LEAD / MODEL & METHODS
Follow the lead.
Account for the mass.
Explore how an assumed ammunition inventory, deposition footprint and soil mass affect a modeled lead concentration. Every result here is a scenario—not a measurement or validated prediction for a conflict site.
Model version 2.3 · Guided introduction added 28 October 2026 · Model equations unchanged · Read the Iwo Jima evidence ↗
START HERE / A TWO-MINUTE EXAMPLE
Same lead. More soil. What changes?
Concentration means the amount of lead per kilogram of soil. Try changing the assumed mixing depth while keeping the lead mass, area and soil density fixed.
Synthetic example. These are invented inputs for learning, not measurements from a conflict site or a safety assessment.
1. Change one assumption
How deep is the lead assumed to mix uniformly into the soil?
Held fixed: 1,242 g retained lead · 10,000 m² area · 1,500 kg/m³ dry bulk density.
2. Read the change
0.828 mg/kg added lead
Both bars use the same zero-based scale: 0–1.656 mg/kg. Background lead is excluded.
3. Does a lower concentration mean the lead disappeared?
No. The assumed retained lead mass stays at 1,242 g. Increasing the modeled soil mass lowers the average concentration. This comparison does not show removal, actual transport, exposure or whether soil is safe.
See the assumptions and arithmetic
The BASE example assumes 10,000 expended rounds × 2.07 g projectile lead per round, with zero primer and other-component lead. Of that inventory, 10% is assumed deposited in the zone and 60% of the deposited mass retained in soil: 1,242 g retained lead.
Added lead (mg/kg) = 1,242 g × 1,000 mg/g ÷ [10,000 m² × mixing depth (m) × 1,500 kg/m³]. At 10 cm, the denominator is 1,500,000 kg of dry soil.
All values—including zeros and fractions—are hypothetical. Depth choices illustrate the equation, not an uncertainty interval or a recommended sampling depth. The full BASE example also includes an assumed 15 mg/kg background, which this comparison excludes.
Ready to explore more? The full calculator lets you change inventory, soil assumptions and background, and record sources.
Replaces the calculator’s current inputs with this synthetic example and your chosen depth. Save existing work first. Your saved browser draft is not changed.
Full calculator & methods Build, save or reopen a scenario
Examples reproduce the workbook’s synthetic scenarios. LOW and HIGH change several assumptions together; they are not uncertainty bounds. The MIXED example adds a second synthetic class with 7.9 g projectile, 0.05 g primer and 0.05 g other lead per round. These values, including explicit zeros, are hypothetical; none is a verified ammunition specification.
What the inputs imply
Which inputs need source review?
Recorded details do not establish evidence quality or field validation.
mg/kg
Modeled lead increment
mg/kg including entered background
Which ammunition contributes the lead?
All bars start at zero and share one scale. Retained lead is part of the inventory, not additional mass.
See the exact values
| Type | Pb g/round | Inventory g | Retained g |
|---|
Follow the lead mass
Three destinations account for the entire modeled inventory.
Zero inventory: no added lead in this scenario.
See the mass accounting
- Total inventory lead
- g
- Outside the modeled zone
- g
- Retained in modeled soil
- g
- Deposited but not retained
- g
- Zone-deposited subtotal
- g
- Dry soil mass
- kg
The three bar segments sum to the inventory. The deposited subtotal overlaps retained and nonretained lead; do not add it again. “Not retained” does not identify a measured destination.
Save or reopen your work
Save one draft on this device, or download a JSON file to move between devices. Imports replace the current inputs. Save your current work first.
Browser drafts stay on this device and may be visible to other people using it. They are not uploaded or synced. Clearing browser data can remove them.
Copy or paste scenario JSON
Downloaded results are recalculated on import. A file cannot certify its own evidence.
How much soil shares the lead?
The same retained lead mass produces a smaller concentration when it is spread through more dry soil. LEAD assumes uniform mixing throughout the volume you enter.
Load an example or enter your inventory and soil inputs to reveal the quantities.
- Surface area
- Mixing depth
- Dry bulk density
of soil ×
= of dry soil
See the equation and units
For each type: lead per round = projectile + primer + other-component lead (g). Retained lead = rounds × lead per round × zone fraction × retained fraction. Sum retained lead across types. Increment (mg/kg) = 1,000 × summed retained lead (g) ÷ [area (m²) × depth (m) × dry bulk density (kg/m³)].
Total = background + increment. The factor 1,000 converts grams to milligrams. The denominator is kilograms of dry soil. This is a uniform-mixing calculation for one shared soil volume. Background is added once. Do not enter whole-round lead in one component and then add the same primer or projectile again.
Inventory lead is not automatically dissolved, mobile or biologically available. Whether this modeled mass matches a laboratory measurement depends on particle size, preparation and analytical method. The calculator does not include changing soil mass, continuous inputs, explicit transport or a time forecast.
Same lead. Different soil assumptions.
Change one soil input while keeping the ammunition inventory and other inputs fixed. The curve shows the added lead concentration, excluding background.
Load an example or complete your inputs to see the graph.
See the sensitivity values
| Input changed | Half input | Double input |
|---|
These are mathematical stress tests, not confidence intervals or field predictions. Area, depth, and density have the same inverse relationship in this uniform-mixing equation; that does not establish their relative uncertainty in real soil.
What would make this a tested field model?
Independent, location-specific ammunition expenditure and lead composition; a mapped deposition footprint; measured soil depth and dry bulk density; local background; and sample-matched lead measurements with analytical quality control. Held-out observations must be independent of parameter selection.
The current workbook does not establish those paired records. Five reported beach-sand samples, a separate six-ID table of triplicate readings, and 38 metallic-fragment measurements remain distinct populations. Author clarification places four of the five samples in one container and one in the other, with separate replicate portions; this does not resolve the six-ID table. Zero-coded nondetects are not measured zero concentrations.
The reported instrument is the Olympus Innov-X X-5000. Original scan exports, detection limits, reference-material results and sample identities still need reconciliation. EPA Method 6200 describes relevant XRF quality-control and matrix considerations; it does not certify these historical measurements.
Why falling concentration does not mean lead disappears
Lead can move into deeper soil, sediment or outside the modeled area. Dilution and changes in sampled soil mass can also change concentrations. Lead is an element: environmental transfer is not destruction. The workbook’s separate reservoir demonstration tracks transfers with synthetic coefficients; it is not a calibrated Iwo Jima forecast.
Measured · Modeled · Reported · Unknown — read the evidence labels ↗