Question

The prime contaminants in the lakes undergo eutrophication by sewage and agricultural wastes are
A. Sulphates and phosphates
B. Nitrates and sulphates
C. Nitrates and phosphates
D. Nitrates and carbonates

Answer 1

Hint: Agricultural practices complete the needs of their nutrients either from the soil or from external sources. The nutrients are specific for a particular crop. These external sources can be fertilizers, pesticides, insecticides, etc, which protect the crop and increase the nutritional value at the same time.

Step by step answer:Eutrophication is when the availability of nutrients increases excessively, the growth of algae starts. This excessive alga can take up the whole oxygen in the water and thus the aquatic animals start to get deprived of oxygen.
Here, particularly talking of the agricultural waste and sewage, the prime nutrient in these wastes is the nitrates and phosphates. Their presence in the water body will make the algae grow by feeding on these nutrients.
Option A: Sulphates and phosphates: Phosphates are right but sulphates are not the major component of the agricultural waste.
Option B: Nitrates and sulphates: Nitrates are right but sulphates are not the major component of the agricultural waste.
Option C: Nitrates and phosphates: They are the main components of the fertilizers. They can harm the environment in different ways. The nitrates from nitrogen and phosphates from phosphorus are when washed away from the fields, they get mixed with lakes and rivers causing eutrophication there.
Option D: Nitrates and carbonates: Carbonates are not present in high quantity in fertilizers.
Hence, the answer is option C: Nitrates and phosphates

Note: Though there is an enrichment of nutrients, the excess of everything proves to be harmful. It declines water quality. To prevent eutrophication, one should treat the agricultural waste before running them into the water bodies. We should prevent the use of fertilizers at a higher content.