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Question

As a Ministry of Environment environmental technician, you are sent to take water for testing. Two of the test sites experienced fish kills and a third, without a fish kill, was used as a comparison site. In an attempt to explain why the fish died at these sites, the water was analyzed for the following chemicals:

Site pH NO31- PO43- Dissolved O2 Suspended solids
A 8.0 0.2 ppm 0.2 ppm 8.0 ppm Low
B 4.3 0.2 ppm 0.2 ppm 7.0 ppm High
C 6.0 5.0 ppm 6.0 ppm 3.0 ppm Medium
Location of sample sites:

Your job, as the environmental technician, is to provide an analysis of the test results you have collected above to come up with a proposed explanation (hypothesis) that can account for the observed fish kills.

Note: Site A did not experience any fish kills and is used as a reference site.

Answer 1

Here is a good site to read about this.
https://en.wikipedia.org/wiki/Fish_kill#Oxygen_depletion

For C look at high nitrate and high phosphate and low dissolved oxygen. For B look at the pH and turbidity. The link above talks about all of this.