2. Sampling Procedures for Common Contaminants

Certain compounds require different sampling methods than others. Check with the laboratory that will perform the analysis about container type and volume, preservation and holding times. Clear descriptions of selected analytes, holding times, their rationale and preservatives to be used should be included in the sample plan before samples are collected. The USEPA SW-846, ADEQ QAPP (1991, pp. 151-166) and Garrett (1988, pp. 24-28) include detailed collection procedures. Here are short descriptions of how to collect and handle the most common types according to EPA-Contract Lab Program methodologies for aqueous samples:

a. Radon

1. Dislodge any bubbles in the tubing.
2. Fill one (or more) labeled 40-ml glass vial(s) by inserting decontaminated tubing into the sample bottle and drawing it up as the surface of the water rises until overflowing.
3. Screw cap on snugly with the PTFE (Teflon) side down.
4. Turn vial upside down, tap and check for bubbles. If bubbles appear, add more sample and recap.
5. Fill additional vials for field and equipment blanks, duplicates or split samples, as necessary.
6. Store vials upside down in an ice-filled cooler with a minimum/maximum thermometer at 4 C.
7. Check with the lab for recommended holding time.

b. Volatile Organic Compounds (VOCs)

Because of their potential to evaporate and degrade, VOC samples require special procedures for collection, preservation and handling. Always use laboratory-cleaned 40-ml amber glass vials, fill them at low-flow rates (<0.5 l/min), preserve with 25 mg of ascorbic acid (if residual chlorine is present) and two or more drops of hydrochloric acid (HCl, a biocide) to reduce the pH to <2, and ship them to the laboratory within recommended holding times. Unless modified by special site factors, the following method for VOC sampling is recommended:

1. Obtain at least four labelled, amber 40-ml vials for each sampling station. Use the first to test for the correct amount of HCl to add to reduce the sample pH to below 2, and the other vials for collecting samples and duplicates. Because the pH of sample water may vary from station to station, different amounts of HCl may need to be added to sufficiently reduce its pH to maintain sample integrity.
2. With a clean pipette, add two drops of 1:1 HCl (one drop for every 20 ml) to the sample. Because the acid is heavier than water, it will sink to the bottom. If residual chlorine is suspected or present, add 25 mg of ascorbic acid to the vial. Wearing gloves and splash-proof goggles, fill the pH test vial completely from the pump, open container or faucet. Cap the vial with the septum PFTE (teflon) side down, and shake vigorously for about a minute. Open the vial and test with a pH meter or special litmus paper. If necessary, add another drop of acid and retest until the pH is less than 2. Note the amount of acid used at this station in your field logbook. Pour the sample into the purge water container, and set the vial aside.
3. Fill out the sample labels in waterproof ink. In addition to your name and the sample number, note the preservative(s) used, and the exact location, date and time of sample collection.
4. Based on the pH test, add two or more drops of 1:1 HCl with a clean pipette to the second vial. It will sink to the bottom of the vial. Be careful when handling HCl. It can cause severe burns!
5. Holding the vial at an angle, slowly fill it at a low-flow rate of 0.1 l/min to as close to the top as possible. To avoid aeration, an alternative method is to insert the tubing into the vial and draw the tubing up as the water rises. Be careful not to wash out any ascorbic acid, if used.
6. Fill the cap with sample water and slowly pour it into the vial to form a meniscus (the curved upper surface of the water formed by surface tension).
7. Screw on the cap so that the PFTE-side of the septum is down. Do not over-tighten!
8. Turn the vial upside down and tap it with a finger. If any bubbles appear, uncap the vial, add more water to the meniscus, recap, turnover and repeat until none appear.
9. Shake the vial for one minute.
10. Repeat steps 4-9 above for QA/QC duplicates, blanks and split samples, if necessary.
11. Wrap the vials in a bubble pack or other type of padded packing material to prevent breakage. Store the vials upside down in an ice filled cooler at 4 C with a maximum/minimum thermometer, and ship by overnight mail. Keep samples away from organic vapors.
12. Analyze the samples within 14 days.

c. Semi-Volatile Organics

Use the following procedure for all semi-volatile organics (also called acid-base-neutral extractables):

1. Fill two labeled 1-liter amber glass bottles (complete filling is not necessary).
2. Cap with teflon-lined septum and plastic screw cap.
3. Fill additional bottles for field and equipment blanks, duplicates or split samples, if necessary.
4. Store bottles in an ice-filled cooler with a minimum/maximum thermometer at 4 C.
5. Make sure laboratory liquid extraction starts within five days.

d. Pesticides/PCBs

Use the same procedure as for semi-volatile organics above.

Use the same procedure as for semi-volatile organics above, except preserve with sufficient concentrated sulfuric acid to reduce sample pH to <2.

Use the same procedure as for semi-volatile organics above, except preserve with 5 ml of concentrated sulfuric acid.

Use the following procedure for all metals except mercury. Consult your sampling plan to determine if filtered or non-filtered samples are required.

1. Filter sample with a capsule filter, if dissolved metals are to be analyzed.
2. Fill one labeled 1-liter plastic bottle avoiding aeration.
3. Add nitric acid to reduce pH below 2. Use gloves and splash-proof goggles when handling acid.
4. Cap with plastic screw cap liner.
5. Fill additional bottles as above for field and equipment blanks, duplicates or split samples, as necessary.
6. Store bottles in an ice-filled cooler with a minimum/maximum thermometer at 4 C.
7. Analyze within 6 months.

h. Mercury

Use the same procedure as for low level metals, except the sample holding time is 28 days instead of 6 months.

Fill one labeled 1-liter plastic bottle avoiding aeration. The label should state "CN analysis, NaOH preserved"

Pour off top 1/2 inch of sample.

Add 0.6 grams of ascorbic acid if residual chlorine is present.

Add sodium hydroxide pellets until pH>12 (check with lab to determine correct amount).

Cap with plastic screw cap liner.

Gently mix for two minutes.

Fill additional bottles as above for field and equipment blanks, duplicates or split samples, if necessary.

Store bottles in an ice-filled cooler with a minimum/maximum thermometer at 4 C.

Analyze within 2 days (ADEQ) or 12 days (EPA). Check with laboratory.

j. Gross Alpha and Gross Beta

This procedure is based on the ADEQ Method. (QAPP, 1991, p. 161)

1. Fill two labeled 1-liter plastic or glass bottles, avoiding aeration.
2. Cap with screw cap.
3. Fill additional bottles for field and equipment blanks, duplicates or split samples, as necessary.
4. Deliver to the lab within five days.
5. Lab personnel will add nitric or hydrochloric acid to reduce pH<2, and analyze the sample after 16 hours.

k. Uranium, Radium

This procedure is the same as for Gross Alpha and Gross Beta except that the sample must be acidified either in the field or within five hours after collection.

The ADEQ and the Arizona Department of Health Services (ADHS) have a detailed, 9-page guidance entitled "Procedures for Collecting and Processing Stream Water Samples for Bacteriological Analysis." Use this field method for analysis of fecal coliform and streptococci bacteria. The method requires specialized equipment, such as sterile, buffered solution water, Whirl-pak bags, Petri dishes, sterile membrane filters, pipets, and incubator and a binocular microscope. If heavy metals are suspected, an appropriate chelating agent (e.g. EDTA) is added prior to sterilization. Because of its length, the guidance is not reproduced here but is available through the Surface Water Monitoring Unit at ADEQ in Tucson or Phoenix.

This procedure employs the ADEQ Method (QAPP, 1991, pp. 164-165).

1. Fill out information on one 1-gallon ziploc bag with a waterproof pen.
2. Assemble clean sampling equipment in the following order: inlet hose, portable pump, connecting hose, filter, housing unit, connecting hose, flow meter, and outlet hose. If the well has a pump, then connect the equipment (without the portable pump) to the faucet tap. Be sure the outlet hose is far from the inlet hose.
3. Pump 40 to 1,000 liters (10 to 250 gallons) of water through the filter at approximately 4 liters per minute.
4. Wearing non-contaminating gloves, carefully unscrew the filter housing and remove the filter with tweezers.
5. Place the filter in a ziploc bag along with the remaining water left in the housing unit and seal bag tightly.
6. Seal this bag in another ziploc bag.
7. Store bag in ice-filled cooler.
8. Ship to the laboratory within 24 hours.
9. Decontaminate all equipment in contact with sample water by circulating a solution of 5% chlorine bleach for at least 20 minutes, followed by a solution of 10% sodium thiosulfate and 0.1-micron filtered water to neutralize the chlorine, followed by flushing with 100 gallons of water.
10. Take an equipment blank sample from the final flush water and have it analyzed for viruses (check with lab for required volume).

Both federal and state QA/QC offices require the collection of additional samples called equipment blanks, field blanks, travel blanks, duplicates, and split samples. These samples are used to check the quality of decontamination, collection, and handling procedures to verify that they have not affected sample-water quality. The number, type and handling of QA/QC samples are clearly specified in the sampling plan.

EPA Region 9 guidance states that all three types of blanks do not have to be collected every day; instead, one blank per day is sufficient with the order of preference being equipment, field and travel blanks. Travel blanks are mostly used for VOC analyses. All QA/QC samples should be sent blind to the laboratory.

The Lab QC Sample is collected for each 10 samples collected or one per week, whichever is greater. This sample is not an additional sample, but a special designation for an existing one. Collect a double volume sample (i.e., twice as many containers as a normal sample.) Containers must clearly be identified as a lab QC sample.

Equipment blanks consist of containers filled with the final rinse water from equipment decontamination. Once analyzed, they reveal the effectiveness of cleaning of field equipment. Collect equipment blanks after sampling the surface water or ground water station with the highest contamination. One per day of sampling is sufficient.

Field blanks are containers of deionized water that are filled at the sampling station, then labeled, packaged, sealed and shipped to the laboratory like other samples. They check for contamination in the laboratory and for cross-contamination during the collection and shipment of the samples. The laboratory requires one field blank for each day of sampling.

Travel blanks are containers of deionized water prepared by the laboratory. They are kept in the same sample cooler as the other samples at every stage of the collection, handling and shipment process. Back at the lab they are analyzed for VOC parameters. If contaminants are found, they could be attributed to contamination that occurred during sample transport, storage or in the lab. At least one for each sample shipment is required.

Duplicate samples are used to check the precision of field collection or laboratory analyses. Duplicates are collected at the same time as the water quality sample at a rate of one in every ten or 10 percent per day, whichever is greater. Collect a duplicate sample from a station that is believed to have elevated levels of a particular compound.

Split samples are additional water quality samples that are collected and handled identically as the others in the field, but are sent to a different laboratory or as a blind sample for analyses to the same lab, as a check on laboratory handling and procedures. Split samples are often most collected at a facility during compliance monitoring.

Background samples are collected to check the results of site evaluation sampling. Background samples are used to establish the background conditions, and are obtained hydraulically upgradient from contaminant sources.

Wrap and pack samples securely so that sample containers are received unbroken at the laboratory. Be sure to pack the blanks in the same way as all other samples, so that the laboratory cannot identify the blanks. Note all identification numbers in the field log book.

The EPA, ADEQ, ADHS, and Mexican agencies all have specific procedures and forms for sample shipment and chain-of-custody protocols. Agency QA/QC offices are consulted when the sample plan is developed. Make sure that you understand all aspects of these procedures.

Ensure that the laboratory has been notified of the time of sample delivery and how the samples will be shipped (by the field sampler, bus, courier, or other). For example, ADHS has "Chain of Custody Record" and "Chemical Analysis Submittal" labels and forms that accompany samples to be analyzed by the state laboratory.

Water and other wastes generated as a result of well purging or equipment decontamination must be disposed of properly. Consult with the responsible federal and state agencies of the United States and Mexico (ADEQ, EPA or SEDESOL, depending on the site location) before sampling takes place, and clearly describe in the Sampling Plan how both uncontaminated and contaminated water (and other wastes) will be handled in the field. In general, do not dispose of purge and decontamination water on site unless the water has been analyzed and found to be non-hazardous. If the water exceeds recommended standards, drum and store it on site in a safe area until disposal by accepted methods is possible.