2. An environmental watchdog group thinks that a particular mining operation is

Question

2. An environmental watchdog group thinks that a particular mining operation is not adequately removing trace metals from the processing water before releasing it back into the adjacent stream. They hire an analytical firm to test their theory by collecting and analyzing water samples collected upstream and downstream from the mine outflow. The copper concentrations they found are listed in Table 1. Is there any evidence that the mine is adding copper to the stream? To answer this question, you must prove that the concentration below the mine is significantly greater than that above the mine. Table 1. Copper concentrations in the Alemada River collected upstream and downstream from the ABC mine. Copper concentration (ug/L) Downstream 0.783 0.799 0.792 0.787 0.779 Sample number Upstream 01 02 03 04 05 0.754 0.701 0.735 0.687 0.776 0 731 ue/L, s0.037

Explanation / Answer

ANSWER:

Five samples have been collected and analysed for presence of Cu. The concentration is given in µg/L.

Average concentration of the samples collected upstream

Cav (upstream) = (0.754 + 0.701 + 0.735 + 0.687 + 0.778 ) / 5 = 0.731µg/L

Cav (downstream) = (0.783 + 0.792 + 0.799 + 0.787 + 0.779 ) / 5 = 0.788µg/L

difference = Cav (downstream) - Cav (upstream) = 0.788µg/L - 0.731µg/L = 0.057µg/L

The difference show that the mine is adding 0.057µg/L of Cu to the water.

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