CRREL REPORT 95-14

A Literature Review on

Decontaminating Groundwater

Sampling Devices

Organic Pollutants

Louise V. Parker July 1995
Abstract

Current protocols for decontaminating devices used to sample groundwater

for organic contaminants are reviewed. Most of the methods given by regulatory agencies provide little scientific evidence that justify the recommended

protocols. In addition, only a few studies that actually compared various

decontamination protocols could be found in the open literature, and those

studies were limited in their scope. Various approaches for decontamination and criteria that are important in determining how effectively a surface

could be decontaminated are discussed.

For conversion of SI units to non-SI units of measurement consult ASTM

Standard E380-93, Standard Practice for Use of the International System

of Units, published by the American Society for Testing and Materials,

1916 Race St., Philadelphia, Pa. 19103.

Cover: Single check-valve bailer, disassembled in a cleaning bath. (Photo

by Peter Keene.)
CRREL Report 95-14

A Literature Review on

Decontaminating Groundwater

Sampling Devices

Organic Pollutants

Louise V. Parker July 1995

Prepared for

U.S. ARMY ENVIRONMENTAL CENTER

SFIM-AEC-ET-CR-95-008

Approved for public release; distribution is unlimited.

US Army Corps


of Engineers

Cold Regions Research &


Engineering Laboratory
PREFACE

This report was prepared by Louise V. Parker, Research Physical Scientist, Applied

Research Division, Research and Engineering Directorate, U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), Hanover, New Hampshire. Funding for this

work was provided by the U.S. Army Environmental Center (USAEC), Aberdeen Proving

Ground, Maryland, Martin H. Stutz, Project Monitor.

The author wishes to thank Martin Stutz and AEC for their support of this work. She

also wishes to thank Thomas A. Ranney, Staff Scientist, Science and Technology Corporation, Hanover, New Hampshire; Daniel Leggett, Research Chemist, CRREL; and Dr. Jacob

Gibs and Thomas Imbrigiotta, both Hydrologists with the New Jersey District of the U.S.

Geological Survey Water Resources Division, West Trenton, New Jersey, for their technical

reviews of this manuscript.

This publication reflects the personal views of the author and does not suggest or

reflect the policy, practices, programs, or doctrine of the U.S. Army or Government of the

United States. The contents of this report are not to be used for advertising or promotional

purposes. Citation of brand names does not constitute an official endorsement or approval of the use of such commercial products.

ii
CONTENTS

Page

Preface ................................................................................................................................. ii

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

Sorption and desorption of organic contaminants ...................................................... 1

Decontamination methods ............................................................................................... 3

Aqueous cleaning methods......................................................................................... 3

Cleaning or rinsing with organic solvents ............................................................... 5

Chemical neutralization methods .............................................................................. 7

Current protocols to decontaminate groundwater sampling devices ...................... 7

Variations in methodology .......................................................................................... 8

Special instructions for cleaning pumps ................................................................... 10

Effectiveness of various decontamination methods .................................................... 10

Low-temperature considerations .................................................................................... 13

Conclusions ........................................................................................................................ 13

Literature cited ................................................................................................................... 14

ILLUSTRATION

Figure

1. Effect of spray temperature on soil removal ........................................................ 4

TABLES

Table

1. Types of pressurized water systems ...................................................................... 5

2. The most commonly used cold solvent cleaners ................................................. 6

3. Decontamination solutions for drilling equipment ............................................ 7

4. Properties of four detergent solutions .................................................................. 8

5. Recommended solvent rinses for soluble contaminants.................................... 9

6. Sorption and desorption of three organic solutes by rigid PVC and PTFE .... 12

iii
SORPTION AND DESORPTION

OF ORGANIC CONTAMINANTS

Several studies have shown that nonpermeable surfaces (e.g., glass, stainless steel) do not

sorb most organic contaminants. Specifically, two

studies (Gillham and O’Hannesin 1990, Parker et

al. 1990) have shown that, under conditions where

there should not be any losses due to biological

activity, there were no losses of a suite of organic

contaminants from aqueous solutions exposed

to stainless steel surfaces. (The contaminants in

these studies all had log Kow values less than 4.)

Reynolds et al. (1990) also found no loss of volatile organic compounds (VOCs) (log Kow < 4)

from aqueous solutions exposed to glass surfaces. However, more hydrophobic contaminants,

such as polychlorinated biphenyls (PCBs), chlorinated pesticides, and polyaromatic hydrocarbons, most likely would be adsorbed by these surfaces. Thus, decontamination of nonpermeable

surfaces such as metals and glass would involve

removing only those highly hydrophobic contaminants that have adsorbed to the surface

(i.e., no absorbed analytes) and any surface contaminants contained in any residual film (either

wet or dry) that is left on the surface when the

sampling device is removed from the well.

In contrast, several studies (Barcelona et al.

1985, Reynolds and Gillham 1985, Gillham and

O’Hannesin 1990, Parker et al. 1990) have shown

that permeable materials, such as polymeric well

casings and tubings used in sampling pumps, sorb

substantial quantities of some organic contaminants from aqueous solutions. All these researchers agree that diffusion within the polymer matrix has occurred. In several studies (Barcelona et

al. 1985, Gillham and O’Hannesin 1990, Ranney

and Parker, in prep.), researchers have noted that

generally the less rigid the material, the more

INTRODUCTION

Dedicating a sampling device to a particular

well reduces the potential of cross contamination

from other wells. However, many sampling devices currently are not dedicated, and decontamination methods are used to reduce the possibility

of cross contamination. In addition, some current

regulatory guidance (e.g., U.S. EPA 1992) recommends that dedicated sampling devices that are

routinely stored outside the well should be

cleaned or decontaminated prior to use. Typically, decontamination procedures for sampling

devices range from simply washing with clean

(high-quality) water to complex cleaning involving acid and solvent rinses. It is the purpose of

this paper to review the literature on decontamination of groundwater sampling devices that are

used for sampling organic contaminants.

The type of sampling device and surface(s) to

be decontaminated and the physical characteristics of the organic contaminant, such as its solubility in water, its volatility, and its propensity

to adsorb on or absorb into materials used in the

sampling device, will determine how readily decontamination can occur. Contact time and the

degree of initial contamination on the surface are

also critical factors. Cleaning a surface that has

been exposed to trace-level organic contaminants is much easier than cleaning a surface exposed to neat (pure product) hydrocarbons or organic solvents. Other types of contaminants such

as grease and oil may also affect removal. Generally, nonpermeable surfaces such as metals will

be more readily decontaminated than permeable surfaces, because desorption of absorbed

contaminants may be a factor with permeable

surfaces. Temperature also has an effect on these

processes, with sorption and desorption slower

in the cold.

A Literature Review on Decontaminating

Groundwater Sampling Devices

Organic Pollutants

LOUISE V. PARKER
sorptive it is. Flexible tubings such as those used

to pump water samples to the surface have been

shown to be very highly sorptive (Barcelona et al.

1985, Reynolds and Gillham 1985, Gillham and

O’Hannesin 1990, Ranney and Parker, in prep.).

For example, Barcelona et al. (1985) found flexible polyvinyl chloride (PVC) and silicone rubber tubing sorbed 80% of the chloroform in an

aqueous solution (100 ppb) in 1 hour. Gillham and

O’Hannesin (1990) compared sorption of low (~1)

ppm levels of six aromatic hydrocarbons (benzene,

toluene, ethylbenzene, and o-, m- and p-xylene)

by rigid and flexible PVC. After 10 minutes, losses of these analytes ranged from 0 to 2% for solutions exposed to rigid PVC vs. 35 to 50% for those

exposed to flexible PVC tubing.

Leggett and Parker (1994) were able to successfully model (predict) equilibrium sorption of organic solutes by polytetrafluoroethylene (PTFE,

one type of Teflon) and rigid PVC based upon

meaningful physical/chemical interaction parameters of the organic contaminants. They used

multiparameter linear solvation energy relationships (LSERs) to describe the equilibrium partitioning. Partitioning was related to the compound’s basicity, acidity, polarity/polarizability,

and molecular volume. These models proved to

be more accurate than octanol–water partition

coefficients in correlating the experimental

partitioning data. This approach may also prove

useful for predicting how readily a surface can be

decontaminated or if desorption of analytes that

have been absorbed within the polymer matrix

could be rapid and extensive enough to affect analyte concentrations.

Thus, for permeable materials, decontamination may involve more than removing surface contaminants, depending upon the kinetics of sorption and desorption, contact times, and contact

volumes. An example of this can be seen when

Devlin (1987) tried to decontaminate tubings made

of polyethylene and an unspecified fluoropolymer (Teflon) that had been exposed to ppb levels

of a suite of VOCs. Devlin found it was harder to

decontaminate polyethylene tubing than the fluoropolymer tubing. At least 5 L of deionized water was required to reduce the concentrations of

these analytes in the leachates from the fluoropolymer tubing to below 1 ppb, and the leachates

from the polyethylene tubing still contained concentrations greater than 1 ppb of several analytes

after 8 L flush. One explanation for these results

may be that polyethylene is more sorptive of

organic solutes than Teflon tubing (Barcelona et

al. 1985, Devlin 1987, Ranney and Parker, in prep.)

and thus decontamination (desorption) takes

longer.

Understanding the kinetics of desorption of

organic contaminants from permeable materials

is critical to determining the potential for effective decontamination. Unfortunately, only a few

studies (Miller 1982, Barcelona et al. 1985, Parker

et al. 1990) have examined desorption of organic

contaminants from polymeric materials. Specifically, Miller (1982) looked for desorption of several volatile organic analytes from polyethylene,

polypropylene, and (rigid) PVC. Parker et al.

(1990) looked for desorption of a suite of organic

contaminants (VOCs, nitroaromatics, and a nitramine) from (rigid) PVC and PTFE. Although neither of these studies followed the kinetics of this

process, they both found that the amount desorbed

did not always parallel the amount sorbed; e.g.,

Parker et al. (1990) found that although p- and mdichlorobenzene were sorbed the most rapidly

and to the greatest extent by PTFE, trichloroethylene (TCE) and trans-1,2-dichloroethylene

appeared to be desorbed the most rapidly (since

they were desorbed to the greatest extent after

3 days). (A biocide was added to prevent any losses due to biological activity in this study.) For

PVC, the amount desorbed tended to correlate

with the amount sorbed. However for PTFE, it

appeared that smaller molecules were more easily or rapidly desorbed than larger molecules, perhaps because diffusion is more rapid for smaller

molecules.

Barcelona et al. (1985) compared desorption of

chloroform from five flexible tubing materials

(polypropylene, polyethylene, PVC, silicone rubber, and PTFE). They found that with all the polymers, 80 to 90% of the desorption they observed

occurred almost immediately (i.e., within the first

5 to 10 minutes) although, the amount desorbed

constituted less than 10% of the total chloroform

sorbed. After 5 minutes, polypropylene and polyethylene desorbed more of the total chloroform

sorbed (on a percentage basis) even though the

silicone rubber and PVC tubings had sorbed more

chloroform more rapidly.

According to several researchers (Brusseau and

Rao 1989, Di Cesare and Smith 1994), soil organic

matter can be envisioned as a three-dimensional

matrix of randomly oriented polymer chains with

a relatively open, flexible structure. An apparently similar pattern of desorption of nonionic organic compounds from natural soils has also

been reported in kinetic studies (Pavlostathis and

2
Jaglal 1991). Desorption consists of an initial rapid phase followed by a continual slower phase.

As an example, Di Cesare and Smith (1994) reported that Pavlostathis and Mathavan (1992)

found approximately 80 to 90% of the TCE sorbed

by a silty clay soil was desorbed in the first day.

They also found that the longer the soil was exposed to TCE (2.5, 5.5, or 15.5 months), the more

TCE appeared to remain bound (i.e., the less desorption occurred).

As with the permeable surfaces, there has been

very little study of desorption of organic contaminants from impermeable surfaces. Parker et al.

(1990) found no desorption of any organic analytes from stainless steel that had been exposed to

ppm levels of a suite of organic solutes (VOCs,

nitroaromatics, and a nitramine) for six weeks.

These results were expected since there had been

no sorption of these analytes by the stainless steel

surfaces during the study. More hydrophobic

contaminants would most likely be adsorbed by

these surfaces and could then desorb.

DECONTAMINATION METHODS

A surface can be decontaminated either by

physically removing the contaminants or by chemically neutralizing them. Methods that physically

remove contaminants include several aqueous

cleaning methods, such as detergent washes and

high-pressure cleaning methods. High-pressure

cleaning methods involve either using a high-pressure washer or steam cleaning. For organics with

poor solubility in water, cleaning or rinsing with

less polar organic solvents is a viable alternative.

There are a number of other methods that physically remove contaminants (e.g., using abrasives,

contact heating, burning, hot gases, microwave

heating, etc.). However, many of these methods

are destructive and do not appear practical or necessary for most routine field cleaning and thus

are not included in this discussion. Most currently

used methods for decontaminating groundwater

sampling devices utilize some combination of

aqueous and nonaqueous cleaning methods. Although methods that physically remove contaminants from surfaces can be effective for decontaminating impermeable surfaces, permeable

materials can still contain considerable quantities

of contaminants within the internal structure, and

this can reduce the efficacy of these methods. Another problem with these methods is that the contaminants are often still contained in the waste

product and thus the waste must also be considered potentially hazardous. Chemical neutralization methods can be more effective in reducing

contamination and are discussed briefly.

Aqueous cleaning methods

Detergent cleaning

There are numerous approaches to aqueous

cleaning. Typically, small items can be cleaned by

soaking in the cleaning solution (in a bath); cleaning by hand using a cloth, sponge, brush, or similar device; ultrasonic cleaning in a bath; or machine washing. Larger items are typically cleaned

in place by circulating the cleaning solution and

rinse solutions.

Water acts as a solvent medium for contaminants, depending upon their solubility. Water can

also act as a dispersal medium for substances that

do not dissolve but can be carried in suspension.

An aqueous cleaning solution must first wet the

contaminated surface. Wetting means that the liquid solution readily spreads over the entire surface. If wetting does not take place, the liquid

beads up and will run off any vertical or inclined

surface. When a cleaning solution wets a contaminated surface, the contaminant is separated from

the solid surface by the cleaning film. The wetting ability of liquids varies: water has less wetting power than ammonia, benzene, acetone, and

most oils (Sandia Laboratories 1969). However,

the wetting ability of water can be increased by

reducing its surface and interfacial tension; this is

done by adding a surface active agent, or surfactant, such as soap or detergent.

For aqueous systems, surfactants are organic

compounds that have a two-component molecular structure; one component is hydrophilic and

water-soluble and the other is hydrophobic and

relatively water insoluble (Di Cesare and Smith

1994). Surfactants are commonly categorized by

the ionic character of the hydrophilic component

or long chain. The long chain may be negatively

charged (anionic), positively charged (cationic),

or neutral (nonionic). Amphoteric or ampholytic

surfactants are also available; they also ionize in

solution but the long chain can carry either a positive or negative charge, depending upon the pH

of the solution (Osipow 1962).

A detergent solution removes contaminants

from a surface in the following manner:

1) It wets the contaminated surfaces,

2) It removes the contamination by either rolling it up and displacing it from the surface,

3
or by removing it in layers from the surface, or by removing it in layers by emulsification, or by penetrating the contamination

to form inverse micelles, followed by the

formation of liquid crystals and solubilization or emulsification,

3) It disrupts the polyvalent cation links and

hydrogen bonds by pH control, ion exchange, and sequestrating the polyvalent

cation (forming coordination complexes),

and

4) It prevents redeposition by maintaining the

contaminants in suspension (Osipow 1962).

The concentration of surfactant at which monomers assemble into aggregates (micelles) is termed

the critical micelle concentration (cmc) (Di Cesare

and Smith 1994). Many organic compounds that

are not very soluble in water dissolve to a considerably greater extent in micellar solutions of both

ionic and nonionic surfactants (i.e., where the concentration is greater than the cmc); this process is

called solubilization (Osipow 1962). Direct evidence that solubilized materials are present

within the micelles is provided by X-ray measurements (Osipow 1962). Solubility enhancements

of (nonionic) organic compounds at surfactant

concentrations below the cmc have only been reported for extremely water-insoluble compounds,

e.g., DDT (Di Cesare and Smith 1994).

In general, according to Osipow (1962), surface

activity is due to nonmicellar surfactant, and the

micelles act as a reservoir for the unassociated

surfactant molecules and ions. At concentrations

greater than the cmc value, the surface tension of

the solution does not decrease further with increasing surfactant concentration (Osipow 1962).

However, the ability of surfactant solutions to solubilize water-insoluble materials starts at the cmc

and increases with the concentration of micelles

(Osipow 1962).

Often, heating an aqueous cleaning solution can

improve cleaning efficiency. Generally, the solubility of organic chemicals is greater in heated solutions. Heat also raises the surface temperature,

thereby facilitating volatilization of sorbed organic

contaminants. In the case of gross contamination

with pure product, heat would also reduce the

viscosity of contaminants, thereby facilitating

physical removal from either the surface or within the pore structure. Keys (1980) compared the

effect of spray wash temperature (21°C vs. 49°C,

or 70°F vs. 120°F) on the ability of two detergent

solutions to remove soil from a surface (Fig. 1).

The hottest water (49°C or 120°F) was more than

twice as effective as the coolest water. Studies that

have assessed the ability of detergent solutions to

remove neat chemical warfare agents from various surfaces (an extreme example of contamination) have also generally found increased removal efficiencies using heated solutions (Mills et al.

1977, Bagley and Weatherhead 1978).

However, according to Osipow (1962), the effect of temperature on surfactant solutions is not

straightforward. For ionic surfactants in the absence of other additives, the cmc generally increases with increasing temperature. (Although for

some ionic surfactants, there is an optimum temperature that produces a minimum cmc.) This

means that, generally, more surfactant will be required in heated cleaning solutions to reach the

cmc. However, temperature also affects the solubility of the surfactants in a way that counters

this trend. The solubility of these (ionic) surfactants is low at low temperatures and increases

slowly and regularly with increasing temperature

until, within a narrow temperature range, it increases very rapidly. According to Osipow (1962),

this is because ionic surfactants in unassociated

Figure 1. Effect of spray temperature on soil removal

(detergents at 0.5% concentration; 15-sec sprays)

(from Keys 1980).

4
form have quite limited solubility in water, while

the micelles are highly soluble. Thus, ionic surfactants will dissolve more readily and to a greater extent in heated water. The effects of temperature can be quite different for some nonionic

surfactants. For some nonionic surfactants, the

cmc has been found to decrease with increasing

temperature, and others are less soluble in hot

water than in cold.

The presence of other substances in the cleaning solution, such as ions (e.g., metals) or organic

contaminants, can also affect removal efficiencies.

According to Osipow (1962), electrolytes lower the

cmc and increase the size and alter the charge of

the micelles of ionic surfactants. Thus, electrolytes

increase the solubilization of nonpolar materials

and may increase or decrease the solubilization of

polar materials, depending upon the compound

being solubilized (Osipow 1962).

In some studies there is mention of adding organic solvents to cleaning solutions to aid in the

dissolution of sorbed organic contaminants. Although not much data on the effectiveness of this

approach was found, some examples of organic

solvents that have been used for this purpose include ethanol, acetone, and butanol. According to

Osipow (1962), added organic compounds increase the micelle volume of ionic surfactants, and

the increased volume of this “pseudophase” is

expected to have an increased solvent action on

other organic materials. (Concentrations of examples given by Osipow were 0.1 to 0.3 moles/1000

g surfactant.) Organic compounds may also affect the cmc of surfactants. Long-chain alcohols

and amines will lower the cmc, and short-chain

alcohols may increase or decrease the cmc depending upon the temperature (Osipow 1962).

Pressurized water cleaning

With steam cleaning, pressure developed in the

steam boiler imparts a high velocity to a mixture

of water droplets and steam, which is directed

from a nozzle onto the target surface. Detergent

and heat from the steam weaken the bonds between the dirt and surface while the high velocity

of the water droplets has sufficient power to remove the debris from the surface (Summers 1982).

Depending upon the contaminant, steam can also

facilitate volatilization, thermal decomposition,

and hydrolysis. Esposito et al. (1985) felt that longterm exposure to steam should theoretically aid

in the removal of subsurface contaminants as well.

Problems associated with steam cleaning include

burns, corrosion of metal surfaces, and liberation

of toxic vapors (if sufficient quantities are present).

With high-pressure water washers, high-pressure pumps produce solid water streams rather

than the small droplets produced by steam cleaning. The advantages over steam cleaning are that

there is increased force available and that the energy requirements are lower because water does

not have to be converted to steam. Summers (1982)

placed pressurized-water washing systems into

three categories: 1) those with relatively low pressure and high flow rates, 2) those with intermediate pressure and flow rates, and 3) those with relatively high pressure jets and intermediate flow

rates (see Table 1 for specific pressures and flow

rates).

Summers (1982) found that adding long-chain

polymers (such as Polyox [Union Carbide], Nalco

[Nalco Corp.], and Superwater [Berkley Chemical Corp.]) to the wash water improved performance. Although the function of these polymers

is not fully understood, Summers believed that

they reduced the flow resistance of the liquids and

maintained the integrity of the jet stream for a

longer distance after it left the nozzle. The efficiency of high-pressure water jets can also be enhanced with other additives, such as abrasive or

nonabrasive particulates (abrasive cleaning),

surfactants, or other additives that affect the physics of interaction between the liquid jet spray and

contaminant residue (Cante et al. 1980).

Cleaning or rinsing with

organic solvents

Typically, organic solvents are used where 1)

water is undesirable (e.g., for electrical and electronic devices or where humidity might corrode

neighboring equipment), 2) contaminants consist

of grease, tar, oil, and rosins, 3) fast evaporation is

Table 1. Types of pressurized water systems (from Summers 1982).

Flow rate

Type Pressure (L/min)

Low pressure 689 kPa 38 to 378

(100 psi) (10 to 100 gal/min)

Intermediate pressure 3445 to 20,700 kPa 18.8 to 94.5

(500 to 3,000 psi) (5 to 25 gal/min)

High-pressure jets 68.9 to 138 MPa 18.8 to 94.5

(10,000 to 20,000 psi) (5 to 25 gal/min)

5
been cleaned by circulation cleaning that all the

solvent be purged from the system.

If mechanical force, such as high-pressure

spraying, hand wiping or brushing, or ultrasonic

energy is applied, inorganic contaminants can be

scrubbed from the surface by the applied energy

(Poliakoff 1973). In the absence of these mechanical aids, solvent cleaners are not effective in removing inorganic and most water-soluble contaminants (Poliakoff 1973). Solvent soaking can be

used to remove contaminants that have penetrated a permeable material but this can be a timeconsuming process, and the solvent may carry

contaminants deeper into the matrix before outward movement occurs (Esposito et al. 1985).

One problem associated with using cold cleaning is that workers will be exposed to vapors of

the organic solvents, and many of these solvents

are toxic. In addition, the solvents may be flammable. A person working with these chemicals

should wear the recommended protective equipment and should be aware that some organic

solvents can penetrate some types of protective

clothing. Another problem with using organic solvents is that many can degrade the surfaces being

cleaned. Many polymers (thermoplastics, thermosets, elastomers, and rubbers) are degraded by

organic solvents, especially the chlorinated hydrocarbons. Alcohols are generally gentler on most

polymeric surfaces, and most organic solvents do

not react chemically with metal surfaces. Disposing of organic solvents is an additional problem

unless the solvents can be sent for recycling.

Vapor cleaning is carried out in a chamber

where the solvent is boiled and the vapor is recondensed by means of cooling coils. The cold

article is placed in the vapor, solvent condenses

on it and dissolves soluble contaminants that drain

from the surface into the heated solvent where

solvent is again vaporized, leaving the involatile

contaminants in the heated solvent sump. The

process continues until the article has attained the

vapor temperature (Wadsworth 1975). Providing

the volume of solvent condensed is sufficient, there

is no possibility of a residual film (Wadsworth

1975). This is why this method is preferred for

items that need to be critically cleaned or ultraclean.

A number of other novel solvent cleaning concepts exist (e.g., using Freon 113 and supercritical

fluids), but these methods would be expensive

and do not appear to be either practical or necessary for most groundwater sampling devices.

Table 2. The most commonly used cold solvent

cleaners (from Poliakoff 1973).

1,2-dichloroethane methylchloroform

acetone methylene chloride

benzene mineral spirits

carbon tetrachloride perchloroethylene

chloroform toluene

ethanol trichloroethylene

isopropanol trichlorotrifluoroethane

methanol turpentine

methyl ethyl ketone

needed, or 4) an ultra-clean product is needed for

manufacturing purposes (adapted from Poliakoff

1973). Organic solvents work primarily by dissolving the contaminants. Generally like dissolves

like. That is, nonpolar solvents dissolve nonpolar

organic contaminants, and polar solvents dissolve

polar organic contaminants. Table 2 lists the most

commonly used solvent cleaners (a large majority

of these solvents would not be suitable for cleaning sampling devices because they are target analytes). Thus, solvent cleaners will soften, dissolve,

and remove contaminants composed of oils, tars,

asphaltics, and other substances that are not readily soluble in water. Materials like salt, soil, and

sugars are not readily dissolved by solvent cleaners (Poliakoff 1973).

Solvent cleaning is typically classified as cold

cleaning or vapor cleaning. Cold cleaning is done

by applying the unheated organic solvent in several ways: 1) wiping the surfaces with a cloth or

scrubbing with a brush, 2) immersing the object

in some type of tank, 3) spraying the surface with

atomized droplets of solvent or flushing it with a

solid stream of solvent, and 4) cleaning equipment in place by circulation cleaning (Poliakoff

1973). The first method utilizes agitation and the

action of the solvent. For immersion cleaning to

be effective, either the piece being cleaned or the

solvent should be agitated to ensure rapid cleaning (Poliakoff 1973). However, this process typically leaves some residual contaminated film on

the surface because the solvent becomes contaminated in the cleaning process. Using a series of

tanks containing cleaner and cleaner solvent can

reduce this problem. For spray cleaning, selecting

the correct pattern of spray is essential for efficient cleaning (Poliakoff 1973). The first three

methods are typically used for smaller items, and

the last method is typically used for larger equipment that cannot be easily moved. Poliakoff (1973)

also cautions that before using a system that has

6
Table 3. Decontamination solutions for drilling equipment (from Moberly 1985).

Chemical Solution Uses/remarks

Sodium carbonate 4 lb/10 gal water Neutralize organic acids, heavy metals, and

metal processing wastes

Sodium bicarbonate 4 lb/10 gal water Neutralize either base or acid (baking soda)

contaminants

Trisodium phosphate 2 lb/10 gal water Similar to sodium carbonate.

(TSP, Oakite) 4 lb/10 gal water Good for solvents and organic compounds

(such as toluene, chloroform, TCE, PCBs)

Calcium hypochlorite 8 lb/10 gal water Disinfectant, bleaching, and oxidizing agent.

(HTH) Used for pesticides, fungicides, chlorinated

phenols, dioxins, cyanides, ammonia, and

other nonacidic inorganic wastes.

Hydrochloric acid 1 pt/10 gal water Used for inorganic bases, alkali and caustic

wastes

Citric, tartaric, 4 lb/10 gal water Used to clean heavy metal contamination.

and oxalic acids

(or their respective

salts)

Organic solvents Concentrated Used to clean equipment contaminated with

(e.g., acetone, metha- organics or surface oils.

nol, methylene

chloride)

Chemical neutralization methods

A number of chemicals can be used to neutralize various organic contaminants. Although this

approach is not commonly used to decontaminate

sampling devices used for monitoring groundwater, the military has found this approach necessary when decontaminating surfaces contaminated with neat chemical warfare agents. Moberly

(1985) outlined a number of chemicals that could

be used for decontaminating drilling equipment

(Table 3). Bleaching agents include calcium hypochlorite (HTH), Super Tropical Bleach (STB),

and household bleach. Bleaches can degrade and

detoxify many of the more toxic contaminants,

such as organo-phosphorus pesticides (Esposito

et al. 1985). Two problems with this type of approach are that many of these decontaminants

are hazardous to work with and they may degrade the surface being decontaminated. For example, bleaches can corrode metal equipment.

Thus, this approach is really only applicable for

extreme cases where one encounters high levels

of very toxic contaminants or where other cleaning methods have proven ineffective in reducing

contaminant levels.

CURRENT PROTOCOLS FOR

DECONTAMINATING

GROUNDWATER

SAMPLING DEVICES

Commonly, guidelines for decontaminating

sampling devices (e.g., U.S. EPA 1992) suggest that

equipment be decontaminated by first washing

with a nonphosphate detergent, then rinsing with

tap water, rinsing with (high-quality) acids and

solvents, rinsing with some type of high-quality

water (e.g., distilled, deionized, organic-free reagent water), and finally air drying. Washing with

detergent and water removes gross contamination and particles, an acid rinse desorbs inorganic

contaminants, a rinse with organic solvents removes less polar organic contaminants, and the

final high-quality water rinse removes the acid

solutions and/or organic solvents.

Almost all methods recommend either using a

nonphosphate (e.g., ASTM 1990, U.S. EPA 1992)

or a laboratory detergent (e.g., U.S. EPA Region

IV 1991), or both. Although the surfactants used

in detergents can be cationic, anionic, amphoteric, or nonionic, there has been little discussion of

7
Variations in methodology

Mickam et al. (1989) compared the decontamination procedures of several state and federal regulatory agencies and found that these procedures

were highly variable. Following is a discussion of

some (but not all) of the variations that have been

found.

While most methods did not stipulate how

aqueous cleaning was to be conducted (i.e., soaking, scrubbing with a brush, or using a high-pressure washer), a few methods [ASTM 1990, U.S.

EPA Region IV 1991, and according to Mickam et

al. (1989) older procedures for Alabama and Pennsylvania] did recommend using a brush during

the cleaning process. In the past, a few state agencies have also recommended using either steam

cleaning [California, New Jersey, and New York

according to Mickam et al. (1989)], or a power

washer [Maryland and New Jersey according to

Mickam et al. (1989)] either to remove gross contamination or for equipment used for collecting

samples to be analyzed for organic contaminants

(California). Region IV of the U.S. EPA also recommended steam cleaning when necessary (U.S.

EPA Region IV 1991). In addition, several research

studies (Bryden et al. 1986, Matteoli and Noonan

1987, Fink and Boyajian 1989) have used steam

cleaning to clean sampling equipment, and a paper by Brice and Kelley (1991) recommended using a high-pressure sprayer.

Brice and Kelley (1991) give one of the most

descriptive and extensive protocols for aqueous

cleaning of sampling devices. They recommended the following cleaning procedure for lightly

contaminated equipment: 1) remove particles using a low-volume, high-pressure sprayer, 2) scrub

in a phosphate-free detergent solution and rinse

Table 4. Properties of four detergent solutions.1

Recommended (%) conc’s, for

% phosphate Type of pH of different water temps

Detergent (as P) detergent 1% sol. Cold Warm Hot

Alconox 7.3 anionic 9.5 1 1* 1†

Liquinox 0 anionic 8.5 1 1* 1†

Detergent 8 0 nonionic 11.0 3–5 2–3* 2–3*†

Citranox 0 ** 2.52 2 2† 2**

1 Information provided by Alconox, Inc.

* Recommended rinse temperature

† For hard-to-remove contamination, use higher concentrations

** Citranox is a blend of organic acids, anionic and nonionic surfactants, and alkolamines.

which type of nonphosphate or laboratory detergent to select. Presumably it was thought that if

the detergent removes similar contaminants from

similar types of surfaces in the laboratory, it

ought to work in the field. ASTM Method D-5088-

90 (ASTM 1990) recommends using a nonphosphate detergent and refers to Alconox and Liquinox by name. Several other methods also refer to

Alconox. However, according to the manufacturer, Alconox is not phosphate-free. Several other

detergents (Liquinox, Citranox, and Detergent 8)

made by the same manufacturer (Alconox, Inc.)

are phosphate-free. Table 4 summarizes the characteristics of these detergents. All four of them

can be used for soaking, brush cleaning, ultrasonic cleaning, and flow-through cleaning in place

(as would be used for a pump), but only Detergent 8 is recommended for spray cleaning. The

manufacturer recommends two phosphate-free

detergents, Liquinox and Detergent 8, for cleaning equipment that will be used for environmental sampling and testing.

Typically, the acid rinse is dilute (0.1 N) hydrochloric or nitric acid. Most protocols do not recommend this step unless inorganic species are

going to be analyzed. Recommended organic solvents vary with the particular protocol but typically include acetone, hexane, or methanol. Obviously, any organic solvent that is used as a rinsing

agent should not be one of the target analytes or

interfere with chemical analyses. In addition, the

waste decontamination fluids need to be disposed

of properly and should be containerized, at least

until it can be determined if the waste is hazardous. Clearly, it is advantageous to find the most

effective decontamination method that generates

the least amount of hazardous waste.

8
instead of a dilute nitric acid rinse when cleaning

stainless steel. They stated that this was because

nitric acid may oxidize steel. However, any acid

solution can corrode a stainless steel surface

(Driscoll 1986). For glass and polymeric surfaces,

the purpose of an acid rinse is to remove sorbed

metal ions from the surface. This procedure

would be of questionable effectiveness for any

metal surface.

Region IV of the U.S. EPA (U.S. EPA Region IV

1991) recommended different protocols for cleaning equipment used to collect samples for trace

organic compounds and metals, depending upon

the material being cleaned. For fluoropolymers

(Teflon) and glass they recommended an acid

rinse, but for stainless steel and other metal sampling devices they did not. They did not explain

why these methods differed. They also gave different protocols for precleaning various types of

sampling tubings. They recommended that stainless steel tubing receive a detergent wash and rinse

with high-quality water and a rinse with (an unspecified) organic solvent. Silastic rubber tubing

would receive a similar wash but would not be

rinsed with organic solvent. In this case, the reason is probably because the rubber tubing would

be degraded by most organic solvents. The glass

and Teflon tubings receive only an organic solvent rinse, followed by air drying for the glass

Table 5. Recommended solvent rinses for soluble contaminants (from

U.S. EPA 1991).

Solvent Soluble contaminants

Water short-chain hydrocarbons

inorganic compounds

salts

some organic acids

some polar organic compounds

Dilute acids basic (caustic) compounds

amines

hydrazines

Dilute bases (detergent, soap) metals

acidic compounds

phenols

thiols

some nitro and sulfonic compounds

Organic solvents, e.g., alcohols, nonpolar organic compounds

ethers, ketones, aromatics,

straight-chain alkanes (e.g.,

hexane), common petroleum

products (e.g., fuel oil, kerosene)

thoroughly with potable water, 3) rinse with deionized or distilled water, and 4) air dry. For grossly

contaminated equipment they recommended the

following protocol: 1) wash with detergent solutions and rinse with potable water, 2) rinse with

an organic solvent (preferably isopropanol), 3)

wash with a detergent solution a second time and

rinse with potable water, 4) rinse with deionized

or distilled water, and 5) air dry. They cautioned

that this equipment should not be used to sample

water suspected of being contaminated at low or

trace levels. However, they did not supply any

data to back up either of these recommended

methods.

The U.S. EPA (1991) gives different recommended solvent rinses for various contaminants (Table

5). However, the list of recommended organic solvents for removing nonpolar organic contaminants is general, and it is doubtful whether a number of the solvents they recommend should be

used. For example, fuel oil or kerosene can both

be target analytes.

When sampling for organics, draft guidance by

the U.S. EPA for RCRA sites (U.S. EPA 1992) recommends two solvent rinses: one with hexane or

methanol, followed by a rinse with acetone, followed by a rinse with organic-free reagent water.

When sampling for metals, this document also recommended using a dilute hydrochloric acid rinse

9
tubing and oven drying for the Teflon. In this instance, it is not clear why they eliminated the detergent wash.

In fact, very little scientific evidence could be

found to justify any of the recommended protocols. Mickam et al. (1989) concluded that the base

of research information is insufficient to permit

an adequate assessment of these methods. Apparently, decontamination methods are either based

on unpublished observations or best guesses.

Special instructions

for cleaning pumps

Cleaning a sampling pump is much more involved than cleaning a bailer. With a pump, there

are more surfaces and crevices and often there are

several different types of materials. Only three

methods that dealt specifically with cleaning

pumps were found in the literature. These methods recommended either circulating or recirculating a series of cleaning fluids through the pump

system. Classen (1982) recommended pumping an

acid-wash solution (100–200 L) through the system and rinsing with deionized water in a similar

fashion. However, he did not supply any data to

prove the effectiveness of this method. Keely and

Boateng (1987) recommended recirculating three

cleaning solutions: 1) detergent in water (the outside surfaces would be scrubbed), 2) 10% (vol/

vol) acetone in clean water (again the outside

would be scrubbed), and 3) rinse with distilled

water, followed by air drying. For high concentrations of nonvolatile organics and pesticides, they

recommended a second distilled water rinse. They

claimed that this method was effective for decontaminating a positive-displacement (Johnson–

Keck) submersible pump that had been used to

sample VOCs, but they did not offer any proof of

this. They also claimed that this series of cleaning

solutions was effective for cleaning a stainless

steel bailer exposed to similar contaminants.

ASTM Method D 5088-90 (ASTM 1990) for decontaminating sampling devices (used at nonradioactive sites) recommends circulating 1) a detergent solution, 2) a rinse of known quality

water, 3) a rinse with 10% nitric acid or hydrochloric acid (this step is deleted if samples are not

analyzed for inorganic contaminants), 4) a rinse

with known-quality water, 5) a rinse with an organic desorbing agent (isopropanol, acetone, or

methanol), 6) a rinse with deionized water, and

following all of this with air drying. Again, this

method did not provide any scientific studies

that justify using this procedure.

EFFECTIVENESS OF VARIOUS

DECONTAMINATION METHODS

When the literature was reviewed, only five

studies (Dunbar et al. 1985, Bryden et al. 1986,

Matteoli and Noonan 1987, Fink et al. 1989, Schuh

et al. 1993) were found that compared the effectiveness of various decontamination protocols. Of

these five studies, only two (Dunbar et al. 1985,

Bryden et al. 1986) were in peer-reviewed journals. Bryden et al. (1986) reported having excellent results decontaminating purging and sampling equipment in the field using a small portable

steam-cleaning machine followed with a rinse

with distilled water or “type II” water (to remove

any contaminants coming from the steam cleaner

or water supply). They did not elaborate on the

types of contaminants they encountered, but reported that the pressure was sufficient to dislodge

particulate matter. They also warned that Teflon

could warp if steam-cleaned too vigorously.

Dunbar et al. (1985) found that rinsing a stainless steel bailer and nylon rope with clean water

was not sufficient to prevent carryover of contaminants (chloroform and benzene) from well to

well. They recommended decontaminating the

bailer by using steam cleaning, washing with detergent, and rinsing with deionized water, and

using new lengths of nylon rope in each well.

However, they did not present any data that substantiates this recommendation. Presumably, the

bailer would be much easier to decontaminate

than the nylon rope.

The next three studies (Matteoli and Noonan

1987, Fink et al. 1989, Schuh et al. 1993) actually

compare the effectiveness of various decontamination protocols. Unfortunately none of these

studies was peer reviewed. However, because

there were no other peer-reviewed studies available and because they do provide us with more

complete data, they were included in this discussion.

Matteoli and Noonan (1987) conducted several

field tests to study decontamination of sampling

tubings. They tested two types of tubing: rubber

hose (neoprene lined with ethylene propylenediene monomer) and fluorinated ethylene propylene (FEP, another type of Teflon). In their first

two field tests, they used a stainless steel submersible pump with the rubber hose. They

pumped well water contaminated with TCE, at

concentrations of approximately 860 to 1100 ppb,

for 2 hours. They then steam cleaned the exterior

of the pump and hose and pumped clean water

10
through the system for another 2–3 hours. At the

end of this time, they were still able to detect low

ppb levels (1.1 to 18) of TCE in water pumped

through the system. They concluded that rubber

hose could not be decontaminated using this method in an acceptable amount of time.

In all of their subsequent tests they used the

same methodology except that they used FEP tubing rather than the rubber hose and the original

exposure time was less, 30 minutes. In the third

test, they found that TCE concentrations were below the detection limit (0.5 ppb) after pumping

clean water for 90 minutes. The initial level of

TCE contamination was similar to the previous

studies, approximately 1200 ppb. In the next

(fourth) trial, they were unable to completely decontaminate the system. They found that, after

pumping clean water through the system for 120

minutes, concentrations of Freon 113 (1,1,2-trichloro-2,2,1-trifluoroethane) ranged from 1.7 to 21 ppb;

initial concentrations of this analyte were approximately 3900 ppb. In the fifth test, 1,1-dichloroethylene concentrations dropped below the detection limit (0.5 ppb) after pumping clean water for

only 7 minutes. However, the initial concentration of this contaminant was much lower, only

about 120 ppb. In the sixth test, dimethyl nitrosamine concentrations fell below the detection limit (0.2 ppb) after pumping clean water for only 3

minutes. Again, initial concentrations were low

(~30 ppb). The next two tests indicated that metal

contaminants are more readily decontaminated.

(Selenium concentrations dropped below the detection limit—5 ppb—after pumping clean water

for only 3 min; initial concentrations were 610 ppb

in the contaminated well. In another test, initial

chromium concentrations in the well water were

43,000 ppb. However after pumping with clean

water for 20 minutes, concentrations were at the

background level.) They concluded that residual

TCE concentrations dropped off more rapidly using Teflon than rubber hose. However, given that

the initial contact time was 4 times longer for the

rubber hose than for the FEP tubing, a valid comparison cannot be made. It is clear from this data

that decontaminating either type of tubing by

steam cleaning the exterior and pumping clean

water through the system can be time-consuming

and ineffective for certain organic contaminants,

especially if the initial concentrations of the contaminants are in the ppm range and contact times

are 30 minutes or more.

Fink et al. (1989) evaluated four methods for

decontaminating a sampling pump. This test compared detergent washes with plain water washes.

Method 1 involved injecting 30 gal warm water

(49°C or 120°F) with detergent (1%), followed by

rinsing with 10 gal of ambient-temperature water. Method 2 was similar, except that only half

the previous amount of cleaning and rinsing solutions were used (15 gal of detergent wash water

and 5 gal of ambient rinse water). Method 3 involved washing with 30 gal warm water (no detergent) followed by a 10-gal rinse with ambienttemperature water. Method 4 was similar except

that the amount of water was again half (15 gal

warm water, 5 gal ambient-temperature water).

The four solutions were pumped through a stainless-steel bladder pump (equipped with a PTFE

bladder) and PTFE-lined sample tubing. After removing the pump from the well, the external surfaces of the pump and tubing assembly were steam

cleaned before circulating the cleaning fluids

through the pump. The pump had been used to

sample VOCs; a minimum of five sampling

pump/tubing assembly volumes of contaminated

water were pumped from the well between decontamination procedures.

In the first study, initial concentrations of TCE

in the well water were 300 mg/L. They found that

all four methods yielded rinse water with no TCE

contamination. In a field test, they found no VOCs

in 26 of 28 quality-control samples taken after using method 2 to clean the sampling device. Although they claimed there was no effect of concentration on decontamination efficiency, the data

do not support this claim. TCE concentrations of

1.0 μg/L and 1.8 μg/L were found in the two samples that were pumped from the two wells with

the highest TCE concentrations (1600 μg/L and

2215 μg/L, respectively). For the rest of the study,

initial concentrations of TCE in well water were

much lower (all but one sample had concentrations of 300 ppb or less) and initial concentrations

of the other VOCs (1,1-dichloroethane, 1,1-dichloroethylene, tetrachloroethylene, and 1,1,1-trichloroethane) were in the low (< 10 μg/L) range.

Schuh et al. (1993) tested the effectiveness of a

distilled water rinse for removing seven pesticides

[bromoxynil, diclofop-methyl, dimethoate, 2-

methyl-4-chlorophenoxyacetic acid (MCPA), methyl parathion, propiconazole, and trifluralin]

from a PVC bailer. They found that the effectiveness of this procedure depended on the analyte’s

solubility in water and its Kow value. Contact time

was brief (1 minute); they felt that a 1-min contact time was representative for samples taken in

a shallow well or gravelly aquifer. They found

11
Table 6. Sorption and desorption of three organic solutes by rigid PVC and PTFE.

Initial concentration = 2000 μg/L

Contact time = 6 wk (1000 hr) Contact time = 24 hr Contact time = 1 hr

Predicted Predicted

Amt. Amt. Amt. amt. Amt. amt.

sorbed* desorbed* sorbed* desorbed sorbed* desorbed

Material Analyte (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)

PTFE CDCE 410 200 80 39 ND —

CLB 1000 280 200 56 ND —

MDCB 1480 355 440 11 ND —

Rigid PVC CDCE 200 80 100 40 ND —

CLB 280 100 100 36 ND —

MDCB 400 200 160 80 ND —

Initial concentration = 50 μg/L

Contact time = 6 wk (1000 hr) Contact time = 24 hr Contact time = 1 hr

Predicted Predicted Predicted Predicted Predicted Predicted

amt. amt. amt. amt. amt. amt.

sorbed* desorbed* sorbed* desorbed* sorbed* desorbed

Material Analyte (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)

PTFE CDCE 10 5 2 1.0 ND —

CLB 25 7 5 1.4 ND —

MDCB 37 9 11 2.8 ND —

Rigid PVC CDCE 5 2 2.5 1.0 ND —

CLB 7 2.5 2.5 0.9 ND —

MDCB 10 5 4.0 2.0 ND —

* Actual values taken from Parker et al. (1990). Desorption time was 3 days.

CDCE = cis-1,2-dichloroethylene

CLB = chlorobenzene

MDCB = m-dichlorobenzene

ND = no loss detected

These studies indicate the importance of the

initial concentration of the contaminants, contact

time, and the relative sorptiveness of the material

being decontaminated. We can use the data from

one of our previous studies (Parker et al. 1990) to

demonstrate this. Table 6 shows the amount of

three organic solutes [cis-1,2-dichloroethylene

(CDCE), chlorobenzene (CLB), and m-dichlorobenzene (MDCB)] sorbed by two rigid polymers

(PVC and PTFE) after 6 weeks contact with the

test solution (at ~2 ppm concentrations) and the

amount desorbed after the test pieces were rinsed

with fresh well water and placed in clean vials

with fresh well water for three days. This table

also shows the amount that was sorbed after 1

hour and 24 hours contact with the test solution.

If we use this data and assume that the relative

rate of desorption remains the same regardless of

the amount sorbed, we can estimate the amount

of analyte that might be desorbed from the samples that had contact times of 24 hours and 1

hour. (Twenty-four hours was selected to simuthat most analytes having a solubility of >500 mg/

L or Kow <200 (log Kow <2.3) were generally

cleaned from a PVC bailer so there was no residual carryover with just one rinse with distilled

water. Analytes having a water solubility of >50

mg/L or Kow <2000 (log Kow <3.3) were generally

effectively cleaned from a PVC bailer following

multiple (>6 rinses) with distilled water. They

found that dimethoate was an exception and that

15 rinses were required before it was removed.

They concluded that in some cases it may be justifiable and appropriate to rely on a distilled water

rinse alone. For this study, it is important to note

that there was no significant loss of these analytes

due to sorption by the bailer during the 1-min

contact time and that contaminant concentrations

were generally less than 20 μg/L. The effectiveness of this method might be quite different if a

longer contact time (that allowed sorption to occur) were used or if the concentration of the

contaminants were higher (at least for the more

water-soluble ones).

12
late the time a pump might remain in a well. Ideally, 10 minutes would best simulate the contact

time of a sample with a bailer. However, since the

shortest time interval for which there was data

was 1 hour, we used these data.) These data were

then used to estimate the amount desorbed if the

concentration of the analytes in the test solution

had been much lower, e.g., 50 μg/L. It is clear

from this table that potential problems with cross

contamination due to desorption of analytes is

greater for the more sorptive material, PTFE, and

decreases substantially for relatively short contact times (24 hr or less).

These values are only estimated, and there are

a number of factors that could affect the ability of

a material to desorb contaminants. For example,

the potential for cross contamination would be

less if the time for desorption were more realistic

of a sampling event and less than the three days

used in this study. On the other hand, more hydrophobic contaminants would be expected to be

more readily sorbed; the most hydrophobic contaminants used in our study (Parker et al. 1990)

were p- and m-dichlorobenzene, which have log

Kow values of 3.39 and 3.38, respectively (Hansch

and Leo 1979). For flexible tubings, sorption is

considerably more extensive. For example, Gillham and O’Hannesin (1990) found that after only

10 minutes contact time, flexible PVC sorbed 50%

of low (~1) ppm levels of m- and p-xylene, and

rigid PVC sorbed little or nothing (losses were 2%

or less). Thus, for a pump that remains in the well

for several hours, a large amount of some analytes could be sorbed by the tubing. These contaminants would be available for desorption and

could cause problems with cross contamination.

A recent study by our laboratory shows that all of

the 20 types of tubing we tested (including several fluoropolymers) were highly sorptive of

some organics (Parker and Ranney, in press).

Given the previous example (Table 6), it is understandable how rigid materials subjected to

low ppb concentrations of relatively water-soluble contaminants for short periods of time may be

easily decontaminated with a single aqueous rinse.

It is also understandable how higher concentrations of these contaminants or similar concentrations of more hydrophobic contaminants may require several rinses or more stringent cleaning

(e.g., detergent cleaning). For flexible materials,

such as pump tubing where contact times would

be much longer than with a bailer, it is clear that

either more extensive cleaning will be necessary

or that new or dedicated tubing may be required

for each well to reduce the possibility of cross contamination, especially for the more hydrophobic

contaminants and when concentrations exceed

more than a few ppb.

LOW-TEMPERATURE

CONSIDERATIONS

While the primary focus of this literature review has been on determining the efficacy of various decontamination methods, the effect of cold

temperatures on this process should also be mentioned. As might be expected, subfreezing temperatures limit the usefulness of aqueous and solvent-based decontamination methods. Richter

and Collentine (1983) reported that decontamination of field equipment in remote areas of Wyoming was frustrating and that subfreezing temperatures of –40°F rendered conventional methods

with soap and water impossible. They recommended taking additional clean equipment in

the field so that decontamination can be conducted later in a specially constructed (i.e., heated)

wash area.

CONCLUSIONS

From these studies the following conclusions

can be made:

1) Although there are a number of published

methods for decontaminating sampling devices, there is a lot of disparity between the

methods.

2) There has been very little systematic study

of the effectiveness of various decontamination protocols and apparently little documented basis for the existing guidance.

3) The type of contaminants, level of contamination, and materials being decontaminated clearly affect desorption and decontamination effectiveness.

4) To clean sampling pumps with flexible tubings (even Teflon tubings), neither a clean

water wash nor a wash with warm detergent followed with a clean water rinse is

generally effective if the pump was exposed

to ppm levels of VOCs. Steam cleaning with

a detergent solution may be more effective,

although this remains untested.

5) Cleaning bailers that have very short contact times with the samples appears to be

much less problematic.

13
6) Using the aqueous solubility or Kow values

of the contaminants or multiple linear solvation energy relationships may be useful

in predicting the ability to decontaminate a

sampling device.

Clearly, further systematic study that evaluates

various decontamination methods is needed.

These studies need to consider the type of material(s) being decontaminated, a range in hydrophobicity of the contaminants, concentrations of

contaminants, and contact time. The kinetics of

desorption also need to be addressed.

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July 1995

A Literature Review on Decontaminating Groundwater

Sampling Devices: Organic Pollutants

Louise V. Parker

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road CRREL Report 95-14

Hanover, New Hampshire 03755-1290

U.S. Army Environmental Center SFIM-AEC-ET-CR-95-008

Aberdeen Proving Ground, Maryland

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22

Chemical neutralization Decontamination

Cleaning methods Organic contaminants

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

Current protocols for decontaminating devices used to sample groundwater for organic contaminants are reviewed. Most of the methods given by regulatory agencies provide little scientific evidence that justify the

recommended protocols. In addition, only a few studies that actually compared various decontamination protocols could be found in the open literature, and those studies were limited in their scope. Various approaches for

decontamination and criteria that are important in determining how effectively a surface could be decontaminated are discussed.