Environmental Science MCQ – Asked in Previous Years, WBCS Mains

Answer – C. NO₂
Explanation-X-ray films are made of cellulose nitrate, which is a flammable material. When cellulose nitrate burns, it produces a number of gases, including NO2. NO2 is a colorless, odorless gas that can be harmful to human health. It can irritate the lungs and cause respiratory problems. In high concentrations, NO2 can even be fatal. X-ray films are no longer commonly used in medical settings. They have been replaced by newer, safer films made of cellulose acetate. However, old X-ray films may still be present in some medical facilities. It is important to be aware of the hazards of NO2 gas and to take precautions when handling old X-ray films.

Answer – C. 5.6
Explanation-A pH in rain below 5.6 is generally regarded as ‘acid rain.’ Acid rain refers to rainwater that has an acidic pH due to the presence of certain pollutants, primarily sulfur dioxide (SO2) and nitrogen oxides (NOx), which react with water vapor in the atmosphere to form sulfuric acid and nitric acid. Acid rain can have harmful effects on ecosystems, vegetation, and infrastructure, and it is a significant environmental concern in areas where industrial activities or high levels of air pollution are present.

Answer – D. Ozone
Explanation-Ozone is the major contributor to photochemical smog. Photochemical smog is a type of air pollution that is formed through complex chemical reactions involving sunlight, nitrogen oxides (NOx), volatile organic compounds (VOCs), and oxygen. These reactions lead to the formation of ground-level ozone, which is a primary component of photochemical smog. Ozone can cause respiratory issues, eye irritation, and other health problems, and it also contributes to the deterioration of materials and vegetation.

Answer – D. 9 ppm
Explanation-
The US Environmental Protection Agency (EPA) has set National Ambient Air Quality Standards (NAAQS) for carbon monoxide. The NAAQS is the level of a pollutant in the air that the EPA deems safe for human health. The primary standard for carbon monoxide is 9 parts per million (ppm). This means that the average concentration of carbon monoxide in the air should not exceed 9 ppm over an 8-hour period. If carbon monoxide levels exceed the NAAQS, it can cause health problems such as headaches, dizziness, nausea, and vomiting. In severe cases, carbon monoxide poisoning can lead to death. There are a number of things that can be done to reduce carbon monoxide levels in the air, such as: Using properly maintained appliances and equipment Keeping combustion appliances away from enclosed spaces Having your furnace or water heater inspected and cleaned annually Installing carbon monoxide detectors in your home and workplace By taking these steps, you can help to reduce your exposure to carbon monoxide and protect your health.

Answer – A. Methane
Explanation-Methane (CH4) is the most abundant hydrocarbon in the atmosphere. Methane is a potent greenhouse gas that contributes to global warming and climate change. It is released into the atmosphere through various natural and human activities, including the decay of organic matter, livestock farming, rice cultivation, and fossil fuel production. Methane plays a significant role in the Earth’s energy balance and is a focus of efforts to reduce greenhouse gas emissions.

Answer – B. Water vapor
Explanation-Water vapor (H2O) is the most abundant greenhouse gas in the atmosphere. Although carbon dioxide (CO2) is often discussed as the primary greenhouse gas associated with climate change, water vapor is actually the most abundant and influential greenhouse gas. Water vapor concentrations in the atmosphere can vary widely depending on temperature and humidity levels. Its greenhouse effect is closely tied to the Earth’s hydrological cycle and the interaction between the atmosphere, oceans, and land surfaces.

Answer – B. Oceans
Explanation-Oceans are the largest sink for carbon dioxide (CO2) gas. The world’s oceans act as a significant carbon sink, absorbing a substantial portion of the atmospheric CO2 emissions resulting from human activities. Through physical and chemical processes, the oceans help to mitigate the effects of increased CO2 in the atmosphere. However, excessive absorption of CO2 leads to ocean acidification, which poses risks to marine ecosystems and organisms.

Answer – D. Sewage water
Explanation- BOD (Biochemical Oxygen Demand) is a measure of the amount of dissolved oxygen consumed by microorganisms in water while decomposing organic matter. Sewage water, which contains a high concentration of organic pollutants, will have a higher BOD value compared to other options such as wastewater, river water, or rainwater. The organic matter present in sewage water provides a rich food source for microorganisms, leading to increased biological activity and oxygen consumption.

Answer – D. Methyl isocyanate
Explanation-During the Bhopal gas tragedy that occurred in 1984, the harmful gas released was methyl isocyanate (MIC). The incident took place at the Union Carbide pesticide plant in Bhopal, India. A storage tank containing a large quantity of MIC experienced a catastrophic failure, resulting in the release of toxic gases into the surrounding environment. The tragedy led to the loss of thousands of lives and had long-lasting health and environmental impacts.

Answer – D. Ultraviolet
Explanation-The depletion of the ozone (O3) layer in the Earth’s atmosphere allows more ultraviolet (UV) radiation from the sun to reach the Earth’s surface. UV radiation is a form of electromagnetic radiation with a shorter wavelength and higher energy than visible light. Prolonged exposure to UV radiation can have harmful effects on human health, including skin damage, eye problems, and an increased risk of skin cancer.