Migration of Heavy Metals from Simulated Small Arms Firing Berms
W. Andy Martin Environmental Engineer, ERDC
Steven L. Larson Research Chemist, ERDC
Steven R. Hearne Senior Fellow Army Environmental Policy Institute
JSEM Conference 22 Mar 06 Project Overview & Objectives
• AEPI coordinated effort with ARDEC Heavy Metals Office (HMO) – Advance knowledge of heavy metals, e.g., tungsten, transport mechanisms from SAFRs – Provide for more informed decision making supporting: • Follow-on transport [e.g., field sampling and field lysimeter] studies • Improved SAFR management and design • Selection of next generation ammo
• Specific Study Objectives: – Evaluate long-term stability of tungsten on SAFR using “Green Bullet” • Simulated berm soils exposed to one year’s worth of rain events – Assess tungsten loss [mass] or release from differing SAFR soils: • Runoff [surface water] and leachate [ground water] • Dissolved [soluble] and particulate forms Firing
Particle size and metal distribution
Mixing and splitting of soil Simulated Berm Material
• ARDEC HMO and Environmental Technology Division made the soils fired on with tungsten-nylon rounds at ERDC’s Big Black testing facility available for this laboratory lysimeter study • This leveraging of research material allowed for a low cost, high knowledge gain project funded by AEPI
Firing
Mixing and splitting of soil Study Approach - Considerations
Batch Lab Lysimeter Field Sampling Testing • Better mimics field conditions in & Lysimeter • Provides first-level accelerated/controlled system • Use actual soils approximation of [e.g., weeks versus months] • Actual site conditions potential mobility • Like batch – use simulated soils • High cost • Simulated soils • Unlike batch - allows sampling • Limited control of • Lowest cost of simulated leachates & runoffs experimental • Correlates well with field efforts variables [based on past metals studies] • Moderate cost Background – Bullet Composition
• Jacket – Copper & Zinc
• Steel Core -Iron
• Tungsten Slug – Tungsten micron sized metal particles pressed with Nylon Weights of 5.56-mm (M855) Bullet Components*
Component Bullet Jacket1 Steel Core2
Nomenclature 9349678 Mass (grams) 9342870 Mass (grams)
Composition Copper alloy Steel 1.2830 0.6480 Weight (grains) 19.8 10.0
Copper (90.0%) 1.1547 Iron (98.0%) 0.6350
Manganese Zinc (9.9%) 0.1270 0.0048 (0.75%) Individual materials Lead (0.05%) 0.0006 Carbon (0.47%) 0.0030
Iron (0.05%) 0.0006 Sulfur (0.05%) 0.0003
Phosphorus 0.0003 (0.04%) Component Lead Slug Tungsten Slug
Nomenclature 9349656 Mass (grams) 12991009 Mass (grams)
Composition Pb-Sb alloy Tungsten-nylon 2.0736 2.0736 Weight (grains) 32.0 32.0
Lead (99.0%) 2.0529 Tungsten (97.0%) 2.0114 Individual materials Antimony (1.0%) 0.0207 Nylon (3.0%) 0.0622
* DefenseAmmunition Center 2005
Background –Tungsten Formulations
Tungsten-Nylon
Tungsten-Tin W +4 H2O Ù 2- + WO4 + 8 H + 6 e-
W-Ni-Co/ Rat Lower pH Study W-Ni-Fe
Water Soluble Ion [Tungstate Anion]
Tungsten steels W Surface area for W-water reaction Relative Amount of W in Composition Methodology – Lysimeter System
Cross-section of lysimeter.
Empty lysimeter cell showing runoff and leachate collection systems Methodology - Experimental Design
C1 C2 C3 C4 C5 C6 C7
Glacial Silty Loess Loess Clay Silty Peat Sand A Till Sand B Silt Silt [Lead] tungsten-nylon tungsten-nylon tungsten-nylon tungsten-nylon tungsten-nylon tungsten-nylon lead
• Soils- 6 Soil types fired on using tungsten-nylon 5.56 mm and lead 5.56 mm rounds at a distance of 25 meters to control fragmentation; 10,000 mg/kg
• Rain- 16 weekly rain events (1.5 inches per rain) to simulate annual rainfall
• Sampling- Leachate & runoff samples analyzed for total and soluble metals • Total- digested water sample with suspended solids • Soluble- filter (0.45 micrometer) water
• Analysis – Leachate & runoff were analyzed for 11 metals representative of constituents found in the tungsten-nylon and lead bullets Methodology - Laboratory Layout
Layout of the experiment at the Hazardous Waste Research Center in Vicksburg, MS. Metals leaving the Lysimeters over 16 Rain Events
Mass of Fe, Mn and Zn Measured Leaving the Seven Lysimeters1 Six metals were noted Sum of Metal Mass in Leachate
Soil Type and Runoff in grams to migrate from the Lysimeter lysimeters: W, Cu, Pb, Fe Mn Zn Fe, Mn, Zn Clay C1 2.09 0.023 0.018 Silty sand C2 4.94 0.576 1.110 A
W, Cu, and Pb Glacial till C3 3.24 0.366 0.171
are discussed in Silty sand C4 2.36 0.359 0.410 more detail B Peat C5 1.04 0.015 0.015
Loess silt C6 1.25 0.017 0.015
Loess silt- C7 2.02 0.011 0.014 lead Key Results
Percentage of Tungsten and Lead Leaving the Lysimeters Over 16 Weekly Rain Events
100.00% 13.60% 13.40% 11.35% 10.00% Tungsten Lead 1.00% 0.09% 0.08% 0.10% 0.07%
0.01% 0.004%
Leaving the Systems the Leaving 0.00% Percentage of Initial Mass Glacial till Silty Silty Clay Peat Loess Silt Loess Sand A Sand B Silt-Lead Simulated Berm Soil Prepared by Firing Tungsten or Lead Rounds at 25 m Background – Physical Forms
Lead Fragment - Discreet Particle
[small surface to mass ratio]
Tungsten Smear - [high surface to mass ratio] Particles Coating Soil Soil Type Dependence on Tungsten Leachability
Total Mass of Tungsten in Total Mass of Tungsten in Digested Runoff and Leachate Digested Runoff and Leachate
1.4 180 Silty sand A Clay 160 1.2 Peat 140 Glacial till 1 120 Silty sand B Loess silt 100 0.8 sten Msten G in ass ram s
sten Msten G in ass ram s Loess silt-lead g
g 80 0.6 60 Tun
Tun 0.4 40
20 0.2 0 0 0 5 10 15 20 0 5 10 15 20 Weekely Rain Events (weeks) Weekely Rain Events (weeks) Filtered (0.45 micron) or Soluble Tungsten in Leachate
Mass of Tungsten in Filtered Leachates
100
80 Clay
60 Silty sand A Glacial till 40 Silty sand B 20 Peat Loess silt
Tungsten Mass in Grams 0 0 5 10 15 20 Loess silt-lead Weekely Rain Events (weeks) Mass of Tungsten in Filtered Leachate
1.5
Clay 1 Peat Loess silt Grams 0.5 Loess silt-lead
Tungsten Mass in Mass Tungsten 0 0 5 10 15 20 Weekely Rain Events (weeks) Soluble Tungsten in Runoff
Mass of Tungsten in Filtered Runoffs
30 25 Clay 20 Silty sand A 15 Glacial till 10 Silty sand B 5 Peat 0 Loess silt Tungsten Mass in Grams 0 5 10 15 20 Loess silt-lead Weekely Rain Events (weeks)
Mass of Tungsten in Filtered Runoff
0.25 0.2 Clay 0.15 Peat 0.1 Loess silt Grams 0.05 Loess silt-lead
Tungsten Mass in Mass Tungsten 0 0 5 10 15 20 Weekely Rain Events (weeks) Copper Migration
Total Mass of Copper Leaving the Lysimeter
1.4
1.2 Clay 1 Silty sand A
0.8 Glacial till Silty sand B 0.6 Peat
0.4 Loess silt MassesLoess silt-lead of Copper and Tungsten Leaving the Lysimeter Copper Mass in Grams Mass Copper 0.2 over the 16-Week Procedure and Ratio of Masses
0 Ratio 0 5 10 15 20 Cu Mass W Mass Soil Type Lysimeter W mass: Leaving g Leaving g Weekely Rain Events (weeks) Cu mass
Clay C1 0.022 1.194 54.2
Copper and Tungsten are both Silty sand A C2 1.200 156.35 130.3
present in the Tungsten-nylon Glacial till C3 0.126 148.96 1087.3 round the ratio of tungsten Silty sand B C4 0.204 119.98 588.1 mass to copper mass leaving the cell ranges from 50 to 1087 Peat C5 0.016 1.028 64.3
Loess silt C6 0.016 0.831 51.9 Lead Migration No lead was detected above 50 mg/L in any of the leachates or runoffs from the seven lysimeters. Particulate lead was measured in the leachates and runoffs from the lysimeters
Mass of lead in Digested Leachates 0.05 0.045 Relatively small 0.04 Clay masses of 0.035 Silty sand A 0.03 Glacial till particulate lead 0.025 Silty sand B was noted leaving 0.02 Peat via leachate 0.015 Loess silt Lead Mass in Grams in Mass Lead 0.01 Loess silt-lead 0.005 0 0 2 4 6 8 1012141618 Weekely Rain Events (weeks) Mass of Lead in Digested Runoff Clay 0.1 Lead mass exiting Silty sand A the cell as 0.08 Glacial till particulates in 0.06 Silty sand B Peat runoff was greater 0.04 Loess silt than observed 0.02 Loess silt-lead from the leachate Lead Mass in Grams digests 0 0 5 10 15 20 Weekely Rain Events (weeks) Summary of Findings
• Tungsten behaves significantly different from lead and copper in both leachate and runoff – Lead and copper transported primarily as particulates – Tungsten migration [approx. half] is in dissolved [soluble] state – Observed rapid corrosion of tungsten into mobile species
• Strong positive dependence between type of soils [permeability] and dissolved tungsten migration – Large mass of tungsten loss in lysimeters containing berm soils with unified soil class SM, e.g., silty sand A, silty sand B, and glacial till – Tungsten-nylon residues in high permeability soils can act as sources for tungsten in runoff and leachate water Questions?