Question 44 Why is it that Biomagnification can cause a contaminant in lipid tis

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Question 44

Why is it that Biomagnification can cause a contaminant in lipid tissue of a fish to become much greater than one would calculate using the ambient water concentration and the K_ow? Why does biomagnification cause contaminant levels to generally increase in fish the older the fish? If you eat only "organic" food, will you really avoid dioxins and PCBs in your diet? Why/why not? In organophosphate pesticides, what kind of linkage is present? Name it and draw it using R groups to denote some kind of organic chain. Aldicarb is a carbamate. What's the linkage present, and is it an insecticide or herbicide? Permethrin is a synthetic pesticide that is based on what kind of natural structure, and is it an insecticide or herbicide? Why isn't the pesticide 2, 4, 5-T manufactured any more? And is it an insecticide or herbicide?

Explanation / Answer

41 Bioaccumulation means the increase in concentration of a pollutant from the environment to the first organism in a food chain while biomagnification means the increase in concentration of a pollutant from one link in a food chain to another.

So, we see that bioaccumulation is different from biomagnification in the manner of exposure of an organism to pollutants.

So, as an example for bioaccumulation, in a water body exposed to pesticide like DDT, small organisms with small lifespans like zooplanktons will get exposed to DDT and some amount of DDT will accumulate in them depending upon the ambient water concentration and Kdw.

But for biomagnification to occur, the pollutant should be long-lived and soluble in fat like DDT.

In this case, the pollutant may accumulate in a higher organism through food chain in greater quantities than possible through direct exposure. As a fish keeps on eating the exposed zooplanktons, DDT will build in its body because it is long-lived and soluble in fat ie. it does not get excreted.

42. Biomagnification causes contaminants to rise as the fish becomes older because the pollutant is long-lived and does not get excreted because it is soluble in fat and not soluble in water. Therefore, as the fish keeps feeding on contaminated organisms, the concentration keeps on increasing with age.

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