Environmental Pollution

Biological treatment of water pollution uses microorganisms like phytoplankton to consume organic pollutants. Phytoplankton (C) are microscopic aquatic organisms that help purify water naturally. Lichens are typically air quality indicators. Fungi decompose matter but are more common in terrestrial environments. None of the above is incorrect since phytoplankton is valid.

Pollution affects the natural flora first because plants are stationary and directly exposed to atmospheric and soil contaminants, making them sensitive indicators of environmental health.

Industrial effluents contain toxic chemicals and heavy metals that contaminate water bodies. These wastes from factories and manufacturing processes are a major source of water pollution worldwide. The other options are natural processes or part of aquatic ecosystems.

Microorganisms like bacteria break down organic matter in sewage through biological treatment processes. Sewage treatment plants use these microbes to purify water before it's recycled or discharged back into water bodies. This is a natural and effective way to treat wastewater.

BOD (Biochemical Oxygen Demand) measures how much oxygen microorganisms need to decompose organic matter in water. Sugar mills discharge large amounts of organic waste that increases BOD, potentially depleting oxygen levels for aquatic life. Higher BOD indicates more severe pollution.

Water pollution reduces dissolved oxygen levels, making oxygen unavailable to aquatic organisms. When organic pollutants decompose, they consume oxygen through bacterial action. This oxygen depletion can lead to fish kills and ecosystem collapse in severely polluted waters.

The main causative factor of water pollution is industrial waste.

2,4-D and pesticides are agricultural chemicals that runoff into water bodies, causing pollution. These toxic compounds contaminate groundwater and surface water, harming aquatic ecosystems. The other options are related to air pollution, not water pollution.

Minamata disease is caused by mercury poisoning, named after the Japanese city where a famous outbreak occurred. Industrial mercury discharge into water accumulates in fish, causing severe neurological damage in humans who consume them. The disease highlights the dangers of heavy metal pollution.

SO2 (sulfur dioxide) pollution primarily affects cell membrane systems by forming acid rain that damages cellular structures. The acidic stress disrupts membrane integrity and function in plant cells. This is why SO2 pollution causes visible damage to leaves and reduces plant productivity.

Hydroelectric power stations generate electricity without burning fuel, so they don't emit air pollutants. The other options all produce emissions: thermal plants burn coal, diesel engines burn fuel, and pollen grains are natural airborne particulates. Hydroelectricity is a clean energy source for air quality.

Lichens and mosses are sensitive to sulfur dioxide and other air pollutants, making them excellent bioindicators. Their presence or absence in an area reveals air quality levels. These organisms disappear from polluted areas and return when conditions improve, providing visible evidence of pollution.

Major Indian cities like Mumbai and Kolkata have significant vehicular traffic and industrial activity, which are primary sources of carbon monoxide and sulfur oxides. Vehicle emissions and industrial discharges create severe air pollution problems. These pollutants are characteristic of rapidly urbanizing developing cities.

Photochemical smog is a type of air pollution formed when sunlight reacts with nitrogen oxides and volatile organic compounds from vehicle exhaust and industrial emissions. This creates secondary pollutants like ozone and peroxyacyl nitrates. It specifically affects atmospheric air quality.

Carbon monoxide (CO) is a toxic gas produced by incomplete combustion, making it a significant atmospheric pollutant from vehicles and industry. While CO2 and O3 occur naturally, they can become pollutants at elevated levels. Nitrogen (N2) is inert and makes up 78% of Earth's atmosphere without causing pollution.

The greenhouse effect is the trapping of reradiated heat from Earth's surface by atmospheric gases including water vapor, carbon dioxide, ozone, and dust. These gases absorb and re-emit infrared radiation, warming the lower atmosphere.

Automobile exhausts and industrial chemicals release the highest quantities of air pollutants including particulate matter, nitrogen oxides, sulfur oxides, and volatile organic compounds into the atmosphere.

Nitrogen oxides from high-altitude aircraft and rocket launches, along with chlorofluorocarbons and halocarbons, are the primary pollutants that catalytically destroy stratospheric ozone. These substances break down ozone molecules through complex chemical reactions.

Stratospheric ozone forms a protective layer that absorbs most of the sun's harmful UV-B and UV-C radiation, preventing DNA damage and protecting living organisms from increased skin cancer and other harmful effects.

The 1984 Bhopal disaster involved a leak of methyl isocyanate (MIC) gas from a Union Carbide pesticide plant, causing thousands of deaths and long-term health effects in the surrounding population.

Chlorofluorocarbons, when released into the atmosphere, migrate to the stratosphere where UV radiation breaks them down, releasing chlorine atoms that catalytically destroy ozone molecules, leading to the ozone hole.

Refrigerators release CFCs and other refrigerants, burning fossil fuels (oil and coal) emits CO2 and other greenhouse gases, and deforestation reduces Earth's capacity to absorb CO2 through photosynthesis, collectively increasing atmospheric greenhouse gas concentrations.

DDT is a synthetic pesticide that persists in the environment for decades, bioaccumulates in fatty tissues, and biomagnifies through food chains, earning its classification as a non-degradable or persistent organic pollutant.