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LeBlanc and Vroblesky—

Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts—SIR 2008–5109
Cover. Photograph shows tank used as a target for artillery practice in the Impact Area, Camp Edwards, Massachusetts Military 

Reservation, Cape Cod, Massachusetts. (Photograph by Darrin Smith, U.S. Army Corps of Engineers, September 2008)
Comparison of Pumped and Diffusion 

Sampling Methods to Monitor 

Concentrations of Perchlorate and 

Explosive Compounds in Ground Water, 

Camp Edwards, Cape Cod, Massachusetts, 

2004–05

By Denis R. LeBlanc and Don A. Vroblesky

Toxic Substances Hydrology Program

Prepared in cooperation with the 

U.S. Army Environmental Command

Scientific Investigations Report 2008–5109

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Suggested citation:

LeBlanc, D.R., and Vroblesky, D.A., 2008, Comparison of pumped and diffusion sampling methods to monitor concentrations of perchlorate and explosive compounds in ground water, Camp Edwards, Cape Cod, Massachusetts, 

2004–05: U.S. Geological Survey Scientific Investigations Report 2008–5109, 16 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Site Description.....................................................................................................................................2

Study Design...................................................................................................................................................2

Monitoring-Well Construction and Selection ..................................................................................2

Pumped Sampling Method..................................................................................................................4

Diffusion Sampling Method.................................................................................................................5

Sample Preservation and Laboratory Analysis Methods ..............................................................6

Laboratory Test of Diffusion Samplers ..............................................................................................6

Comparison of Pumped and Diffusion Sampling Methods .....................................................................7

Results of Laboratory Test of Diffusion Samplers ...........................................................................7

Pumped and Diffusion Samples from the Monitoring Wells..........................................................8

Factors Affecting Agreement Between the Methods ....................................................................8

Limitations of Study and Suggestions for Future Investigations ................................................11

Summary........................................................................................................................................................14

Acknowledgments.......................................................................................................................................14

References Cited..........................................................................................................................................14

Figures

1. Map showing location of monitoring wells, water table, plumes of ground-water 

contamination, and the Impact Area at Camp Edwards on the Massachusetts 

Military Reservation, Cape Cod, Massachusetts ....................................................................3

2–3. Photographs showing—

2. Diffusion sampler showing rigid, porous polyethylene tubing and slip-on end 

caps with valves ..................................................................................................................5

3. Vertical arrangement of diffusion samplers as they are retrieved from a well ........6

4–6. Graphs showing—

4. Comparison of (A) perchlorate, (B) RDX, and (C) HMX concentrations for 

pumped and diffusion samples collected from 15 wells, including two 

replicate samples, near the Impact Area at Camp Edwards on the 

Massachusetts Military Reservation, Cape Cod, Massachusetts, 2005 ..................11

5. Comparison of perchlorate, RDX, and HMX concentrations for pumped and 

diffusion samples collected from selected wells near the Impact Area at 

Camp Edwards on the Massachusetts Military Reservation, Cape Cod, 

Massachusetts, 2005.........................................................................................................12

6. Time history of (A) perchlorate, (B) RDX, and (C) HMX concentrations for 

pumped and diffusion samples collected from monitoring well MW-165M2 

at Camp Edwards on the Massachusetts Military Reservation, Cape Cod, 

Massachusetts, August 2003 to August 2007................................................................13
iv

Tables

1. Characteristics of monitoring wells used for collection of pumped and diffusion 

samples at Camp Edwards, Massachusetts Military Reservation, Cape Cod, 

Massachusetts..............................................................................................................................4

2. Ordnance-related compounds analyzed in pumped and diffusion samples collected 

from monitoring wells at Camp Edwards, Massachusetts Military Reservation, 

Cape Cod, Massachusetts, 2004–05 ..........................................................................................6

3. Concentrations of perchlorate and explosive compounds in samples from rigid, 

porous polyethylene diffusion samplers set in carboys containing ground water 

collected from wells at Camp Edwards, Massachusetts Military Reservation, 

Cape Cod, Massachusetts, May 2004 .......................................................................................7

4. Installation and collection specifications and concentrations of perchlorate, RDX, 

HMX, and other explosive compounds in diffusion and pumped samples collected 

from monitoring wells at Camp Edwards, Massachusetts Military Reservation, 

Cape Cod, Massachusetts, November 2004–August 2005.....................................................9

Conversion Factors, Datums, and Abbreviations

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

inch (in.) 25,400 micrometer (μm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.4047 hectare (ha)

Volume

gallon (gal) 3.785 liter (L)

quart (qt) 946.4 milliliter (mL)

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Mass

ounce, avoirdupois (oz) 28.35 gram (g) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).
v

ABBREVIATIONS

AFCEE Air Force Center for Engineering and the Environment

HMX octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine

IAGWSP Impact Area Groundwater Study Program

IRP Installation Restoration Program

MMR Massachusetts Military Reservation

PCE tetrachloroethene

PVC polyvinyl chloride

RDX hexahydro-1,3,5-trinitro-1,3,5-triazine

TCE trichloroethene

USAEC U.S. Army Environmental Command

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

VOC volatile organic compound
THIS PAGE INTENTIONALLY LEFT BLANK
Abstract

Laboratory and field tests were conducted at Camp 

Edwards on the Massachusetts Military Reservation on Cape 

Cod to examine the utility of passive diffusion sampling 

for long-term monitoring of concentrations of perchlorate 

and explosive compounds in ground water. The diffusion 

samplers were constructed of 1-inch-diameter rigid, porous 

polyethylene tubing. The results of laboratory tests in which 

diffusion samplers were submerged in containers filled with 

ground water containing perchlorate, RDX (hexahydro1,3,5-trinitro-1,3,5-triazine), and HMX (octahydro-1,3,5,7-

tetranitro-1,3,5,7-tetrazocine) indicate that concentrations 

inside the diffusion samplers equilibrated with concentrations 

in the containers within the 19-day-long test period. Field 

tests of the diffusion samplers were conducted in 15 wells 

constructed of 2- or 2.5-inch-diameter polyvinyl chloride 

pipe with 10-foot-long slotted screens. Concentrations of 

perchlorate, RDX, and HMX in the diffusion samplers placed 

in the wells for 42 to 52 days were compared to concentrations 

in samples collected by low-flow pumped sampling from 

53 days before to 109 days after retrieval of the diffusion 

samples. The results of the field tests indicate generally 

good agreement between the pumped and diffusion samples 

for concentrations of perchlorate, RDX, and HMX. The 

concentration differences indicate no systematic bias related to 

contaminant type or concentration levels.

Introduction

Long-term monitoring of water quality is an important 

part of ground-water remediation. During most remediation 

projects, many monitoring wells are installed to determine 

the spatial distribution of contaminants and to obtain 

hydrogeologic information needed to design the remediation 

approach. Once the approach is implemented, monitoring 

changes in water quality may continue for many years. The 

success of a monitoring program generally requires frequent 

sampling of many sites to discern temporal and spatial 

trends in contaminant concentrations and to obtain evidence 

of natural and enhanced attenuation of contaminant levels 

(National Research Council, 2000; Sara, 2006; Wiedemeier 

and others, 2006). Therefore, the cost of long-term monitoring 

can be a substantial part of the cost of a remediation program.

Common methods for collecting water samples from monitoring wells include purging with a submersible pump that is set 

in the well and lifts the water to the surface, and purging with 

a suction pump that draws the water to the surface by suction 

through a sampling tube. These pumped sampling methods 

can involve the use of heavy or cumbersome pump reels, 

generators, and gas cylinders; require two or more people 

to operate the equipment safely; and necessitate disposal of 

water purged from the well prior to sample collection 

(U.S. Army Environmental Command, 2007a; Nielsen and 

Nielsen, 2006). Passive diffusion sampling is a low-cost 

alternative to pumped sampling in many situations (Vroblesky 

and Hyde, 1997; Interstate Technology & Regulatory Council, 

2008). In the passive diffusion sampling method, a diffusion 

chamber filled with an appropriate fluid, usually water free 

of the contaminants of interest, is set in the well screen for a 

sufficient duration before retrieval to allow concentrations in 

the sampler and well screen to reach an equilibrium by diffusion across the membrane of the sampler (Vroblesky, 2001a). 

Installation and retrieval can commonly be done by one person 

using minimal equipment, and no purge water is produced.

The use of passive diffusion samplers to monitor 

concentrations of volatile organic compounds (VOCs) has 

been widely documented (Vroblesky and Hyde, 1997; Church, 

2000; Savoie and others, 2000; Vroblesky, 2001b; Archfield 

and LeBlanc, 2005; Interstate Technology & Regulatory 

Council, 2008). The diffusion membranes of samplers used 

to monitor VOCs typically are made from low-density 

polyethylene bags or lay-flat tubing (Vroblesky, 2001a). Many 

contaminants of interest, such as inorganic species, cannot 

diffuse through the low-density polyethylene membrane, 

however, so other membranes have been proposed for use in 

Comparison of Pumped and Diffusion Sampling Methods 

to Monitor Concentrations of Perchlorate and Explosive 

Compounds in Ground Water, Camp Edwards, Cape Cod, 

Massachusetts, 2004–05

By Denis R. LeBlanc and Don A. Vroblesky
2 Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts

passive diffusion samplers, including regenerated-cellulose 

dialysis membranes (Vroblesky and others, 2002; LeBlanc, 

2003; Ehlke and others, 2004); nylon mesh (Vroblesky and 

others, 2002; Vroblesky and others, 2003); rigid, porous 

polyethylene tubing (Parsons, 2005); and perforated tubing 

(Vroblesky and Casey, 2007).

Passive diffusion sampling is used at the Massachusetts 

Military Reservation (MMR) on Cape Cod to monitor 

concentrations of VOCs in a glacial sand and gravel 

aquifer (Archfield and LeBlanc, 2005; Air Force Center for 

Environmental Excellence, 2005). The VOCs are present 

in 12 contaminant plumes that extend as far as 3 mi from 

the reservation; originate from historical sources such as 

aircraft maintenance, fuel use, and fire-training areas; and are 

presently (2008) the focus of a major remediation effort (Air 

Force Center for Engineering and the Environment, 2007).

The sand and gravel aquifer also contains 11 plumes of 

perchlorate and explosive compounds from historical testing, use, and disposal of military munitions at Camp Edwards 

on the MMR (fig. 1). The plumes are present mostly in the 

northern part of the MMR in an area referred to as the Impact 

Area. These plumes also are the subject of a major remediation effort (U.S. Army Environmental Command, 2007b) that 

includes the drilling and regular sampling of many monitoring 

wells. There is a concern that the monitoring program, which 

involves repeated visits to wells with vehicles and equipment, detrimentally affects the restoration and preservation of 

ecological habitats in the northern 14,000 acres of the MMR, 

which are managed jointly as the Upper Cape Cod Groundwater Reserve by the Massachusetts National Guard and 

the state’s environmental agencies (Massachusetts National 

Guard, 2008a). Therefore, there is an interest in whether passive diffusion sampling methods can be used for the long-term 

monitoring of concentrations of perchlorate and explosive 

compounds at Camp Edwards.

Purpose and Scope

This report evaluates the results of laboratory and field 

tests of rigid, porous polyethylene diffusion samplers for 

monitoring concentrations of perchlorate and explosive 

compounds in ground water at Camp Edwards. The field tests 

were conducted near the Impact Area in 15 monitoring wells 

typical of the monitoring wells at the MMR known to contain 

various levels of these contaminants. Ground-water samples 

were collected from the 15 wells in 2005 by both pumped 

and diffusion sampling methods. The results presented in 

this report are intended for use in evaluating whether passive diffusion sampling is a useful alternative for long-term 

monitoring at the site. This study was done cooperatively by 

the Toxic Substances Hydrology Program of the U.S. Geological Survey (USGS) and the Impact Area Groundwater Study 

Program (IAGWSP) of the U.S. Army Environmental Command (USAEC). 

Site Description

The study was conducted in the shallow unconfined 

aquifer that underlies the western part of Cape Cod (fig. 1). 

The aquifer is composed of sand and gravel, with some silt 

and clay, which were deposited near the end of the Pleistocene Epoch, 15,000 to 16,000 years ago (Oldale, 1992; Walter 

and Masterson, 2003). In the study area, the sand and gravel 

aquifer is about 200 to 300 ft thick and overlies crystalline 

bedrock. The only source of water to the aquifer is about 

27 in/yr of recharge from precipitation. The water table of 

western Cape Cod forms a mound with its highest point on 

the eastern side of the MMR (fig. 1). Ground water flows 

radially outward from the top of the mound at a rate of 1 to 

2 ft/d toward discharge areas at streams, ponds, coastal wetlands, and the ocean (LeBlanc and others, 1986; Walter and 

Whealan, 2005).

The MMR has been used for military purposes since the 

early 1900s. The reservation was home to Camp Edwards 

during World War II and Otis Air Force Base during the Cold 

War. Since about 1973, the Massachusetts National Guard’s 

Training Site Camp Edwards, Otis Air National Guard Base, 

and Coast Guard Air Station Cape Cod have been the major 

tenants on the MMR (Massachusetts National Guard, 2008b). 

Two environmental programs—the Installation Restoration 

Program (IRP) and the IAGWSP—are presently (2008) 

addressing ground-water contamination from the historical 

military activities at the MMR.

Study Design

The study included several rounds of field tests of the 

rigid, porous polyethylene diffusion samplers in wells near the 

Impact Area. The wells were installed by the IAGWSP during 

earlier investigations. The field tests included collection of 

water samples by pumped and diffusion sampling methods 

and laboratory analysis of the samples for concentrations of 

perchlorate and explosive compounds. The field tests were 

preceded by a laboratory test of the diffusion samplers in 

which the samplers were immersed in water collected from 

wells known to contain ordnance-related compounds.

Monitoring-Well Construction and Selection

The monitoring wells used in this study are sampled 

regularly by the IAGWSP. The selected wells (fig. 1 and 

table 1) are known from historical data to contain a range 

of concentrations of the contaminants of interest, primarily 

perchlorate, RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), 

and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). 

The wells were already scheduled for sampling by pumped 

methods during the time period of this study; thus, the cost of 

collecting and analyzing pumped samples solely for this study 

was obviated.
Study Design 3

Figure 1. Location of monitoring wells, water table, plumes of ground-water contamination, and the Impact Area at Camp 

Edwards on the Massachusetts Military Reservation, Cape Cod, Massachusetts.

Snake

Pond

Weeks

 Pond

SANDWICH

BOURNE

EXPLANATION

40

45

50

55

60

65

65

35

30

25

MW-31S

MW-31M

MW-76M2

MW-76S

MW-163S

MW-289M2

MW-234M1

MW-172M2

MW-165M2

MW-157M3

MW-143M1

MW-114M2

MW-114M1

MW-111M2

MW-100M1

MW-203M2

MW-39M2

MW-226M2

£¤6

70°32'30" 70°30'

41°44'

41°42'

0 0.5 MILE

0 0.5 KILOMETER

Base from Office of Geographic and Environmental Information (MassGIS), orthophoto, 1:5000, 2003

Massachusetts state plane projection, North American Datum 1983

Plumes mapped by U.S. Army Environmental Command (2007b)

and Air Force Center for Engineering and the Environment (2007);

Water table mapped by Walter and Whealan (2005)

55

MW-39M2

IMPACT AREA

Areal extent of plumes of

 ground-water 

 contamination, 2007

Boundary of Massachusetts 

 Military Reservation

Boundary of Impact Area

Water-table contour—altitude 

 of water table. Contour interval

 is 5 feet. Datum is NGVD 29

Monitoring well—with identifier

Direction of ground-water flow

0 20 MILES

0 20 KILOMETERS

42°00'

42°30'

41°30'

71°00' 70°00'

ATLANTIC OCEAN

Massachusetts

Bay

Nantucket

Sound

BOSTON

Impact 

Area 

71°30' 70°30'
4 Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts

The wells are constructed of 2.0- or 2.5-in.-diameter 

polyvinyl chloride (PVC) pipe and are finished with slotted PVC screens that are 10 ft long (with the exception of 

a 5-ft-long screen for well MW-31S, which was used only 

as a source of water for the laboratory test) (table 1). The 

length of the standing water columns in the wells used for the 

diffusion-sampler field tests ranged from about 23 to 122 ft. 

The wells were installed by hollow-stem auger, dual-casing air 

rotary, and sonic drilling methods according to the protocols 

described in U.S. Army Environmental Command (2007a).

Pumped Sampling Method

Water samples were collected from the monitoring wells 

by contractors for the IAGWSP by positive-displacement 

pumping methods according to sampling protocols in U.S. 

Environmental Protection Agency (USEPA) (1996). The 

wells used for this study were fitted quasi-permanently 

with dedicated air-bladder pumps and Teflon-lined 3/8-in.-

diameter polyethylene discharge tubing. The pump intakes 

generally were set near the middle of the screened interval. 

Approximately 6 to 8 gallons of water were pumped to waste 

prior to sample collection to ensure that field water-quality 

parameters had stabilized and formation water was sampled. 

The methods used to collect and preserve the water samples 

are described in U.S. Army Environmental Command (2007a).

The pumps had to be removed temporarily from the wells 

during the field tests of the diffusion samplers. Therefore, 

the pumped samples had to be collected before the diffusion 

samplers were set in the wells or after they were retrieved. 

The interval between collection of the pumped and diffusion 

samples ranged from 0 to 109 days.

Table 1. Characteristics of monitoring wells used for collection of pumped and diffusion samples at Camp Edwards, Massachusetts 

Military Reservation, Cape Cod, Massachusetts. Well locations shown in figure 1.

[Source of data: Impact Area Groundwater Study Program (IAGWSP) Environmental Data Management System (EDMS). Altitude in feet relative to National 

Geodetic Vertical Datum of 1929 (NGVD 29). Location in meters relative to North American Datum of 1983 (NAD 83). m, meter; ft, foot; in., inch]

IAGWSP 

well name

X-coordinate 

east NAD 83

(m)

Y-coordinate 

north NAD 83

(m)

Altitude of 

land surface 

(ft)

Altitude of 

top of screen

(ft)

Altitude of 

bottom of 

screen 

(ft)

Waterlevel date

Altitude of 

water level 

(ft)

Diameter of 

well casing 

(in.)

MW-100M1 280014.064 829891.049 200.92 21.92 11.92 6/27/2005 65.88 2.5

MW-111M2 278895.250 829748.877 198.07 16.07 6.07 6/27/2005 62.86 2.5

MW-114M1 278624.895 827326.319 146.73 -30.27 -40.27 4/26/2005 63.79 2.5

MW-114M2 278624.892 827325.708 146.73 26.73 16.73 4/26/2005 63.80 2.5

MW-143M1 281463.009 827463.085 101.83 -42.17 -52.17 6/27/2005 69.75 2.5

MW-157M3 281506.605 827207.673 81.80 11.80 1.80 6/27/2005 70.00 2.5

MW-163S 281435.757 827938.391 109.15 71.15 61.15 5/11/2004 68.66 2.5

MW-165M2 278299.704 827235.262 143.15 18.65 8.65 4/26/2005 62.77 2.0

MW-172M2 278298.909 827149.926 128.08 -40.92 -50.92 4/26/2005 62.72 2.0

MW-203M2 279468.281 831146.038 204.37 28.37 18.37 6/27/2005 60.34 2.5

MW-226M2 276758.007 828642.881 164.18 -10.82 -20.82 6/27/2005 53.82 2.0

MW-234M1 281851.990 828824.384 173.91 43.91 33.91 5/12/2004 68.19 2.5

MW-289M2 281917.110 829049.263 169.18 7.16 -2.84 6/27/2005 69.51 2.5

MW-31M 279206.575 827488.120 153.59 40.59 30.59 6/27/2005 66.60 2.5

MW-31S 279206.575 827488.430 153.59 55.59 50.59 5/11/2004 64.98 2.0

MW-39M2 279006.632 830016.878 201.63 26.63 16.63 6/27/2005 62.55 2.0

MW-76M2 278963.550 827388.991 136.06 31.06 21.06 4/26/2005 64.46 2.0

MW-76S 278963.558 827388.380 136.06 51.06 41.06 4/26/2005 64.47 2.0
Study Design 5

Diffusion Sampling Method

The passive diffusion samplers used in this study were 

constructed of rigid, porous polyethylene tubing (fig. 2) 

similar to the aeration tubing used in fish aquariums. The 

tubing had an outside diameter of 1.5 in., was about 7 in. 

long, and had a pore size of 6 to 15 μm. Tubing sections 

longer than 7 in. could not be used because water would leak 

spontaneously through the tubing walls under pressure heads 

greater than those that could be counteracted by the capillary 

suction head in the pores. The ends of the tubing were 

sealed with polyethylene slip-on caps fitted with stopcock 

syringe valves with Luer connections. The entire assembly 

for each diffusion sampler was enclosed in a flexible openmesh polyethylene sleeve (fig. 3) for protection and ease of 

deployment and retrieval.

The samplers were prepared in advance by capping one 

end, filling the tubing with distilled, deionized water, capping the other end, submerging the sampler in a container of 

the water, and forcing air from the pores of the tubing with 

a syringe attached to one of the valves. The samplers were 

stored submerged in the container until they were installed in 

the wells. Each sampler contained about 160 mL of distilled, 

deionized water.

The samplers were set in the wells by fastening them to 

braided polypropylene twine using plastic cable ties passed 

through the polyethylene mesh and loops tied in the twine at 

predetermined locations. The bottom end of the twine was 

tied to a 1-in.-diameter, 7-in.-long, stainless-steel weight 

to counteract the slight buoyancy of the twine and sampler 

materials. The top end of the twine was tied to a rubber 

stopper that fit tightly into the top of the well casing so that 

the samplers were suspended at the desired points within the 

screened interval of the wells.

To obtain a detection limit sufficient for this study, about 

500 mL and 100 mL of water sample were needed for the 

analysis of explosive compounds and perchlorate, respectively. 

To obtain this sample volume, four samplers were suspended 

in each well for periods of 42 to 52 days (fig. 3). Immediately 

upon retrieval, the samplers were extracted from the polyethylene mesh and wrapped tightly in polyethylene wrap to 

limit leakage through the tubing walls. Then, water from the 

four samplers was decanted into a 1-L amber glass bottle for 

explosive-compound analysis and mixed by gentle swirling. 

Finally, about 100 mL were decanted from the 1-L glass bottle 

into a 125-mL polyethylene bottle for perchlorate analysis.

Figure 2. Diffusion sampler showing rigid, porous polyethylene tubing and slip-on end caps with valves.
6 Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts

Sample Preservation and Laboratory Analysis 

Methods

Water samples for analysis of the explosive compounds 

were collected in 1-L amber glass bottles, chilled immediately, 

and stored chilled and in the dark until analysis. Samples 

for analysis of perchlorate were collected in 125-mL polyethylene bottles and stored in the dark at room temperature 

until analysis.

The samples were analyzed for 20 compounds (table 2). 

The explosive compounds were analyzed by a modification of 

USEPA method 8330 (U.S. Environmental Protection Agency, 

1994). Perchlorate was analyzed by USEPA method 314.0 

(U.S. Environmental Protection Agency, 1999). The pumped 

samples were analyzed by laboratories under contract to the 

IAGWSP; the reporting limits ranged from 0.25 to 10 μg/L 

(table 2). The diffusion samples were analyzed by Severn 

Trent Laboratories; the reporting limits for the diffusion 

samples were similar to those shown in table 2.

Laboratory Test of Diffusion Samplers

The diffusion-sampler design was tested in the laboratory 

prior to deployment of the diffusion samplers in the field to 

verify that diffusion of the perchlorate and explosive compounds through the rigid, porous polyethylene tubing would 

result in concentrations in the sampler that approximately 

Figure 3. Vertical arrangement of diffusion samplers as they are 

retrieved from a well. Note flexible polyethylene mesh enclosing 

each diffusion sampler.

Table 2. Ordnance-related compounds analyzed in pumped 

and diffusion samples collected from monitoring wells at Camp 

Edwards, Massachusetts Military Reservation, Cape Cod, 

Massachusetts, 2004–05.

[Reporting limits are shown for the pumped samples. USEPA, U.S. Environmental Protection Agency; RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine; 

HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; MMR, Massachusetts 

Military Reservation; PETN, Pentaerythriotol tetranitrate; μg/L, microgram 

per liter]

Method Analyte

Reporting 

limit

(μg/L)

USEPA 314.0 Perchlorate 1.0

USEPA 8330 explosives RDX 0.25

HMX 0.25

1,3,5-trinitrobenzene 0.25

1,3-dinitrobenzene 0.25

Tetryl 0.25

Nitrobenzene 0.25

2,4,6-trinitrotoluene 0.25

4-amino-2,6-dinitrotoluene 0.25

2-amino-4,6-dinitrotoluene 0.25

2,6-dinitrotoluene 0.25

2,4-dinitrotoluene 0.25

2-nitrotoluene 0.25

3-nitrotoluene 0.25

4-nitrotoluene 0.25

MMR-specific explosives 2,6-diamino-4-nitrotoluene 0.5

2,4-diamino-6-nitrotoluene 0.25

Picric acid 0.25

Nitroglycerin 5

PETN 10
Comparison of Pumped and Diffusion Sampling Methods 7

equaled those in the surrounding ground water. The diffusion 

samplers were prepared according to the methods described 

above, except that they were not enclosed in the flexible polyethylene mesh. The samplers were submerged in eight 2.5-gal 

polyethylene carboys that were stored in the dark at 4°C for 

19 days. Two carboys were filled with distilled, deionized 

water. The other three pairs of carboys were filled with ground 

water collected by the IAGWSP from three monitoring wells 

(MW-163S, MW-234M1, and MW-31S, fig. 1) known to contain a range of concentrations of perchlorate and RDX typical 

of the plumes on the MMR.

The carboys were gently shaken about every 4 days during the equilibration period. At the end of the 19-day period, 

the diffusion samplers were removed from the carboys and 

decanted into the appropriate sample containers as described 

above. Water from the diffusion samplers in the matched pairs 

of carboys was blended to obtain a sufficient sample volume. 

Water samples also were collected from the carboys and 

preserved in the same manner. The water samples collected 

from the diffusion samplers and carboys at the end of the test 

were analyzed for concentrations of perchlorate and explosive 

compounds as described above, except that perchlorate was 

analyzed by using USEPA method 8321A (U.S. Environmental 

Protection Agency, 2007) to obtain a lower detection limit than 

that for USEPA method 314.0.

Comparison of Pumped and Diffusion 

Sampling Methods

The comparison of pumped and diffusion sampling 

methods includes the preliminary laboratory test of the 

diffusion samplers and several rounds of field tests in selected 

monitoring wells at Camp Edwards. The laboratory test 

was conducted to confirm that perchlorate and explosive 

compounds diffuse through the porous polyethylene tubing. 

The field tests were conducted to determine whether diffusion 

sampling is a useful method for monitoring these contaminants 

in wells on the MMR.

Results of Laboratory Test of Diffusion Samplers

The concentrations of the major contaminants of 

interest—perchlorate, RDX, and HMX—in the water collected from the diffusion samplers and carboys were in close 

agreement at the end of the 19-day equilibration period of the 

laboratory test (table 3). The concentrations of several other 

explosive compounds (2-amino-4,6-dinitrotoluene; 4-amino2,6-dinitrotoluene; and 2,4,6-trinitrotoluene) in the diffusion 

and carboy samples also agreed reasonably well. Only the 

compounds detected in at least one sample are shown in 

table 3.

Table 3. Concentrations of perchlorate and explosive compounds in samples from rigid, porous polyethylene diffusion samplers set 

in carboys containing ground water collected from wells at Camp Edwards, Massachusetts Military Reservation, Cape Cod, 

Massachusetts, May 2004.

[Analysis by Severn Trent Laboratories. Ground-water samples collected by AMEC Earth & Environmental, Inc. RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine; 

HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; DIFF, sample from diffusion sampler; CRBY, sample from carboy at end of experiment; DIBLANK, 

carboy filled with distilled, deionized water; μg/L, microgram per liter; J, estimated value; <, value less than reporting limit shown]

Well name Perchlorate

2-amino-4,6-

dinitrotoluene

(μg/L)

4-amino-2,6-

dinitrotoluene

(μg/L)

2,4-dinitrotoluene

(μg/L)

RDX

(μg/L)

HMX

(μg/L)

2,4,6-trinitrotoluene

(μg/L)

MW-31S-DIFF 4.7 1.4 <1.0 0.44J 63 <1.0 4.0

MW-31S-CRBY 5.1 1.3 <1.0 <1.0 61 <1.0 2.7

MW-163S-DIFF 44 <0.20 <0.20 <0.20 1.6 <0.20 <0.20

MW-163S-CRBY 45 <0.20 <0.20 <0.20 1.7 <0.20 <0.20

MW-234M1-DIFF 2.7 1.9 0.58 <0.20 3.5 1.8 <0.20

MW-234M1-CRBY 3.0 2.2 0.81 <0.20 4.0 1.9 <0.20

DIBLANK-DIFF 0.0017J <0.20 <0.20 <0.20 <0.20 <0.20 <0.20

DIBLANK-CRBY <0.010 <0.20 <0.20 <0.20 <0.20 <0.20 <0.20
8 Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts

The close agreement indicated that the 19-day period 

was sufficiently long for concentrations inside the diffusion 

samplers to equilibrate with concentrations in the surrounding 

water. Except for the very low estimated concentration of perchlorate (0.0017 μg/L) in the diffusion sampler set in distilled, 

deionized water, there was no indication of contamination 

derived from the sampler materials. The diffusion-sampler 

concentrations were not compared to the concentrations in the 

original well water used to fill the carboys. The volumes of 

water varied among the carboys, and the concentrations in the 

original water were effectively diluted an unknown amount by 

the water in the samplers. Therefore, the valid comparison was 

between the water in the carboys and the water in the diffusion 

samplers at the end of the test.

Pumped and Diffusion Samples from the 

Monitoring Wells

The concentrations of perchlorate, RDX, HMX, and 

other minor explosive compounds in the diffusion and pumped 

samples collected from the monitoring wells during the field 

tests mostly were in close agreement (table 4). Only results for 

compounds detected in at least one sample are shown in 

table 4. The concentrations for the diffusion samples were 

compared to the concentrations for pumped samples collected 

on one or two pumped-sampling dates nearest the diffusionsampling date. The diffusion samplers were left in the wells 

for an equilibration period of 42 to 52 days, which was 

substantially longer than the 19-day equilibration period for 

the laboratory tests.

The concentrations in the pumped and diffusion samples 

for the contaminants of greatest interest—perchlorate, RDX, 

and HMX—are compared graphically in figure 4. Concentrations below the reporting limit were plotted as values of 

0.1 μg/L (zero values cannot be shown on a logarithmic scale). 

If the diffusion and pumped sampling methods produced 

samples with equal concentrations, all the points on the graphs 

would fall on the 1:1 lines. The finding that most of the points 

fell close to the lines indicated that the results from the diffusion samples were comparable to the results from the pumped 

samples. There is no evidence of a systematic bias in the 

concentration differences on the basis of type of contaminant 

or concentration level. This finding contrasts with the observation by Archfield and LeBlanc (2005) of a small systematic 

bias toward lower concentrations of trichloroethene (TCE) 

and tetrachloroethene (PCE) in diffusion samples compared to 

pumped samples.

The good agreement was observed at different concentration levels, as illustrated in figures 5A, C, and D for wells 

with low (MW-100M1), intermediate (MW-143M1), and high 

(MW-114M2) contaminant levels, respectively. The good 

agreement also was observed during two separate sampling 

events at wells MW-100M1 (figs. 5A and B) and MW-143M1 

(table 4). This finding is similar to the observation by 

Archfield and LeBlanc (2005) of a consistent degree of agreement between the methods for a given well.

For several wells, the agreement between concentrations 

for pumped and diffusion samples was poorer than the 

generally close agreement observed at most of the wells. The 

data for these wells plotted substantially off the 1:1 lines of 

exact agreement shown in figure 4. Wells characterized by 

poor agreement between the methods include MW-165M2, 

MW-289M2, MW-31M, and MW-76M2 (table 4). None of 

these wells was tested a second time, so it is unknown if the 

poor agreement was characteristic of the wells or was a onetime anomalous result.

Factors Affecting Agreement Between the 

Methods

The differences in concentrations observed for the 

pumped and diffusion samples for several wells (table 4) 

were partly explained by the time lag between collection of the 

pumped and diffusion samples, particularly for wells in which 

concentrations were changing rapidly with time. For example, 

pumped samples were collected from well MW-165M2 at 

54 days before and 62 days after collection of the diffusion 

sample. During this time period, concentrations of perchlorate, 

RDX, and HMX were decreasing rapidly (fig. 6). As a result, 

concentrations in the diffusion sample were substantially 

lower than the concentrations in the first pumped sample 

(fig. 5E) and substantially higher than the concentrations in the 

second pumped sample (fig. 5F). Temporal changes in groundwater concentrations also may be factors in the generally poor 

agreement between sampling methods at wells MW-289M2 

and MW-76M2.

Even for samples collected on or about the same day, 

concentrations that are changing with time could affect the 

degree of agreement between the methods. Concentrations 

in pumped samples, which are collected by using low-flow 

methods, represent concentrations near the well screen at the 

time of sampling. Concentrations in the diffusion samples, 

which rely on chemical diffusion through the sampler membrane, represent concentrations in the ground water passing 

through the well screen during the equilibration period. The 

diffusion-sample concentration is most strongly influenced by 

concentrations near the end of the equilibration period; therefore, the concentration differences between samples collected 

on or about the same day would potentially be greatest when 

ground-water concentrations are changing rapidly.

The concentrations in both types of samples also may 

be affected by various hydraulic and chemical factors at the 

wells, including well construction, chemical and geological 

heterogeneity near the well screen, and fluid circulation 

within the wellbore during and between sampling events. 

For example, concentrations can vary considerably over long 

screened intervals (Reilly and LeBlanc, 1998), and fluid can 

circulate vertically inside long screens during and between 

sampling events (Church and Granato, 1996; Vroblesky and 
Comparison of Pumped and Diffusion Sampling Methods 

9

Table 4. Installation and collection specifications and concentrations of perchlorate, RDX, HMX, and other explosive compounds in diffusion and pumped samples collected from monitoring wells at Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, November 2004–August 2005.—Continued[Analyses by Severn Trent Laboratories. Pumped samples collected by AMEC Earth & Environmental, Inc. RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine; HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; μg/L, microgram per liter; J, estimated value; <, value less than the reporting limit shown; --, no data]

Well name Sample type Date diffusion sampler set Date diffusion or pumped sample collected Days diffusion sampler in well Days between collection of diffusion and pumped samples Perchlo- rate (μg/L) RDX (μg/L) HMX (μg/L) Tetryl (μg/L) Nitro- glycerin (μg/L) 4-amino- 2,6-dinitro- toluene (μg/L) 2,6-dinitro- toluene (μg/L)

MW-100M1 Diffusion 11/30/04 01/11/05 42 -- 0.52J 2.1 0.34 2.0 5.7 <0.28 <0.28

Pumped 01/11/05 -- 0 0.53J 2.1 0.29 <0.25 <5 <0.25 <0.25

MW-100M1 Diffusion 06/27/05 08/18/05 52 -- 0.50J 1.9 0.32 <0.26 <5.2 <0.26 <0.26

Pumped 08/22/05 -- 4 0.41J 2.2 0.33 <0.25 <5 <0.25 <0.25

MW-111M2 Diffusion 06/27/05 08/18/05 52 -- <1.0 <0.27 <0.27 <0.27 <5.4 <0.27 <0.27

Pumped 08/19/05 -- 1 0.47J <0.25 <0.25 <0.25 <5 <0.25 <0.25

MW-114M1 Diffusion 04/26/05 06/07/05 42 -- 2.0 0.46 <0.27 <0.27 <5.4 <0.27 <0.27

Pumped 04/13/05 -- -551 1.7 -- -- -- -- -- --Pumped 06/21/05 -- 13 -- 0.26 <0.25 <0.25 <5 <0.25 <0.25

MW-114M2 Diffusion 04/26/05 06/07/05 42 -- 55.5 130 27 <0.27 <5.4 2.0 <0.27

Pumped 04/13/05 -- -551 54 140 27 <0.25 <5 1.9 <0.25

MW-143M1 Diffusion 11/30/04 01/11/05 42 -- 5.0 0.73 5.2 <0.27 <5.5 <0.27 <0.27

Pumped 01/12/05 -- 1 4.0 0.80 6.7 <0.25 <5 <0.25 <0.25

MW-143M1 Diffusion 06/27/05 08/17/05 51 -- 5.6 0.59 5.3 <0.32 <6.3 <0.32 <0.32

Pumped 08/19/05 -- 2 5.2 0.69 6.6 <0.25 <5 <0.25 <0.25

MW-157M3 Diffusion 06/27/05 08/17/05 51 -- 0.45J <0.28 1.4 <0.28 <5.6 <0.28 <0.28

Pumped 06/03/05 -- -751 0.78J <0.25 3.2 <0.25 <5 <0.25 <0.25Pumped 10/10/05 -- 53 0.53J <0.25 2.9 <0.25 <5 <0.25 <0.25

MW-165M2 Diffusion 04/26/05 06/07/05 42 -- 4.7 4.6 0.76 <0.27 <5.5 <0.27 <0.27

Pumped 04/14/05 -- -541 9.8 23 2.1 <0.25 <5 <0.25 <0.25Pumped 08/08/05 -- 62 0.62J 0.56 <0.25 <0.25 <5 <0.25 <0.25
10 Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts Table 4. Installation and collection specifications and concentrations of perchlorate, RDX, HMX, and other explosive compounds in diffusion and pumped samples collected from monitoring wells at Camp Edwards, Massachusetts Military Reservation, Cape Cod, Massachusetts, November 2004–August 2005.—Continued [Analyses by Severn Trent Laboratories. Pumped samples collected by AMEC Earth & Environmental, Inc. RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine; HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; μg/L, microgram per liter; J, estimated value; <, value less than the reporting limit shown; --, no data] Well name Sample type Date diffusion sampler set Date diffusion or pumped sample collected Days diffusion sampler in well Days between collection of diffusion and pumped samples Perchlo- rate (μg/L) RDX (μg/L) HMX (μg/L) Tetryl (μg/L) Nitro- glycerin (μg/L) 4-amino- 2,6-dinitro- toluene (μg/L) 2,6-dinitro- toluene (μg/L) MW-172M2 Diffusion 04/26/05 06/07/05 42 -- 3.7 <0.29 <0.29 <0.29 <5.7 <0.29 <0.29 Pumped 04/05/05 -- -631 2.1 <0.25 <0.25 <0.25 <5 <0.25 <0.25 MW-203M2 Diffusion 06/27/05 08/18/05 52 -- <1.0 1.9 <0.27 <0.28 <5.4 <0.27 <0.27 Pumped 08/19/05 -- 1 <1.0 1.7 <0.25 <0.25 <5 <0.25 <0.25 MW-226M2 Diffusion 06/27/05 08/17/05 51 -- 0.52J <0.27 <0.27 <0.27 <5.4 <0.27 <0.27 Pumped 08/22/05 -- 5 0.71J -- -- -- -- -- -- MW-289M2 Diffusion 06/27/05 08/17/05 51 -- 10.2 3.4 2.0 <0.31 11 <0.31 <0.31 Pumped 08/22/05 -- 5 14.8 2.8 1.7 <0.25 <5 <0.25 <0.25 MW-31M Diffusion 06/27/05 08/17/05 51 -- 2.3 97 66 <0.28 <5.7 <0.28 <0.28 Pumped 04/30/05 -- -1091 16 120 27 <0.25 <5 0.32 <0.25 MW-39M2 Diffusion 06/27/05 08/18/05 52 -- <1.0 <0.27 0.75 <0.27 <5.3 <0.27 <0.27 Pumped 08/19/05 -- 1 <1.0 <0.25 0.57 <0.25 <5 <0.25 <0.25 MW-76M2 Diffusion 04/26/05 06/07/05 42 -- 10.1 28 11 <0.27 <5.3 0.74 <0.27 Pumped 04/13/05 -- -551 25 62 27 <0.25 <5 0.88 0.30 MW-76S Diffusion 04/26/05 06/07/05 42 -- 3.8 6.6 1.1 <0.27 <5.5 <0.27 <0.27 Pumped 04/13/05 -- -551 3.2 3.9 0.48 <0.25 <5 <0.25 <0.25

1 Negative value in days indicates that diffusion sample was collected after pumped sample.
Comparison of Pumped and Diffusion Sampling Methods 11

others, 2007). The concentration variations and vertical flow 

may complicate direct comparison between pumped and 

diffusion sampling methods. Archfield and LeBlanc (2005) 

report that the degree of agreement between the sampling 

methods for VOCs in wells at the MMR was better in wells 

with 2-ft-long screens than in wells with 5-ft-long screens. 

Huffman (2002), Church (2000), and Vroblesky (2001b) 

report, however, that VOC concentrations in diffusion 

samples collected from wells with screens longer than 5 ft 

agreed well with concentrations in pumped samples from the 

wells. In the present study, water from diffusion samplers 

set at four intervals along the 10-ft-long well screens was 

blended to provide sufficient volume for the chemical 

analyses, and at least one screen volume was purged to 

waste during pumped sampling prior to sample collection 

(John Ehret, U.S. Army Corps of Engineers, oral commun., 

2008). The sampling methods may have effectively averaged 

concentration variations along the well screens and improved 

the comparability of the two types of samples.

During this study, concentrations of perchlorate and 

explosive compounds in samples collected from two monitoring wells by diffusion and pumped sampling methods 

agreed closely in two separate sampling events. Archfield and 

LeBlanc (2005) report that, on the basis of a larger number 

of wells with multiple sampling events, the degree of agreement of VOC concentrations in pumped and diffusion samples 

was repeatable for a given well, although they were unable to 

determine which well-construction or aquifer characteristics 

affected the degree of agreement. They recommend that a onetime well-by-well comparison between pumped and diffusion 

sample results could determine which wells are good candidates for the use of diffusion samplers. A similar approach 

could be used to determine the applicability of the diffusion 

sampling method for long-term monitoring of perchlorate and 

explosive compounds near the Impact Area at the MMR.

Limitations of Study and Suggestions for Future 

Investigations

The concentrations of the ordnance-related compounds 

in the pumped and diffusion samples were compared qualitatively in this study because too few wells were sampled to 

enable comparison of concentrations by statistical methods. 

The comparison also was complicated by the large variation 

in time lags between collection of the pumped and diffusion samples. The small sample size and sampling time lags 

resulted from the limited scope of this initial assessment and 

the logistical considerations associated with working in a 

military training area. Future studies could include sample collection from a larger number of wells to allow data analysis by 

the statistical methods used by Archfield and LeBlanc (2005) 

to examine diffusion sampling at the MMR for VOCs. Shorter 

time lags between collection of the diffusion and pumped 

samples may aid in identifying wells appropriate for long-term 

monitoring of ordnance-related compounds at the MMR by 

diffusion sampling methods.

Figure 4. Comparison of (A) perchlorate, (B) RDX, and (C) HMX 

concentrations for pumped and diffusion samples collected from 

15 wells, including two replicate samples, near the Impact Area at 

Camp Edwards on the Massachusetts Military Reservation, Cape 

Cod, Massachusetts, 2005.

PERCHLORATE

0.1

1

10

100

0.1 1 10 100

0.1 1 10 100 1,000

PUMPED SAMPLE CONCENTRATION, 

IN MICROGRAMS PER LITER

DIFFUSION SAMPLE CONCENTRATION, IN MICROGRAMS PER LITER

RDX

0.1

1

10

100

1,000

HMX

0.1

1

10

100

A

B

0.1 1 10 100

C
12 Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts

Figure 5. Comparison of perchlorate, RDX, and HMX concentrations for pumped and diffusion samples collected from 

selected wells near the Impact Area at Camp Edwards on the Massachusetts Military Reservation, Cape Cod, Massachusetts, 

2005. (Note different Y-axis concentration scales.)

0.0

0.5

1.0

1.5

2.0

2.5

Perchlorate RDX HMX Perchlorate RDX HMX

Perchlorate RDX HMX Perchlorate RDX HMX

Diffusion

Pumped

MW-100M1 1/11/05

0.0

0.5

1.0

1.5

2.0

2.5

B MW-100M1 8/18/05

0

2

4

6

8

MW-143M1 8/17/05 C D

0

40

80

120

160

MW-114M2 6/7/05

0

5

10

15

20

25

MW-165M2 6/7/05

Pumped

sample

4/14/05

E

0

5

10

15

20

25

MW-165M2 6/7/05 

Pumped

sample

8/8/05

F

A

CONCENTRATION, IN MICROGRAMS PER LITER

CONTAMINANT

Perchlorate RDX HMX Perchlorate RDX HMX
Comparison of Pumped and Diffusion Sampling Methods 13

Figure 6. Time history of (A) perchlorate, 

(B) RDX, and (C) HMX concentrations for 

pumped and diffusion samples collected 

from monitoring well MW-165M2 at Camp 

Edwards on the Massachusetts Military 

Reservation, Cape Cod, Massachusetts, 

August 2003 to August 2007.

0

20

40

60

80

100

120

140

Aug-03 Aug-04 Aug-05 Aug-06

RDX CONCENTRATION, 

IN MICROGRAMS PER LITER

HMX CONCENTRATION,

 IN MICROGRAMS PER LITER

RDX in pumped

sample

RDX in diffusion

sample

A

0

2

4

6

8

10

12

HMX in pumped

sample

HMX in diffusion

sample

B

0

20

40

60

80

100

120

140

PERCHLORATE CONCENTRATION,

IN MICROGRAMS PER LITER

Perchlorate in

pumped sample

Perchlorate in

diffusion sample

C

Aug-07

Aug-03 Aug-04 Aug-05 Aug-06 Aug-07

Aug-03 Aug-04 Aug-05 Aug-06 Aug-07

DATE
14 Pumped and Diffusion Sampling Methods to Monitor Perchlorate and Explosives, Camp Edwards, Massachusetts

were related to changing concentrations in the ground water 

coupled with time lags from 0 to 109 days between collection 

of the pumped and diffusion samples. Earlier studies report 

that the degree of agreement between the methods may be a 

consistent characteristic of the individual monitoring wells, 

although too few wells were sampled during this study to 

examine this hypothesis for the ordnance-related compounds.

The results of the laboratory and field tests indicate 

that passive diffusion sampling may be a useful method for 

long-term monitoring of concentrations of perchlorate and 

explosive compounds in wells at the MMR and in similar 

hydrogeologic settings. One-time well-by-well comparisons 

between pumped and diffusion sampling results could be used 

to determine which wells are good candidates for the use of 

the diffusion sampling method.

Acknowledgments

The authors thank Andrew Massey, Jennifer Savoie, 

Megan Chaisson, Jonathan King, Jessica Cochrane, 

David Robison, and Nicholas Geboy of the USGS, and 

Shirley Rieven, Timothy Dwyer, and Thomas Remmers of 

AMEC Earth & Environmental, Inc., for their assistance in 

planning and conducting the field effort. The authors also 

thank Mark Zimmerman and Thomas Imbrigiotta of the USGS 

for their reviews of this report and Benjamin Gregson for 

coordinating the IAGWSP support of the project.

References Cited

Air Force Center for Engineering and the Environment, 2007, 

Groundwater plume maps & information booklet: Cape 

Cod, Mass., Massachusetts Military Reservation, Air 

Force Center for Engineering and the Environment, 36 p., 

accessed January 18, 2008, at http://www.mmr.org/2007_

booklet.htm

Air Force Center for Environmental Excellence, 2005, 

Ashumet Valley SPEIM chemical monitoring network 

optimization, final project note: Otis Air National 

Guard Base, Mass., 4P-F41624-03-D-8595, prepared by 

CH2MHill, Inc., for AFCEE/MMR Installation Restoration 

Program, July 12, 2005, variously paged.

Archfield, S.A., and LeBlanc, D.R., 2005, Comparison of 

diffusion- and pumped-sampling methods to monitor 

volatile organic compounds in ground water, Massachusetts 

Military Reservation, Cape Cod, Massachusetts, 

July 1999–December 2002: U.S. Geological Survey 

Scientific Investigations Report 2005–5010, 53 p.

Summary

Long-term monitoring of water quality is an important 

part of ground-water remediation efforts. Most monitoring 

programs include regular collection by pumped sampling 

methods of ground-water samples from a network of monitoring wells. The costs of monitoring can be substantial. In 

addition, the monitoring process can require disposal of contaminated water produced during well purging prior to sample 

collection and can cause damage to the local environment by 

repeated visits to the well sites by field crews and their equipment and vehicles. Passive diffusion sampling is an alternative 

to pumped sampling that may offer the advantages of lower 

cost, no production of purge water, and lessened adverse 

impacts at well sites.

In this study, laboratory and field tests were done to 

determine the utility of the passive diffusion sampling method 

for monitoring concentrations of perchlorate and explosive 

compounds in wells near the Impact Area at Camp Edwards 

on the Massachusetts Military Reservation on Cape Cod. The 

sand and gravel aquifer at this site has been contaminated by 

historical use, testing, and disposal of military ordnance. The 

contaminant plumes emanating from the site are presently 

(2008) being remediated by the Impact Area Groundwater 

Study Program of the U.S. Army Environmental Command, 

the cooperating agency for this study.

The diffusion samplers tested during this study were 

constructed of 1-in.-diameter, 7-in.-long sections of rigid, 

porous polyethylene tubing (6- to 15-μm pore size) filled with 

distilled, deionized water. Laboratory tests of the diffusion 

samplers were conducted by submerging the samplers in 

test chambers that were filled with ground water collected 

from monitoring wells containing various concentrations of 

perchlorate, RDX, and HMX. The results of the laboratory 

tests indicate that concentrations of perchlorate and explosive 

compounds in the water inside the diffusion samplers had 

equilibrated with concentrations in the water surrounding the 

samplers in the test chambers by the end of the 19-day-long 

test period.

Field tests of the diffusion sampling method were 

conducted in 15 wells near the Impact Area. Four diffusion 

samplers were set in each well screen for equilibration 

periods of 42 to 52 days. The wells were constructed of 2- or 

2.5-in.-diameter PVC and had 10-ft-long screens. The water 

from the four diffusion samplers was blended together to produce sufficient volumes for laboratory analysis. For comparison, water samples were collected from the wells by low-flow 

pumped sampling methods either before or after the diffusionsampler tests. Most wells had close agreement between 

concentrations of perchlorate, RDX, and HMX in samples 

collected by diffusion and pumped sampling methods. There 

was no apparent systematic bias in the concentration differences between the methods related to contaminant type or 

concentration levels. For several wells, substantial differences 

between concentrations for the pumped and diffusion samples 
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Church, P.E., 2000, Evaluation of a diffusion sampling method 

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Massachusetts: U.S. Geological Survey Water-Resources 

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data caused by well-bore flow in long-screen wells: 

Ground Water, v. 34, no. 2, p. 262–273.

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U.S. Geological Survey Water-Resources Investigations 

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LeBlanc, D.R., Guswa, J.H., Frimpter, M.H., and Londquist, 

C.J., 1986, Ground-water resources of Cape Cod, Massachusetts: U.S. Geological Survey Hydrologic Investigations 

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Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

Director

U.S. Geological Survey

Massachusetts-Rhode Island Water Science Center

10 Bearfoot Road

Northborough, MA 01532

or visit our Web site at:

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