X-ray fluorescence was used to characterize metals in marine sediments at a contaminated mine site. XRF provided rapid, cost-effective analysis of over 500 samples with good precision. XRF results correlated well with laboratory ICP but exhibited a high bias. While XRF improved site characterization for risk assessment, particle size effects require further study. Overall, XRF is a valuable tool for sediment remediation investigations.

1. Characterization
of Metals in
Marine Sediments
using
X-Ray
Fluorescence
4th
International Conference on Remediation of Contaminated Sediments
Wolfgang Calicchio, Peter Baker, Tige Cunningham, and
Chris Ricardi
MACTEC Engineering and Consulting, Inc.
Callahan Mine
Superfund Site
Brooksville, Maine

2. Let’s Expand Use of XRF
Tailings Pile
Tailings Pile

3. Why discuss XRF?
 Widely Used ??
 Widely Accepted - ??
 Resource Trustees and
Regulatory Agency Concerns
 Cost effective, greater data
density, improved risk
characterizations, decision making

4. Presentation Outline
 Introduction to the Site
 Sampling Approach
 XRF Method vs. ICP
Method
 Comparison of XRF to ICP
Data
 Particle Size Implications
 Risk Assessment Statistics
 Production Rates & Costs

5. Background
 Callahan Mine Site, Brooksville, ME
 Open Pit Mine in Dewatered Estuary
 Operated 1968 to 1972
 Copper, Lead, Zinc – primary metals
 Estuary re-flooded - 1972
 Superfund Site – 2002
 Consent Order – 2005
 Expedited RI/FS - 2005
Brooksville

6. Callahan
Mine
Site
Location

7. Aerial View of Open Pit

8. Existing Conditions
 Callahan Mine
 6 source areas
 Seeps
 Surface Water
Run-off

9. Sediment
Sampling
 110 Vibracore
Locations
 30 Hand Core
Locations
 200 ft. Spacing
 602 Samples
Collected Overall
 532 samples
analyzed by XRF
 37 split samples by
ICP

10. Sediment Sampling Cont’d
 Lateral/Vertical extent
delineated in single phase
 15 day event
 Real time data - fill the
gaps

11. Element Detection Limits - XRF
Antimony - 120
Cobalt - 10
Nickel – 70
Arsenic - 10
Copper - 20
Selenium - 9
Barium - 200
Lead - 16
Silver - 75
Cadmium - 40
Manganese – 80
Thallium - 18
Chromium - 60
Mercury -14
Zinc – 30Units – mg/kg

12. Project Action Levels vs. Detection
Limits
Element
Sediment Project
Action Levels (mg/kg)
Screening Level Laboratory
ICP
Quantitation
Limit (mg/kg)
Field XRF
Instrument
Reporting
Limit (mg/kg
dry weight)
Human
Health Ecological
Copper 290 19 2.5 20
Lead 40 30 0.5 16
Zinc 1500 98 2.5 30

13. Field XRF Method – EPA 6200
 Decant standing water (from sample container)
 Remove 10 to 15 gram aliquot
 Dry in oven for 2 to 4 hours (T < 150ºC)
 Remove large non-representative material (shells,
twigs, rocks)
 Sieve dried sample (250 µm stainless steel mesh)
 Calibrate XRF instrument with standard reference
material
 Place sample on instrument and analyze for 60 secs.

14. Lab ICP Method – EPA 6010
 Decant standing water (from sample container)
 Remove large non-representative material
(shells, twigs, rocks)
 Remove 1 to 2 gram aliquot to digestion
receptacle
 Acid Digestion on hot plate
 Calibrate ICP instrument with standard
reference material
 Place sample on ICP instrument and analyze
Note: No Drying or Sieving in Prep for std lab
method

15. Data Analysis
 Correlation
 Accuracy
 Precision
 Effects of Particle
Size
 Comparison of Risk
Statistics
 Cost

16. Data Comparison XRF vs. ICP
Copper
Analysis of Field XRF vs. Laboratory ICP
Copper Results
0
2,000
4,000
6,000
8,000
10,000
0 2,000 4,000 6,000 8,000 10,000
Laboratory ICP Results (mg/kg)
FieldXRFResults(mg/kg)
Linear
Regression
y = 1.62x
+ -147
R2
= 0.92

17. Data Comparison XRF vs. ICP
Lead
Analysis of Field XRF vs. Laboratory ICP
Lead Results
0
500
1,000
1,500
2,000
2,500
0 500 1,000 1,500 2,000 2,500
Laboratory ICP Results (mg/kg)
FieldXRFResults(mg/kg)
Linear
Regression
y = 1.54x
+ 16
R2
= 0.93

18. Data Comparison XRF vs. ICP
Zinc
Analysis of Field XRF vs. Laboratory
Zinc Results
0
5,000
10,000
15,000
20,000
0 5,000 10,000 15,000 20,000
Laboratory ICP Results (mg/kg)
FieldXRFResults(mg/kg)
Linear
Regression
y = 1.44x
+ -11
R2
= 0.95

19. XRF vs. Lab Data
Relative Percent Difference (RPD) Accuracy
Mean RPDs
Copper – 24 %
Lead – 58 %
Zinc – 38 %
XRF Data Exhibited High Bias
100
)(5.0
)(
x
LabAmountXRFAmount
LabAmountXRFAmount
RPD
+
−
=

20. Summary
Correlation Evaluation
Target
Element
m r2
Correlation
Bias
Ave. RPD (%)
Copper 1.62 0.92 High High (24)
Lead 1.54 0.93 High High (58)
Zinc 1.44 0.95 High High (38)

21. Sampling Precision
XRF Field Duplicate RPD Statistics
Analyte Copper Lead Zinc
Number of Duplicates 35 35 35
Average (%) 5 11 9
Median (%) 0 10 6
Minimum (%) 0 0 0
Maximum (%) 33 55 29

22. Analytical Precision
XRF Lab Duplicate RPD Statistics
Analyte Copper Lead Zinc
Number of Duplicates 20 20 20
Average (%) 4 5 4
Median (%) 0 3 3
Minimum (%) 0 0 0
Maximum (%) 20 25 10

23. Analytical Precision
ICP Lab Duplicate RPD Statistics
Analyte Copper Lead Zinc
Number of Duplicates 6 6 6
Average (%) 8 8 12
Median (%) 8 7 11
Minimum (%) 1 1 1
Maximum (%) 15 23 22

24. Particle Size Comparison
Copper
Plot of Silt Clay Content vs. Comparison RPDs for Copper
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
Percent Composition of Silt and Clay
XRF/ICPRPDsforCopper
Actual Data

25. Particle Size Effects
 No significant correlations noted
 Limited data set
 Uniform grain sizes
 Larger particles sizes may effect accuracy
 Factor to be considered when designing
approach

26. Risk Statistics
Metal n Min - Max Min - Max Mean 95% UCL
Copper 34 218 96 - 3370 20 - 5700 1106 460 2735 1147
Lead 34 218 26 - 720 16 - 2600 313 234 390 437
Zinc 34 218 430 - 31000 38 - 26000 4647 1930 6311 3694
Laboratory ICP Data
Field XRF Data

27. Risk Assessment Implications
Use of XRF Data would provide
 Greater range of detected concentrations
 More accurate estimate of true variability
 Better Assessment of Contaminant Extent
 Better Estimates of Mean and 95% UCL
 More representative estimate of actual risk

28. Cost Comparison
 Production rate – 100
samples/day estimated with one
chemist
 Sample throughput - up to 79
samples/day (limited by samples
collected)
 XRF Analysis $- $40/sample
(includes 5% confirmatory off-site
analysis )
 Off-site Lab Analysis $ -
$205/sample
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NumberofAnalyses

29. Correlation - Good
Precision - Excellent
Accuracy – XRF High Bias for Cu, Pb , Zn
Particle Size Effects
Improved Site and Risk Characterization
Very Cost Effective
Expedited Field Work
Expanding End Uses
Summary