Sample Handling and Collection This section provides guidance on sample

han-dling procedures, such as filtration, and specific techniques for collection of samples that will be analyzed for various classes of groundwater pollutants, such as SVOCs. For detailed sam-pling procedures and preservation of samples, refer to Appendix B of this handbook. It is im-portant to remember that COC procedures should be followed for all groundwater sampling events and that all samples (except for metals) remain on ice during both sample collection and shipment to

the laboratory. Details regarding the use of COC procedures are provided in Chapter 3.

8.8.1. Sampling for Metals

Certain regulations require metals analyses to be performed on unfiltered groundwater samples.

The reason for these requirements is to obtain a representative sample as it actually occurs in the aquifer and to maintain consistency between sample handling for inorganic and organic ana-lyses. If a particular situation demands consid-eration of dissolved metals, both filtered and non-filtered samples should be collected for analysis.

The regulatory document or approved SAP should be consulted for monitoring requirements.

The differences obtained as a result of sample handling (filtered versus non-filtered) are depen-dent on the type of association between the spe-cific inorganic ion and the particulate matter.

Studies show that when an inorganic ion is not closely associated with particulate matter (e.g., sodium), the differences between total and dis-solved concentrations are small and random.

Ideally, the sample can be split into two portions, one for filtration and the other for immediate preservation and subsequent analysis for total metals concentration. By analyzing the two fractions separately, differences between dis-solved and total metals can be compared.

The decision of whether to filter metals samples should be based on the physical quality of the samples, the objectives of the monitoring pro-gram, and the policy of the regulation or agency controlling the sampling event. If filtering is allowed and chosen, it is imperative that it be performed in a manner that will preserve the integrity of the sample and allow for consistent reproduction of technique.

Filtration of groundwater samples for dissolved metals analyses should be performed with a pre-cleaned filtering apparatus. Sampling devices should be cleaned using ultra-pure nitric acid when low-level metals contaminants are being measured. Filtration must be done immediately upon sample collection, prior to preservation.

Samples transported to the lab for filtration and

preservation should be documented, because sample composition will change during transport.

The sample should be collected and filtered through a 0.45-µm pore diameter cellulose acetate filter. If using a vacuum filter is impractical, pressure filtration must be performed. Care should be taken to follow the manufacturer’s recommended procedure if vacuum filtration is used. All filter apparatus should be laboratory-cleaned and dedicated; however, disposable filters are acceptable. For each sampling event, a new disposable filter must be used to avoid cross-contamination of samples.

Groundwater samples to be analyzed for both total metals and dissolved metals are collected in plastic bottles and preserved with nitric acid to pH < 2. All appropriate data should be recorded in the FLB/FN.

8.8.2. Sampling for VOCs

At each site, samples for analysis of VOCs are collected first. Care should be taken to prevent volatilization of the sample when placing

groundwater into the vial. Groundwater samples collected for analysis of VOCs, either from pas-sive diffusion bags, low-flow pumps, or bailers, must be placed into 40-milliliter vials with a septum.

A sacrificial 40-milliliter sample should be ob-tained to determine preservation requirements before VOC samples are collected. Fill the vial with sample water, then add 1:1 HCl, drop-by-drop, and test the pH until it is < 2. If the test sample effervesces when the HCl is added, the samples should not be acid preserved and should be analyzed within 7 days of collection. Record the amount of HCl added. Alternatively, prepre-served VOC vials may be obtained from the analytical laboratory.

The procedure for collecting a VOC sample is described below:

1. Remove the cap from a 40-mililiter septum (Teflon®-faced silicon rubber) vial. Avoid contact with the inner surface.

2. Add the established amount of HCl necessary for sample preservation (if prepreserved vials have not been supplied by the laboratory).

3. Fill the vial with sample water, taking care to minimize aeration, and screw on the cap tightly to achieve zero headspace. The Tef-lon®-lined side of the cap must face the aqueous sample.

4. Inspect the vial for air bubbles. If air bubbles are present, discard the vial and restart with step 1.

5. Label the vial, and place it in a resealable bag.

6. Record appropriate data in the FLB/FN.

8.8.3. Sampling for Extractable Organics The procedure for collecting groundwater sam-ples for analysis of SVOCs is described below.

1. Remove the Teflon®-lined cap from a 1-liter amber glass bottle. Avoid contact with the in-ner surface of the cap.

2. Fill the bottle with groundwater.

3. Replace the cap tightly, attach the sample label, and place the sample bottle in a cooler with enough bagged ice to cool the sample to

≤ 6°C.

4. Repeat steps 1 through 3 for additional sam-ples.

5. Record appropriate data in the FLB/FN.

8.8.4. Sampling for Cyanide

The procedure for collecting groundwater sam-ples for analysis of total cyanide is described below.

1. Place groundwater into a 1-liter wide-mouth plastic bottle.

2. Determine if sulfide is present. Pour a small aliquot of sample from the 1-liter wide-mouth plastic bottle into a clean 100-mililiter beaker and test for sulfide using a lead acetate test strip. If sulfide is:

 Present and visible solids are present, go to step 3

 Present and no visible solids are present, go to step 5

 Not detected, go to step 8.

3. If sulfide is present and visible solids are present, filter the sample through a 0.45-µm cartridge filter within 15 minutes of collection.

The sample should be pumped through the fil-ter using new Tygon® tubing into a second clean, 1-liter wide-mouth plastic bottle.

4. Place the spent 0.45-µm cartridge filter in a 1-gallon resealable bag, label the bag with the appropriate sample number and collection time, and place the filter cartridge and bag into the freezer. The frozen filter can be sent to the laboratory for analysis of cyanide.

5. For the presence of sulfide, add 1 gram of solid lead carbonate to the 1-liter wide-mouth sample bottle, cap the bottle, and mix by in-verting the bottle several times.

6. Check for the removal of sulfide. Pour a small aliquot of lead carbonate-treated sample into a clean 100-milliliter beaker and test for sulfide again using the lead acetate test strip. If sul-fide is present, add another gram of lead car-bonate to the sample, cap the bottle, and mix by inverting the bottle several times. Repeat this step until sulfide is not detected by the lead acetate test strip.

7. Filter the lead carbonate-preserved sample through a new 0.45-µm cartridge filter to re-move residual chemical addition and lead sul-fide formed during the precipitation reaction.

Collect the filtrate in a clean 1-liter plastic wide mouth bottle. Discard the 0.45-µm car-tridge filter.

8. Determine if total chlorine is present. Pour a small aliquot of sample from the 1-liter wide-mouth plastic bottle (preserved, if sulfide was present) into the appropriate vials of the chlo-rine test kit and analyze for total chlochlo-rine. If total chlorine is present in the sample, add 0.1 gram of sodium borohydride (NaBH4), cap the bottle, and mix by inverting the bottle several times. If chlorine is not detected, go to step 10.

9. Check for the removal of chlorine. Pour a second small aliquot of NaBH4-treated sample into the appropriate vials of the chlorine test

kit and analyze for total chlorine. If chlorine is present, add another 0.1 gram of NaBH₄. Re-peat this step until chlorine is no longer de-tected. Generally, 0.1 gram/liter NaBH4 will reduce 50 mg/liter of chlorine.

10. Adjust the pH of the sample to > 12 using sodium hydroxide (NaOH), and place the sample on ice to lower the temperature to ≤ 6°C prior to shipping to the laboratory. When the sample has cooled, pack and ship using normal procedures. Record all preservation procedures in the FLB/FN.

8.8.5. Sampling for Conventional Parameters and Nutrients

Conventional pollutants typically include BOD, O&G/TPH, TOC, COD, TDS, TSS, and chloride.

Nutrients include ammonia, nitrate, and total phosphorous. Bottle and preservation require-ments will differ based on each particular analyte.

The procedure for collecting groundwater sam-ples for analysis of conventional pollutants and nutrients is described below:

1. Remove caps from sample bottles. Avoid contact with the inner surface.

2. Fill bottles to about 90 percent full. Add appropriate preservative to the samples per Appendix B of this handbook or the SAP.

3. Replace and tighten caps, attach labels, seal in resealable bags, and place sample bottles in a cooler with enough bagged ice to cool the samples to ≤ 6°C.

4. Record all appropriate data in the FLB/FN.

8.8.6. Sampling for Radioactive Elements Groundwater samples typically are analyzed for the following radioactive constituents: gross alpha, gross beta, tritium, strontium-90, combined radium-226/228, and uranium. Other radioactive elements, such as plutonium, cesium-137, or americium-241, also may be included in ground-water sampling programs, depending on the historical uses at the site. The types of sample bottles and the required volume of the groundwa-ter sample will vary depending on the radioactive element. The SAP must contain information on sample bottles, sample preservation, and sample

holding times for specific radioactive elements that will be analyzed. When preparing the SAP, refer to the Multi-Agency Radiological Laborato-ry Analytical Protocols (MARLAP) guidance on field sampling of radioactive analytes

(http://www.epa.gov/radiation/docs/marlap/402-b-04-001b-10-final.pdf).

Note: Shipment of radioactive samples to the laboratory may require special handling procedures. Samples to be shipped off site must be field-screened to determine the levels of radiation present. The screening will allow for proper packaging and shipping via International Air Trans-port Association (IATA) Dangerous Goods Regulations.

By IATA definition, a material with an activity level of more than 2,000 pCi/g is considered radioactive. If groundwater samples exceed this level, special IATA packaging procedures are required for shipment by air.

Packaging procedures for radioactive samples must be included in the SAP, and special training of field personnel may be required for the handling and packaging of radioac-tive groundwater samples.

8.8.7. Sampling for Light, Non-aqueous Phase Liquids

Light, non-aqueous phase liquids (LNAPLs) are generally considered to be low density, immisci-ble organics, including gasoline, petrochemicals, and other chemicals with specific gravities of less than water. They are usually present in aquifers as a separate phase due to their low solubility in water. These chemicals tend to float on the water surface in a water table environment and com-monly occupy the capillary fringe zone above the water table. If LNAPLs are suspected to be floating on the water table, all shallow wells installed in the area under investigation must be screened across the water table.

Note: Samples of the floating organic layer must be collected before the well is purged.

In a confined aquifer, LNAPLs are found along the upper surface of the permeable material and also within the overlying confining layer. When immiscible organics with a specific gravity less than water are the contaminants of concern, or if contaminants are suspected in more than one stratified layer in the well column, sampling procedures must be modified. It may be neces-sary to lower the sampling bailer to a particular depth in the well or to utilize a double

check-valve bailer. Sampling procedures for LNAPLs differ substantially from those for other pollu-tants. If more than one distinct LNAPL layer is present in a well, each layer should be sampled.

Samples should be analyzed for chemical compo-sition (e.g., for VOCs and base-neutral extrac-tables) and physical parameters (e.g., specific gravity, water solubility, vapor pressure of the liquid, and Henry’s Law Constant).

Measurement of the thickness of the floating layer can be accomplished by using a water indi-cator paste or gel with a weighted steel tape to determine the depth to the top of the floating layer and to the water surface. The difference between these two readings is the thickness of the floating layer. Measurement of the thickness of the floating layer also may be accomplished by using an interface probe or a clear Teflon® bailer (if the product thickness is less than the length of the bailer). Electric water level sounders will not work properly for these determinations.

After a monitoring well is initially constructed, it should be developed and pumped to remove stagnant water. Then the well should sit idle for at least 2 weeks to allow the water level and floating layer(s) to stabilize fully. Prior to purg-ing the monitorpurg-ing well, a sample of the floatpurg-ing layer can be obtained using a bailer that fills from the bottom.

The collection of a water sample from a well containing free-floating product is challenging and at times problematic. This is true even if the LNAPL floating in the well has been removed during the purging process (the LNAPL can still coat the inside casing, or be entrained in the screen and sand pack, and likely is emulsified below the air/water interface). Care should be taken to lower the bailer just through the floating layer but not significantly down into the underly-ing groundwater. Care also should be taken in proper planning when sampling water from such wells and interpreting the resulting data (e.g., to determine if the sample is representative of the actual groundwater concentrations). Various sampling methods may be used to provide greater confidence in the results of the analysis. Stilling

tubes may be used to help prevent the sampling device from contacting residual LNAPL that can impact the collected water sample. Discrete interval samplers also may be used to ensure that emulsified product does not enter the sampler during emplacement below the water level in the well. Samples should be analyzed to determine the chemical composition and physical properties of the LNAPL. After following typical evacua-tion procedures discussed previously in this section, a sample of formation water may be obtained from the well.

8.8.8. Sampling for Dense, Non-aqueous Phase Liquids (DNAPLs)

DNAPLs include chlorinated solvents and other chemicals with specific gravities greater than water. They are usually present in aquifers as a separate phase due to their low solubility in wa-ter. DNAPLs tend to migrate downward through both the unsaturated zone and the saturated zone due to their high density. If the volume of the DNAPL introduced into the subsurface is larger than the retention capacity of the vadose and saturated zones, a portion of the DNAPL will spread out as a layer of free liquid on the bottom of the aquifer or on lower permeability beds within the aquifer.

Measurement of the thickness of DNAPLs must be performed prior to purging the well. Mea-surement of the DNAPL can be accomplished by using a water indicator paste or gel with a

weighted steel tape (if no LNAPL is present) to determine the depth of the top of the DNAPL and the bottom of the well. The difference between these two measurements is the thickness of the DNAPL. An interface probe also may be used to measure DNAPL thickness in the well.

Note: Samples of the settled organic layer must be col-lected before the well is purged.

Prior to purging the monitoring well, a sample of the DNAPL can be obtained using a dual check-valve bailer or a bladder pump. If both LNAPLs and DNAPLs are present, it may be necessary to purge the well of one casing volume of water prior to sampling the DNAPL. Efforts should be made not to disturb the DNAPL in the bottom of

the well by setting the pump intake of the sub-mersible or suction-lift pump several feet above the DNAPL.

Samples should be analyzed to determine the chemical composition of the DNAPL and its physical properties (e.g., specific gravity, water solubility, equilibrium vapor pressure of the liquid, and Henry’s Law Constant). After the well is purged, a sample of the groundwater may be obtained for laboratory analysis.