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The size of the dead zone in the Gulf
of Mexico changes from year to year. One way to explore
a possible link between nitrates and the dead zone is
to observe the size of the dead zone compared to the
amount of nitrates that flow into the Gulf from the
Mississippi River each year.
The Mississippi River Basin includes
the Mississippi River and all its tributaries. The basin
encompasses 41% of the land of the continental United
States, including much of the country's farmland. The
nitrates that enter the Mississippi River come from
organic or inorganic sources. Organic nitrates occur
naturally. Sources include manure from animals, human
sewage, and nitrogen products produced by certain types
of plants. Inorganic sources include fertilizers and
industrial waste.
! Compare the two charts below. Look
for any patterns between the area of the dead zone and
the amount of nitrate flux into the Gulf.
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