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Preliminary exam CSAT May 06, 2024

1. Read the following passagenand answer the items that follow each passage. Your answers to
these items should be based on the passages only.


Passage
The law in many parts of the world increasingly restricts the discharge of agricultural slurry into
watercourses. The simplest and often the most economically sound practice returns the material to
the land as semisolid manure or as sprayed slurry. This dilutes its concentration in the environment
to what might have occurred III a more primitive and sustainable type of agriculture and converts
pollutant into fertilizer. Soil microorganisms decompose the organic components of sewage and
slurry and most of the mineral nutrients become available to be absorbed again by the vegetation.
The excess input of nutrients, both nitrogen and phosphorus - based, from agricultural runoff (and
human sewage) has caused many 'healthy' oligotrophic lakes (low nutrient concentrations, low plant
productivity with abundant water weeds, and clear water) to change to eutrophic condition where
high nutrient inputs lead to high phytoplankton productivity (sometimes dominated by bloomforming toxic species). This makes the water turbid, eliminates large plants and, in the worst
situations, leads to anoxia and fish kills; so called cultural eutrophication. Thus, important ecosystem
services are lost, including the provisioning service of wild-caught fish and the cultural services
associated with recreation.
The process of cultural eutrophication of lakes has been understood for some time. But only recently
did scientists notice huge 'dead zones' in the oceans near river outlets, particularly those draining
large catchment areas such as the Mississippi in North America and the Yangtze in China. The
nutrient-enriched water flows through streams, rivers and lakes, and eventually to the estuary and
ocean where the ecological impact may be huge, killing virtually all invertebrates and fish in areas up
to 70,000 km2
in extent. More than 150 sea areas worldwide are now regularly starved of oxygen as
a result of decomposition of algal blooms, fuelled particularly by nitrogen from agricultural runoff of
fertilizers and sewage from large cities. Oceanic dead zones are typically associated with
industrialized nations and usually lie off'- 'countries that subsidize their agriculture, encouraging
farmers to increase productivity and use more fertilizer. 

The passage refers to the conversion of "pollutant to fertilizer". What is pollutant and what is
fertilizer in this context?

General Studies

Political Science and International Relations

Sociology

Some Reference Essays

List of previous year essay topics (1997-2019)

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