Table 7. Measurements of Pb in soil mix-
Table 8. Measurements of Hg and Pb on and
tures using different analysis periods.
below disks of Lebanon Landfill soil using dif-
ferent periods of analysis.
Analysis
Instr.†
Sample period
Manual*
Hg
(%)
(s)
PbK
Comp.**
(ppm)
Analysis
Manual*
Target
Depth
period
Background
96
50
1400
354
HgK
Comp**
(g)
Moisture
(cm)
(s)
0.625
96
185
835
3000
AD††
50
920
none
0.5
96
0.625
10
15
85
3400
AD††
15
105
none
0.5
10
1.25
96
315
790
5000
AD††
210
840
0.25
0.5
96
1.25
10
25
85
5100
AD††
30
100
0.25
0.5
10
2.5
96
700
830
6400
AD††
115
869
0.5
1.0
96
2.5
10
60
90
6300
AD††
1.0
10
5
90
0.5
5.0
96
980
740
7100
5.0
10
115
65
7100
Pb
10
96
1500
825
8500
Analysis
10
10
170
80
8400
Instr.†
Manual*
Target
Depth
period
Pb Comp.** (ppm)
(g)
Moisture
(cm)
(s)
* Manually measured fluorescent energies,
baseline-corrected.
AD††
40
920
380
none
0.5
96
† Instrumental measurements based on Pb
AD††
5
105
930
none
0.5
10
(mg/kg) in soil standards.
265
930
1900
0.25
20%
0.5
96
** Compton peak.
25
85
2600
0.25
20%
0.5
10
490
800
3100
0.5
20%
0.5
96
45
75
5100
0.5
20%
0.5
10
AD††
135
880
1400
0.5
1.0
96
Detection level of rapid analysis
AD††
10
95
1200
0.5
1.0
10
The sensitivity of elemental detection in envi-
ronmental matrices performed by XRF depends
* Manually measured fluorescent energies, baseline-
corrected.
upon several factors, including the length of anal-
† Instrumental measurements based on Pb (mg/kg) in soil
ysis time. The sensitivity for rapid analyses with
standards.
the MAP-3 scanner was assessed by analyzing
** Compton peak.
†† Air dried.
mixtures of the LLF soil and Pb(NO3)2 held in
XRF cups and pillows of both the Pb and Hg salts
beneath the modified XRF cups (Tables 7 and 8)
before quantitative measurements could be per-
for either 10 or 96 seconds. The 10-s measurement
formed. Ideally, correction factors could be also
period is the fastest analysis time for this instru-
be applied so that measured metal concentrations
ment. The objective of this experiment was not to
could be converted readily to estimations of prim-
establish the smallest amount of Pb or Hg that
er concentration [i.e., 1.4 times for Pb(N3)2 and
could be measured, but to determine if percent
Hg(CNO)2 or 2 times for C6HO6N3Pb].
levels could be quickly detected.
The results in Table 7 show that Pb was easily
SUMMARY
detectable using a 10-s analysis period when
mixed with soil so that ≥0.625% was present.
This study shows that the MAP-3 XRF analyzer
Likewise, it appears that 0.5-g quantities of these
is well suited for rapidly determining if either
two metals could be rapidly detected even when
lead or mercury exists on or near the surface in
covered with 0.5 cm of soil (Table 8).
high concentrations (percent levels). This system
A comparison between the changes in response
has several features that are not currently
relative to metal concentration as seen by the
matched by other commercially available porta-
manual and instrumental measurement methods
ble XRF spectrometers, most importantly the use
is also shown in Table 7. For a 16-fold increase in
of a Co-57 source. This source, coupled with the
Pb, the manual method established an 8.1- to 11-
instrument's capability for rapid analyses and a
fold increase in PbK peak intensity, but the Pb
complete spectral display of both the K and L
concentrations (mg Pb/kg) determined by the
lines of energy for these two metals, not only pro-
calibrated instrument method only showed a 2.8-
vides immediate information as to the concentra-
to 2.5-fold increase. The large discrepancy in
tions present, but their location within the first 1.5
range of relative response between the two meth-
cm of the surface as well. In addition, the manu-
ods of analysis indicates that a different approach
facturer can provide calibrations for Hg in soil
to instrumental calibration would be necessary
upon request.
8
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