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Matchless Mine Tailings

Experiment 7 Analytical Chemistry

Arielle Boucher & Ivy Goldson

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Where is it from?

The Matchless Mine, Leadville CO

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Research question

Is the lead concentration in the leadville mine tailings collected from the tabor mines acceptable by EPA standards?

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Procedural Summary

Week 1

  1. Acid washing glassware
  2. Digestion of samples
  3. Method blank
  4. filtration

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Week 2

  1. Dilution of digestion filtrate
  2. Creating standard additions
  3. Using spectroscopy to test standard additions

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Week 3

  1. Re filtration of digestion samples
  2. Making of spiked solutions
  3. Using ICP-OES to run the samples.

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What is GFAAS and how was it used in this experiment?

  • Excites atomized analyte
  • Cathode composition emits emissions that correspond with analyte
  • Emissions measured to find concentration
  • LOD 1-100 micrograms/L

Graphite Furnace Atomic Absorption Spectroscopy

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GFAAS Standard Additions

Sample 2

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Slope:

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x-intercept:

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Sample 1

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Slope:

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x-intercept:

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GFAAS Blank

  • Matrix affects lowered the slope
    • Galena (PbS)
  • Causes amount of metal in blank to differ significantly with a 95% confidence interval from 0

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GFAAS Results

Sample 1

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Concentration of lead in soil:

42.6 mg/kg

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Color: yellow

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Texture: fine and powdery

Sample 2

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Concentration of lead in soil:

119 mg/kg

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Color: grey

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Texture: course and metallic

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What is ICP-OES and how was it used in this experiment?

  • Excites each element and separates them into spectral lines
  • Used to find the total metal concentrations in the samples

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Sample 1

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Concentration of lead in soil:

40.65 mg/kg

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Color: yellow

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Texture: fine and powdery

Sample 2

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Concentration of lead in soil:

95.5 mg/kg

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Color: grey

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Texture: course and metallic

The samples were taken only a few inches apart, but their lead concentrations are drastically different

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Limit of Detection

LOD

LOD=3*STDEV STDEV=6.402*10^-3

LOD=3*(6.402*10^-3)=1.92*10^-2 mg/L

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  • Based on this LOD there was a measurable amount of lead in the sample recovered

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Spike Recovery

  • Blank recovery: 97%
    • Indicated the method does not interfere
  • Sample 1 recovery: 348 %
    • uhoh
  • Sample 2 recovery: 207%
    • uhoh
  • The matrix is definitively interfering with the analysis.
  • There must be something else in the soil causing this interference
    • Galena (PbS)

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Sample 1: 40.65 mg/kg

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Sample 2: 95.5 mg/kg

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Sample 1: 42.6 mg/kg

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Sample 2: 119 mg/kg

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ICP-OES

GFAAS

Method Comparison

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  • Matrix effects in ICP-OES > GFAAS
    • ICP-OES Spike Recovery vs tcalc compared to ttable
  • Therefore GFAAS results are more reliable

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Final Results

Epa standards: 1200 ppm

Our results: 42.6-119 ppm

Conclusion: The amount of lead is well within epa standards and not a hazard to Leadville residents. There is not that much lead in Leadville.

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Sources

https://www.atsdr.cdc.gov/csem/leadtoxicity/safety_standards.html