United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Las Vegas NV 89193-3478
Research and Development
EPA/600/S4-87/021 Jan. 1988
Project Summary
Evaluation of a Prototype Field-
Portable X-Ray Fluorescence
System for Hazardous Waste
Screening
G. A. Raab, D. Cardenas, S. J. Simon, and L A. Eccles
A prototype field-portable X-ray
fluorescence system developed by EPA
and NASA was evaluated at a site con-
taminated with Pb, Zn, and Cu. The
objective of the field test was to evaluate
the effectiveness of the instrument as a
field analytical tool for locating hot spots
and as a preliminary screening device
where immediate data feedback aids in
decision-making in the field.
By making use of an analytical method
designed specifically for the XRF sys-
tem, all routine field measurements for
Cu, Zn, and Pb were made on site by
placing the probe on the surface of the
ground ("In situ" measurements).
Subsequently, confirmatory samples
were collected and analyzed in the
laboratory with an Inductively Coupled
Plasma spectrometer (ICP) while adher-
ing to EPA Contract Laboratory Program
(CLP) protocols.
The quality assurance consisted of
measuring NBS standard reference
materials to verify the data measured in
the field and in the laboratory in addition
to duplicates.blanks, and replicate
sample analysis.
The analytical results were plotted on
the sampling grid. One can immediately
locate the hotspots for Cu, Zn, and Pb
on site. The instrument detection limits
for Cu, Zn, and Pb are 250, 200, and
70 ppm, respectively. Comparison of
the XRF results with the ICP results
showed an overall mean percent error
(MPE, which means lack of precision
and bias incorporated into one term)
from NBS concentrations of only a few
percent for Cu, Zn, and Pb. Precision
and accuracy of the In situ measure-
ments were within plus or minus 10
percent of the true value when com-
pared to the samples analyzed in the
laboratory.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Las Vegas, NV, to
announce key findings ot the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
The Environmental Protection Agency,
Environmental Monitoring Systems
Laboratory, Las Vegas asked Lockheed
Engineering and Management Services
Company, Inc. (LEMSCo) to field test and
evaluate the performance of a field-
portable X-ray fluorescence system for
making in situ measurements. The use of
in situ measurements with the XRF
system would allow technicians to im-
mediately locate surface hotspots of lead,
copper, and zinc on the national priority
list (NPL) sites and other sites. The objec-
tive of this report is to describe the steps
necessary to complete the field test, re-
view the analytical work, and assess the
instrumental performance. These steps
are as follows:
• design a sound in situ analytical
method for a field-portable X-ray
fluorescence system prior to the field
test,
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• analyze each of the 40 samples in
situ with the field-portable XRF
system at 40 locations on a 60 foot
by 150 foot grid with sample intervals
at every 15 feet,
• subsequently collect confirmatory
surface soil samples from the same
locations,
• analyze the samples in the laboratory
following the ICP CLP protocol,
• compare the XRF results with those
obtained from the ICP.
The EPA has recently expressed more
interest in XRF systems than in previous
years because the use of microprocessors
and state-of-the-art technology have
made the equipment smaller and thus
portable. Such field-portable XRF systems
have been used to delineate hazardous
waste site hotspots for priority metals in
the field With immediate data feedback
from the field-portable XRF system, all
samples can be collected with the know-
ledge of their approximate concentration.
This leads to a decrease in the number of
unnecessary samples which would be
analyzed normally. The XRF field data
allows an analyst in the laboratory to
calibrate his laboratory instrument to the
proper concentration on the first try; thus
decreasing the number of attempts at
bracketing the correct one. Another use
is as a laboratory analytical instrument to
screen samples of unknown concentra-
tions quickly providing the analyst with
an approximate concentration. All of these
applications of the XRF systems net an
overall decrease in time and in money
spent.
Three levels of analytical requirements
are described for establishing the extent
of environmental contamination. The first
or highest level of analysis is used to
develop data for litigation and regulatory
enforcement (see Figure 1). This level
demands the most rigor in sample pre-
paration and instrument time as well as
the highest degree of precision and ac-
curacy. The seond level of analysis is
used to evaluate and assess average con-
taminant exposures to people and animals.
The data from the third level of analysis
is used for screening in order to obtain a
preliminary profile of sites. This data can
be used for decision making while in the
field. Third level data may be used also to
select which samples should be sent to
the laboratory for first level analysis fol-
lowing the Contract Laboratory Program
(CLP) analytical protocols. This report
discusses the results obtained by using a
portable XRF system under the third level
of analytical requirements.
Field Test and Procedure
The objective of the field test was to
assess the performance of the Martin
Marietta Aerospace field-portable XRF
system on an NPL site with regard to
effectively identifying hotspots of lead,
copper, and zinc. This was accomplished
by analyzing in situ and by subsequently
collecting surface soil samples on site at
40 locations on a 60 feet by 150 feet grid
with sample intervals at every 15 feet
(Figure 2). In situ measurements are those
measurements made by the XRF probe
while in direct contact to the ground
surface. These measurements are con-
ducted without any sampling and sample
preparation other than clearing the
ground surface to expose the soil. An in
situ XRF measurement represents the
data obtained from only the exposed
ground surface and does not reflect any
of the subsurface. The contaminants in a
hot spot would not register a response to
the X-rays if the hot spots were covered
Three Levels of Analytical Requirements for Metals
Level 1
Level II
Level III
Degree of Analytical Requirement
(Precision) (Accuracy) | fIDLJ
(+5%)
H
f±10%)
K
(±10%)
Very High
(+10%)
Moderately High
(±15%)
Moderate to Low
(±50%)
(ppb)
(ppm)
(
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with as little as 1 cm of uncontaminated
soil. Therefore, caution must be exercised
in the use of data obtained from in situ
measurements. Technicians analyzed
each of the 40 samples in situ for total
Pb, Cu, Zn, and Fe with the field-portable
XRF system and processed the data for
on site decision making.
The same samples were then collected
for later confirmatory analysis in the
laboratory. To further corroborate the XRF
field data, we used the known and ac-
cepted CLP methods of preparation and
analysis. Because the CLP method of
sample preparation uses a relatively weak
extraction, we also used a Parr bomb
method to provide a stronger extraction
method that was likely to more closely
approach the NBS certified values. The
Parr bomb method was performed on 13
selected samples but under CLP instru-
mental requirements for the ICP.
NBS standard reference materials
(SRM) were used as quality assurance/
quality control standards. The NBS stan-
dards were incorporated to give us
reference data of known quality. Those
used were SRM 1633a, coal fly ash,
SRM 1645, river sediment, and SRM
1648, urban air paniculate. The NBS
standards were analyzed in the field with
the XRF system. These values were
compared against the SRM-certified
values.
The quality assurance (QA) procedures
developed for the XRF field analysis
allowed for the proper verification of the
data. The verification establishes the
quality of the data. To evaluate the repro-
ducibility of measurements offers many
advantages. The data from the initial
screening allows field crews to:
(1) identify the hotspots,
(2) restrict the investigation to the con-
taminated area,
(3) either go to the next level of in-
vestigation or stop at the screening
level, and
(4) make decisions based on the data
base which is generated from the
analyses.
The next level of investigation above
screening requires confirmatory samples
be taken and analyzed. These can be
analyzed in the field. If this were in an
area being investigated for the first time,
the hotspot would be identified and the
locations registering as "background"
(non-contaminated) by in situ XRF
analysis need not be sampled for con-
firmation. In our case, the intensified
effort would be restricted to the area
marked "waste site" in Figure 2. This
would decrease the number of samples,
which might otherwise be analyzed, and
thereby reduce overall analytical costs.
As more samples are -analyzed, the
data base for the area grows. The initial
screening provides the foundation from
which the investigation proceeds. The
subsequent measurements then provide
data of higher quality from which plots
can be generated. Field crews can make
decisions based on these plots and this
data base.
Conclusions
• The XRF system produced data of
known quality from 229 in situ
measurements (defined as measure-
ments made by placing the probe on
the ground surface and by analyzing
the same surface without moving
the probe). The XRF field results on
the NBS standards compared rela-
tively well with the certified NBS
values of the same standards.
• Field personnel can greatly decrease
the time spent on site by making in
situ measurements. If necessary, the
technician can collect a confirmatory
sample after each XRF analysis.
• The detection limits are low enough
for obtaining data when third level
requirements are necessary for
analytical work on hazardous waste
site investigations.
• The NBS standards were adequate
for quality control and quality assur-
ance. These standards were SRM
1633a, coal fly ash; SRM 1645, river
sediment; and SRM 1648, urban
particulate.
• The instrument uses cryogenics to
cool the silicon-lithium detector
which requires a Dewar container
filled with liquid nitrogen. Even
though the Dewar container will last
8 hours before a refill is necessary,
maintaining a continuous supply of
liquid nitrogen in the field can be
difficult in some locations.
• The overall advantages of all X-ray
fluorescent systems include: minimal
sample preparation time, rapid turn-
around time for analyses, multi-
element analytical capability, non-
destructive analyses, and sample size
required for analysis is small or
possibility of surface analysis with-
out the need for sampling at all.
These advantages make the XRF
system very cost effective.
Recommendations
• A field methods manual should be
written for field XRF measurements
and should incorporate field sam-
pling, sample preparation techniques,
and analysis.
• Characterized spiked soils should be
prepared for the XRF systems as
reference standards. These would
be spiked at concentrations ranging
from 5 to 10 times the IDL, to the
highest likely to be encountered; or
at levels considered to be a public
health hazard.
• A procedure for primary calibration,
field update of calibration and of
QA/QC checks of the instrument
accuracy and precision should be
worked out.
• The investigation of a sample pre-
paration method for non in situ
measurements should be tested. This
should include examination of both
the palletizing and fusing techniques,
and the use of loose soil. Indications
are that one would obtain different
levels of precision.
• The Martin Marietta XRF system
should be compared with other com-
mercially available field XRF systems.
The detection limits, precision, and
accuracy of each instrument could
be determined side by side in the
laboratory with the ICP or AAS
by using rigorous QA/QC protocols,
characterized samples, and certified
spiked standards.
• Once the instrument detection limits
are established for XRF field-portable
systems, the initial steps may be
implemented in developing these
instruments for characterization of
uncontrolled hazardous waste sites
with respect to specific toxic metals.
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G. A. Raab, D. Cardenas, and S. J. Simon are with Lockheed Engineering and
Management Services. Company, Inc., Las Vegas, NV 89119; and the EPA
author, L. A. Eccles, is with Environmental Monitoring Systems Laboratory,
Las Vegas, NV 89193-3478
Kenneth W. Brown is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of a Prototype Field-Portable X-Ray
Fluorescence System for Hazardous Waste Screening," (Order No. PB 87-
227 633/AS; Cost: $11.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA22161
Telephone: 703-487-4650
The EPA Officer can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Las Vegas. NV 89193-3478
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use S300
EPA/600/S4-87/021
• 0000329 PS
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