All questions of Environmental Pollution for BPSC (Bihar) Exam

• DO, BOD, COD Presence of organic and inorganic wastes in water decreases the dissolved oxygen (DO) content of the water.
• Water having DO content below 8.0 mg L-1 may be considered as contaminated. Water having DO content below. 4.0 mg L-1 is considered to be highly polluted. DO content of water is important for the survival of aquatic organisms.

Correctly Matched Terms and their Descriptions:

1. Arresters - These are used to separate particulate matters from contaminated air
2. Scrubbers - These are used to clean air for both dusts and gases by passing it through a dry or wet packing material

Explanation:

The given statements are related to air pollution control devices. The first statement is about Arresters and describes their function, which is to remove particulate matter from contaminated air. The second statement is about Scrubbers, which clean air by passing it through dry or wet packing material. Both of these statements are correctly matched with their respective devices.

Hence, option 'C' is the correct answer.

DDT, Salts of heavy metals, Radioactive substances are some of the examples of non-biodegradable pollutants.

Explanation:

Photochemical smog is a type of smog that is formed when sunlight reacts with certain chemicals in the atmosphere. Ground-level ozone is a major component of photochemical smog. Let's analyze each statement individually to determine their correctness.

Statement 1: Photochemical smog is a term used to describe air pollution that is a result of the interaction of sunlight with certain chemicals in the atmosphere.
This statement is correct. Photochemical smog is formed when sunlight interacts with pollutants such as nitrogen oxides (NOx), volatile organic compounds (VOCs), and other reactive organic gases. These pollutants are emitted from various sources including vehicle exhaust, industrial processes, and chemical solvents. When these pollutants react with sunlight, they form a complex mixture of secondary pollutants such as ozone, peroxyacyl nitrates (PANs), and aldehydes. These pollutants contribute to the formation of smog and can have adverse effects on human health and the environment.

Statement 2: Ground-level ozone is formed when vehicle emissions contain nitrogen oxides and volatile organic compounds.
This statement is also correct. Ground-level ozone is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. Vehicle emissions are a significant source of these pollutants. Nitrogen oxides are released from the combustion of fossil fuels in vehicles' engines, while volatile organic compounds can come from vehicle exhaust, fuel evaporation, and other sources. When these pollutants are emitted and exposed to sunlight, they undergo a series of chemical reactions that lead to the formation of ground-level ozone. Ground-level ozone is a harmful pollutant and a key component of photochemical smog.

Therefore, both statements are correct. Photochemical smog is formed when sunlight interacts with certain chemicals in the atmosphere, and ground-level ozone is a major component of photochemical smog that is formed when vehicle emissions contain nitrogen oxides and volatile organic compounds.

Statement 1: Biocides, polychlorinated biphenyls (PCBs), and heavy metals directly eliminate sensitive aquatic organisms.

Explanation:
Biocides, PCBs, and heavy metals are all toxic substances that can have harmful effects on aquatic organisms. These substances can be introduced into water bodies through various sources such as industrial discharges, agricultural runoff, and improper waste disposal. When present in water, they can directly eliminate sensitive aquatic organisms by causing toxicity or even death. Biocides are specifically designed to kill or control the growth of organisms, while PCBs and heavy metals can have toxic effects on aquatic organisms at certain concentrations.

Statement 2: Hot waters discharged from industries, when added to water bodies, lowers its DO content.

Explanation:
When hot water is discharged from industries into water bodies, it can have several negative impacts on the aquatic ecosystem. One such impact is the reduction in dissolved oxygen (DO) content. Dissolved oxygen is essential for the survival of aquatic organisms as they rely on it for respiration. However, when hot water is added to water bodies, it can cause several changes that lead to a decrease in DO levels:

1. Increased water temperature: Hot water increases the temperature of the receiving water body. As water temperature rises, the solubility of oxygen decreases, leading to a decrease in DO levels.

2. Reduced oxygen diffusion: Higher water temperatures reduce the ability of oxygen to dissolve and diffuse into the water. This further contributes to a decrease in DO levels.

3. Increased metabolic rates: The introduction of hot water can increase the metabolic rates of aquatic organisms. This increased metabolic activity leads to higher oxygen consumption, further depleting DO levels.

Overall, the addition of hot water from industries to water bodies can result in a decrease in DO content, which can be detrimental to aquatic organisms that rely on oxygen for survival.

Conclusion:
Based on the explanations provided, both statements 1 and 2 are correct. Therefore, the correct answer is option 'D' - Neither 1 nor 2.

• Alpha particles can be blocked by a piece of paper and human skin.
• Beta particles can penetrate through the skin, while can be blocked by some pieces of glass and metal.