Excessive use of which of the following fertilizers may be responsible for the presence of a toxic substance in groundwater?
- A.Nitrogen
- B.Phosphate only
- C.Potassium only
- D.Phosphate and potassium
Correct answer
Explanation
The correct answer is A, Nitrogen. Excess nitrogen fertilizer turns into nitrate, which dissolves easily, seeps down through the soil and contaminates groundwater.
Urea and other nitrogen fertilizers are converted by soil bacteria into nitrate ions. Because nitrate is highly soluble and is not held by soil particles, whatever the crop does not take up is leached into wells and aquifers, as seen in intensively farmed areas such as Punjab. High nitrate in drinking water causes methaemoglobinaemia, or "blue baby syndrome", in infants; the Indian standard limit is 45 mg per litre.
B is wrong because phosphate binds tightly to soil particles and mostly reaches surface water through runoff, causing eutrophication rather than groundwater toxicity.
C is wrong because potassium is also held by soil and is not a recognised toxic groundwater pollutant.
D is wrong because neither phosphate nor potassium leaches into groundwater the way nitrate does.
Exam tip: nitrate in groundwater → blue baby syndrome; phosphate runoff in lakes → eutrophication.
Practice Questions
View allWhich one of the following tiger reserves of India has "Bhoorsingh the Barasingha" as its official mascot ?
- A.Nameri tiger reserve
- B.Ranthambhore tiger reserve
- C.Panna tiger reserve
- D.Kanha tiger reserve
Show answer
In 2017 Kanha in Madhya Pradesh became the first tiger reserve in India to adopt an official mascot, a cartoon barasingha named Bhoorsingh.
Read the full explanation →Leakage of which one of the following gases had caused Bhopal Gas Tragedy in the year 1984 ?
- A.Methyl isocyanate
- B.Hexamethylene diisocyanate
- C.Isophorone diisocyanate
- D.Isothiocyanate
Show answer
On the night of 2-3 December 1984, methyl isocyanate (MIC) gas leaked from the Union Carbide pesticide plant in Bhopal.
Read the full explanation →Which of the following diseases are caused by the consumption of water contaminated by mercury and nitrate ?
- A.Minamata disease and Osteoporosis
- B.Osteoporosis and Blue Baby Syndrome
- C.Minamata disease and Blue Baby Syndrome
- D.Osteoporosis and Minamata disease
Show answer
Mercury in water causes Minamata disease, and excess nitrate causes blue baby syndrome.
Read the full explanation →Where is Asan Conservation Reserve located?
- A.Himachal Pradesh
- B.Uttarakhand
- C.Sikkim
- D.Arunachal Pradesh
Show answer
The Asan Conservation Reserve lies in Dehradun district of Uttarakhand. The reserve is a stretch of the Asan river near its meeting with the Yamuna, where a barrage built in 1967 created a wetland.
Read the full explanation →Which one of the following is the main reason of acid rains ?
- A.Dissolution of sulphur and nitrogen oxides in rain
- B.Dissolution of minerals in rain
- C.Dissolution of dust particles in rain
- D.Dissolution of soil solution in rain
Show answer
These gases react with water in the air to form sulphuric and nitric acids, which fall as acid rain. Sulphur dioxide comes mainly from burning coal and oil in power plants and smelters, and nitrogen oxides from vehicle engines and high-temperature furnaces.
Read the full explanation →