The problem that the class was presented with was how Polychlorinated Biphenyls made their way into remote Alaskan lakes that were untouched by humans. Polychlorinated Biphenyls or PCBs are compounds that were once used as insulators in electrical transmission lines and in the production of polymers. Due to their high toxicity, there was a world wide ban on the production of PCBs in 1977. PCBs are extremely stable and difficult to break down, so some are still found in the environment. All PCBs are presumed to be produced by humans, seeing as there is no known natural process that would produce PCBs. So how do PCBs appear in remote Alaskan lakes untouched by humans? The group I was a part of hypothesized that there were companies dumping chemical waste in those lakes, which could include PCBs. To test this hypothesis, we suggested that the lake water be tested daily, and chemicals found be compared with those being produced by companies in a close vicinity to the lake. We were then given the information that the global circulation of PCBs was in part due to atmospheric transport, the PCBs enter the atmosphere through the burning of organic material and then becoming evaporated in warmer climates, explaining how they found their way into areas untouched by humans. Also, that the level of PCBs are higher in lakes at the beginning of a river rather than an isolated lake. This new knowledge caused our group to alter our hypothesis. We said that lakes at the beginning of a river would have higher levels of PCBs because vegetation such as trees would be less dense, and in more of an open area where more PCBs could get into the lake through atmospheric transport. In a remote location the lake would be surrounded by a lot more trees and harder for PCBs to enter into. The final conclusion about the contamination of the lakes was that sockeye salmon who were returning from the ocean in order to spawn...
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