PHYSICAL AND CHEMICAL FIELD SAMPLING

 

 

EQUIPMENT LIST

clipboard,  data sheet,  pencils,  watch,  duct tape

peristaltic pump with attachment for filter holders

12 volt battery and cables to run pump

1/4" I.D. tygon tubing to reach lake bottom,  1000 and 250 ml graduated cylinders

sample bottles  (one set per sampling depth plus one extra set for blind)

pre-weighed filters for total particulate matter

sediment traps and lids, poison, retrieval hook  (Trout, Sparkling, and Crystal lakes)

temperature/oxygen meter (YSI-58)

filters (0.45µ Nuclepore polycarbonate) loaded in filter holders

cooler (with icepack during summer)

(Primary productivity gear:  pipe, cooler, suck tube, pipe-to-cooler tube, light screens)

 

BEFORE LEAVING TROUT LAKE STATION

Take a barometric pressure reading, and record it in the lab notebook and on the field data sheet.

Check the checklist to be sure you have everything you will need in the field.

Attach the cable leads to the front of the YSI temp/O₂ meter.  Leave the probe in the moist plastic bag.  Set the function switch to ZERO and allow the meter to warm up for at least 15 minutes, or until on station at lake.

 

SET UP (on station at the lake)

Record the lake, station, date, observers, and time on the data sheet.

Calibrate the YSI-58 oxygen meter.

- The meter should be turned on to warm up for at least 15 minutes before calibrating.  Leave the probe in the moist bag during calibration.

- Turn the stirrer on.

- Use the O₂ZERO knob to set the display to 0.0.

- Set the function switch to the TEMP position; record the probe temperature.

- Determine the correct oxygen saturation value for the probe temperature and barometric pressure using the table on the inside of the clipboard cover or the calculation sheet on the iPAQ pda.

- Set the function switch to the 0.01 mg/l position and use the O₂CALIB knob to set the display to the correct oxygen saturation value.

- The probe may now be removed from the plastic bag.  The YSI-58 may be moved without loss of calibration.

Line up the open end of the tubing with the sensors on the probe.  Use duct tape to attach the tubing to the oxygen probe, being careful to avoid covering the pressure compensating port with tape or tubing.

 

TEMPERATURE AND OXYGEN MEASUREMENT

Determine oxygen and temperature values at meter intervals down through the water column.

  Record the time that you start and finish the measurements.  Be sure to allow enough time at each depth for the meter to stabilize.  In general, the greater the change from the last value, the longer the time needed for stabilization.  To avoid probe damage and mixing of sediments into the water column, do not lower the probe into the sediments.

Read the oxygen on the 0.01mg/l scale, but record the oxygen values to tenths.

 

WATER SAMPLE COLLECTION

Select the sample depths according to the temperature profile.  During stratification (late May to late October), collect samples at the surface, the bottom of the epilimnion, mid-thermocline, top of the hypolimnion, mid-hypolimnion, and one meter off the bottom.  During mixis and winter, collect samples from the surface, mid water column, and one meter off the bottom.  The depths selected should be depths at which chlorophyll measurements will be made.  Record bottle numbers in the appropriate columns on the field data sheet.  Take a replicate ("blind") set of samples from one of the depths.  The blind depth is selected randomly before going out in the field.

 

Clear the sample tubing.  The tubing inlet should be at the bottom sample depth, one meter off the bottom, after taking the temperature and O₂ profile.  Connect the tubing to the pump and run the pump long enough to flush slightly more than one tubing volume from the tubing.  Each meter of 1/4" I.D. tygon tubing holds a volume of approximately 32 ml.  Therefore a 10 meter length of tubing, for example, should have a least 320 ml pumped through it before filling any sample bottles.  The tubing must be cleared at every depth before collecting samples at that depth.

 

Collect the water samples avoiding contamination of bottles or filters.  Rinse each bottle three times with a small amount of the lake water it is to be filled with.  Flush each filter by pumping a small amount of lake water through it before collecting any filtered samples.  Change filters at least every time you change sampling depths.  Do not touch inside or rims of bottles, inside of bottle caps, or inlet/outlet holes on the filter holders.  Keep used filters out of the clean filter container.  Place bottles in a cooler immediately after collection.  Keep samples cold and dark until analysis.

 

We sample for water chemistry at two levels of intensity.  Routine, approximately monthly, sampling includes collection of samples for nitrate, nitrite, ammonia, phosphorus, inorganic and organic carbon, silica, and pH.  Four times a year we also collect samples for major cations, major anions, conductivity, color, and alkalinity.

 

                     Routine Samples                           Quarterly Extra Samples

         Filtered                     Unfiltered                  Filtered                     Unfiltered

         20ml 'N'                    20ml pH                    20ml 'V'                    20ml alkalinity

         125ml 'S'                  125ml pH                  125ml color              125ml cond.

         15ml 'DIC DOC'       125 ml 'S'

         TPM filters                15ml 'TIC TOC'

 

The 'N' vials are for nitrogen analysis and will be frozen upon return to the lab.  Fill only to shoulder of bottle to keep them from breaking when frozen.

The 'V' vials are for sulfate and chloride and should be filled completely.

The 'S' bottles for nutrient analysis should be filled to the shoulder of the bottle and acidified with 1 ml concentrated OPTIMA HCl back at the lab.

The water for pH, alkalinity, and carbon analyses should not be agitated or exposed to air.  This is to avoid carbon dioxide loss or invasion.  Fill these bottles gently to the top plus some overflow, and carefully screw on the displacement cap so that the sample contains no air bubbles.  Invert the bottle and check for bubbles.  Dump out and refill if there is a bubble in the sample.

The filters for total particulate matter (TPM) have been weighed before sample collection.  Filter lake water through these into a 250 ml graduated cylinder, stopping when the filter is clogged or when you have pumped 250 ml.  Record the filter holder number and the volume filtered on the field data sheet.  At the lab remove the filters from the holders and return them to the numbered plastic cases; freeze.

 

Record the time you start and finish collection of chemistry samples.

 

In Trout, Sparkling, and Crystal Lakes two sediment traps must be retrieved and replaced each chemistry sampling week.  Details of the sediment trap procedure are in the Sediment Trap / TPM protocol document.

 

CLEAN-UP

FIELD:  Turn meters off.    Record an 'off station' time.

LAB:  Preserve and store chemistry samples and TPM filters.  Process sediment trap samples;  rinse traps.

Wash filter holders, place in hood to dry.  Set bottle bags out to dry.

Rinse and wipe coolers;  leave open to dry.

Rinse sample tubing with milliQ.  Store tubing full of milliQ.

 

(reviewed 1/05 pkm)