Question

Match the column I with column II and mark the appropriate choice. $$ \begin{array}{|l|l|l|l|} \hline \text { (A) } & \begin{array}{l} \text { Biodegradable } \\ \text { pollutants } \end{array} & \text { (i) } & \text { DDT } \\ \hline \text { (B) } & \begin{array}{l} \text { Non-biodegradable } \\ \text { pollutants } \end{array} & \text { (ii) } & \mathrm{SO}_{2} \\ \hline \text { (C) } & \text { Primary pollutants } & \text { (iii) } & \text { PAN } \\ \hline \text { (D) } & \text { Secondary pollutants } & \text { (iv) } & \text { Sewage } \\ \hline \end{array} $$ (a) \((\mathrm{A}) \rightarrow\) (iii), (B) \(\rightarrow\) (iv), (C) \(\rightarrow\) (ii), (D) \(\rightarrow\) (i) (b) \((\mathrm{A}) \rightarrow(\mathrm{ii}),(\mathrm{B}) \rightarrow(\mathrm{iii}),(\mathrm{C}) \rightarrow(\mathrm{iv}),(\mathrm{D}) \rightarrow\) (i) (c) \((\mathrm{A}) \rightarrow(\mathrm{i}),(\mathrm{B}) \rightarrow(\mathrm{ii}),(\mathrm{C}) \rightarrow(\mathrm{iii}),(\mathrm{D}) \rightarrow(\mathrm{iv})\) (d) \((\mathrm{A}) \rightarrow(\mathrm{iv}),(\mathrm{B}) \rightarrow(\mathrm{i}),(\mathrm{C}) \rightarrow(\mathrm{ii}),(\mathrm{D}) \rightarrow(\mathrm{iii})\)

Short answer

(A) \rightarrow (iv), (B) \rightarrow (i), (C) \rightarrow (ii), (D) \rightarrow (iii)

Step-by-step solution

Identify Biodegradable Pollutants

Biodegradable pollutants can be broken down by biological processes. An example is sewage (iv), which can be decomposed by bacteria.

Identify Non-biodegradable Pollutants

Non-biodegradable pollutants cannot be easily broken down by natural processes. DDT (i) is an example of a non-biodegradable pollutant.

Identify Primary Pollutants

Primary pollutants are emitted directly from a source. Sulfur dioxide, SO2 (ii), is an example of a primary pollutant because it comes directly from sources such as burning fossil fuels.

Identify Secondary Pollutants

Secondary pollutants are not emitted directly. Instead, they form in the air when primary pollutants react or interact. PAN (peroxyacetyl nitrate) (iii) is an example of a secondary pollutant.

Key concepts

Biodegradable Pollutants

Biodegradable pollutants are substances that are capable of being broken down by natural biological processes. The process involves living organisms, typically microorganisms, transforming the pollutants into less harmful substances or elements that can be incorporated back into natural cycles.

For instance, sewage (iv) is a classic example of a biodegradable pollutant. Sewage consists of organic matter that can be decomposed by bacteria and other microorganisms into simpler, harmless compounds like carbon dioxide, water, and minerals. These byproducts can serve as nutrients for plants, closing the natural biological cycle.

In an educational context, understanding the mechanisms of biodegradation is critical because it outlines the potential for certain pollutants to be managed through natural processes and aids in evaluating the long-term impact of waste products on the environment.

Non-biodegradable Pollutants

Non-biodegradable pollutants, on the other hand, are materials that do not easily break down or decompose in the natural environment. These substances can persist for years, decades, or even indefinitely. Non-biodegradable pollutants often accumulate in ecosystems, leading to environmental and health problems.

DDT (i) is a well-known non-biodegradable pollutant. Once widely used as a pesticide, DDT is resistant to degradation and can accumulate in the food chain, leading to toxic effects on wildlife and humans. As it does not decompose naturally, the persistence of DDT in the environment makes it a significant concern. Students must recognize the importance of monitoring and regulating non-biodegradable pollutants to prevent long-lasting damage to the ecosystem.

Primary Pollutants

Understanding primary pollutants is essential for pinpointing the sources of environmental pollution. Primary pollutants are directly emitted from a source into the atmosphere, presenting immediate pollution challenges. They originate from various processes such as industrial production, vehicle emissions, or volcanic eruptions.

Sulfur dioxide, SO2 (ii), is emitted when substances containing sulfur, like coal or oil, are burned. It is a primary pollutant of great concern due to its contribution to health issues and environmental problems like acid rain. By identifying primary pollutants, measures can be taken at the source to reduce emissions and consequently manage air quality more effectively.

Secondary Pollutants

Secondary pollutants are not emitted into the atmosphere directly. Instead, they form when primary pollutants undergo chemical reactions in the presence of sunlight, water vapor, and other compounds. These reactions can occur over time and often result in pollutants that are more harmful than their precursors.

An example is peroxyacetyl nitrate (PAN) (iii), which forms when nitrogen oxides and volatile organic compounds react in the presence of sunlight. PAN, along with other secondary pollutants like ozone, has harmful effects on human health, vegetation, and materials. Educating students about secondary pollutants underlines the complexity of atmospheric chemistry and the need for comprehensive strategies to control air pollution, including addressing emissions of precursor substances.