Environmental Engineering Reference
In-Depth Information
(e) To compare if the soil pollution source is due to the atmospheric deposition of an
upwind smelter.
20. Explain what type of the laboratory QC samples should be used in the following cases:
(a) To determine the effects of matrix interferences on analytical accuracy of a sample.
(b) To determine the analytical precision of a sample batch.
(c) To establish that laboratory contamination does not cause false positive results.
(d) To determine whether memory effects (carryover) are present in an analytical run
with an instrument.
(e) To know whether an extraction procedure is appropriate or not.
21. The table below has a list of QC parameters and the primary means of general QC
procedure. Match the right column of each corresponding QC procedure to the left
column. Explain.
QC parameter
Place a letter here
QC procedure
1. Accuracy
a. Analysis of blanks
2. Precision
b. Analysis of matrix spikes
3. Cross-contamination
c. Analysis of replicate samples
4. Extraction efficiency
d. Analysis of reference materials or
samples of known concentrations
22. A 100-mL stock solution containing 1000 mg/L Pb was added to a 100-mL groundwater
sample as the matrix spike and acid digested. The Pb concentration measured by ICP-
MS was 0.095 mg/L after a tenfold dilution. Calculate the percentage recovery.
23. Chromium (Cr) concentration can be determined by colorimetric spectrometry. The
calibration curve was determined to be: y¼0.045 x (mg/mL)þ0.0005, where y is the
absorbance reading. A 10-mL surface water sample was spiked with a Cr stock solution
to reach a concentration of 6 mg/L. The matrix spike has an absorbance of 0.250 against
a DI water as the blank. This original surface water sample has an absorbance reading of
0.012. Calculate the percentage recovery.
24. Discuss how the chemical used in a surrogate spike is different from a spike used for
recovery test?
25. Twenty soil samples have been collected and sent to the laboratory for the analysis of
lead contents. (a) What would be the appropriate analytical method. (b) What QC
samples are required for this analysis?
26. Based on the information in the text and literature search, recommend the test methods
by filling in the blanks with appropriate method numbers.
27. There is a need to determine if a manufacturing facility can landfill its waste solids from
the manufacturing of plastic resins. Compounds suspected to be in the waste solids
include semivolatile organic compounds such as 2,4,6-trichlorophenol, pentachlorophe-
nol, pyridine, and cresols. The required EPA procedure is TCLP of SW 846 method
1311. You are responsible for the development of this procedure in your new lab.
Explain briefly the TCLP procedure and give a list of the equipment and chemical
reagents needed to develop such a method.
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