Question

Consider the following statements: (1) PAN is secondary air pollutant. (2) BOD and COD values are indicators of water polution level. Which of the statements given above is/are correct? (a) Both 1 and 2 (b) 1 only (c) 2 only (d) Neither 1 nor 2

Short answer

The correct answer is (a) Both 1 and 2.

Step-by-step solution

Understanding Statement 1

Statement 1 asserts that PAN is a secondary air pollutant. PAN stands for Peroxyacetyl Nitrate, which indeed is a secondary pollutant formed in the atmosphere from primary pollutants through chemical reactions, typically involving volatile organic compounds (VOCs) and NOx in the presence of sunlight.

Understanding Statement 2

Statement 2 claims that BOD and COD values are indicators of water pollution level. BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) are measures used to assess the amount of organic pollution in water. High values indicate high levels of pollution due to organic matter.

Evaluating Correctness of Statements

Both statements need to be evaluated for their correctness. Based on the information about PAN, it being a secondary air pollutant is true. Also, since BOD and COD are established indicators of water pollution, this statement is true as well.

Choosing the Correct Option

Since both statements 1 and 2 are correct, the option that represents this is (a) Both 1 and 2.

Key concepts

Air Pollutants

Air pollutants are substances in the atmosphere that can harm human health or the environment. They come in various forms, such as gases, solids, or liquids, and can originate from natural sources like wildfires or volcanic eruptions, or from human-made sources like vehicle emissions and industrial activities.
Some primary pollutants are emitted directly into the air, such as carbon monoxide (CO) and sulfur dioxide (SO2). Secondary pollutants, however, form in the atmosphere through chemical reactions between primary pollutants.
For instance, Peroxyacetyl Nitrate (PAN) is a secondary pollutant that forms from volatile organic compounds (VOCs) and nitrogen oxides (NOx) in sunlight. Understanding the difference between primary and secondary pollutants is crucial in tackling air pollution effectively.

Water Pollution

Water pollution occurs when harmful substances enter water bodies like lakes, rivers, or oceans, degrading the water quality and harming aquatic life. Common sources of water pollution include agricultural runoff, industrial discharge, and sewage release.
Chemical contaminants such as heavy metals, pesticides, and nitrates can be particularly problematic, as they might be toxic to plants and animals even in small quantities.
Water pollution doesn't just affect ecosystems. It can also impact human health and economies, leading to illnesses or affecting industries dependent on clean water, such as fishing and tourism. Preventing water pollution requires careful management of land and industry practices.

Biochemical Oxygen Demand (BOD)

Biochemical Oxygen Demand (BOD) is a critical measure that reflects the level of organic pollution in water. It measures the amount of dissolved oxygen needed by aerobic organisms to break down organic material in a water sample over a specified period, usually five days.
A high BOD value indicates a high level of organic pollution, which can deplete oxygen levels in water, threatening aquatic life. This is especially important in ecosystems where oxygen is already limited.
Monitoring BOD is essential for managing water quality, as it helps identify areas where pollution is affecting aquatic life and human health. Regular monitoring helps in making informed decisions to improve water quality.

Chemical Oxygen Demand (COD)

Chemical Oxygen Demand (COD) is a similar indicator to BOD but measures the total amount of oxygen required to oxidize both biodegradable and non-biodegradable organic matter in water. While BOD only assesses materials that bacteria can decompose, COD provides a more comprehensive overview, as it includes chemical oxidation of resistant organic materials.
Higher COD values indicate large amounts of oxidizable pollutants in the water. This can result from industrial contaminants or natural organic materials.
Using COD, chemists and environmental scientists can get a quick snapshot of water quality, helping them identify pollution sources and take corrective actions. Regularly measuring COD, along with BOD, provides a fuller picture of water health.