Problem 39 - A Complete Resource Book in Chemistry for JEE Main

Question

Spraying of DDT causes pollution of (a) air (b) air and water (c) air and soil (d) air, water and soil

Step-by-Step Solution

Answer

The correct answer is (d) air, water, and soil.

Step 1: Understand the Problem

We need to determine the scope of pollution caused by spraying DDT, a chemical insecticide that was widely used for pest control.

Step 2: Identify Characteristics of DDT

DDT is a persistent organic pollutant that, once sprayed, can remain in the environment for a long time due to its ability to metabolize slowly and its low water solubility.

Step 3: Analyze How DDT Enters the Environment

When DDT is sprayed, it can become airborne, contaminating the air. It can also settle on the soil and, through runoff, contaminate water bodies.

Step 4: Determine the Extent of Pollution

Since DDT can be transported through air, deposit on soil, and washed into water bodies, it has the potential to pollute all three domains: air, water, and soil.

Step 5: Select the Correct Option

Based on the analysis, DDT causes pollution of air, water, and soil. Therefore, the most comprehensive answer is (d) air, water, and soil.

Key Concepts

Persistent Organic Pollutants

Persistent Organic Pollutants, or POPs, are a group of harmful chemicals that persist in the environment. Their longevity is due to their ability to resist degradation. POPs can remain intact for long periods, measured as years or even decades.
These pollutants pose significant threats not only to ecosystems but also to human health. They can travel long distances from their original sources through wind and water currents. As a result, POPs can affect areas far away from where they were initially released.

• Long-lasting: POPs don’t break down easily, allowing them to accumulate in the environment.
• Global reach: They can travel across international borders, affecting distant ecosystems.
• Bioaccumulation: They tend to accumulate in the fatty tissues of living organisms.

Due to these properties, the impact of POPs like DDT must be carefully managed. Focused efforts are needed to mitigate their presence in the environment to protect health and biodiversity.

Chemical Insecticides

Chemical insecticides are synthetic substances used to kill or control insect populations. They are a critical tool in agriculture for protecting crops from pests, ensuring better yields. However, their use comes with environmental concerns.

These insecticides can enter the ecosystem in several ways:

• Spraying: Direct application on crops and plants to eliminate pests.
• Runoff: Chemicals may be washed away into water bodies from irrigated fields.
• Airborne: Wind can carry sprayed particles to unintended areas.

The impact of chemical insecticides like DDT was widely recognized when they started showing adverse effects on non-target organisms. They can affect beneficial insects, such as pollinators, and other wildlife. Moreover, the tendency to slowly degrade means these chemicals can remain active in the environment for a long time, contributing to larger ecological issues.

DDT and Ecosystem

DDT, or dichloro-diphenyl-trichloroethane, is a type of chemical insecticide that became infamous for its extensive environmental impact. Originally used to combat diseases like malaria by eliminating mosquitoes, it was later banned or restricted in many places due to its harmful effects.

Once introduced to the environment, DDT can settle on soil surfaces, be carried through the air, and eventually infiltrate water systems. The cumulative pollution affects air, water, and soil simultaneously, illustrating its far-reaching impact.

• Soil contamination: DDT particles settle on soils, affecting terrestrial life forms.
• Water pollution: Runoff from rainfall can carry DDT residues into bodies of water, impacting aquatic life.
• Air contamination: Spray particles can be inhaled by animals and humans or deposited into ecosystems by wind.

Beyond environmental contamination, DDT also impacts food chains. Once absorbed by plants or small organisms, it moves up the food chain, increasing in concentration. This phenomenon, known as biomagnification, poses significant risks to predators, including humans, threatening entire ecosystems.