Arctic LTER - Landwater Protocols

(updated June 1996)

CONTENTS:

(I) Field Sampling and Processing

(II) Gas Sampling

(III) DIC Sampling

(IV) pH Determination

(V) DIC Determination

(VI) Silica Determination

(VII) Low-level PO4- Determination

(VIII) Total and Dissolved Organic P Determination

(IX) Phytoplankton Sampling

(X) Carle GC Operating Instructions

(XI) QA/QC Procedures

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(I). Field Sampling and Processing (for Landwater, Lakes, Streams)

PREPARATION:

Pack all of the equipment you will need the night before so that nothing will be forgotten. Prepare the following items:

1. Sample bottles labeled and divided into separate ziplocs for each site.

2. DIC kit: permanent marker

taped bottles (more than number of sites)

numerous aluminum caps with Teflon septa

HgCl2 bottle

HgCl2 syringe and needle (2)

H2O syringes (at least 2)

crimper

3. Gas kit: permanent marker

H2O syringe (at least two)

nylon syringes (more than number of sites)

extra stopcocks

4. Filtering kit: clean filter holders (do not load filters the night before - they will break)

box of GF/F combusted filters

forceps (2)

DI water to rinse filter holders

5. Field notebook with sharpened pencil (prepare data sheet before going into the field)

6. pH and conductivity meters with extra pH probe, buffers, filling solution, batteries, and DI water

If taking soil samples:

7. Steel needles

8. Temperature probe and meter

9. Thaw depth probe and meter stick or ruler

10. Well depth stick

FIELD COLLECTION:

The sampling order does not need to be followed strictly. However, the following order has proven most efficient. Don't forget to write down the date and the weather conditions for that day and the previous days.

if taking soil samples:

1. soil temperature

2. thaw depth

3. well depth

otherwise:

4. H2O temperature

5. pH

6. conductivity

7. DIC

8. gas samples (see sampling protocol) -- take duplicates at TW Weir and for surface waters. Also take ambient gas samples at the weir and at each transect.

9. filtering for water chemistry-expel 20 mL of sample water through the filter in order to rinse the

filter. (Note: if there is plenty of water, fill the alkalinity bottle first. This will help rinse the filter). Rinse all of the bottles with a couple mLs of filtered water before collecting sample.

Filtering priority Amount of water Label on bottle

1. Nutrients 30 mL plastic HDPE bottle (min. 5 mL) F-HCl or H2SO4 (if stored)

2. DOC 20 mL glass scint vials (min 10 mL) F-HCl or F-H2SO4 (NEVER HgCl2)

3. TDN/TDP 20 mL glass scint vial F-HCl

4. DON 40 mL in 60 mL plastic LD bottle F-(frozen)

5. Anions 30 mL plastic HDPE bottle F

6. Cations 60 mL plastic HDPE bottle F-HCl

7. Alkalinity exactly 60 mL in plastic HDPE bottle F

8. Particulate filter - GF/F combusted filter with amount H2O (in mL) filtered written on petri dish or aluminum foil packet; freeze or dry filter at <60C. (The filter is not kept for soil waters).

LABORATORY ANALYSIS:

Once you get back to the lab unload all of the equipment and samples. Open up all of the kits and remove contents to dry. Be sure to dry off the crimper so that it doesn't rust. Then prepare the samples as follows:

1. Take 5 mL of filtered water for DOC samples (only for soil waters or anything colored) and place in a

new, labeled DOC bottle. Add 15 mL of DI H2O to the bottle and then acidify (1 mL of 6N H2SO4 or

HCl per 1 mL of sample). Rinse the dedicated DOC sample bottle with DI H2O (the bottle can be reused

for the next sampling). Put approx. 15 mL of DI water in a scint vial for a blank.

2. Acidify (1 mL of acid/1 mL of sample) all other samples that need to be preserved (non-soil DOC

samples, cations, and nutrients if they are being stored).

3. Deliver nutrient samples to the autoanalyzer lab to be run.

4. Store the remainder of the samples in the appropriate spot (DONs and filters in the freezer, the rest of

the samples should be stored dark in the refrigerator (especially alkalinities).

5. Run wet chemistry analyses if such procedures are being done (don't forget the 2x blank).

6. Run the gas samples or the alkalinities (don't forget to bring them to room temperature) depending on

which machine is free (see GC method).

7. Data entry (see QA-QC procedure).

Additional water samples:

There are a few samples that you will receive to analyze which you did not collect. Check with the coordinators in charge to find out which days they will be collecting these samples. Ask politely if they will save leftover water for you. However, remind them the day they go out. It is your responsibility to get the water from them (except for Prudhoe Bay samples), not their responsibility to bring it to you. The samples are:

Prudhoe Bay Samples (from weekly Toolik visitor; generally shows up on taxi days):

1. Deal with the gas syringes first. When you transfer the gas, be sure to measure the temperature of the water in which the syringes were stored.

2. Filter for water chemistry (setup in lab).

a. nutrients

b. DOC

c. TDN/TDP

d. DON

e. alkalinity

f. anions/cations (only for the Kuparuk River)

g. particulates

h. chemistry (if it wasn't collected in the field write the pH, temp, cond. in the data book)

Lake Samples (all depths from Lakes folks; you collect surface samples):

1. Toolik Lake

a. all depths, every week: DOC

b. surface, every other week: pH, gas, DIC, alkalinity,

2. N1 and N2 (control and fertilized)

a. all depths, every week: DOC

b. surface, every other week: pH, gas, DIC, alkalinity

Stream Samples (get from Streams folks):

1. Kuparuk River, every week: DOC, TND/P

2. Oxs Creek, every week: DOC, TDN/P

Additional Surveys:

1. Surface gases from lakes

Take surface gas samples whenever time prevails (at least once a week if not more often). Get a complete depth profile for each lake at the beginning and end of the season (additional would be a benefit). The lakes to sample are: a. Toolik, b. N1, c. N2F and N2C

2. Thaw Depth Survey

This survey must be performed on the same days each year. The dates are 2 Jul 94 and 11 Aug 94. Thaw depth is recorded for a specific transect in the tussock watershed.

(II). Dissolved Gas Sampling Protocol (for Landwater, Lakes, Streams)

Preparing the 60 mL BD syringe

1. Rinse syringe twice with sample water.

2. Fill syringe again, hold tip upward and draw in extra air, swirl water and air to remove bubbles from the stopper, expel the air then tap the syringe hard to move all air bubbles to the tip.

3. Expel the air bubbles, then the water, leaving about 0.5 mL water in the syringe.

4. Place syringe back in sample and expel the remaining water. If syringe is removed from sample source, repeat this procedure to ensure that all air bubbles are removed before taking a sample. After expelling the rinse water, hold syringe under water to withdraw the final sample.

Taking the sample

1. Draw water in slowly and fill syringe full.

2. Make sure there are no bubbles.

3. Expel water until 40 mL of sample remains. (Calibrate the syringe to determine exactly how much water is contained by the syringe plus the valve at various markings on the syringe).

4. Hold syringe away from you and into the wind and draw in 20 mL of ambient air so that the plunger is at the 60 mL marking. Close the valve immediately.

5. Hold the syringe by the bottom of the barrel so as not to warm the water with your hands, submerse the syringe back in the sample water, and shake syringe for at least 1 minute to equilibrate.

Transferring the sample

1. Make sure that no water is trapped in the syringe valve.

2. Break the "seal" (stiffness) on a nylon syringe by moving the plunger back and forth.

3. Insert the tip of the nylon syringe valve into the side vent of the 3-way valve on the sample syringe; hold the sample syringe vertically so that the nylon syringe is perpendicular to it.

4. Open the nylon syringe valve and then the sample syringe valve and transfer a small amount of gas (1-2 mL) from the sample syringe to the nylon syringe. Close the sample syringe valve, then turn the valve on the nylon syringe and expel the gas to flush out the syringe tip and valve. Note that in operating these valves it takes two hands; one to support the valve itself and one to turn the handle.

5. Transfer the remaining gas from the sample to the nylon syringe, making sure that no water is transferred.

6. Close the nylon syringe valve immediately. Apply slight pressure to the nylon syringe plunger and place a rubber band around the valve and plunger.

7. Repeat all steps with a second syringe to get a duplicate sample.

8. Use a third and fourth syringe to take duplicate samples of the atmosphere in order to calculate how much CO2 was initially present in the headspace before equilibration with the water.

Shipping or analysis

1. Place nylon syringes in protective container for transport (plastic box or equivalent) to the lab or shipping.

2. Analyze samples as soon as possible. The nylon syringes will hold the sample for at least several days without substantial gas leakage. Samples can be held up to 2-3 weeks in emergencies, but obviously the results become more and more qualitative with increasing storage time.

(III). DIC Sampling Protocol (for Landwater, Lakes, Streams)

Preparation:

Pack the following items in your DIC kit:

1. labeled 30 mL glass DIC bottles (more than the number of sites)

2. numerous aluminum caps with Teflon septa

3. small (30 mL) plastic bottle with saturated HgCl2 (6g HgCl2 per 100mL)

4. two HgCl2 syringes (1mL) with needles

5. two 60mL H2O syringes with 3-way valves

6. crimper

7. permanent marker and extra labeling tape

Sampling:

1. Fill the 1mL syringe with HgCl2

2. Rinse the 60 mL H2O syringe three times with sample water

3. Prepare the 60 mL syringe then draw up 60 mL of sample water into H2O syringe without bubbles (see gas sampling protocol "preparing the 60 mL BD syringe")

4. Put tip of stopcock of syringe into DIC bottle, tilt the bottle to avoid generating bubbles during filling, and flush the bottle by letting H2O flow out of the neck of the bottle

5. With 5mL of water left in the syringe, slowly raise the syringe out of the neck of the bottle, continuing to expel water

6. As the last bit of water is expeled from the syringe, make sure the sample water has a positive meniscus above the neck of the DIC bottle

7. Insert the needle of the 1mL syringe into the sample water and add 0.2mL of HgCl2

8. Carefully place an aluminum cap with Teflon septa on the DIC bottle

9. Holding the bottle in one hand, take the crimper in the other and quickly and firmly crimp down on the cap

10. Redo if there are any air bubbles larger than 2-3mm in diameter

11. Label the bottle with the site and date

(IV). pH Determination (for Landwater, Lakes, Streams)

(A) Field measurement:

1. Calibrate the pH meter in the lab before going out into the field. The meter can be calibrated in the field, but only after all buffers and probes have come to equilibrium with the field temperature. Thus it is better to calibrate the meter in the lab where everything is already at a stable temperature.

2. After calibration fill the probe cap with DI water or surface water so that the probe can begin to equilibrate with the low ionic strength solution that will be similar to the field samples.

3. In the field, before starting any other procedures, place the pH probe in the water sample - be careful not to have the water flowing past the probe too quickly, and don't put the probe in a backwater that is not representative of the stream or lake. Let the probe equilibrate for as long as possible.

4. For soil waters, take the water sample with a syringe, rinse the pH probe, then fill a beaker with the sample and put the probe into the beaker immediately. Swirl the probe to stir the sample then take a reading as quickly as possible-the soil water will degas rapidly and change the pH.

5. After all other sampling is finished, read the pH and record the value and the temperature.

(B) Sampling in the field for later lab determination:

1. In the field, fill two, 60 mL BOD bottles with sample from each sampling station. Fill slowly from the bottom to avoid air contamination using either a hand pump with tygon tubing, or an air-free syringe with a tygon end. Allow bottle to overfill, replace stopper. Keep BOD bottle cool and dark.

2. In the lab, allow the BOD bottles to reach room temperature (keep them in the dark). Use a small stir bar and magnetic stirrer in the BOD bottle.

3. Place the pH probe into the first BOD bottle and let the probe equilibrate (10-15 minutes).

4. After equilibration, place the stir bar and probe into the second BOD bottle. Allow the reading to stabilize (usually 3-5 minutes), and record the pH value and the temperature.

Note: The probe tip may collect small air bubbles from the stirring action. If this happens, wait until the reading stabilizes and then gently shake or stir the probe tip to remove the bubbles. Record the pH of the sample when bubbles have been removed (it is usually the same).

(V). DIC Determination (for Landwater, Lakes, Streams)

1. Use a clean 60 mL syringe marked as "DIC" and a long metal needle for a tip.

2. Push down on the plunger with force to expel all air. Draw in 3-4 mL of 0.2N sulfuric acid. Draw in air and slowly move the air bubble from the tail to the tip so that it removes small air bubbles. Tap the side of the syringe to remove small bubbles clinging to the rubber plunger.

3. Tap the syringe with the tip pointed upwards to force any remaining air bubbles to the top. Then expel air bubbles and acid until there is exactly 1mL of acid in the syringe.

4. Insert needle of syringe to the bottom of the DIC bottle taking care not to bend the needle; support the bottom of the needle shaft.

5. Insert a small needle into the DIC bottle to eliminate the vacuum created while withdrawing sample.

6. Slowly withdraw exactly 19 mL of water from the DIC bottle until there is a total of 20 mL of liquid in the syringe.

7. Close the three way valve so that contents of the syringe are sealed off and remove the needle from the syringe. Be sure to grip the syringe valve so it does not come loose.

8. Use nitrogen for equilibration. Make sure the regulator is backed out on the nitrogen tank. Turn the main valve on and open the small valve. Turn up the pressure slightly until you hear a slight hiss from the exit tube. Flush for 20 seconds. Insert the DIC syringe into the exit tube and slowly fill with 40 mL of nitrogen.

9. Gently shake the syringe for 4 minutes to allow equilibration.

10. Let the syringe sit for one extra minute in case the air became super-saturated from shaking.

11. Draw in about 20 mL of nitrogen (or air) into a nylon dry gas syringe and use that gas to flush the tip of the DIC 60 mL sample syringe.

12. Open the dry gas syringe valve and then the DIC syringe valve and transfer a small amount of gas (about 1-2 mL) form the DIC syringe to the dry gas syringe. Close the DIC syringe valve, then turn the valve on the dry gas syringe and expel the gas to flush out the syringe tip and valve. Note that in operating these valves it takes two hands; one to support the valve itself and one to turn the handle.

13. Inject the gas into the dry gas syringe. Close the three-way valve of the dry gas syringe before pulling it away from the three-way valve on DIC 60mL syringe.

14. The dry gas syringe is now ready to be injected into a gas chromatograph.

(VI). Silica Determination (for Landwater, Lakes, Streams)

Reagents and Standards:

1. A. 5% NaMoO4 solution: 25 g NaMoO4 + 7 ml H2SO4 to 500 ml total volume

B. 50% H2SO4

C. SnCl2 solution: [Stock: 40 g SnCl2 per 100 mL concentrated HCl]

2. Standards must be made up prior to the day of running and stored in a refrigerator. A good range of standards is as follows: 0, 2, 5, 10, 20, 40, 80, 200 umol/L Si

3. Reagents should also be prepared ahead of time. Sodium Molybdate must be made before the running day and stored in a dark bottle. Concentrated stannous cloride (SnCl2) must also be made ahead of time and stored in the refrigerator.

Spectrophotometer setup:

1. Turn on the spec (Shimadzu, at Univ. Michigan) and let it warm up for at least 5 minutes.

2. Select the test you want to run. Choose the test menu option (number 6) and hit enter.

3. Choose number 1 (load test) and then hit enter.

4. Load the silica test by choosing number 2 and hit enter (you will see other silica tests on the menu; these tests use different parameters). The parameters used for test number 2 are as follows:

Sample Num 1

WL (nm) 870.0

Init Delay (sec) 1

Hi Limit 9999

Lo Limit 0.000

Unit Label UM

Curve Type 1st Order

Num Stds 6

Curve Mode New

Baseline System

Response Medium

Lamp Change WL (nm) 340.0

Vis Lamp On

UV Lamp Off

Text Print On

5. In order to look at the test parameters or change the number and concentration of standards, go to the options menu by hitting the return key (you will change the number and concentration of the standards used according to the concentrations of your samples).

6. To set the number of standards, choose number 4 (num stds). Then enter the number of standards you want to run and hit enter.

7. To change the concentrations of the standards you will run, go to curve data (number 6) and hit enter. Then change each standard concentration as necessary.

8. Escape out of the setup screen by hitting the forward key on the keypad.

9. Before starting to run, you must zero the spec. Do this by placing two 1 cm cells filled with DI water into each cell holder, one of which is the reference cell and one of which is the sample cell. Close the sliding top door and hit the auto zero key. Take out the sample cell, but leave the reference cell. This will remain in place for the duration of your sample running.

Running standards and samples:

1. Take the standards and reagents out of the refrigerator and allow them to warm up to room temperature.

2. Pour Na-molybdate and H2SO4 into two 20 mL scint vials with screw-on caps.

3. Make up the SnCl2 by pipeting 1 mL of the concentrated solution into a 100 mL volumetric flask partially filled with DI H2O. (Do all of this under a hood). Top off the DI H2O in the flask to exactly 100 mL of solution. Mix the solution.

4. Pour the diluted SnCl2 into a 20 mL scint vial.

5. Place all three vials into the wooden sample tray in the following order: Na-molybdate, H2SO4, SnCl2.

NOTE: Set up your standards and samples in the sample tray before you begin running. This will minimize the confusion in running samples. The easiest way to run the samples is in multiples of eight.

Run a set of standards to check the curve before beginning your samples:

1. Number small scint vials consecutively, depending on how many standards you will run.

2. Add exactly 2 mL of each standard into the vials (increasing in concentration) and record the vial number and concentration. Don't forget to run a blank; your first standard (number 1) will be DI H2O.

3. Set the vials in the sample rack and set up a time sheet to keep track of when to add the reagents and read the sample. Below is an example of how to set up your time sheet (for four standards).

Sample Na-Molybdate H2SO4 SnCl2 Read

1 12:00 12:15 12:16 12:31

2 12:02 12:17 12:18 12:33

3 12:04 12:19 12:20 12:35

4 12:06 12:21 12:22 12:37

4. Use a different pipet for each reagent. Label them appropriately so as not to confuse them.

5. Start adding reagents to your standards when your digital watch reads 12:00 (for the example above). Add 0.2 mL Na-molybdate, wait 15 minutes and then add 0.5 mL H2SO4, and then wait one minute before adding 0.1 mL SnCl2. Lightly shake the vials after adding each reagent. Cross out times on your time sheet when you have completed each step.

6. Read your samples at the appropriate times by pouring the entire contents of each vial into a clean, dry cell. Place the cell into the slot inside the spec, making sure that you place it the same way each time (there is usually a faint letter 'G' in an upperhand corner of the cell. Make sure it faces the same direction each time you place it in the spec). Slide the top closed and hit the start key on the keypad.

7. After the reading is complete (it will only take a few seconds), clean the cell. Dump the waste in an appropriate container (do not put it down the sink) and rinse the cell with DI H2O three times. Then remove as much water as possible from the cell by forcefully shaking it. Go on to the next reading.

8. When you have finished reading all your standards run a regression on the absorbancies to check the r2 value. If it is greater than or equal to 0.9990, start running your samples.

9. A set of standards should also be run at the end of all your samples for each day you are running!

Running samples:

1. Samples should be obtained from bottles labeled 'anions.' Shake each bottle before opening and then pour a small amount into the anion bottle lid. Pipet 2 mL out of the lid and put into small scint vials.

2. Samples are run in the same fashion as the standards. You may, however, want to run more than eight samples at a time. In order to achieve maximum output per time, start your ninth sample immediately after you read your first sample in the spec. For example, if you were following the time table shown above, you would add Na-Molybdate to sample 9 at 12:32.

(VII). Low-level PO4- Determination (for Landwater, Lakes, Streams)

MAGIC: Magnesium-induced coprecipitation method for dissolved phosphorus. Karl and Tien, 1992.

A. Reagents:

This method is designed to determine nanomolar concentrations of either SRP or TDP, so all reagents should be at least analytical grade. All sources of contamination, especially reagents used must be carefully accounted for, given the low concentrations occurring in analysis by this method.

1. 0.1 N HCl = 8.20 mL trace-metal grade HCl in 1 liter DI.

2. 1 N NaOH = 40.0 g NaOH dissolved in 1 liter RODI.

3. 1 M MgCL2 = 203.3g MgCL2.6H2O dissolved in 1 liter DI.

B. Brucite Precipitation Method:

1. Karl and Tien suggest that if total particulate phosphorus (PP) is < 10% of the expected TDP concentration, than filtration is not necessary and even undesirable because of potential contamination.

2. After samples are collected into clean plastic 50 mL tubes they should either be immediately frozen or treated with NaOH. See #5 below.

3. Duplicate 40 mL aliquots of each sample should be placed into clean polypropylene centrifuge tubes.

4. Add 600 uL of 1M MgCL2 to each sample, mix.

5. Add 1.0 mL of 1M NaOH to each 40 mL sample (1:40 vol./vol. ratio) to induce the milky white brucite precipitation. Mix thoroughly.

6. Incubate for 5 minutes at room temperature, mix thoroughly, and incubate for another 5 minutes.

7. Centrifuge tubes (1000 x g) for 60 minutes at room temperature.

8. Aspirate the clear supernatant with a Pasteur pipette attached to a vacuum supply and discard.

9. Add ~ 8.0 mL of 0.1 M HCl and mix until pellet is completely dissolved.

9. Bring the sample volume up to 10.0 mL with the 0.1 M HCl; you have now created a 4 fold increase in SRP concentration.

10. From this point, the concentrated samples are treated exactly as untreated samples, and analyzed by the standard molybdenum blue method for SRP.

C. Standards:

1. Intermediate stock solution is 0.2 ug PO4-P/liter.

2. Working Standards:

uM desired Add To

0.032 1mL 2 liters

0.065 1mL 1 liter

0.129 1mL 500mL

0.258 2mL 500mL

0.646 1mL 100mL

1.937 3mL 100mL

3.875 6mL 100mL

(VIII). Total and Dissolved Organic P Determination (for Landwater)

Introduction:

To determine total phosporus (TP) levels, potassium persulfate is added to an unfiltered water sample. The persulfate oxidizes all phosphorus in the sample, liberating organic phosphorus as inorganic phosphorus which will react with the molybdate-ascorbic acid-antimony mixed reagent. Thus the procedure is identical to SRP analysis but with the addition of a pre-treatment digestion with the persulfate reagent.

Reagents:

The persulfate reagent is made by mixing 5% w/v K2S2O8 in distilled deionized water (e.g., 5g K2S2O8 in 100mL distilled deionized water). This solution must be made fresh daily.

Procedure:

1. Persulfate reagent is added to the unfiltered water sample in the ratio of 16 mL/100 mL sample. Number each TP tube and use an autopipette to remove 10mL of sample from each tube. Use a 1-10 mL serological pipet to add 6.4mL of persulfate reagent to each tube and recap.

2. Weigh and record the weight of each tube.

3. Autoclave samples for 0.5h at 15 lbs/in2

4. Evaporation may occur during autoclaving, resulting in a loss of sample volume. After samples have cooled, reweigh them and, if necessary, add distilled deionized water to bring the weight back to the value recorded before autoclaving.

5. Follow all procedures for SRP analysis.

(IX). Phytoplankton Sampling (for Landwater, Lakes, Streams)

Sampling and preservation:

1. Phytoplankton samples are collected in clean, labeled 250 mL amber plastic bottles.

2. In shallow waters, the bottle is rinsed once with sample water, then filled to the "shoulder".

3. In deep waters, rinse a tygon tube twice of length sufficient to reach the bottom of the upper mixing layer by lowering the tube slowly, pinching off the surface end of the tube, retrieving the tube from depth, then releasing the surface end of the tube allowing it to drain. The sample is collected in the same way except that the sample is drained into the collection bottle.

4. In the field, add Lugols until the sample is "tea colored" ( ~ 4 mL / 250 mL sample).

5. In the lab, add buffered formalin solution. Either add 1.5 mL to the entire 250 mL, or add 3 drops of formalin after settling procedure (described below).

Settling (Sample settling and volume reduction):

1. Mix the amber sample bottle thoroughly and pour 250 mL of sample into a clean, dry, labeled, 250 mL graduated cylinder. If there is less than 250 mL, record the total volume of sample, and rinse the sample bottle with 5 mL of DI water and pour into the graduated cylinder.

2. Cover the graduated cylinder with aluminum foil and place in a dark place (top shelf of large storage cabinet in the lab). Let settle undisturbed for 5 or more days.

3. Gently siphon the water from the top of the graduated cylinder until 10-15 mL of sample remains (be careful not to stir or mix the bottom water). Pour the 10-15 mL of concentrated sample into a labeled scintillation vial with a poly seal cap. Rinse the graduated cylinder twice with ~ 4mL of DI water and add to the vial. If formalin was not added previously, add the 3 drops now, and add Lugols if the sample is not a tea color.

*Note: Siphoning may be done with a hand vacuum pump, using a disposable glass pipette on the end of a 2 ft. latex tubing connected to a one gallon reservoir.

(X). Carle GC Operating Instructions (Toolik) (for Landwater, Lakes, Streams)

Starting the GC:

1. Turn on the helium to 40 psi; check for leaks.

2. Turn thermistor switch to "off." Turn on main power.

3. Turn helium down to 15-20 psi during warm-up period (a couple hours).

4. After warm-up turn helium back up to 40 psi. Let He flow for 5 minutes, then turn bridge setting to "thermistor." Turn on integrator, hit "monitor" to follow baseline of TCD, or hit "plot" and then enter.

5. For FID (CH4) channel, turn air and hydrogen on at main tanks making sure that the regulator is backed out. Turn H2 to 25psi.

6. Let H2 flow for 5 minutes. To light the FID, push the red ignite button until a quiet "pop" is heard, release the button and quickly turn the air up to 20 psi. Check to see that it is lit by monitoring the FID channel (#2). (Hit the monitor button twice. If FID is lit, the mV reading will jump).

7. Turn H2 down 4-5psi (about 1/8th turn) to about 20 psi for running.

8. Set the operating conditions on the GC (for Landwater):

Range=10

TCD Output=1

FID Output=8

9. Set the operating conditions on the integrator. Hit the "atten" button and set to "0." Hit "speed" and set to "3.5". Note the instructions for loading programs on the wall - load the program for Landwater.
10. Check the baseline by pressing "plot" on the integrator. The baseline can be centered with the "coarse" dial on the TCD channel on th GC. Re-zero the machine by hitting "zero" on the integrator.
11. Run a test sample of room air. Turn the handle to load, push through about 5mL, turn handle to inject, and press "start 1" and "start 2" on the integrator. After the CO2 peak is printed, hit "stop 1" and "stop 2" on the integrator.
12. If there is an air peak, but no CO2 peak, change the attenuation. If the baseline is not stable, the machine is not yet warmed up, or there is a leak.

Shutting down the GC (for use within 48 hours):

1. Turn off the air and then the H2 at the main tanks. Back out the regulators to reach 0 psi (it will take several hours for the H2 to reach 0 psi).

2. Turn off the thermistor.

3. Turn down the He to 15-20 psi (takes six ½ turns).

4. Turn off the integrator.

5. Turn the furnace up to 140 C for bake-out overnight.

6. For long-term shutdown, turn the machine off, wait for two hours, and turn the He off at the main tank.

(XI). QA/QC Procedures (for Landwater)

A. Gas Samples:

1. Go though field book and verify that all samples collected in field have been recorded correctly in both the gas book and the gas computer file. As you check each date, verify that all equilibration temperatures match the values recorded in the field book.

2. Once you have verified the values in the computer, check the quality of your standard curves. The correct way to run the regression is with the area of your standard being the independent variable and the concentration of your standard as the dependent variable; let the regression compute the y-intercept. You should have an R-squared value which is at least 0.999. If your R-squared value is less than 0.999, then you must graph the standard curve and delete the outlying points.

3. Using the x-coefficient and the constant of your regression, plug in the area of your standards and calculate the Y-hat value in the following manner:

PCO2_HS = {(peak area) (x-coefficient)} + constant

The results should be close to the concentrations of your standards. If not, your regression is off. Often when a high (10,000 ppm) standard is used, low concentration values will be off because the slope of your regression is slightly weighted towards higher concentrations. As a result, you often have to calculate a second standard curve for your low range samples (such as ambient air samples). To do this, follow the above procedure, but force the curve through zero (this is acceptable because nitrogen blanks give zero for a peak on the GC, hence there is no machine blank) and check your low range Y-hat values and see if they are any closer to the actual concentration of your standards. If the values are still off, delete the high standards from the curve, and only use the lower values for the curve (still forcing the curve through zero).

3. Once you have a good standard curve for low and high samples, use the above formula to calculate your sample concentrations, using values from the appropriate curve.

4. Sort your samples by concentration and compare the values from date to date, and from site to site. If you find any negative values, or extremely high values go back and check the field book for notes on that sample, check the gas book for possible problems analyzing the sample, and if nothing is found flag the sample and show the results to George. Often these outlying samples can be found quickly by graphing the sample concentrations in Quattro Pro or Reflex by site or date.

B. Dissolved Organic Carbon Samples:

1. Before you run any DOC samples, invert the bottle a few times and check for any particulates or fungal growth in the sample, as these will plug the lines in the DOC machine. If samples have particulates present, first try sonicating the sample for several hours. If this does not remove the particulates, try adding a small amount of NaOH. If this does not work, the sample must be filtered onto a pre-weighed ashed filter. Dry the filter in the drying oven and then reweigh the filter. If there is at least 100 ug of particulates present on the filter, analyze the filter on the CHN machine. The reason for this is that all of the samples are filtered in the field, so the particulates or fungal growth could have decreased the DOC concentration in the sample during formation.

2. Each sample should be analyzed on two different runs (days), using different standard curves. The DOC calculation program then averages these and gives the relative percentage difference between duplicate runs. Flag any samples that have percent differences greater than 2.5% and show to George.

3. (not complete...)