Incremental Sampling Methodology (ISM) for Metals: Number of Increments and Milling Necessity

Transcription

1 Incremental Sampling Methodology (ISM) for Metals: Number of Increments and Milling Necessity Jay Clausen, Ph.D. Thomas Georgian, Ph.D. April 29, 214

2 Soil Sampling Issues Unrepresentative results using conventional grab soil sampling at military ranges with energetic & metallic residues Poor precision for grabs (e.g., for duplicates) Large uncertainty at concentrations near decision limits Increasing State regulatory insistence for Incremental Sampling Methodology (ISM) for soils USEPA SW-846 work group to update Method 35B to Method 35C with ISM. By late 215? 2

3 Kimama, ID Small Arms Range 21 ISM 3 Grab Demonstration Sites Camp Ethan Allen, VT Small Arms Range 43 ISM 36 Grab Fort Wainwright, AK Small Arms Range 63 ISM 52 Grab Fort Eustis, VA Small Arms Range 27 ISM 33 Grab 3

4 Metallic Residues 4

5 Incremental Sampling Methodology (ISM) 5

6 Decision Units (DUs) Volume of soil to be sampled for which a decision needs to be made using the sample results. Source Areas Exposure Areas Size, shape, and type of DU determined during systematic planning and depend on Data Quality Objectives (DQOs). 6

7 Incremental Sampling increment 7

8 Can ISM samples be split in the field to reduce the mass that needs to be shipped to and processed in the laboratory? 8

9 Field Cone-and-Quartered Splits Boxplot of Sb (mg/kg) Boxplot of Cu (mg/kg) Sb (mg/kg) 2 15 Cu (mg/kg) Split Split 3 4 Boxplot of Pb (mg/kg) Boxplot of Zn (mg/kg) Pb (mg/kg) 25 2 Zn (mg/kg) Split Split 3 4 9

10 Background Metals Boxplot of Ba (mg/kg) Boxplot of Co (mg/kg) Ba (mg/kg) Co (mg/kg) Split Split 3 4 Boxplot of Ni (mg/kg) Boxplot of V (mg/kg) Ni (mg/kg) 11. V (mg/kg) Split Split 3 4 1

11 Number of Increments 11

12 Number of Increments vs. Relative Standard Deviation ISM Percent Relative Standard Deviation (RSD) m Al Cr Cu Fe Mn Ni Pb Sb V Zn m = number of increments per MI sample 12

13 Lead Concentration vs. Number of Increments of ISM Field Replicates 13

14 Sb (mg/kg) Number of Increments (m) for Small Arms Metals (Sb, Pb, Cu, & Zn) Antimony (mg/kg) Boxplot of Sb (mg/kg) Number of Field Increments Number of Increments Pb (mg/kg) Lead (mg/kg) Boxplot of Pb (mg/kg) Pb (mg/kg) Number of Field Increments Number of Field Increments Number of Increments Boxplot of Pb (mg/kg) Lead (mg/kg) Number of Increments Copper (mg/kg) 9 Boxplot of Cu (mg/kg) Zinc (mg/kg) Boxplot of Zn (mg/kg) Cu (mg/kg) Zn (mg/kg) of Field Increments Number of Increments of Field Number of Increments 14

15 Bootstrap Simulation: Number of Bootstrap Mean, Pb (mg/kg) Increments per ISM Sample bootstrap replicates for each value of m Mean of 48 grab samples = 432 mg/kg No. Increments (sample size) m 15

16 Number of Bootstrap Means Distributions of Simulated Bootstrap Lead Means Distribution of means becomes Gaussian & variability decreases as m increases, consistent with central limit theorem (CTL) m= 5 m= 7m= 1 m= 25 m= 15m= 2 m= 3 m= More Mean of Pb from m Increments (mg/kg) 16

17 Standard Error of Mean (mg/kg) Bootstrap Standard Error of Mean Simulation y 2 x -1 r².99 Grab Samples ISM Samples Power (Grab Samples) Number of Grab Samples or Increments per ISM Sample 17

18 To mill or not mill: Whether tis nobler in the mind to not mill and suffer the slings and arrows of outrageous fortune or to mill to obtain reproducible results 18

19 Milled and Unmilled Comparison Sample #1 Sample #2 19

20 To Mill or Not To Mill (1) Concentration (mg/kg) Lead - Unmilled Replicate 2

21 To Mill or Not To Mill (2) Concentration (mg/kg) Lead Unmilled Replicate 21

22 To Mill or Not To Mill (3) 4 35 Pb Unground Pb Ground #1 Pb Ground #2 Concentration (mg/kg) Replicate 22

23 Type Mass (g) Digestion Mass for Milled & Unmilled Samples Milled Unm illed Milled Unm illed Milled Unm illed Milled Unm illed Milled Unmilled Boxplot of Pb (mg/kg) 23 Pb (mg/kg)

24 Probability of One Lead Particle by Aliquot Mass for Unmilled Soil 24

25 Probability of One Lead Particle by Aliquot Mass for Unmilled Soil 25

26 Relative Standard Deviation (%) Puck Mill Precision Acceptance Criteria Milling Interval (seconds) Cu Pb Sb Zn 26

27 SAR Metal Concentration by Puck Mill Milling Time Boxplot of Pb (mg/kg) Boxplot of Cu (mg/kg) Pb (mg/kg) Cu (mg/kg) Puck Mill Grind Time ( se c ) Puck Mill Grind Time ( se c ) 12 3 Boxplot of Sb (mg/kg) Boxplot of Zn (mg/kg) Sb (mg/kg) 3 2 Zn (mg/kg) Puck Mill Grind Time (sec) Puck Mill Grind Time (sec)

28 Relative Standard Deviation (%) Ball Mill Precision Acceptance Criteria Cu Pb Sb Zn Time (hours) 28

29 SAR Metal Concentration by Ball Mill Milling Time Boxplot of Pb (mg/kg) Boxplot of Sb (mg/kg) Pb (mg/kg) 4 Sb (mg/kg) Ball Mill Grind Time (hrs) Ball Mill Grind Time (hrs) 16 2 Boxplot of Cu (mg/kg) Boxplot of Zn (mg/kg) 12 1 Cu (mg/kg) 9 Zn (mg/kg) Ball Mill Grind Time (hrs) Ball Mill Grind Time (hrs)

30 Milling by Device Type Boxplot of Pb (mg/kg) 5 4 Pb (mg/kg) Ball Mill MP Puck #1 Puck #2 Grinder Type Puck & Ring Unmilled #1 Unmilled #2 3

31 Performance Assessment Activity Yes No ISM, 3+ increments Grab Sampling Field Splitting Sieving Milling necessity Increased digestion mass Increased digestion time Subsampling 31

32 No ISM-Lite ISM 32

33 Cost Comparison Grab ISM Systematic Project Planning $ $ Site Preparation $$ $ Field Sampling $$ $$$ Laboratory Sample Processing $ $$$ Analysis $$ $ Data Validation $$ $ Per Sample Cost $-$$ $$-$$$ Number of Samples ### # Total Project Cost $$-$$$ $-$$ 33

34 Conclusions Field splitting not recommended when metal particles expected Minimum of 3-increments per ISM sample Number of increments is a function of expected degree of heterogeneity Larger digestion aliquot in lieu of milling does not work Milling is necessary when metal particles are present Marginal improvements in data quality with larger digestion aliquots for milled samples Recommend 5 minutes milling with Puck and 8 hours with Roller Mills 34

35 References Clausen Sampling of Soils with Metallic Residues Collected from Military Small-Arms Ranges. PhD Dissertation. University of New Hampshire. Clausen et al Cost and Performance of Incremental Sampling Methodology (ISM) for Metallic Residues, ESTCP Project ER2918. ERDC/CRREL TR Clausen et al Demonstration of Incremental Sampling Methodology for Soil Containing Metallic Residues. ERDC/CRREL TR Clausen et al Incremental Sampling Methodology (ISM) for Metallic Residues. ERDC/CRREL TR Clausen et al Evaluation of Sampling and Sample Preparation Modifications for Soil Containing Metal Residues. ERDC TR

36 References (Continued) Hewitt et al EPA Federal Facilities Forum Issue Paper: Site Characterization for Munitions Constituents. EPA-55-S Clausen, J. et al Metal Residue Deposition from Military Pyrotechnic Devices and Field Sampling Guidance. ADA Clausen, J. and N. Korte. 29. The distribution of metals in soils and pore water at 3 U.S. military training facilities. Soil Sed Cont J. 18(5):