 Water Catastrophe 13
5.2 RAD7 Care 13
5.3 Exchanger Care 13
5.4 Desiccant Regeneration 13
5.5 Water Probe Troubleshooting 13
5.5.1 Air Path Integrity 13
REFERENCES 14
Table of Contents
3

INTRODUCTION
e Water Probe is an accessory for the DURRIDGE RAD7 Electronic Radon Detector. It is a device to bring the
radon concentration in a closed air loop into equilibrium with the radon concentration in the body of water in
which it is submerged. It consists of a length of hydrophobic yet gas-permeable membrane tubing, called an
“exchanger”, that brings the radon in a closed air loop into equilibrium with the surrounding water. e radon in
the air loop is monitored continuously by the RAD7.
e partition coefficient, the ratio of radon concentration in the water to that in the air at equilibrium, is
determined by the temperature at the air/water interface. is temperature is measured with a temperature probe
inserted into the water. As an example, at a water temperature of 10 degrees Celsius, the partition coefficient is
about 1:3. at means there is three times higher concentration of radon in the air than in the water, so there is,
in effect, a gain of three times in the sensitivity of the system to radon in water, compared to radon in air.
It takes time for the water to deliver radon to the air loop and for the RAD7 to respond to the changed radon
concentration. With optimum configuration the response time of the system is around 2 hours.
Fig. 1 Assembled Water Probe
Introduction
4
CAUTION
There is a potential for biofouling to occur in long-term monitoring applications. The
Water Probe should therefore be inspected periodically to ensure that there is good
contact between the radon exchange tubing and the surrounding water.

1 WATER PROBE SETUP
1.1 Connections
1.1.1 Air Loop
Two pieces of tubing connect the RAD7 and drying
unit to the Water Probe air/water exchanger, as
shown in Fig. 2. ese two pieces of tubing can be
several tens of meters long. e standard tubing
supplied with the RAD7/Water Probe is sufficient for
a connection up to ten feet between the exchanger
and the RAD7.
Connect the OUTLET of the RAD7 to either of the
Water Probe air ports. For this, the 5long, 3/16" ID
tubing, with a 1/8" ID section at one end, may be
used. e 1/8" end fits on the RAD7 outlet, and the
3/16" end fits the Water Probe. Connect the other
3/16” hose connector between the other Water Probe
air port and the Laboratory Drying Unit.
Connect the other end of the Laboratory Drying Unit
(there should be at least one inch of blue desiccant
leat this end) to the air inlet filter (with 1/8" ID
tubing at the filter end), which is then placed on the
RAD7 INLET. e Luer taper ensures an airtight
connection.
Fig. 2 RAD7 Water Probe Standard Setup
1.1.2 DRYSTIK
Please note that the above instructions are for use of
the Water Probe without a DRYSTIK humidity
exchanger. A DRYSTIK, if available, should be placed
between the exchanger and the drying unit, and the
outer sheath should be purged with dry air from the
RAD7 outlet. See Fig. 3 in Section 3. More details are
provided in the DRYSTIK user’s manual.
1.1.3 RAD7 and Exchanger Location
Place the RAD7 on a clean, dry surface. If it has to be
located in a harsh environment, then it should be
protected from the elements (especially water). A
simple way to do this is to place the RAD7 inside a
large transparent plastic bag, such as the one in which
it was originally shipped. e bag opening should be
gathered around the inlet and outlet tubes, so that the
instrument is inside a closed space, completely
Introduction
5

protected from the elements, while still allowing
observation of the LCD and print-out, and operation
of the key pad.
e Water Probe may be lowered directly into the
body of water that is to be measured. Alternatively, it
can be placed in a container with the incoming water
released at the bottom of the container and
overflowing or exiting through an outlet at the top.
e water in the container should be completely
refreshed with incoming water at least twice an hour.
1.1.4 Temperature Probe
If you are using a Temperature Probe (sold
separately), it should be inserted into the water as
close as possible to the membrane tubing where the
water-air radon exchange is taking place. e probe
should be plugged into the Temperature Data Logger,
which should be put in its own plastic bag to protect
it, once it has been launched.
1.2 Water Flow and Source
e Water Probe should be fully submerged below
the surface of the water, which should be clean and
free from debris. e flow of water through the Water
Probe should be sufficient to replace the water
around the device on a timescale shorter than its
response time (roughly 2 hours). is condition is
easily met for any flowing body of water, but care
should be taken when planning measurements of
stagnant water.
1.3 Air Flow and Pump Setting
For proper air flow, the RAD7 pump should be set to
Auto. e pump, in Auto operation, pumps for five
minutes at the beginning of every cycle, and then for
one minute in every five throughout the remainder of
the cycle.
1.4 Protocol
1.4.1 RAD7 Protocol, Mode and Cycle
First, please read the RAD7 manual and learn how to
use the instrument for measurement of radon in air.
e RAD7 should normally be operated with mains
power applied, to keep the batteries in a fully charged
condition.
Set the RAD7’s Mode to Auto, which starts the
instrument in Sniffmode (counting 218-polonium
decays only), and switched automatically to Normal
Mode (counting 218-polonium and 214-polonium
decays) aer 3 hours, once secular equilibrium
between 222-radon, 218-polonium and 214-
polonium has been reached. Due to the radioactive
half lives of intermediate radionuclides in the radon
decay chain, the RAD7’s response time in Normal
mode is around 3 hours. Short-term changes in radon
concentration are not usually of interest in long-term
monitoring applications, but in order to minimise the
response time, the RAD7’s Mode may instead be set
to Sniff. In that case, the response time of the entire
apparatus is limited by the exchange of radon from
the water to the air, rather than by radioactive decay.
Note that the RAD7’s sensitivity in Sniffmode is
approximately 50% of its Normal mode sensitivity.
e length of each cycle is chosen by the user. Since
the air-water equilibration takes 2 hours or more,
there is little to be gained by choosing a cycle time
shorter than, say, 1 hour.
1.4.2 Water Probe Protocol
Switch on RAD7. Push the MENU key. Go to:
SETUP, CYCLE, push [ENTER]. Set the cycle time
required (as discussed above).
SETUP RECYCLE to 00, for continuous operation.
SETUP MODE: As discussed above, choose AUTO.
SETUP THORON: Choose OFF.
SETUP PUMP: As discussed above, choose AUTO.
SETUP TONE: Choose what you like.
SETUP FORMAT: Choose what you like, but LONG
format uses more paper. You will probably not need
to use the printer at all, in the field.
SETUP UNITS: Your choice.
SETUP SAVUSER: Push [ENTER]. When it says “Are
you sure?” choose “Yes” and push [ENTER].
1.4.3 User Protocol
You now have your personalized USER protocol
saved. To recall your settings, go to SETUP,
PROTOCOL, USER and push [ENTER]. To make a
change, simply display the parameters to be changed,
make your changes then, once more, go to SETUP
SAVUSER and save them.
Introduction
6

2 MEASUREMENT PROCEDURE
2.1 Start Up
2.1.1 Temperature Probe
If you are using a Temperature Probe (sold
separately), load the temperature logger soware and
connect the Temperature Logger to the PC using the
serial cable provided. Configure the logger to take
temperature readings at frequent intervals (these may
be far more frequent that the RAD7 test cycles.)
Choose the second (external) temperature sensor.
Connect the Temperature Probe to the logger and
note that when you hold the probe the indicated
temperature rises.
When everything is set, begin recording. e logger’s
LED may flash periodically. Once the logger has
begun running, you may remove the serial cord from
both the logger and the PC.
Warning! Make sure that previous temperature data
has been downloaded before launching the logger.
e launching process may erase previous data.
Insert the Temperature Probe into the water next to
the Water Probe.
2.1.2 Start Measurement
Switch on the RAD7 (have the printer switched on if
you are using it. e RAD7 will then print a header
for the data printout, including a review of the setup,
before it gives you a ‘Test’ prompt.)
Provided that the RAD7 has been set up properly (see
above), at the ‘Test’ prompt, push [ENTER] then the
right arrow, to see ‘Test Start’ on the LCD, then
push [ENTER] to start the test.
2.2 Speed of Response
2.2.1 Measurement in Progress
e instrument is now measuring the radon in the
closed air loop that includes the Water Probe’s
membrane tubing. With high radon activity
concentration in the surrounding water it will take
half an hour or more before there is much of a
reading, and 2 - 3 hours before you can rely on the
count rate being close to the equilibrium value. Aer
that you need to accumulate sufficient counts for the
precision desired. For example, 100 counts would
give a reading with a standard deviation of 10%. At
very low concentrations, it may take hours, and
averaging over many cycles, to reach a sufficiently
precise value.
2.2.2 Influencing Factors
ere are two processes requiring time. One is for the
air in the closed loop to approach equilibrium with
the surrounding water and the other is for the RAD7
to respond to the changed radon concentration in the
air loop. e first is a property of the exchange tubing
and the second is determined by the half life of the
first daughter of radon, namely 218-polonium (Sniff
mode), or the half lives of intermediary 214-lead and
214-bismuth (Normal mode). See the RAD7 manual,
Section 3 for more details.
2.2.3 Air Flow Rate
ere is also a small contribution to the response
time from mixing of the radon-laden air around the
closed air loop. is depends on the duty cycle of the
RAD7’s pump. However, even with the pump set to
AUTO, this delay is only around 20 minutes, which is
small compared with the 2-hour timescale for radon
exchange across the membrane tubing and the 3-hour
95% response time of the RAD7 running in Normal
mode. For this reason, it is almost always sufficient to
set the pump to AUTO mode, in which the air is
circulated around the closed air loop for one minute
in every five. Air will remain stationary in the Water
Probe for four minutes before moving to the
Laboratory Drying Unit where it waits another four
minutes before entering the RAD7. While in the
Water Probe, the stationary air may approach
equilibrium with the water thus inhibiting further
radon transfer from the water to the air. It will be
about 15 to 20 minutes before that parcel of air
returns to the Water Probe. We can therefore estimate
that the response time of the system will be increased
by about 20 minutes if the pump is set to AUTO
Having the pump set to AUTO would normally be
associated with having the RAD7 cycle time of 30
minutes or longer. So an extra 15 to 20 minutes on
the response time will not be excessive.
Section 2 Measurement Procedure
7

2.2.4 RAD7 Mode
In AUTO (the default) mode, the RAD7 will
automatically switch from SNIFF mode to NORMAL
mode aer three hours into the run. is is to take
advantage of the additional counts provided by the
214-polonium decays that will, by then, have
approached equilibrium with the (steady) radon
concentration in the measurement chamber.
For slow, long-term measurements with long cycle
times AUTO mode for the RAD7 is appropriate. e
RAD7’s response time will be a couple of hours or so.
For fastest response, the RAD7 can be forced to stay
in SNIFF mode (Setup, Mode, Sniff [ENTER]).
It will then always count only the 218-Po decays,
giving it a 13-minute 95% response time. However,
the improvement in overall response time is marginal
due to the 2-hour timescale for radon exchange
across the membrane tubing, and this has to be
weighed against the reduction in sensitivity (and
consequent reduction in precision) that comes with
switching from NORMAL to SNIFF mode.
2.3 Long Term Measurement
2.3.1 Desiccant
As set up, above, the system will continue making
measurements indefinitely. ere are, however,
various resources that are being used up in the
process, and which must be replenished. e most
obvious is the desiccant. A new, or regenerated,
Laboratory Drying Unit will normally last for about
ten days of continuous use in a temperate climate. In
this application, however, it is operating in a closed,
dry air loop where the only moisture entering the
loop comes from tiny leaks of ambient air. erefore,
each Laboratory Drying Unit can be expected to last
several weeks. When the remaining length of blue
(dry) desiccant is less than one inch, the desiccant
should be replaced. Please see the RAD7 manual on
desiccant regeneration. If the desiccant is not
replaced, and the relative humidity in the instrument
rises above about 20%, then the sensitivity drops off
and the reading is lower than the true value.
2.3.2 Memory
e capacity of the internal memory of the RAD7 is
1,000 records or cycles. If each cycle is two hours,
that would be data for 2000 hours, or just over 80
days. Every time the desiccant is changed, therefore,
all the stored data should be downloaded to a PC,
backed up, and erased from the RAD7 memory. It is
also possible to monitor the RAD7’s output remotely,
including the relative humidity, which can be used as
an indicator that the desiccant needs to be replaced.
Please see the CAPTURE manual for more
information on remote monitoring.
Section 2 Measurement Procedure
8

3 DATA
3.1 Data Handling
3.1.1 Infrared Printer
e RAD7’s infrared printer will print out data in
short, medium or long format - see the RAD7 manual
for details. In the long format, there will be a
spectrum printed at the end of every cycle.
3.1.2 RAD7 Memory
e internal memory of the RAD7 stores numerous
properties for each data cycle, including the date and
time, radon concentration, live time, total counts, and
a host of other parameters; see the RAD7 manual for
details. e data can be downloaded to a computer at
any time, during or aer a run, using DURRIDGE’s
CAPTURE soware, which is discussed below.
Once the data has been downloaded and backed up
securely, you should erase the data on the RAD7, to
prevent it from accumulating and filling the device’s
memory.
3.1.3 CAPTURE Software for Windows and macOS
Data recorded to the RAD7 may be downloaded and
graphed using DURRIDGE’s CAPTURE soware,
which is available from the DURRIDGE website
[www.durridge.com/soware/capture/].
To view Water Probe data in CAPTURE, first make
sure RADLINK is installed on the RAD7, and
connect the RAD7 to the computer using the
provided USB to serial adaptor cable. Download the
RAD7 data. en, if using a Temperature Logger,
obtain its data as explained in Section 3.1.4. Aer the
radon data is opened in a Graph Window, select a
run of Water Probe data, open the Run Parameters
Window, and set the Radon Measurement Method to
Water Probe as shown in Fig. 3 on the following page.
Next specify the water temperature source as
instructed. e water temperature information is
used by CAPTURE to calculate the radon in water
concentrations. For detailed instructions, please see
the Water Probe information in the CAPTURE user’s
manual, which is available from the DURRIDGE
website.
3.1.4 Temperature Data
To obtain the water temperature data (optional),
connect the temperature logger to the computer and
run its soware to download the data. e program
will take a moment to download the entire memory
of the logger, and then display it as a graph. You
should save it to your hard drive before doing
anything else. You can then export it to a comma-
delineated .TXT file for use with CAPTURE, or for
incorporating into a spreadsheet or database
program.
Alternatively, the temperature logger data can be read
directly into CAPTURE using the controls in the Run
Parameters Window; see the instructions in the
CAPTURE user’s manual for details.
Warning! Make sure that the Temperature Logger
data is properly downloaded and saved to the
computer before starting the logger again. Restarting
the logger operations may erase its previous data.
3.1.5 Time Relationship
A water temperature reading is made at the moment
in time indicated with the reading. A radon reading,
in contrast, is the average value taken over the cycle
whose end occurred at the time indicated. For
constant radon and temperature values this is of no
consequence, but if the temperature was changing
quickly then the temperature readings during the
course of the radon cycle should be averaged to give
the average temperature at the air-water interface
when the radon being measured was leaving the
water. is is handled automatically by the
CAPTURE soware.
Section 3 Data
9

3.2 Data Conversion Formulas
3.2.1 Fritz Weigel Formula
e RAD7 gives an accurate reading of the radon
concentration in the closed air loop. With the Water
Probe, this air reaches equilibrium with the
surrounding water. To convert the air concentration
to water concentration, the air concentration must be
multiplied by the partition coefficient, which is given
by the Fritz Weigel equation (Weigel, 1978):
a = 0.105 + 0.405 * exp(-0.0502*T)
where T is the temperature in degrees Celsius.
At 10 degrees Celsius, a is around 0.35, giving, at
equilibrium, a three-to-one ratio of radon in air to
water. e Fritz Weigel formula is applied
automatically in CAPTURE when the Water Type is
set to Fresh Water in the Run Parameters Window, as
shown in Fig. 3, below.
3.2.2 Schubert Et. Al. Formula
If the Water Type is set to Saline Water in
CAPTURE’s Run Parameters Window, the radon in
water concentration is calculated using the Schubert
et al. formula, which is a function of both water
temperature and salinity. (See Schubert et. al., 2012.)
e Run Parameters Window provides a field for
specifying the salinity of the water, in parts per
thousand. Note that this formula is suitable for water
samples with any degree of salinity, including zero.
When the salinity value is set to zero, it produces
results that are nearly identical to those produced by
the Fritz Weigel formula.
Fig. 3 The CAPTURE Run Parameters Window
Section 3 Data
10

4 DRYSTIK
4.1 Passive DRYSTIK
A passive DRYSTIK may be installed in the Water
Probe system without modifying any other part of the
system or the operating conditions. e inner
membrane tube goes between the exchanger and the
desiccant while the outer sheath is purged by dry air
from the RAD7 outlet. e two flows should be in
opposite directions along the DRYSTIK. A 12”
DRYSTIK will increase the life of the desiccant by a
factor of about five.
4.2 DRYSTIK ADS-3 and ADS-3R
DURRIDGE’s DRYSTIK ADS-3 and ADS-3R models
include a pump upstream of the inner membrane
tube, and a needle valve downstream of the tube. is
increases the pressure inside the tube, which
increases its efficiency.
A typical setup has the RAD7 pump set to OFF
(Setup, Pump, Off [ENTER]), the DRYSTIK
pump running continuously and the needle valve
adjusted to give a flow rate of about 0.2 L/min.
When using an active DRYSTIK, a Small Drying
Tube or larger Laboratory Drying Unit full of
desiccant can be added to keep the air sample in the
RAD7 below 7% RH. It should be inserted between
the DRYSTIK air outlet and the inlet filter on the
RAD7, as shown in Fig. 4 on the following page. e
desiccant will last for a very long time, and the drying
tube will add only a tiny volume to the air loop.
4.3 Effect on Response Time
With a flow rate of only 0.2 L/min it will take about
20 minutes for the air in the loop to go around once.
is will add an extra 10 or 15 minutes to the
response time for radon. For long term studies the
slower response is generally not important, whereas
the frequency of replacing the desiccant may be. So
an active DRYSTIK may be of considerable benefit.
4.4 Custom DRYSTIK Settings
e standard 0.2 L/min flow rate of the DURRIDGE
DRYSTIK is typically used because it matches the
average flow rate of a RAD7 in AUTO mode, and it
also matches the performance of the installed pump
at a pressure of 44 PSI (3 atmospheres). DURRIDGE’s
Active DRYSTIK models can be set to maintain a 44
PSI pressure inside the inner membrane tubing and a
flow rate of 1L/min or even more, to restore the speed
of response of the system while virtually eliminating
the need to periodically replace the desiccant. See the
DRYSTIK user’s manual for details.
Section 4 DRYSTIK
11

Fig. 4 Water Probe configuration with Active DRYSTIK
Section 4 DRYSTIK
12

5 CARE, MAINTENANCE, AND TROUBLESHOOTING
5.1 Water Catastrophe
If water ever enters the RAD7, or if the RAD7 ever
goes swimming in the water, it will probably cease to
operate and immediate steps should be taken to
minimize the impact on the instrument.
Keep the RAD7 upright. is will prevent water from
touching the detector, which is close to the face plate
at the top of the dome. Put a piece of tubing on the
RAD7 outlet with the other end in a sink. Use the
RAD7 pump if it still works or, otherwise, an external
pump into the inlet, to blow air through the
instrument. When water ceases to be blown out of
the outlet, put desiccant upstream of the RAD7 to dry
out the air path. When the air path is fully dry (aer
dry air has been blown through it for approximately
one hour), remove the face plate from the case, empty
the water out of the case and blow dry the case and
the RAD7 electronics.
Once there is no visible water in or on the
instrument, it can be put in an oven at 50°C for a few
hours to dry out completely. Additionally, desiccated
air can be passed through the air path until the air
leaving the RAD7 drops below 10% RH. Aer this
treatment further corrosion will be prevented, and
the RAD7 will boot once more and you can use the
internal RH sensor to measure how dry the air path
is. At this point the instrument should be returned to
DURRIDGE for service.
5.2 RAD7 Care
Water, particularly salt water, is hostile to electronic
instruments. Please keep the RAD7 in a relatively
clean and dry environment. One way is to enclose the
instrument in a large, transparent plastic bag; see
Section 1.2.3. Should it ever be seriously splashed
with salt water, please follow the instructions in
Section 7.1, above.
As a preventive measure, plastic cling wrap can be
placed over the RAD7 face plate and down the sides
of the RAD7. Push it down around the hose
connections, push the power and RS232 plugs into
their sockets, and push the lid onto its hinges. e
wrap will make the RAD7 almost watertight. If it
tears it can be easily replaced at any time. e
instrument should, in any case, be returned every
year for recalibration.
It is useful to look at a cumulative spectrum
periodically. is may be obtained by having the
printer on and allowing the RAD7 to complete a run.
e “Recycle” number may be set to the current cycle
number (Setup, Recycle, NN [ENTER]). When
the RAD7 reaches the end of the current cycle it will
then print out the end of run summary including the
cumulative spectrum. Look to see that the peaks are
clean and in their normal positions.
5.3 Exchanger Care
ere is a potential for biofouling to occur in long-
term monitoring applications. e exchanger should
be kept as clean as possible in the circumstances. e
Water Probe should therefore be inspected
periodically to ensure that there is good contact
between the radon exchange tubing and the
surrounding water, and no clogging with weeds,
algae, etc.
5.4 Desiccant Regeneration
Please see the RAD7 manual for information on the
care and regeneration of the desiccant. Regenerated
desiccant, aer a few regenerations, loses most of its
indicating ability (due, we believe, to migration of the
cobalt chloride to the interior of the calcium sulphate
crystals). One way to ‘indicate’ the status is, every
time you refill the laboratory drying unit with
regenerated desiccant, you first add half an inch or so
of new, blue desiccant, out of the jar. is way, you
can always tell if the unit is still working, as the new
desiccant will only turn pink when the rest of the
desiccant, upstream, has become hydrated.
5.5 Water Probe Troubleshooting
5.5.1 Air Path Integrity
When drawing a sample from a remote location, air
path integrity is essential to prevent dilution of the
sample with ambient air. Always make sure that there
are no loose connections or leaky fittings (such as the
screw cap of the Laboratory Drying Unit) in the air
loop, particularly upstream of the RAD7. In the event
of unexpectedly low radon values, check the air path
for integrity.
Section 5 Care, Maintenance, and Troubleshooting
13

REFERENCES !
!
The following references are in chronological order.
Weigel, F, 1978. Chemiker Zeitung, 102 (1978) 287.
Schubert, M., Schmidt, A., Paschke, A., Lopez, A., & Balcázar, M. (2008). In situ determination of radon in surface
water bodies by means of a hydrophobic membrane tubing. Radiation Measurements, 43(1), 111–120.
De Weys, J., Santos, I. R., & Eyre, B. D. (2011). Linking groundwater discharge to severe estuarine acidification during
a flood in a modified wetland. Environmental Science and Technology, 45(8), 3310–3316.
Hofmann, H., Gilfedder, B. S., & Cartwright, I. (2011). A novel method using a silicone diffusion membrane for
continuous 222Rn measurements for the quantification of groundwater discharge to streams and rivers.
Environmental Science and Technology, 45(20), 8915–8921.
Santos, I. R., Maher, D. T., & Eyre, B. D. (2012). Coupling automated radon and carbon dioxide measurements in
coastal waters. Environmental Science and Technology, 46(14), 7685–7691.
Schubert, M., Paschke, A., Lieberman, E., Burnett, W.C. (2012). Air−Water Partitioning of 222Rn and its Dependence
on Water Temperature and Salinity. Environmental Science and Technology, 46, 3905-3911.
Gilfedder, B. S., Frei, S., Hofmann, H., & Cartwright, I. (2015). Groundwater discharge to wetlands driven by storm
and flood events: Quantification using continuous Radon-222 and electrical conductivity measurements and dynamic
mass-balance modelling. Geochimica et Cosmochimica Acta, 165, 161–177.
Carlo, L., Alessandra, B., Dario, S., Mauro, C., Gianfranco, G., Michele, S., & Paola, T. (2019). Testing the radon-in-
water probe set-up for the measurement of radon in water bodies. Radiation Measurements, 128, 106179.
Durejka, S., Gilfedder, B. S., & Frei, S. (2019). A method for long-term high resolution 222Radon measurements using
a new hydrophobic capillary membrane system. Journal of Environmental Radioactivity, 208–209(February), 105980.
Section 5 Care, Maintenance, and Troubleshooting
14

15
DURRIDGE Company Inc.
900 Technology Park Drive
Billerica, MA 01821
Telephone:"(978)-667-9556
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Revision 2021-08-31
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