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,

-------
  • 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)
(
-------
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.

-------
    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

-------