Collecting water samples
Surface water and hyporheic (sub-surface) water samples can be collected to determine the total and dissolved nutrients of the water through lab analysis. Depending on the purpose of the collection, it is important to follow a few guidelines to ensure that your measurements are accurate.
Surface water samples
Materials
Nalgene bottle(s) - 60 mL (wide and narrow neck)
Cooler with ice
Syringe (50 mL) and syringe filter holders
Whatman GF/F filters (25mm to fit the syringe filter holders)
Forceps
250 mL (or any size >100 mL) Nalgene bottle
Methods
Glass or plastic bottles can be used depending on the parameter to be tested.
Be sure to use bottles that have been thoroughly cleaned and rinsed in an acid bath. (In the Winkenwerder lab these bottles can be found in the tan metal cupboard and the green plastic storage container beneath the table where the phone is located.)
Take the sample in a place where the water is believed to be well-mixed,
preferably the thalweg of the stream, unless another stream location
is of interest (e.g., outwelling of a gravel bar)
Rinse the bottle and cap of a 250ml bottle in the streamwater once or twice before the sample is collected.
Take the sample about 30cm below the surface of the stream water at a 45-degree angle to the direction of flow.
For total nutrients
Shake the bottle to mix sample and pour a little into the wide-mouth bottle, shake to rinse and dump out. Pour sample into the bottle until it is half full.
Place the sample on ice.
Back at the lab, adjust the volume to 20 mL (exactly) and freeze until analysis.
For dissolved nutrients
Place a filter on the holder and attach to the syringe.
Fill (~10 mL) with water, push some through the filter, shake the syringe to rinse, and dump out. Fill to 50 mL with the sample.
Filter some water into a narrow necked bottle, shake to rinse and dump out.
Filter more water into the bottle until full.
Transport bottles from the stream to the lab in a cooler with a cold icepack or, if the stream is nearby, with streamwater to ensure that the samples remain as close to their original temperature as possible.
Place samples in lab freezer until ready to analyze.
Hyporheic water samples
Materials
Nalgene bottle(s) - 60 mL (wide and narrow neck)
Cooler with ice
Drill with peristaltic pump head
Drill batteries (charged)
Sampling tube
Syringe (50 mL) and syringe filter holders
Whatman GF/F filters (25mm to fit the syringe filter holders)
Forceps
250 mL (or any size >100 mL) Nalgene bottle
Methods
Attach sample tube to the pump head and place the other end down the well.
Using the drill, pump water out of the well and into the large plastic bottle.
Rinse once then fill again with well water.
For total nitrogen and phosphorus
Shake bottle to mix sample and pour a little into the wide mouth bottle, shake to rinse and dump out. Pour sample into the bottle until ½ full. Place sample on ice.
Back at the lab, adjust the volume to 20 mL (exactly) and freeze
until analysis.
For dissolved nitrogen and phosphorus
Place a filter on the holder and attach to the syringe. Fill (~10 mL) with water, push some through the filter, shake the syringe to rinse, and dump out. Fill to 50 mL with sample.
Filter some water into a narrow necked bottle, shake to rinse and dump out. Filter more water into the bottle until half full.
Transport bottles from the stream to the lab in a cooler with a cold icepack or, if the stream is nearby, with streamwater to ensure that the samples remain as close to their original temperature as possible.
Place samples in lab freezer until ready to analyze.
Notes
The amount of sample water collected using these methods is necessary for analysis by Kathy Krogslund in the analytical lab (School of Oceanography). Required volumes may change if samples are sent to a different lab or done by hand.
Kathy Krogslund,
Marine Chemistry Laboratory
346 OSB
kkrog@u.washington.edu
543-9235
When taking replicates, each water bottle should be filled individually (i.e., do not hold all three bottles in your hand and fill at the same time).
If sampling for dissolved organic carbon, the filters should be ashed in the muffle furnace to be cleaned of carbon (400 oC for 4 hours)
When sampling for total and dissolved nutrients, it is important to keep the replicates together (i.e., 1 large bottle = 1 total + 1 dissolved sample).