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ENV4001_s10_hw5 - ENV 4001 ENVIRONMENTAL SYSTEMS...

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p. 1/4 ENV 4001: E NVIRONMENTAL S YSTEMS E NGINEERING Spring 2010 University of South Florida Homework #5 Civil & Environmental Eng. Due: Wed., Feb. 22, 2010 Prof. J.A. Cunningham Each homework assignment will be graded on a 100-point scale. For this assignment, point values of each problem are indicated. ASSIGNMENT FOR SPRING 2010 : Answer problems 1, 2, 3, and 5. Skip problem 4 . 1. (24 pts) Answer the following problems in your text book: 6.10, 6.12, and 6.14. Each problem is worth 8 points. 2. (21 pts) Suppose a toxicologist ran some tests to determine the acute toxicity of Chemical Z on zebrafish. Groups of zebrafish (100 zebrafish in each group) were given different doses of Chemical Z, and the toxicologist monitored how many zebrafish died under each dose. The results are given in the following table. Dose of Chemical Z Number of (mg of Chemical Z zebrafish that died per kg of zebrafish (out of 100 fish in body mass) each group) ----------------------- ------------------------- 5.4 1 7.1 12 8.2 34 10.1 81 11.9 98 a. (7 pts) Do these data appear to follow a Gaussian model for dose-response? (If you wish, I can give your group a sheet of special Gaussian graph paper to help make this determination.) b. (7 pts) Explain in words what the term “LD50” means in the context of acute toxicity. Estimate the LD50 for Chemical Z on zebrafish. c. (7 pts) Explain in words what the term “NOAEL” means in the context of acute toxicity. Why can’t we tell the NOAEL for Chemical Z on zebrafish from the data given? Can you come up with a decent estimate for the NOAEL?
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