Discussion 10-17-07 396
Lake Study Lab Part I
We have ruled out that the problem is caused by pesticides in the water because the samplings have shown that the levels of these substances are below toxic levels for most fish. The dissolved oxygen level is well within acceptable standards for normal lake water. The levels of calcium and mercury in the water were within acceptable margins for the survival of fish. We hypothesize that since the levels of lead and iron are above normal safe levels, either iron, lead or a combination of the two are causing the problems with the fish. We came to this conclusion because after comparing the levels of iron and lead from our samples with the levels in the literature and realizing that our levels appeared to be high. *See attached Data Table 1
Part II
When it came to finding experimental data, we limited our experiments to those which would test our hypothesis. For each of our experiments, we used the average concentrations from our samples as the amount of the substance in the water. Our conclusion is that there is too high of an iron concentration in the water, which is causing the death of nearly half of the fish. We determined this by doing controlled tank tests of both lead and iron. The lead testing seemed to have a negligible effect on the death rate, whereas the concentration of iron lead to a nearly fifty percent death in rate the fish. *See attached Data Table 2
Question 4
One extra experiment which we might conduct would be one in which lead and iron concentrations were tested together to determine whether the combination of the two would give any additional effect. A second experiment which we might conduct would be to dissect the dead fish and run tests on them to find out how much of these substances are on the gills of the fish or in the fish.
Data Table 1
Calcium Sample Temp. C (ppm) 1 19.00 23.6 2 21.12 25.1 3 22.62 23.8 4 22.05 22.2 5 19.37 22.4 6 21.70 24.8 7 21.22 26.3 8 21.32 24.1 Average 21.05 24.03 Lead (ppm) 0.69 0.69 0.64 0.67 0.66 0.69 0.66 0.69 0.67 Iron (ppm) 1.71 1.38 1.31 1.30 1.57 1.71 1.86 1.65 1.56 Mercury (ppb) 3.6 4.3 4.7 3.4 3.1 3.8 4.2 4.7 3.97 DDT (ppt) 0.59 0.60 0.93 0.50 0.61 0.45 0.50 0.50 0.58 PCB (ppt) 0.61 0.90 0.58 0.89 0.46 0.86 1.07 0.59 0.74 Dieldrin (ppt) 0.56 0.99 0.57 0.57 0.85 0.56 0.59 0.70 0.67 Oxygen (ppm) 9.09 9.31 9.39 9.65 9.55 9.63 9.41 9.90 9.49
Data Table 2
Test 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Duration Amount of Percent Number of Fish Substance (days) Substance dead 40 7 Control 0 7 40 7 Control 0 0 40 7 Control 0 7 40 7 Control 0 7 40 7 Control 0 5 40 7 Lead 0.67 5 40 7 Lead 0.67 5 40 7 Lead 0.67 5 40 7 Lead 0.67 5 40 7 Lead 0.67 7 40 7 Iron 1.56 40 40 7 Iron 1.56 55 40 7 Iron 1.56 47 40 7 Iron 1.56 47 40 7 Iron 1.56 46