Environmental Issues and Pollutants Questions and Answers

Answer: A

The hazardous type is chemical waste.

Hazardous waste is waste that is toxic, corrosive, flammable or reactive and so poses a substantial danger to health or the environment. Chemical waste from industries and laboratories, such as solvents, acids, heavy metals and pesticides, falls squarely in this class and is regulated separately in India under the Hazardous and Other Wastes Rules.

Household, commercial and agricultural waste are classified by their source. They may contain some hazardous items, such as batteries or pesticide containers, but as classes they are general or non-hazardous waste, not hazardous waste.

Answer: A

The major source of fecal contamination is domestic effluent.

Fecal contamination comes from human and animal excreta. Domestic effluent, the sewage from homes, carries human feces and with it pathogenic bacteria, viruses and parasites; coliform counts in water are used as the indicator of this sewage pollution. Untreated sewage entering rivers and groundwater is the main cause of waterborne diseases such as cholera and typhoid.

Chemical, steel plant and pharmaceutical effluents are industrial wastewaters. They pollute water with chemicals, metals and drug residues, but they do not carry fecal matter.

Answer: A

Ozone depletion is mainly caused by chlorofluorocarbons.

CFCs, once widely used in refrigerators, air conditioners and aerosol sprays, are very stable and drift up into the stratosphere. There ultraviolet radiation breaks them apart, releasing chlorine atoms, and each chlorine atom can destroy thousands of ozone molecules in a chain reaction. This is why the Montreal Protocol of 1987 phased out CFCs.

Chlorine is the agent that destroys ozone, but it reaches the stratosphere mainly from CFCs, which are the source the question asks for. Sulfur dioxide causes acid rain, and carbon dioxide is a greenhouse gas responsible for warming, not for ozone depletion.

Answer: D

Noise level is measured in dB (decibels).

The decibel is a logarithmic unit of sound pressure level: an increase of 10 dB means ten times the sound intensity. Normal conversation is around 60 dB, and prolonged exposure above about 85 dB can damage hearing.

The joule is a unit of energy, ppm (parts per million) measures concentration of pollutants in air or water, and the bit is a unit of information.

Answer: C

The result is Biomagnification.

Persistent toxic substances such as DDT or mercury are not broken down or excreted easily. As each organism eats many smaller ones, the chemical becomes more concentrated at each higher level of the food chain, so top predators carry the highest concentrations. This increase along the food chain is biomagnification.

Accumulation (bioaccumulation) is the build-up within a single organism over time, while excretion and elimination are the removal of a substance from the body.

Answer: A

Agricultural residue is not hazardous waste.

Hazardous wastes are those that are toxic, corrosive, flammable or reactive and so endanger health or the environment. Crop residues such as straw, husks and stalks are organic and biodegradable; they can be composted or used as fodder or fuel, and their main problem arises only when they are burnt in the open.

Chemical wastes, waste paint (with its solvents and heavy-metal pigments) and electroplating waste (with cyanides and heavy metals such as chromium, nickel and cadmium) are all classed as hazardous.

Answer: D

Human and animal anatomical waste is disposed of by incineration.

Under India's biomedical waste rules, human anatomical waste (tissues, organs and body parts) and animal anatomical waste go into the yellow category, whose prescribed treatment is incineration (or deep burial where no incinerator is available). Burning at high temperature destroys the tissue and its pathogens completely.

Autoclaving and microwaving sterilise wastes such as contaminated plastics, sharps and cultures, but they do not destroy body parts. Composting is for ordinary biodegradable waste and would spread infection from infected tissue.

Answer: A

E. coli indicates sewage contamination.

Escherichia coli lives in the intestines of humans and warm-blooded animals and is passed in their faeces. Finding it in water shows faecal contamination, usually from sewage, and so the likely presence of pathogens causing cholera, typhoid and dysentery.

Oil, pesticides and herbicides are chemical pollutants detected by chemical tests; a bacterium from the gut tells us nothing about them.

Answer: B

The daytime limit for residential areas is 55 dB.

The Noise Pollution (Regulation and Control) Rules, 2000 set daytime limits of 75 dB(A) for industrial areas, 65 dB(A) for commercial areas, 55 dB(A) for residential areas and 50 dB(A) for silence zones. The night limit for residential areas is 45 dB(A).

75 dB and 65 dB are the industrial and commercial limits, and 80 dB is not among the ambient standards.

Answer: C

Excess growth is due to an increase in nitrates and phosphates.

Nitrates and phosphates from fertiliser run-off, sewage and detergents are plant nutrients. When they build up in lakes and ponds, algae and aquatic plants grow excessively, a process called eutrophication, which reduces oxygen and harms aquatic life.

Nitrates or phosphates alone each give only part of the cause, and sodium is not a limiting nutrient for plant growth.

Algal blooms block sunlight, and when the algae die their decomposition uses up dissolved oxygen, which kills fish and other aquatic life.