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Case Study: Lead in Water

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    301693

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    Flint Michigan Case Study:  Analysis of lead in drinking water

    CHEM/EVSC 4090, CHEM 5710

    Learning Goals:

    • Practice tailoring method development to the application at hand
    • Consider the complexity involved in sample selection
    • Consider narrowing down the problem and sample treatment (i.e. soluble lead vs particulates)
    • Be able to list the common figures of merit used to rate and choose between methods
    • Select a method based on its figures of merit

    You are an analytical chemist, recently hired by the EPA to help measure the amount of lead present in Flint Michigan’s water.  Consider the following.

    Pre-class assignment

    Instructions:

    • To prepare for class, read this C&E News article, and watch the 5-minute video at the end.  
    • Complete this worksheet and submit in Collab prior to class.
      • You may type your answers directly into the document.
      • Write your answers in blue font so that we can find them easily.
      • Answers may be found in the article, or you can search from them online or in textbooks.
    1. When lead is found in drinking water, where (what part of the infrastructure) did it most likely come from?

     

     

    1. Based on the article, list three chemical strategies are usually used to minimize lead content in drinking water. All three failed in Flint Michigan.

     

    1. The article discusses how changes in the pH of the water supply can lead to increased lead in the water.
      1. Does lead leach more into acidic or basic water?

          

      2. Why? (Hint: think about solubility rules for lead and what else is in the water)

         

         

      3. Why did the lead-contaminated water often appear brown or orange, although lead ions are colorless?

     

    1. Summarize the EPA Lead and Copper Rule, including the “action limit” above which a municipality is required to take action to alleviate contamination (1 sentence).

     

    1. The Lead and Copper rule is given in ppb. What is 1 ppb in the more intuitive unit mg/L?

     

     

    Flint Michigan Case Study:  Analysis of lead in drinking water

    In-class activity

     

    1. How might you take a sample of water for lead testing? What factors need to be considered?















       
    2. What specifically do you want to measure in the sample? How will you ensure that you have the correct sample?















       
    3. What criteria should you consider when comparing possible methods?























       
    4. Referring to the figures of merit below, which method(s) may be best for your specific analysis? Why?

     

    Inductively-coupled plasma mass spectrometry

    Atomic Absorption Spectroscopy

    UV-Vis spectroscopy

    Anodic stripping voltammetry

    What you measure

    mass/charge ratio of gaseous ions

    absorbance of gaseous atoms/ions

    absorbance of molecules in solution

    deposit metal on electrode; record current from oxidizing it off

    RSD (a.k.a. CV)

    0.2%

    0.40%

    8-10%

    7-12%

    LOD

    0.1 ppt

    < 1 ppb

    2 ppb

    10 ppb

    % recovery

    100%

    100%

    96-108%

    95-105%

    Linear range

    6 orders of magnitude

    1-150 ug/mL

    2-150 ug/mL

    10-700 ug/L

    Time needed

    ≤ 10 min for analysis

    30 min setup, ≤ 5 min for analysis

    3 min setup, ≤ 10 min for analysis

    ≤ 3 min for analysis

    Instrument cost

    $750,000

    $20,000

    $20,000

    low

    Cost per test

    $50-100

    $20

    $4-5

    $4-5

     

     

     

     

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