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Water chemistry sampling

By: K. Gajewski

This procedure should be followed to collect and process water samples for nutrient and trace element analysis. Note that the actual water chemistry is done in the lab using the various instruments (ICP, etc.). This procedure was shown to me by Paul Hamilton of the Canadian Museum of Nature.

A) Preparation before leaving for the field

Before sending the equipment to the field site the following washing procedure must be used:
1. Wash and scrub filtration units with non-phosphate detergent.
2. Rinse with tap water and soak overnight in 5 – 10% HCl.
3. Clean tubing by soaking overnight in 5 – 10% HCl.
4. Rinse unit and tubing with tap water followed by distilled/deionized water.

Use the buckets of dilute acid in the corner of the pollen processing lab. The next day, carefully take them out (use gloves, obviously, and be careful that the solution does not go over the top of your gloves) and wash them using a jet of tap water. Then, rinse them in deionized water and place them to dry in the green clean-air hood. After the equipment is dry, wrap it in aluminum foil and pack it to send. The sample bottles should be prepared by acid washing as well, unless using City of Ottawa bottles. Tape should be wrapped around them for the label, and they should be labeled with the codes (e.g. K901, K902, ...) or that season. For each lake you will need the following:

  • 1 1-L plastic collection bottle
  • 4 PEP bottles from the City of Ottawa (1 metals [white cap], 1 TP/TKN, 1 filtered TP/TKN/DOC, 1 Alkalinity/Anions/Cations [green caps])

Note that the chemicals (nitric and sulphuric acid etc.) cannot be shipped by ordinary freight, so you need to make special arrangements to have the bottles sent to the field station.

B) Field sampling

The information you collect depends a lot on the time available, the space you have (ie. In the helicopter) to carry equipment, etc.
Minimum collection includes:

  • pH, conductivity and temperature of the surface
  • 1 L water sample
  • 3 300-mL bottles filled
  • Plankton tow
  • Sediment sample

If possible the following should also be collected:

  • Secchi depth
  • Conductivity, temperature and oxygen profile
  • Glew core(s)
For more detailed work:
  • samples at several areas around the shore
  • samples of water at several depths

At the lake, inflate the boat and get out to the central part. You should first collect the water samples. Rinse bottles 3 times with lake water before filling. Fill them below the water surface up to your elbow. Be careful not to touch the spout, inside of caps, etc.

Chlorophyll a filtering procedure:
1. Rinse filtering apparatus in lake water.
2. Place GF/C glass microfibre filter on apparatus using tweezers.
3. Fill 1-L graduated cylinder with lake water from elbow depth (after rinsing 3 times), pour into filtering apparatus and pump through. If lake is productive use 500 mL or less depending on rate of flow.
4. Keep apparatus shaded while filtering.
5. Remove lid, fold filter in half using tweezers, wrap in foil, label with lake name, date, and volume filtered. Freeze immediately by placing between 2 ice packs.


Measure the pH, conductivity and temperature of the surface water. If you can get a vertical profile of conductivity/temperature/oxygen, this is certainly useful. A Secchi depth can be recorded, and 2-3 sediment samples collected using a Glew corer or an Ekman Dredge. On the way back to the shore, tow the plankton net behind you and put contents in a whirl pack. They should be “fixed” with Lugol’s solution as soon as possible.

C) Processing water

The procedure here doesn’t need to be followed in any particular order, but individual steps should be closely followed.
1. For the following, use gloves and be very careful to avoid contamination. The concentrations of the ions in lake water are very small, and touching the sample containers can lead to serious contamination. Add 0.5 mL of HNO3 (metals grade) to the metals bottle, and 0.5 mL of 30% H2SO4 to the TP/TKN sample. Guideline is 2ml/1L of H2O and we are using 300 ml collection bottles.
2. For the filtered TP/TKN, use the cellulose acetate filter papers (47 mm diameter, pore size 0.45; order number CO45G047A). For this procedure, you will be keeping the water that goes through the filter. Place the filter on the filter holder,
ensuring it is centred, and close it tightly. Use the small (250 mL) filter holder and a glass flask, and you will need the rubber stopper, or any other part that may come in contact with the water. Put 10-20 mL of lake water in the filter holder. Connect the vacuum pump, suck this water through, swish it around the flask and discard. Filter between 250-300 mL of water by pouring in increments into the filter holder. Maintain a vacuum of 7 or less. When the water has passed through, disconnect, toss the filter paper and pour the filtrate into the appropriate 300 mL PEP bottle. Rinse the unit with distilled H2O. Add 0.5 mL of 30% H2SO4 to the filtered TP/TKN sample.
3. Place all the water samples in the cooler and keep refrigerated.

D) Shipping and storage

Samples should be shipped back to the lab as soon as possible. They should be kept cool, but not frozen during this whole procedure.

E) Back in the lab

Back in the lab the samples should be processed as soon as possible. The bottles are sent out for analysis to the City of Ottawa, Water Environment Protection Division.

F) Materials

This needs to be modified, depending on the number of sites and space available. Here is the minimum amount we usually take; you can add extra filter holders, flasks, etc., in case of breakage and also to run more samples at a time if there are many analyses to do.

  • 1-L collection bottles with caps, acid-washed (~10) (1 per lake)
  • 300-mL PEP sample bottles; 3 with green caps for alkalinity, cations, anions; TP/TKN; filtered TP/TKN; and 1 with white cap for metals
    labels from City of Ottawa (4 per lake)
  • Pkg Filters, 47 mm cellulose acetate, 0.45 um for filtered TP/TKN
  • GF/C Whatman glass microfibre filter paper for chla (42.5 mm diameter, 0.45 um) (1 per lake)
  • Vacuum pump (x2)
  • Tubing for pump
  • 500-mL plastic filter holder, with plastic reception vessel, caps for all openings
  • 250 mL plastic filter holder, with caps (x2)
  • 500 mL ehrlenmeyer glass flasks (x2)
  • rubber stoppers (x2)
  • 100 mL glass graduated cylinder (x2)
  • 1 L plastic graduated cylinder (x2)
  • Plastic funnel
  • pH meter (portable) (x2), pH test kit, batteries
  • Conductivity meter with probe
  • Oxygen meter with probe, YSI oxygen probe service kit
  • Equipment manuals
  • Plankton net
  • Secchi disk
  • Glew mini corer
  • Glew extruder
  • 10 mL pipettes (x 2-3)
  • 1 mL pipette
  • Acid dispensers (x2)
  • Cooler(s), ice packs
  • Plastic bottles to fill with water and freeze for ice to supplement ice packs
  • Red/grey fishing tackle box with coring/filtering paraphanelia
  • Including tweezers for filters, cleaning brush, exacto knife and scissors, goop, T joints and clamps, one-way valve, markers and pencils, rubber stoppers, clamps, black tape, manuals, forceps
  • Aluminum foil, saran wrap, plastic for covering table and equipment, whirl pack bags, large and small ziploc bags
  • Concentrated nitric acid (metals grade) for preservation of metals in water samples, 30% sulphuric acid (30 ml H2SO4 acid, 70 ml H2O) for preservation of TP/TKN water samples (total and filtered)
  • Lugols solution (5 g iodine, 10 g potassium oxide, 10 g glacial acetic acid and 100 mL water [1 mL per 100 mL water sample]) for preservation of zooplankton samples
  • Turkey basters (x2)
  • Non-phosphate detergent
  • Plastic distilled water dispensers (squeeze bottles) (x2)
  • 1 Box large nitrile gloves
  • 1 Box large latex gloves
  • Deionized water
  • Pasteur pipettes and bulbs
  • Safety goggles (x2)
  • Lab coat
  • Rope
  • Boat, life jackets, anchor (burlap bags), paddles
  • Log books, log sheets for individual lakes
  • Bear spray

 

 

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