Environmental Engineering Test 2 Nddc Scholarship

Supersonic aircraft fly at very high altitudes to reduce drag and increase efficiency, typically cruising in the stratosphere. Because the stratosphere is more stable than the troposphere (it has very little vertical mixing), the exhaust gases—particularly water vapor and nitrogen oxides—can persist for long periods, potentially contributing to ozone depletion.

Iron and manganese are usually dissolved in water in their 'reduced' forms. To remove them, the water is first aerated or chemically treated to oxidize these metals into insoluble solid particles. Once they have formed solids, they can be easily removed through settling (sedimentation) and final filtration.

Printing effluents contain complex dye molecules that are often resistant to biological treatment. Electrolytic decomposition (or electrocoagulation) uses an electric current to break the chemical bonds of the dyes or to generate coagulants that trap the color particles, making it a highly effective method for decolorization specifically in industrial printing waste.

Chemical toxicity is often temperature-dependent. For potassium cyanide, a common industrial pollutant, a 10°C rise in water temperature can double its toxicity to aquatic life. This is particularly dangerous because warmer water also holds less dissolved oxygen, making it even harder for fish and other organisms to survive the chemical stress.

Greenhouse gases (like CO2 and methane) are related to air pollution and climate change, but they have no effect on sound waves or acoustic management. Silencers, vibration damping (insulation), and tree belts are all physical methods used to absorb, block, or reduce the intensity of noise.

Ozone levels fluctuate seasonally based on atmospheric circulation and temperature. In the Indian subcontinent, the minimum ozone concentration (depletion) is typically observed during the winter months, specifically in December, before beginning to rise again as solar intensity increases in the spring.

Normal human speech typically falls in the range of 40 to 60 decibels. Therefore, 45 decibels is the most accurate representation of a standard, quiet conversation. For comparison, 10 dB is a whisper, 90 dB is a shouting match or lawnmower, and 115 dB is a loud rock concert.

All the substances listed—dust, mists, smoke, fumes, and soot—are physical particles (either solid or liquid droplets) suspended in the air. Photochemical smog also contains high concentrations of secondary particulate matter like nitrates and organic aerosols. Since every item listed fits the definition of a particulate, 'None of these' is the correct choice.

Activated carbon is a highly porous material with an incredibly large surface area. It works through a process called adsorption, where organic compounds responsible for bad taste and foul odors (like chlorine byproducts or decaying algae) stick to the surface of the carbon. Alum is used for settling solids, and bleaching powder is primarily for disinfection.

Aquatic ecosystems are sensitive to various pollutants. Toxic organics can disrupt biological functions; suspended solids can clog fish gills and block sunlight for plants; and heavy metals or cyanides are direct poisons. Therefore, all these factors combined are considered deleterious (harmful) to aquatic life.