Question

In the human-induced process called acid precipitation, the main biogeochemical cycles that are altered are the ………… cycles and one effect in lakes is to ………. the population of nitrifying bacteria.
A. Phosphorus and nitrogen, decrease
B. Nitrogen and sulphur, decrease
C. Nitrogen and sulphur, increase
D. Phosphorus and sulphur, decrease

Answer 1

Hint: Carbon, nitrogen, hydrogen, oxygen, phosphorus and sulphur are the six common elements associated with the variety of organic molecules that may exist for long periods in the atmosphere, on land, in water or under the Earth’s surface. Several geologic processes, such as weathering and erosion, play a role in the cycling of these elements on Earth.

Complete answer:
The six elements, carbon, nitrogen, hydrogen, oxygen, phosphorus and sulphur are used by organisms in various ways. Hydrogen and oxygen are found in water and are essential to life. Carbon is present in all organic molecules and nitrogen is found in proteins and nucleic acids. Phosphorus is present in nucleic acids and biological membranes. Sulphur is essential to the three-dimensional shape of proteins. The cycling of these elements between living organisms and their nonliving environment is called biogeochemical cycles.
The human-induced process acid precipitation is the acid rain. Emission of acidic gases on the large scale into the atmosphere from thermal power plants, industries and automobiles cause acid rain. The common acidic gases are sulphur dioxide, nitrogen oxides and volatile organic carbons. Sulphur dioxide and nitrogen oxides mix with rainwater and form sulphuric acid and nitric acid. When such rain falls on land, it acidifies the soil and water. The population of nitrifying bacteria decreases in the acid stressed water and soil.

Thus, option B. Nitrogen and sulphur, the decrease is the correct answer.

Note:
Acid rain formed by mixing of oxides of sulphur and nitrogen in rainwater. Acid rain falls on the earth and it causes a decrease in the population of nitrifying bacteria.