#1229
Rev 0
7/26/04
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U.S.EPA REGION 9 LABORATORY
RICHMOND, CALIFORNIA
FIELD SAMPLING GUIDANCE DOCUMENTS #1229
TRACE METAL CLEAN SAMPLING OF NATURAL WATERS
4.0 Interferences and Contamination Problems
5.0 Equipment/Apparatus
6.0 Reagents
7.0 Procedures
7.1 Manual Sampling
7.2 Grab Sampling
7.3 Continuous Flow Sampling
7.4 Field Filtering
7.5 Re-cleaning Equipment in the Field
8.0 Calculations
9.0 Quality Assurance/Quality Control
9.1 Equipment Blanks
9.2 Field Blanks
9.3 Duplicates
10.0 Data Validation
11.0 Health and Safety
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SOP #1229
TRACE METAL CLEAN SAMPLING OF NATURAL WATERS
1.0 Scope and Application
This Standard Operating Procedure (SOP) describes collection, handling, filtration, preservation
and quality control procedures for sampling natural waters. These methods include the sample handling,
analysis, and quality control procedures necessary for reliable determination of trace metals in aqueous
samples. Samples will be subsequent analyzed for determination of total recoverable metals and/or
dissolved (<0.45 µm) metals. It is designed to prevent contaminating ambient water samples with the
metal(s) of interest and to yield accurate measurement via proposed EPA analytical methods listed in
Table 1. Implementation of these sampling techniques supports water quality monitoring and permitting
programs administered under the Clean Water Act. This SOP is derived from EPA Method 1669,
Sampling Ambient Water for Determinations of Metals at EPA Water Quality Criteria Levels.
This SOP is applicable to the metals listed below and other metals, metals species, and elements amenable
to determination at trace levels; i.e., ambient concentrations in the part-per-trillion (ppt) to low part-per-
billion (ppb) range. It is not intended for determination of metals normally found in untreated discharges
from industrial facilities, in-process waters, landfill leachates, processed inorganic substances and other
samples containing mid- to high-level (part-per-thousand to part-per-million) concentrations of the
analytes listed below.
Analyte Symbol
Chemical Abstract Services
Registry Number (CASRN)
Antimony (Sb) 7440-36-0
Arsenic (As) 7440-38-2
Cadmium (Cd) 7440-43-9
Chromium (III) Cr
+3
16065-83-1
Chromium (VI) Cr
+6
18540-29-9
Copper (Cu) 7440-50-8
Lead (Pb) 7439-92-1
Mercury (Hg) 7439-97-6
Nickel (Ni) 7440-02-0
Selenium (Se) 7782-49-2
Silver (Ag) 7440-22-4
Thallium (Tl) 7440-28-0
Zinc (Zn) 7440-66-6
This SOP includes techniques to maximize the ability of the sampling team to reliably collect samples,
eliminate sample contamination, and maintain sample integrity during filtration and preservation.
Procedures for manual sampling, grab sampling, continuous-flow sampling, field filtering and re-cleaning
sampling equipment in the field are explained in Section 7.0. These clean techniques are based on
findings of researchers collecting and performing trace metal analyses in aqueous samples from natural
waters including pristine streams, large lakes, bays or oceanic waters.
For dissolved metal determinations, samples must be filtered through a 0.45 :m pore size capsule filter at
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the field site. The filtering procedures are described in this method. The filtered samples may be
preserved in the field or
transported to the laboratory for preservation. Procedures for field preservation
are detailed in this sampling method; whereas procedures for laboratory preservation are provided in the
analytical methods referenced in Table 1. Field preservation requirements are summarized in Table 2.
It cannot be overemphasized as to the ease of contaminating ambient water samples with the metal(s) of
interest and/or interfering substances. The only way to measure the performance of these clean
techniques is through the collection and analysis of uncontaminated blank samples in accordance with this
guidance and the methods in Table 1. Thus it is a performance based sampling method; it is highly
recommended that any modifications be thoroughly evaluated and demonstrated to be effective before
ambient water samples are collected.
The terms "clean" and "ultraclean" have been used in other Agency guidance to describe the techniques
needed to reduce or eliminate contamination in trace metals determinations. These terms are not used in
this sampling method due to a lack of exact definitions.
Procedures outlined below are for use only by personnel thoroughly trained in the collection of samples
for determination of metals at ambient water quality control levels.
2.0 METHOD SUMMARY
This SOP describes field sampling procedures commonly referred to as “clean hands, dirty hands”
techniques. Upon arrival at the sampling site, one member of the two-person sampling team is designated
as "dirty hands"; the second member is designated as "clean hands." All operations involving contact
with the sample bottle and transfer of the sample from the sample collection device to the sample bottle
are handled by the individual designated as "clean hands." "Dirty hands" is responsible for preparation of
the sampler (except the sample container itself), operation of any machinery (pump), and for all other
activities that do not involve direct contact with the sample.
The “clean hands, dirty hands” technique has been included and adapted for three methods to collect
natural waters samples. Manual sampling is the simplest and requires the least equipment. Subsurface
samples are collected by either grab immersion sampling or pumping the sample to the surface. Grab
sampling with a specialized device can be used to collect discrete samples and can convienently obtain
samples at several depths. Continuous flow sampling via pump systems is used to collect numerous
samples at various depths. Field filtering and re-cleaning equipment in the field are also included in this
SOP since they apply to three sampling methods.
The success of trace metal clean sampling depends upon the sampling personnel. Section 4 details
contamination problems, which must be acknowledged and adapted by field samplers both in the
laboratory prior to arrival at the site as well as during the sampling event. This new mind-set needs to be
accepted as doctrine by the samplers (see Section 4 & 7).
Trace metal clean sampling does not require sophisticated sampling equipment. It does require metal-free
sampling apparatii and sufficient re-training of personnel to modify collection procedures to maintain
sample integrity; e.g., minimize contamination sources. To achieve low detection levels in ambient water
samples, personnel must complete significant preparation in the laboratory prior to travelling to the
sampling site. Also, they must evaluate the environmental conditions which may affect sampling free of
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contamination. For example, whenever possible, samples are collected facing upstream and upwind to
minimize introduction of contamination. Another example is to manually fill a sample bottle by rapid
immersion in water and capping to minimize exposure to airborne particulate matter. This equipment is
scrupulously cleaned to be free of metal contamination as outlined in SOP #140–Trace Metal Labware
cleaning procedures.
EPA protocol calls for field filtration to collect samples for dissolved metals. Unpreserved samples are
filtered through a 0.45 :m capsule filter at the field site. After filtering, the samples are double-bagged
and iced immediately. Sample containers are shipped to the analytical laboratory.
Acid preservation of samples (unfiltered and filtered) can be performed either in the field or the
laboratory. The sampling team may prefer
to utilize laboratory preservation of samples to expedite field
operations and to minimize the potential for sample contamination since it it can be performed under
HEPA filters inside a Class 100 clean bench. Samples can be field preserved inside a glove box designed
to provide a particulate free environment.
Via SOP #140, the laboratory is responsible for generating an acceptable equipment blank to demonstrate
the sampling equipment and most notably sample containers are free from trace metals contamination
before used by the field sampling team. An acceptable blank is one that is free from contamination below
the quantitation level (QL) specified in analytical method 1640.
Quality control samples must be collected while sampling in the field. This includes equipment blanks,
field blanks, field duplicates. The laboratory or cleaning facility must prepare a large carboy or other
appropriate clean container filled with reagent water for use with collection of field blanks during
sampling activities. The reagent-water-filled container should be shipped to the field site and handled as
all other sample containers and sampling equipment.
NOTE: Specific details for collecting aqueous mercury samples are provided in italics.
3.0 SAMPLE CONTAINERS, HANDLING, PRESERVATION AND STORAGE
Apparatus—Throughout this method, the sample containers, sampling devices, instrumentation, and all
other materials and devices used in sample collection, sample processing, and sample analysis activities
will be referred to collectively as the Apparatus.
Before samples are collected, all sampling devices and sample containers are cleaned in a laboratory
using detergent, mineral acids, and reagent water. Most sampling devices and containers must be
constructed of nonmetallic material and free from material that contains metals. Acceptable materials are
high- and low-density polyethylene, polycarbonate, or polypropylene, unless mercury is the target analyte
when fluoropolymers (FEP, PFA or PTFE) are required. Details on material construction can be found in
section 5. Sample containers must be acid-cleaned and prepared for field use in a class 100 clean room.
After cleaning, sample containers are filled with weak acid solution, individually double-bagged, and
shipped to the sampling site. All sampling equipment is also bagged for storage or shipment.
Samples collected for dissolved metal determinations are to be filtered in the field (section 7.4). They can
be acid preserved in the field or in the laboratory. Field preservation may introduce undesired
contamination; therefore laboratory preservation is recommended
.
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4.0 CONTAMINATION PROBLEMS AND INTERFERENCES
Much of the historical metals data in samples from natural waters are inaccurate due to contamination
from sampling methods or containers. In the mid-1970's, when analytical chemists devised new
techniques and applied them to environmental sampling, then it was revealed much of the ambient waters
trace metals data were erroneously high. Preventing contamination of aqueous samples during the
sampling, handling and analytical process is the greatest challenge faced in accurate trace metals
determinations. Thus, it is imperative samplers use forethought while considering sampling orientation at
the site. Also samplers must practice extreme care to reduce contamination and avoid compromising the
integrity of ambient water samples.
Thorough presentation of requirements and suggestions for controlling sample contamination are given in
corresponding EPA sampling Method 1669 and EPA analytical methods (e.g., Method 1640) listed in
Table 1.
Contamination Control
There are numerous routes by which samples may become contaminated. Potential sources of trace
metals contamination during sampling include metallic or metal-containing sampling equipment,
containers, labware (e.g. talc gloves that contain high levels of zinc), reagents, and deionized water;
improperly cleaned and stored equipment, labware, and reagents; and atmospheric inputs such as dirt and
dust from automobile exhaust, cigarette smoke, nearby roads, bridges, wires, and poles. Even human
contact (hair or dental work) can be a source of trace metal contamination.
Use metal-free Apparatus—When possible obtain and use equipment that is completely free of the
metal(s) of interest. Only fluoropolymer (FEP, PFA), conventional or linear polyethylene, polycarbonate,
polysulfone, polypropylene, or ultrapure quartz should come in contact with the samples. PFA is less
desirable than FEP due to expense. Regardless of construction, all materials that will directly or
indirectly contact the sample must be cleaned prior to use (see SOP 140).
Avoiding contamination—Avoid exposure of the sample and sampling apparatus by performing
operations in an area known to be free from contamination. Two of the most important factors are: (1)
awareness of potential sources of contamination and (2) strict attention to work being performed.
Minimize exposure—Contact or expose samples or blanks only in a clean room, under a clean bench,
inside a glove box, or clean plastic bag, so that exposure to atmospheric inputs is minimized. When not
being used, the Apparatus should be covered with clean plastic wrap, stored in the clean bench or in a
plastic box or glove box, or bagged in clean, colorless zip-type bags (most convenient).
Wear gloves—Personnel must wear clean, nontalc gloves (Section 5.0) while handling the Apparatus,
samples and blanks. If another object or substance is touched, the glove(s) must be changed before
handling the Apparatus again.
Contamination by carryover—At sites where more than one sample will be collected, the sample known
or expected to contain the lowest concentration of metals should be collected first with the sample
containing the highest levels collected last (Section 7). This will help minimize carryover of metals from
high- concentration samples to low- concentration samples. Without prior knowledge of the waterbody,
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sampling team should rinse the collection equipment with dilute acid and reagent water between samples
and then collect a field blank (Section 7.5).
Contamination by indirect contact—Apparatus that may not directly contact samples may still be a source
of contamination. For example, clean tubing placed in a dirty plastic bag may pick up contamination
from the bag and subsequently transfer the contamination to the sample. Therefore, it is imperative that
every piece of the Apparatus that is directly or indirectly used in the collection of ambient water samples
be cleaned as specified in the analytical method(s) referenced in Table 1.
Contamination by airborne particulate matter—Samples may easily be contaminated by airborne dust,
dirt, particulate matter, or vapors from automobile exhaust; cigarette smoke; nearby corroded or rusted
bridges, pipes, poles, or nearby roads; and even human breath (mercury amalgam in dental fillings).
Muddy rain gear has the potential to contaminate samples, so it must be free of dirt and particulate matter
prior to sampling. This is also true of dried sediment particles inside a boat, wash the boat prior to
sampling whenever possible. Areas where nearby soil is bare and subject to wind erosion should be
avoided.
Contamination by samples—This sampling method is not intended for application to samples containing
high concentrations (part per thousand to part per million) of metals such as untreated effluents, landfill
leachates, in-process waters. Such high level samples must NOT be collected, processed, or shipped with
ambient samples being collected for trace metals determinations.
Interferences—Interferences resulting from samples will vary considerably from source to source,
depending on the diversity of the site being sampled. If a sample is suspected of containing substances
that may interfere in the determination of trace metals, sufficient sample should be collected to allow the
laboratory to identify and overcome interference problems.
While contamination control is essential, personnel health and safety remain the highest priority.
Requirements and suggestions for personnel safety are given in Section 11 of this sampling SOP.
Additional techniques are described in analytical methods in Table 1.
5.0 EQUIPMENT/APPARATUS
All sampling equipment and sample containers must be precleaned in a laboratory or cleaning facility,
before they are shipped to the field site. Cleaning procedures are described in SOP# 140; or more briefly
in Section 3.0. Clean equipment should be packaged and arranged to minimize field preparation.
Here is a quick checklist of sampling appartii; additional comments for most items appear later in this
section.
Sample Bottles—pre-cleaned, of either polyethylene or fluoropolymer construction material
Gloves—Clean, nontalc polyethylene, latex, vinyl, or PVC; wrist and or shoulder-length
Storage Bags—Clean, zip-type, nonvented, colorless polyethylene (various sizes)
Plastic Wrap—Clean, colorless polyethylene
Double bagged ice packs—to keep samples chilled in the cooler during shipment
Cooler—Clean, nonmetallic, with white interior for shipping samples
Filter—0.45 :m, 15 mm diameter or larger, encapsulated filters, OR
Filters—0.4 :m, 47 mm polycarbonate Nuclepore (or equivalent) used with vacuum filtration setup
Filter holder—plastic material with plastic clamps, for mounting filter to the gunwale of the boat
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Pump and Pump Apparatus—peristaltic or submersible type for continuous flow sampling
Batteries to operate submersible pump—12 V, 2.6 amp, gel cell, or equivalent
Tubing and connectors—sufficient length and extra "barbed" straight connectors
Carboy—for collection and storage of dilute waste acids used to store bottles
Eppendorf auto pipet and colorless pipet tips—(optional) for acid preservation in field
Fluoropolymer wash bottles—one filled with DI water, one with high- purity 10% Hcl for rinsing
Metal-free sampling pole—for extension of sampling tubing away from the boat gunwhales
Field-Portable Glove Bag—portable, non-metallic or equivalent, covered with inexpensive polyethylene
bag.
When possible obtain and use equipment that is completely free of the metal(s) of interest. Only
fluoropolymer, conventional or linear polyethylene, polycarbonate, polysulfone, polypropylene, or
ultrapure quartz should come in contact with the samples. Fluoropolymer (FEP, PFA, or PTFE) or glass
containers should be used for samples that will be analyzed for mercury because mercury vapors can
diffuse in or out of other materials, resulting either in contamination or low-biased results (Reference 3).
Avoid use of Pyrex, Kimax, methacrylate, polyvinylchloride, nylon, and Vycor (Reference 6). In
addition, avoid material such as highly colored plastics, paper cap liners, pigments (used to mark
increments on plastics and rubber) all of which contain trace levels of metals. PTFE is less desirable than
FEP because the sintered material in PTFE may contain contaminants and is susceptible to serious
memory effects (Reference 6).
Materials such as gloves, storage bags, and plastic wrap, may be used new without additional cleaning
unless the results of the equipment blank pinpoint any of these materials as a source of contamination. In
this case, either a different supplier must be obtained or the materials must be cleaned.
Sample Bottles—Fluoropolymer (FEP, PFA), conventional or linear polyethylene, polycarbonate, or
polypropylene; 500 mL or 1 L with lids. If mercury is a target analyte, FEP bottles must be used.
Previously cleaned sample bottles (SOP# 140) should be filled with 0.1% HCl (v/v); individually stored
in double plastic bags. In most cases, it may be possible to empty the weak acid solution from the sample
bottle immediately prior to transport to the field site.
Surface Sampling Devices—Surface samples are collected using a grab sampling technique. Samples
may be collected manually by direct submersion of the bottle into the water or by using a grab sampling
device. Examples of grab samplers are shown in Figures 1 and 2 and may be used at sites where depth
profiling is neither practical nor necessary.
The grab sampler in Figure 1 consists of a heavy fluoropolymer collar fastened to the end of a 2-m-long
polyethylene pole, which serves to remove the sampling personnel from the immediate vicinity of the
sampling point. The collar holds the sample bottle. A fluoropolymer closing mechanism, threaded onto
the bottle, enables the sampler to open and close the bottle under water, thereby avoiding surface
microlayer contamination (Reference 14). Polyethylene, polycarbonate, and polypropylene are also
acceptable construction materials unless mercury is a target analyte.
An alternate grab sampler design is shown in Figure 2. This grab sampler is used for discrete water
samples and is constructed so that a capped clean bottle can be submerged, the cap removed, sample
collected, and bottle recapped at a selected depth. This device eliminates sample contact with
conventional samplers (e.g., Niskin bottles), thereby reducing the risk of extraneous contamination.
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Subsurface Sampling Devices—Subsurface sample collection may be appropriate in lakes and sluggish
deep river environments or where depth profiling is determined to be necessary. Subsurface samples are
collected by continuous-flow pumping of water into a sample bottle (new Figure 3).
Pump and Pump Apparatus—peristaltic or submersible type. Required for use with the jar sampling
system (Section 6.5.1) or the continuous-flow system (Section 6.5.2). Peristaltic pump; 115 V a.c., 12 V
d.c., internal battery, variable-speed, single-head, Cole-Parmer, portable, "Masterflex L/S," Catalog No.
H-07570-10 drive with Quick Load pump head, Catalog No. H-07021-24, or equivalent.
Peristaltic pumps do not require cleaning; however, touching the metal head and metal controls
necessitates changing of gloves before touching the Apparatus. If a submersible pump is used, a large
volume of sample should be pumped to clean the stainless steel shaft (hidden behind the impeller) that
comes in contact with the sample. Pumps with metal impellers should not be used.
Flexible tubing—for use with peristaltic pump. SEBS resin, approximately 3/8 in. i.d. by approximately
3 ft, Cole-Parmer size 18, Cat. No. G-06464-18, or approximately 1/4 in. i.d., Cole-Parmer size 17,
Catalog No. G-06464-17, or equivalent. Tubing is cleaned by soaking in 5-10% HCl solution for 8-24
hours, rinsing with reagent water in a clean bench in a clean room, and drying in the clean bench by
purging with mercury-free air or nitrogen. After drying, the tubing is double-bagged in clear
polyethylene bags, serialized with a unique number, and stored until use.
Hard case Tubing—For connection to peristaltic flexible pump tubing. Fluoropolymer, 3/8 or 1/4 in. o.d.,
in lengths as required to reach the point of sampling. If sampling will be at some depth from the end of a
boom extended from a boat, sufficient tubing to extend to the end of the boom and to the depth will be
required.
Tubing connectors—Appropriately sized PVC, clear polyethylene, or fluoropolymer "barbed" straight
connectors cleaned as the tubing above. Used to connect multiple lengths of tubing.
Batteries to operate submersible pump—12 V, 2.6 amp, gel cell, YUASA NP2.6-12, or equivalent. A 2
amp fuse connected at the positive battery terminal is strongly recommended to prevent short circuits
from overheating the battery. A 12 V, lead-acid automobile or marine battery may be more suitable for
extensive pumping.
Continuous-flow sampler—(depicted in new Figure 3), consists of a peristaltic or submersible pump and
one or more lengths of precleaned fluoropolymer or styrene/ethylene/butylene/ silicone (SEBS) tubing. A
filter is added to the sampling train immediately prior to sampling for dissolved metals. Easy to use,
more work required prior to arriving at field site.
Advantages of this flow-through sampling system include (1) all wetted surfaces are fluoropolymer or
SEBS and can be readily cleaned; (2) the suction device is located in the boat, isolated from the sample
bottle; (3) the sample does not travel through long lengths of tubing that are difficult to clean and keep
clean; and (4) in-line filtration is possible, minimizing field handling requirements for dissolved metals
samples.
Boat--For most sampling situations (i.e., most metals under most conditions), the use of an existing,
available boat is acceptable. A flat-bottom, Boston Whaler-type boat is preferred because sampling
materials can be stored with reduced chance of tipping. Immediately before use, the boat should be
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washed to remove any dust or dirt accumulation. All samples should be collected upstream of boat
movement and upsind of any fossil fuel exhaust.
When sampling for mercury, a fiberglass boat with battery-powered engine and wooden or fiberglass oars
is preferred. Before first use, the boat should be washed and stored in an area that minimizes exposure to
dust and atmospheric particles. If motor engine is require(remember that gasoline or diesel motor exhaust
can be a source of contamination), it should be shut off at a distance far enough from the sampling point
to avoid contamination, then the sampling team should manually propel the boat to the sampling point.
Personnel may wear an unlined, long-sleeved wind suit consisting of pants and jacket and constructed of
nylon or other synthetic fiber to prevent mercury adsorbed onto cotton or other clothing materials from
contaminating samples. (See Method 1631 or 1669 for more explanation.)
6.0 REAGENTS
"Trace-metal grade" reagents must
be used in place of "reagent grade" chemicals because acids, bases and
other materials labeled "reagent grade" contain concentrations of metals that will interfere in the
determination of trace metals at levels listed in Table 1.
6.1 Reagent Water—Water in which the analytes of interest and potentially interfering substances are
not detected at the Method Detection Limit (MDL) of the analytical method used for analysis of
samples. Prepared by distillation, deionization, reverse osmosis, anodic/cathodic stripping
voltammetry, or other techniques that remove the metal(s) and potential interferent(s). A large
carboy or other appropriate container filled with reagent water must be available for the collection
of field blanks.
6.2 Hydrochloric acid—Dilute (10%), trace-metal grade, shipped with sampling kit for cleaning
equipment between samples.
6.3 Nitric acid—Dilute (10%), trace-metal grade, shipped with sampling kit for cleaning equipment
between samples.
7.0 PROCEDURES
Site Selection--Overview of Sampling Considerations
Selection of a representative site for surface water sampling is based on many factors including: study
objectives, water use, point source discharges, non-point source discharges, tributaries, changes in stream
characteristics, types of stream bed, stream depth, turbulence, and the presence of structures (bridges,
dams, etc.). When collecting samples to determine ambient levels of trace metals, the presence of
potential sources of metal contamination are of extreme importance in site selection.
Ideally, the selected sampling site will exhibit a high degree of cross-sectional homogeneity. It may be
possible to use previously collected data to identify locations for samples that are well mixed or are
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vertically or horizontally stratified. Since mixing is principally governed by turbulence and water
velocity, the selection of a site immediately downstream of a riffle area will ensure good vertical mixing.
Horizontal mixing occurs in constrictions in the channel. In the absence of turbulent areas, the selection
of a site that is clear of immediate point sources, such as industrial effluents, is preferred for the collection
of ambient water samples.
To minimize contamination from trace metals in the atmosphere, ambient water samples should be
collected from sites that are as far as possible (e.g., at least several hundred feet) from any metal supports,
bridges, wires or poles. Similarly, samples should be collected as far as possible from regularly or
heavily traveled roads. If it is not possible to avoid collection near roadways, it is advisable to study
traffic patterns and plan sampling events during lowest traffic flow.
The sampling activity should be planned to collect samples known or suspected to contain the lowest
concentrations of trace metals first, finishing with the samples known or suspected to contain the highest
concentrations. For example, if samples are collected from a flowing river or stream near an industrial or
municipal discharge, the upstream sample should be collected first, the downstream sample collected
second, and the sample nearest the discharge collected last. If the concentrations of pollutants is not
known and cannot be estimated, it is necessary to use precleaned sampling equipment at each sampling
location.
When sampling from a boat, the bow of the boat should be oriented into the current (the boat will be
pointed upstream). Ideally, the team should approach the site from down current and downwind to
prevent contamination of the sample by particles sloughing off the boat or equipment. All sampling
activity should occur from the bow, preferably pointed upwind and
upstream.
If the samples are being collected from a boat, it is recommended that the sampling team create a stable
workstation by arranging the cooler or shipping container as a work table on the upwind side of the boat,
covering this worktable and the upwind gunnel with plastic wrap or a plastic tablecloth, and draping the
wrap or cloth over the gunnel. If necessary, duct tape is used to hold the wrap or cloth in place.
Although the duties of "clean hands" and "dirty hands" would appear to be a logical separation of
responsibilities, in fact, the completion of the entire protocol may require a good deal of coordination and
practice. For example, "dirty hands" must open the box or cooler containing the sample bottle and unzip
the outer bag; clean hands must reach into the outer bag, open the inner bag, remove the bottle, collect the
sample, replace the bottle lid, put the bottle back into the inner bag, and zip the inner bag. "Dirty hands"
must close the outer bag and place it in a cooler.
All operations involving contact with the sample bottle and with transfer of the sample from the sample
collection device to the sample bottle (if the sample is not directly collected in the bottle) are handled by
the individual designated as "clean hands." "Dirty hands" is responsible for all activities that do not
involve direct contact with the sample; e.g., sample documentation.
Extreme care must be taken during all sampling operations to minimize exposure of the sample to human,
atmospheric, and other sources of contamination. For mercury sampling, samplers should avoid
breathing directly on the sample.
Before heading off to the sampling site, the sampling team should consider the type of sample to be
collected, the amount of sample needed, and the devices to be used (grab, surface, or subsurface
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samplers). Sufficient sample volume should be collected to allow for necessary quality control analyses,
such as sample duplicates, matrix spike/matrix spike duplicate analyses and various blanks (Section 9).
This SOP describes three sampling procedures: manual collection, grab sampling with device, and
continuous flow sampling, i.e., with pumps.
7.1 Manual Sampling--collection of surface samples directly into the sample bottle
At the site, all sampling personnel must put on clean gloves (Section 5) before commencing sample
collection activity. Note that "clean hands" should put on shoulder-length polyethylene gloves and "dirty
hands" should put on wrist length PVC gloves.
If samples are to be analyzed for mercury, the sampling team must also put their precleaned wind suits on
at this time.
7.1.1 "Dirty hands" must open the cooler or storage container, remove the double-bagged sample bottle
from storage, and unzip the outer bag.
7.1.2 Next, "clean hands" opens the inside bag containing the sample bottle, removes the bottle, and
reseals the inside bag. "Dirty hands" then reseals the outer bag.
7.1.3 "Clean hands" unscrews the cap and, while holding the cap upside down, discards the dilute acid
solution from the bottle into a carboy for wastes (Section 5) or discards the reagent water directly
into the water body.
7.1.4 "Clean hands" then submerges the sample bottle, and allows the bottle to partially fill with sample.
"Clean hands" screws the cap on the bottle, shakes the bottle several times, and empties the rinsate
away from the site. After two more rinsings, "clean hands" holds the bottle under water and allows
bottle to fill with sample. After the bottle has filled (i.e., when no more bubbles appear), and while
the bottle is still inverted so that the mouth of the bottle is underwater, "clean hands" replaces the
cap of the bottle. In this way, the sample has never contacted the air.
7.1.5 Once the bottle lid has been replaced, "dirty hands" reopens the outer plastic bag, and "clean
hands" opens the inside bag, places the bottle inside it, and zips the inner bag.
7.1.6 "Dirty hands" zips the outer bag.
7.1.7 If the sample is to be analyzed for dissolved metals, it is filtered in accordance with the procedure
described in Section 7.4.
7.1.8 Documentation—After each sample is collected, the sample number is documented in the sampling
log, and any unusual observations concerning the sample and the sampling are documented.
7.2 Grab Sampling--collection with grab sampling device
The following steps detail sample collection using the grab sampling device shown in Figure 1. The
procedure is indicative of the "clean hands/dirty hands" technique that must also be used with alternative
grab sampling devices.
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The sampling team puts on gloves. Ideally, a sample bottle will have been preattached to the sampling
device in the laboratory. If it is necessary to attach a bottle to the device in the field, "clean hands"
performs this operation inside the field-portable glove bag.
7.2.1 "Dirty hands" removes the sampling device from its storage container and opens the outer
polyethylene bag.
7.2.2 "Clean hands" opens the inside polyethylene bag and removes the sampling device.
7.2.3 "Clean hands" changes gloves.
7.2.4 "Dirty hands" submerges the sampling device to the desired depth and pulls the fluoropolymer pull
cord to bring the seal plate into the middle position so that water can enter the bottle.
7.2.5 When the bottle is full (i.e., when no more bubbles appear), "dirty hands" pulls the fluoropolymer
cord to the final stop position to seal off the sample and removes the sampling device from the
water.
7.2.6 "Dirty hands" returns the sampling device to its large inner plastic bag, "clean hands" pulls the
bottle out of the collar, unscrews the bottle from the sealing device, and caps the bottle. "Clean
hands" and "dirty hands" then return the bottle to its double-bagged storage.
7.2.7 Closing mechanism—"Clean hands" removes the closing mechanism from the body of the grab
sampler, rinses the device with reagent water (Section 6.1), places it inside a new clean plastic bag,
zips the bag, and places the bag inside an outer bag held by "dirty hands." "Dirty hands" zips the
outer bag and places the double-bagged closing mechanism in the equipment storage box.
7.2.8 Sampling device—"Clean hands" seals the large inside bag containing the collar, pole, and cord
and places the bag into a large outer bag held by "dirty hands." "Dirty hands" seals the outside bag
and places the double-bagged sampling device into the equipment storage box.
7.2.9 If the sample is to be analyzed for dissolved metals, it is filtered in accordance with the procedure
described in Section 7.4.
7.
2.10 Documentation—After each sample is collected, the sample number is documented in the sampling
log, and any unusual observations concerning the sample and the sampling are documented.
7.3 Continuous Flow Sampling--uses peristaltic pump to pump sample through the pre-cleaned
tubing on to boat, shore, or dock to collect sample.
7.3.1 Before putting on wind suits or gloves, the sampling team removes the bags containing the pump,
SEBS-resin tubing, batterie), gloves, plastic wrap, wind suits, and, if samples are to be filtered, the
filtration apparatus from the coolers or storage containers in which they are packed.
7.3.2 "Clean hands" and "dirty hands" put on PVC gloves.
7.3.3 "Dirty hands" removes the pump from its storage bag, and opens the bag containing the SEBS-
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resin tubing.
7.3.4 "Clean hands" installs the tubing while "dirty hands" holds the pump. "Clean hands" immerses the
inlet end of the tubing in the sample stream.
7.3.5 Both "clean hands" and "dirty hands" change gloves. "Clean hands" also puts on shoulder length
polyethylene gloves.
7.3.6 "Dirty hands" turns the pump on and allows the pump to run for 5-10 minutes or longer to purge
the pump and tubing.
7.3.7 If the sample is to be filtered, "clean hands" installs the pre-cleaned cartidge filter at the end of the
tubing, and "dirty hands" sets up the filter holder on the gunwale as shown in Figure 4.
NOTE: The filtration apparatus is not attached while flushing the sample tubing with ambient
water, rather wait until immediately before sampling to prevent buildup of particulates from
clogging the filter.
7.3.8 The sample is collected by rinsing the sample bottle and cap three times and collecting the sample
from the flowing stream.
7.3.9 Documentation—After each sample is collected, the sample number is documented in the sampling
log, and any unusual observations concerning the sample and the sampling are documented.
7.4 Field Filtering
Sample Filtration—The filtration procedure described below is used for samples collected using the
manual or grab collection systems. This setup describes, in-line filtration using the peristaltic pump or
continuous-flow approach because this setup is optimal for reducing contamination. One cartridge can be
used for numerous samples although the tubing may need to be either cleaned or exchanged for each new
piece.
Because of the risk of contamination, it is recommended that samples for mercury be shipped unfiltered
by overnight courier and filtered when received at the laboratory.
7.4.1 Set up the filtration system inside the glove bag, using the shortest piece of pump tubing as is
practicable. Place the peristaltic pump immediately outside of the glove bag and poke a small hole
in the glove bag for passage of the tubing. Also, attach a short length of tubing to the outlet of the
capsule filter.
7.4.2 "Clean hands" removes the water sample from the inner storage bag using the technique described
in Sections 8.2.5.2 through 8.2.5.4 and places the sample inside the glove bag. "Clean hands" also
places two clean empty sample bottles, a bottle containing reagent water, and a bottle for waste in
the glove bag.
7.4.3 "Clean hands" removes the lid of the reagent water bottle and places the end of the pump tubing in
the bottle.
7.4.4 "Dirty hands" starts the pump and passes approximately 200 mL of reagent water through the
tubing and filter into the waste bottle. "Clean hands" then moves the outlet tubing to a clean bottle
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and collects the remaining reagent water as a blank. "Dirty hands" stops the pump.
7.4.5 "Clean hands" removes the lid of the sample bottle and places the intake end of the tubing in the
bottle.
7.4.6 "Dirty hands" starts the pump and passes approximately 50 mL through the tubing and filter into
the remaining clean sample bottle and then stops the pump. "Clean hands" uses the filtrate to rinse
the bottle, discards the waste sample, and returns the outlet tube to the sample bottle.
7.4.7 "Dirty hands" starts the pump and the remaining sample is processed through the filter and
collected in the sample bottle (final volume 500 mL). If preservation is required, the sample is
acidified at this point.
7.4.8 "Clean hands" replaces the lid on the bottle, returns the bottle to the inside bag, and zips the bag.
"Clean hands" then places the zipped bag into the outer bag held by "dirty hands."
7.4.9 "Dirty hands" zips the outer bag, and places the double-bagged sample bottle into a clean, ice-filled
cooler for immediate shipment to the laboratory.
7.5 RE-CLEANING EQUIPMENT IN THE FIELD
7.5.1 Ideally sampling activity can be planned so that samples known or suspected to contain the lowest
concentrations of trace metals are collected first with the samples known or suspected to contain
the highest concentrations of trace metals collected last. In this manner, cleaning of the sampling
equipment between samples in unnecessary. If it is not possible to plan sampling activity in this
manner, dedicated sampling equipment should be provided for each sampling event.
7.5.2 If samples are collected from adjacent sites (e.g., immediately upstream or downstream), rinsing of
the sampling Apparatus with water that is to be sampled should be sufficient.
7.5.3 If it is necessary to cross a gradient (i.e., going from a high-concentration sample to a low-
concentration sample), such as might occur when collecting at a second site, the following
procedure may be used to clean the sampling equipment between samples:
7.5.3.1 Inside the glove bag, use the "clean hands/dirty hands" procedure to process the dilute
nitric acid solution (Section 7.2) through the Apparatus.
7.5.3.2 Dump the spent dilute acid in the waste carboy or in the waterbody away from the
sampling point.
7.5.3.3 Process 1 L of reagent water through the Apparatus to rinse the equipment and discard
the spent water.
7.5.3.4 Collect a field blank as described in Section 9.2.
7.5.3.5 Rinse the Apparatus with copious amounts of the ambient water sample and proceed
with sample collection.
8.0 CALCULATIONS
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This section is not applicable to this SOP.
9.0 QUALITY ASSURANCE/QUALITY CONTROL
The sampling team shall employ a strict quality assurance/ quality control (QA/QC) program. The team
MUST collect equipment blanks and field replicates. It is also desirable to include equipment and field
collection blanks and QC samples.
The sampling team is permitted to modify the sampling techniques described in this method to improve
performance or reduce sampling costs, provided that reliable analyses of samples are obtained and that
samples and blanks are not contaminated. Each time a modification is made to the procedures, the
sampling team is required to demonstrate that the modification does not result in contamination of field
and equipment blanks.
9.1 Equipment Blanks
Before using any sampling equipment at a given site, the laboratory is required to generate equipment
blanks to demonstrate that the equipment is free from contamination. Equipment blanks must be run on
all equipment that will be used in the field. If, for example, samples are to be collected using both a grab
sampling device and the jar sampling device, then an equipment blank must be run on both pieces of
equipment. Two types of equipment blanks are required: bottle blanks and sampling equipment blanks.
Equipment blanks are generated in the laboratory by processing reagent water through the equipment
using the same procedures that are used in the field (Section 7.0). Therefore, the "clean hands/dirty
hands" technique used during field sampling should be followed when preparing equipment blanks at the
laboratory. Sampling personnel must collect a clean equipment blank before performing on-site field
activities.
Detailed procedures for collecting equipment blanks are given in the analytical methods referenced in
Table 1. If any metal(s) of interest or any potentially interfering substance is detected in the equipment
blank at the minimum level specified in the referenced method, the source of contamination/interference
must be identified and removed.
9.2 Field Blank
To demonstrate that sample contamination has not occurred during field sampling and sample processing,
at least one field blank must be generated for every 10 samples that are collected at a given site. Field
blanks are collected before sample collection.
Field blanks are generated by filling a large carboy or other appropriate container with reagent water
(Section 7.1) in the laboratory, transporting the filled container to the sampling site, processing the water
through each of the sample processing steps and equipment (e.g., tubing, sampling devices, filters, etc.)
that will be used in the field, collecting the field blank in one of the sample bottles, and shipping the
bottle to the laboratory for analysis in accordance with the method(s) referenced in Table 1. For example,
manual grab sampler field blanks are collected by directly submerging a sample bottle into the water,
filling the bottle, and capping. Subsurface sampler field blanks are collected by immersing the tubing into
the water and pumping water into a sample container.
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Filter the field blanks using the procedures described in Section 7.4.
If it is necessary to acid clean the sampling equipment between samples (Section 7.5), a field blank
should be collected after the cleaning procedures but before the next sample is collected.
9.3 Field Duplicate
To assess the precision of the field sampling and analytical processes, at least one field duplicate sample
must be collected for every 10 samples that are collected at a given site.
The field duplicate is collected either by splitting a larger volume into two aliquots in the glove box, by
using a sampler with dual inlets that allows simultaneous collection of two samples, or by collecting two
samples in rapid succession. Field duplicates for dissolved metals determinations must be processed
using the procedures in Section 7.4.
9.4 MS/MSD—The sampling team must prepare one matrix spike (MS) and one matrix spike duplicate
MSD for a 10% minimum of aqueous field samples.
If, through historical data, the background concentration of the sample can be estimated, the MS and
MSD samples should be spiked at a level of one to five times the background concentration.
If field samples are collected for dissolved metals determinations, it is necessary to process an MS and an
MSD through the 0.45 :m filter as described in Section 7.4.
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10.0 DATA VALIDATION
This section is not applicable to this SOP.
11.0 HEALTH AND SAFETY
When working with potentially hazardous materials, follow U.S. EPA, OSHA and specific health
and safety procedures.
Decontamination can pose hazards under certain circumstances even though performed to protect
health and safety. Hazardous substances may be incompatible with decontamination methods. For
example, the decontamination solution or solvent may react with contaminants to produce heat, explosion,
or toxic products. Decontamination methods may be incompatible with clothing or equipment; some
solvents can permeate or degrade protective clothing. Also, decontamination solutions and solvents may
pose a direct health hazard to workers through inhalation or skin contact, or if they combust.
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TABLE 1. ANALYTICAL METHODS, METALS, AND CONCENTRATION LEVELS
APPLICABLE TO METHOD 1669
Method Technique Metal
MDL (:g/L)
1
ML (:g/L)
2
1631
Oxidation/Purge &
Trap/CVAFS
Mercury 0.0002 0.0005
1632 Hydride AA Arsenic 0.003 0.01
1636 Ion Chromatography Chromium(VI) 0.23 0.5
1637 CC/STGFAA Cadmium 0.0075 0.02
Lead 0.036 0.1
1638 ICP/MS Antimony 0.0097 0.02
Cadmium 0.013 0.1
Copper 0.087 0.2
Lead 0.015 0.05
Nickel 0.33 1
Selenium 0.45 1
Silver 0.029 0.1
Thallium 0.0079 0.02
Zinc 0.14 0.5
1639 STGFAA Antimony 1.9 5
Cadmium 0.023 0.05
Chromium(III) 0.10 0.2
Nickel 0.65 2
Selenium 0.83 2
Zinc 0.14 0.5
1640 CC/ICP/MS* Antimony 0.01*
Arsenic 0.15
Beryllium 0.015
Cadmium 0.004
Chromium 0.03
Cobalt 0.004
Copper 0.02
Lead 0.005
Nickel 0.01
Selenium 0.015
Thallium 0.005
Vanadium 0.02
Zinc 0.2
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1
Method Detection Limit as determined by 40 CFR Part 136, Appendix B.
2
Minimum Level (ML) calculated by multiplying laboratory-determined MDL by 3.18 and
rounding result to nearest multiple of 1, 2, 5, 10, 20, 50, etc., in accordance with procedures
used by EAD and described in the EPA Draft National Guidance for the Permitting, Monitoring,
and Enforcement of Water Quality-Based Effluent Limitations Set Below Analytical
Detection/Quantitation Levels, March 22, 1994.
*MDL for Method 1640 based upon laboratory work by county environmental lab using
“metal clean” seawater as reagent water. Values represent reasonable and achievable MDL
levels.
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TABLE 2. ANALYTES, PRESERVATION REQUIREMENTS, AND CONTAINERS
Metal Preservation Requirements Acceptable Containers
Antimony
Arsenic
Cadmium
Copper
Lead
Nickel
Selenium
Silver
Thallium
Zinc
Add 5 mL of 10% HN0
3
to 1-L
sample; preserve on-site or
immediately upon laboratory
receipt.
500 mL or 1 L fluoropolymer,
conventional or linear polyethylene,
polycarbonate, or polypropylene
containers with lid
Chromium
(III)
Add 1 mL chromium (III)
extraction solution to 100 mL
aliquot, vacuum filter through
0.4 :m membrane, add 1 mL
10% HN0
3
; preserve on-site
immediately after collection.
500 mL or 1 L fluoropolymer,
conventional or linear polyethylene,
polycarbonate, or polypropylene
containers with lid
Chromium
(VI)
Add 50% NaOH; preserve
immediately after sample
collection.
500 mL or 1 L fluoropolymer,
conventional or linear polyethylene,
polycarbonate, or polypropylene
containers with lid
Mercury Total: Add 0.5% high-purity
HCl or 0.5% BrCl to pH < 2;
Total & Methyl: Add 0.5% high-
purity HCL; preserve on-site or
immediately upon laboratory
receipt
Fluoropolymer or borosilicate glass
bottles with fluoropolymer or
fluoropolymer-lined caps
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Addendum: Details for collection and field preservation of aqueous chromium (III) samples
Reagents—
6.4 Sodium Hydroxide—Concentrated, 50% solution for use when field-preserving samples
for hexavalent chromium determinations (Section 8.4.5).
6.5 For field-processing aliquots for trivalent chromium determinations:
Nitric Acid, Ultrapure—For use when field-preserving samples for trivalent chromium determinati
o
Ammonium Iron (II) Sulfate Solution (0.01M)—Used to prepare the chromium (III)
extraction solution (Section 7.4.3) necessary for field preservation of samples for trivalent
chromium (Section 8.4.4). Prepare the ammonium iron (II) sulfate solution by adding 3.92 g
ammonium iron (II) sulfate (ultrapure grade) to a 1 L volumetric flask. Bring to volume with
reagent water. Store in a clean polyethylene bottle.
Chromium (III) extraction solution—For use when field-preserving samples for trivalent
chromium determinations (Section 8.4.4). Prepare this solution by adding 100 mL of
ammonium iron (II) sulfate solution (Section 7.4.2) to a 125 mL polyethylene bottle. Adjust pH
to 8 with approximately 2 mL of ammonium hydroxide solution. Cap and shake on a wrist-
action shaker for 24 hours. This iron (III) hydroxide solution is stable for 30 days.
Hydrochloric acid—High-purity, 10% solution, shipped with sampling kit in
fluoropolymer wash bottles for cleaning trivalent chromium sample preservation equipment
between samples.
Chromium stock standard solution (1000 :g/mL)—Prepared by adding 3.1 g anhydrous
chromium chloride to a 1 L flask and diluting to volume with 1% hydrochloric acid. Store in
polyethylene bottle. A commercially available standard solution may be substituted.
Standard chromium spike solution (1000 :g/L)—Used to spike sample aliquots for
matrix spike/matrix spike duplicate (MS/MSD) analysis and to prepare ongoing precision and
recovery standards. Prepared by spiking 1 mL of the chromium stock standard solution
(Section 7.4.5) into a 1 L flask. Dilute to volume with 1% HCl. Store in a polyethylene bottle.
Ongoing precision and recovery (OPR) standard (25 :g/L)—Prepared by spiking 2.5 mL
of the standard chromium spike solution (Section 7.4.6) into a 100 mL flask. Dilute to volume
with 1% HCl. One OPR is required for every 10 samples.
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Additional QC for Collection of Trivalent Chromium Aliquots
Method blank—The sampling team must prepare one method blank for every ten or fewer field
samples. Each method blank is prepared using the steps in Sections 8.4.4.1 through 8.4.4.6 on a
100 mL aliquot of reagent water (Section 7.1). Do not use the procedures in Section 8.3 to
process the method blank through the 0.45 :m filter (Section 6.14.1), even if samples are being
collected for dissolved metals determinations.
Ongoing precision and recovery (OPR)—The sampling team must prepare one OPR for every
ten or fewer field samples. The OPR is prepared using the steps in Sections 8.4.4.1 through
8.4.4.6 on the OPR standard (Section 7.4.7). Do not use the procedures in Section 8.3 to process
the OPR through the 0.45
:m filter (Section 6.14.1), even if samples are being collected for disso
lved metals determinations.
MS/MSD—The sampling team must prepare one MS and one MSD for every ten
or fewer field samples.
If, through historical data, the background concentration of the sample
can be estimated, the MS and MSD samples should be spiked at a level of
one to five times the background concentration.
For samples in which the background concentration is unknown, the MS and
MSD samples should be spiked at a concentration of 25 :g/L.
Prepare the matrix spike sample by spiking a 100-mL aliquot of sample with 2.5 mL of the
standard chromium spike solution (Section 7.4.6), and processing the MS through the steps in
Sections 8.4.4.1 through 8.4.4.6.
Prepare the matrix spike duplicate sample by spiking a second 100-mL aliquot of the same
sample with 2.5 mL of the standard chromium spike solution, and processing the MSD through
the steps in Sections 8.4.4.1 through 8.4.4.6.
If field samples are collected for dissolved metals determinations, it is necessary to process an
MS and an MSD through the 0.45 :m filter as described in Section 8.3.
