Based on the elevated lead levels in children that she and her colleagues had seen, Dr. Eliot believed that lead ores from the nearby mining district may have contaminated both the soil and water in the area. Contained within this 15-square-mile area is the California Gulch watershed. It empties into the nearby Arkansas River and provides the community with agricultural irrigation, recreation, and municipal drinking water.

Dr. Elliot and several other prominent citizens have been able to successfully persuade local officials to contract an environmental study of the area’s soil and water. You are a chemist who works with the contracted environmental lab. Your primary area of concern is water testing for the presence of lead in groundwater samples using atomic absorption spectrophotometry (AA). Colleagues will be testing for other metals in the water. Residential soil samples from Lake County will also be tested.

Questions

1. Outline how flame spectrophotometry works by explaining the following:

   • The absorption of light energy at characteristic wavelengths.
   • The proportionality of light absorbed to sample concentration using Beer’s Law.
2. Define and diagram the basic parts of an atomic absorption spectrophotometer including the nebulizing chamber (or aspirator), the flame, light source, monochromator, and detector.
3. Why must all equipment in this analysis be acid washed?
4. What concentration (ppm) of lead in drinking water is considered dangerous (“action level”) by the U.S. Environmental Protection Agency (EPA)?

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