Biological Oxygen Demand (BOD) serves as a way to test the level of pollution in our water. Students from USD went into Tecolote Canyon to test the BOD and found that levels were in the 'very good' range, bordering on the 'moderately clean' range, meaning that the waters in Tecolote Canyon are not heavily polluted by organic material.
Students in USD's Environmental Chemistry class went out seeking to determine the BOD levels in Tecolote Canyon and collected water samples from a creek near the golf course. After the samples were collected, the bacteria that consumes the organic material (pollutants) were still present in the water, so by storing this sample for seven days, bacteria in the water was allowed to consume the pollutants without the bacteria or pollutant level changing. The difference in dissolved oxygen between the first day and the seventh day was the amount of oxygen that was used in the process of bacteria consuming pollutants.If this difference is very large, then there are a lot of pollutants to be consumed by the bacteria. If the difference is small, then the bacteria did not have a lot of organic material to be consumed. In this case, the difference between the first and seventh day was 2.34, which is in the 'very good' range. Above a 3 is considered 'moderately clean' and above 5 is 'somewhat polluted'.
The samples were also used to analyze the specific molecules in the sample. A gas chromatography machine allows us to put samples in and it uses known samples for comparison and outputs a spectrum of molecules found in the sample and properties of those molecules, then it makes its best guess as to what those molecules are. The molecules mostly seemed to be long chains of carbons and hydrogens, which might be indicative of fuels. Also found were various pollutants resulting from plastic production. No molecules were found in high concentrations that were toxic.Overall, the samples collected were rather free of pollution.
It would be interesting to test the BOD levels in various locations within Mission Bay, especially as I've often found several dead fish and other marine animals floating near the surface and along the shoreline. Perhaps BOD levels within some locations in the bay are rather high?
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