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Mercury Sampling:
Methodology used by Martin Shafer of the Water Chemistry Program
at University of Wisconsin-Madison
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image from http://wi.water.usgs.gov/pubs/FS-216-95/
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Clean Suits and Gloves Must Be Worn For All The Following
Steps.
Lowering Tubing Line
Open plastic cartons containing sampling line and kevlar
support rope. Tie kevlar rope to loop of Teflon string attached
to sampling-line weight. (The end of the rope is two feet
above sampling intake). Slowly and carefully begin removing
lower end of sampling line (i.e.
Teflon weight end) from plastic bag (use extreme caution
to avoid kinking and contamination), insert weight through
receptacle on end of boom and lower into river to first
depth (0.2 x River Depth). Secure kevlar support rope onto
starboard plastic cleat. Keep remainder of sampling line
tubing in plastic bag until pump head tubing is attached.
Note: Rope is marked in one foot increments -
beginning six inches from the end. Use the six inches to
tie off to Teflon string. The distance from sampling ports
to top of Teflon string is two feet. A double line is marked
every five feet, and a triple line is marked every 10 feet.
To drop the sampling line to the lower depth, the kevlar
rope is un-cleated, and both rope and Teflon sampling line
slowly let out to (0.8 x River Depth). It is usually necessary
to uncouple Sampling Line from pump-head tubing before lowering
line. Clean-hands uncouples and re-couples sampling line
from pump-head tubing.
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Geo-Pump Loading and Sample Line Connection Load
pump-head tubing into Geo-Pump using clean protocol. {Gloved dirty
hands opens pump head clamp lever and holds outer bag of pump-head
tubing, while gloved clean hands removes inner bag and loop of
tubing. Clean hands inserts closed tubing loop into pump head
and dirty hands closes clamp lever making sure that tubing is
properly positioned. Dirty hands makes sure that Teflon Tubing
Adaptor Fitting (TTAF) and plexiglass clamp ring (PCR) are ready.
At this point dirty hands re-gloves, and retrieves open end of
sampling line from storage bag, while clean hands opens pump head
tubing loop. Dirty hands gives clean hands sampling line who inserts
it into pump head tubing. Dirty hands collects TTAF bag and opens
outer bag, while clean hands opens inner bag and removes TTAF
and tightly inserts it into the long end of the pump head tubing.
The TTAF bags should be kept in the sample transport cooler during
sampling (inner bag is always kept inside dirty outer bag. Dirty
hands, with new gloves, collects PCR from storage bag, removes
PCR, and holds it while clean hands inserts TTAF into PCR. Dirty
hands then inserts assembly into groove in sampling platform.
The PCR bag should also be kept in the cooler during sampling
to minimize contamination and prevent it from being blown away.
Sample Collection
Place the appropriate sample bottles into the plastic sample
organizing container using the following protocol. The outer bags
should have been previously labeled with site and sample type
information. The outer bags are removed using clean techniques
and sample bottles with inner bag are placed in the organizing
container. Dirty hands (with new gloves) retrieves appropriate
double bagged Teflon sample bottle and opens outer bag. Clean
hands (with new gloves) pulls inner-bag out of outer bag and places
single-bagged bottles in the organizing container. Outer bags
are stowed in the sample transport cooler, out of the wind.
The typical sampling sequence will be:
[1] 250 mL Unfiltered sample for Trace Metals
[2] 500 mL Unfiltered sample for Mercury
[3] 125 mL Unfiltered sample for Methyl Mercury (see Note)
[4] 1000 mL Unfiltered sample for SPM and DOC
[5] 250 mL Filtered sample for Trace Metals
[6] 500 mL Filtered sample for Mercury
[7] 125 mL Filtered sample for Methyl Mercury (see Note)
Filling each bottle ½ full.
Note: For Methyl Mercury; Sheboygan, Manistique, Pere
Marquette, and Grand rivers only.
This sequence will be repeated at the lower depth (except that
filtered samples will be collected first) to fill the remaining
½ of bottle and then samples are acidified, and double-bagged.
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Upper Depth
Unfiltered Sample Collection
Dirty hands starts Geo-pump and adjusts to moderately high speed
to flush lines (Verify that water flow is correct, through platform
hole, and not splashing sides). Sampling lines are flushed for
a minimum of five minutes before unfiltered samples are collected.
Sample Bottle Handling: Clean hands (with new gloves) pulls appropriate
bottle out of inner-bag leaving inner-bag in organizing container.
Trace Metal Sample Collection: Teflon bottles are supplied empty
and dry. Clean hands reaches under water stream and partially
(c) fills bottle. The bottle is loosely capped and gently shaken
to rinse. This process is repeated for a total of three bottle
rinses. On the fourth collection the bottle is filled ½
full. Do Not Touch Bottle Mouth To TTAF Or Any Other Surface.
Clean hands then returns sample bottle to inner-bag in organizing
container. The bags do not have to be sealed at this point. Dirty
hands removes and replaces organizing container lid during sampling.
Mercury Sample Collection: Teflon bottles are supplied filled
with dilute HCl. Clean hands dumps acid into waste container.
Do Not Touch Bottle Mouth To Waste Container Or Any Other Surface.
Clean hands reaches under water stream and partially (c) fills
bottle. The bottle is loosely capped and gently shaken to rinse.
This process is repeated for a total of four bottle rinses. On
the fifth collection the bottle is filled ½ full. Clean
hands then returns sample bottle to innerbag in organizing container.
The bags do not have to be sealed at this point. SPM - Carbon
Sample Collection: One-Liter polyethylene bottles are supplied
empty and dry. Clean hands reaches under water stream and partially
fills bottle. The bottle is loosely capped and gently shaken to
rinse. This process is repeated for a total of three bottle rinses.
On the fourth collection the bottle is filled ½ full. Clean
hands re-gloves after handling the poly bottle.
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Filtered Sample Collection
After all unfiltered samples are obtained from the upper depth,
dirty hands reduces pump speed and then shuts off pump. Dirty
hands re-gloves, retrieves a bagged Calex filter, and opens outer
bag. Clean hands opens inner bag, removes filter capsule, opens
vents, and drains off storage MQ into river (The filter bags may
be discarded - the filter capsule is a disposable, single-site
use, item). Dirty hands removes PCL/TTAF assembly from sampling
platform, and clean hands uncouples TTAF and screws filter capsule
onto TTAF. Clean hands inserts filter capsule into support on
sampling platform. Dirty hands starts Geo-pump and adjusts to
moderate speed to flush capsule (Verify that water flow is correct,
through platform hole, and not splashing sides). The filter capsule
is flushed for five minutes or approx. 3 L before filtered samples
are collected. At this point Filtered Trace Metal samples and
Filtered Mercury samples are collected in an identical manner
to unfiltered samples as described above. To minimize the potential
for filter clogging, dirty hands shuts off pump after each rinse
or sample has been obtained. Upon completion of Filtered sample
collection from the upper depth, cleanhands un-couples Teflon
sampling line from pump-head tubing and dirty hands lowers tubing
to 0.8 depth. When at depth, the sample tubing line is then reattached
to the pump-head tubing using the clean technique. |
Lower Depth
The collection process is identical to that described above
for Upper Depth, except that obviously ½ full bottles
are not rinsed and filtered samples are collected first.
The protocol for flushing and equilibration of sampling
line and filter is similar to Upper Depth, except that here
one is flushing the line and filter as a unit. Flushing
as a unit for five minutes should not present a problem
except under conditions of very high suspended solids levels.
If during Upper Depth sampling or early stages of Lower
Depth flushing, significant reduction of sample flow rate
through the filter is noted, do the following to minimize
filter clogging. Uncouple filter capsule from the TTAF and
flush the sample tubing line for the full five minutes.
While tubing is flushing, drain the river water from the
capsule filter. After tubing is flushed, connect to drained
filter and flush filter for 90 seconds. Clean techniques
must be followed. Bottles are filled to near capacity, leaving
space for preservation acid. After each sample bottle is
filled, and before rebagging, preservation acid is added
to the sample. |
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image from http://wi.water.usgs.gov/pubs/FS-216-95/
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Acidification
Trace Metal Sample Acidification (250 mL Sample Bottles)
Acid (50% Ultrex HNO3) is supplied pre-measured in small Teflon
Vials, one for each sample. Acid transfer to the sample must be
quantitative. Dirty hands (with new gloves) retrieves the bag
containing acid vials and opens it. Clean hands reaches in and
removes a vial. Dirty hands wrenches open the vial while clean
hands holds it. Clean hands then removes vial cap and pours acid
into sample bottle which should be available and loosely capped
on work surface. Used acid vials are re-capped and placed into
a designated Zip-bag, to be returned to Water Chemistry Lab along
with metal samples. Note the acid batch number on the field data
sheet. The acidified sample is ready to be double-bagged using
clean-hands protocol after the cap is wrenched tight. Clean hands
holds bottle tightly while dirty-hands takes a double-bagged channel-lock
pliers to cap. Clean-hands twists bottle to secure cap. Place
new bags on the wrench before use at each site, and during a sampling
period if the bags appear worn.
Mercury Sample Acidification (500 mL Sample Bottles)
Acid (50% HCl) is supplied in a 250 mL double-bagged Teflon bottle.
Also supplied is a Teflon measuring vial into which acid is poured
to measure out 10 mL aliquots. Before starting the acidification
process, verify that the samples to be acidified are organized
on the clean work surface, and that their bottle caps are loose.
Dirty-hands retrieves acid bottle and opens outer bag.
Clean hands opens inner bag and removes Teflon acid bottle, setting
it on plastic covered work surface. Dirty-hands retrieves Teflon
measuring vial and opens outer bag. Clean hands opens inner bag
and removes vial. Temporarily place acid and vial bags (inner
bag inside outer bag) in the sample organization box. Clean hands
pours acid into the vial up to the etched line and then quickly
pours contained volume into the sample bottle. Do not let acid
measuring vial touch lip of sample bottle. Clean-hands - dirty-hands
procedures are then used to wrench shut and double-bag sample
bottles, and to double bag acid bottle and measuring vial.
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