Oxygen Demand and Pollution Effects

The video tutorial explains the oxygen sag curve and biological oxygen demand (BOD). It describes how pollutants, especially organic ones, enter water bodies and affect dissolved oxygen levels. The tutorial outlines different zones in water bodies, such as clean, decomposition, septic, recovery, and clear zones, and discusses the impact of organic pollution. It emphasizes the role of decomposers in increasing oxygen demand and the subsequent recovery of aquatic life.

What is the primary cause of the oxygen sag curve in water bodies?

• Increase in sunlight exposure

• Increased fish population

• Introduction of organic pollutants

• Decrease in water temperature

How does the demand for oxygen change as bacteria decompose organic waste?

• It does not change

• It increases initially and then decreases

• It decreases initially and then increases

• It remains constant

What happens to the dissolved oxygen levels as the demand for oxygen increases?

• They increase

• They fluctuate randomly

• They decrease

• They remain constant

Which zone in a polluted water body is characterized by the lowest levels of dissolved oxygen?

• Recovery zone

• Septic zone

• Decomposition zone

• Clean zone

In which zone do fish start to reappear in a polluted water body?

• Decomposition zone

• Recovery zone

• Septic zone

• Clean zone

What type of pollution is primarily responsible for the oxygen sag curve?

• Noise pollution

• Organic pollution

• Thermal pollution

• Inorganic pollution

Which of the following is NOT a source of organic pollution?

• Storm drains

• Plastic waste

• Animal waste

• Untreated sewage

What is the role of decomposers in the oxygen sag curve?

• They break down organic matter

• They reduce the biological oxygen demand

• They increase the water temperature

• They increase the sunlight exposure

What is the primary function of biological oxygen demand (BOD) in water bodies?

• To measure water temperature

• To evaluate the noise levels

• To assess the amount of sunlight

• To indicate the demand for oxygen by decomposers

Which of the following can cause an increase in biological oxygen demand?

• Presence of organic pollutants

• Decrease in sunlight exposure

• Increase in water temperature

• Introduction of inorganic chemicals